Article

The function of the sawfish's saw

Authors:
  • Sharks And Rays Australia, Cairns, Australia
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Abstract

Jawed fishes that possess an elongated rostrum use it to either sense prey or to manipulate it, but not for both. The billfish rostrum, for instance, lacks any sensory function and is used to stun prey [1 • Shimose T. • Yokawa K. • Saito H. • Tachihara K. Evidence for use of the bill by blue marlin, Makaira nigricans, during feeding.Ichthyol. Res. 2007; 54: 420-422 • Crossref • Scopus (15) • Google Scholar ], while paddlefishes use their rostrum to detect and orient towards electric fields of plankton [2 • Miller M.J. The ecology and functional morphology of feeding of North American sturgeons and paddlefishes.in: LeBreton G. Beamish F. McKinley R. Sturgeons and Paddlefish of North America. Kluwer Academic Publishers, 2005: 87-102 • Crossref • Google Scholar ]. Sturgeons search through the substrate with their electroreceptive rostrum, and engulf prey by oral suction [2 • Miller M.J. The ecology and functional morphology of feeding of North American sturgeons and paddlefishes.in: LeBreton G. Beamish F. McKinley R. Sturgeons and Paddlefish of North America. Kluwer Academic Publishers, 2005: 87-102 • Crossref • Google Scholar ]. Here, we show that juvenile freshwater sawfish Pristis microdon are active predators that use their toothed rostrum — the saw — to both sense prey-simulating electric fields and capture prey. Prey encountered in the water column is attacked with lateral swipes of the saw that can stun and/or impale it. We compare sawfish to shovelnose rays, which share a common shovelnose ray-like ancestor [3 • Wueringer B.E. • Squire L.J. • Collin S.P. The biology of extinct and extant sawfish (Batoidea: Sclerorhynchidae and Pristidae).Rev. Fish Biol. Fish. 2009; 19: 445-464 • Crossref • Scopus (49) • Google Scholar ] and lack a saw.

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... From a distance of around 40 cm between predator and prey, electroreception guides the predatory strike [reviewed in Peters et al., 2007] . Detailed ethograms of predatory strikes and subsequent prey manipulation behaviors exist for sphyrnid and carcharhinid sharks and rhinobatid and pristid rays [Kajiura and Holland, 2002; Kajiura, 2003; Wueringer et al., 2012]. Sharks and rays display innate feeding responses towards prey-simulating weak electric fields [Tricas, 1982; Kajiura, 2003; Wueringer et al., 2012]. ...
... Detailed ethograms of predatory strikes and subsequent prey manipulation behaviors exist for sphyrnid and carcharhinid sharks and rhinobatid and pristid rays [Kajiura and Holland, 2002; Kajiura, 2003; Wueringer et al., 2012]. Sharks and rays display innate feeding responses towards prey-simulating weak electric fields [Tricas, 1982; Kajiura, 2003; Wueringer et al., 2012]. One behavioral study indicates that the small spotted catshark Scyliorhinus canicula is unable to distinguish the biological electric fields of crustaceans from artificial dipole fields of the same strength [Kimber et al., 2011]. ...
... During prey manipulation, the crustacean and teleost prey of shovelnose rays is still alive when it is pinned onto the substrate with the pectoral disc [Wilga and Motta, 1998] and, therefore, mouth repositioning has to be fast and accurate. In sawfish, free-swimming teleost prey has been stunned and wounds may have been inflicted with the rostral teeth during lateral swipes of the rostrum , before the animal repositions its mouth to ingest the prey [Wueringer et al., 2012]. Ventrally, the number of pores along the rostrum of sawfish is comparable to shovelnose rays, although the sawfish rostrum comprises at least 20–22% of the total length [Thorson, 1982; Taniuchi et al., 1991]. ...
Article
Full-text available
The ampullae of Lorenzini are the electroreceptors of elasmobranchs. Ampullary pores located in the elasmobranch skin are each connected to a gel-filled canal that ends in an ampullary bulb, in which the sensory epithelium is located. Each ampulla functions as an independent receptor that measures the potential difference between the ampullary pore opening and the body interior. In the elasmobranch head, the ampullary bulbs of different ampullae are aggregated in 3-6 bilaterally symmetric clusters, which can be surrounded by a connective tissue capsule. Each cluster is innervated by one branch of the anterior lateral line nerve (ALLN). Only the dorsal root of the ALLN carries electrosensory fibers, which terminate in the dorsal octavo-lateral nucleus (DON) of the medulla. Each ampullary cluster projects into a distinctive area in the central zone of the DON, where projection areas are somatotopically arranged. Sharks and rays can possess thousands of ampullae. Amongst other functions, the use of electroreception during prey localization is well documented. The distribution of ampullary pores in the skin of elasmobranchs is influenced by both the phylogeny and ecology of a species. Pores are grouped in distinct pore fields, which remain recognizable amongst related taxa. However, the density of pores within a pore field, which determines the electroreceptive resolution, is influenced by the ecology of a species. Here, I compare the pore counts per pore field between rhinobatids (shovelnose rays) and pristids (sawfish). In both groups, the number of ampullary pores on the ventral side of the rostrum is similar, even though the pristid rostrum can comprise about 20% of the total length. Ampullary pore numbers in pristids are increased on the upper side of the rostrum, which can be related to a feeding strategy that targets free-swimming prey in the water column. Shovelnose rays pin their prey onto the substrate with their disk, while repositioning their mouth for ingestion and thus possess large numbers of pores ventrally around the mouth and in the area between the gills.
... Behavioural studies have revealed that the well-developed electrosensory system of the pristid rostrum is used to detect and localise prey (Wueringer et al., 2012a(Wueringer et al., , 2012b. Rostral teeth stun, impale and injure prey enabling it to be pinned down and manoeuvred to the mouth using cues from the mechanosensory system (Wueringer et al., 2011a(Wueringer et al., , 2011b. ...
... Given that both sensory systems detect signals at a close range, the elongation of the pristiophorid rostrum provides an increased sampling area. The enhanced electrosensory hypothesis, which was developed for sphyrnids (Kajiura, 2001) and expanded for pristids (Wueringer et al., 2011b(Wueringer et al., , 2012a, thus also likely applies to pristiophorids. ...
... This may also be the reason why pristiophorids, unlike other sharks or pristids, do not possess a mandibular canal (Chu & Wen, 1979). The pristid mandibular canal is thought to help guide the ingestion of prey after it has been disabled with lateral swipes of the saw and pinned down, which is especially important as the diet of pristids can include large catfish with venomous spines (Wueringer et al., 2012a;Wueringer et al., 2012b). Like pristids, it is therefore possible that pristiophorids rely on direct capture or stunning of prey with their rostra, but their prey capture might not include pinning behaviour. ...
Article
It has long been assumed that the elongated rostra (the saws) of sawsharks (Fam. Pristiophoridae) and sawfish (Fam. Pristidae) serve a similar function. Recent behavioural and anatomical studies have shed light on the dual function of the pristid rostrum in mechanosensory and electrosensory prey detection and prey manipulation. Here, we examine the distributions of the mechanosensory lateral line canals and electrosensory ampullae of Lorenzini in the southern sawshark, Pristiophorus nudipinnis and the longnose sawshark, Pristiophorus cirratus. In both species, the receptive fields of the mechano- and electrosensory systems extend the full length of the rostrum indicating that the sawshark rostrum serves a sensory function. Interestingly, despite recent findings suggesting they feed at different trophic levels, we recorded minimal interspecific variation between the two species. However, compared to pristids, the pristiophorid rostrum possesses a reduced mechanosensory sampling field but higher electro-sensory resolution, which suggests pristiophorids may not use their rostrums to disable large prey like pristids do. This article is protected by copyright. All rights reserved.
... Like sharks, skates, and rays, sawfish are elasmobranchs. Active predators, sawfish use their rostra to detect, kill, and manipulate prey (Kirkland and Aguillon-Martinez 2002;Wueringer et al. 2009Wueringer et al. , 2012. Known for this unique neurocranial appendage, sawfish are culturally known as a novelty and their rostra have been widely collected (Fig. 1). ...
... The anatomical properties of the sawfish skeleton, including the rostrum, are similar to those of rays, sharks, and skates, including teeth-like modified scales (Hamlett 1999, Fowler et al. 2005). Sawfish rostra are distinct cranial appendages with lateral protruding rostral teeth and are covered in placoid scales, also called dermal denticles (Shellis and Berkovitz 1980, Miyake et al. 1992, Hamlett 1999, Cicimurri 2007, Wueringer et al. 2012). The underlying cartilage structure has both mineralized and nonmineralized areas. ...
... However, a lost tooth is not replaced, and the socket remains empty and eventually closes. Sawfish use the rostral teeth to attack and manipulate prey, which are consumed using rows of true teeth within its mouth located below the rostrum (Kirkland and Aguillon-Martinez 2002, Wueringer et al. 2012, Whitty et al. 2013. ...
Article
After over two decades of planning and 5 years of conserving, packing, and moving, the Museum of Indian Arts and Culture has finished the first two phases of the largest move of archaeological artifacts in the museum's history and quite possibly in the American Southwest. Framed within the historical background of evolving collection storage over many decades, the Archaeological Research Collections were moved from the Laboratory of Anthropology and another off-site storage location to a new state of the art off-site storage facility at the Center for New Mexico Archaeology (CNMA). Decisions that eased the overall move, including issues resulting from the move and how they were remedied, are discussed. Overall, this particular collections move demonstrates the capabilities that a small staff can have if given enough time, volunteers, and grant resources.
... Although the notion of such functions has been widely held, it was not until recently that the purpose of the rostra of sawfishes was investigated from an anatomical and behavioural standpoint. Such work has shown that the rostrum contains a high density of electroreceptors (Wueringer et al., 2011a) and facilitates the sensing of prey in both the water column and on the substratum (Wueringer et al., 2012a, b). Once detected, prey is then struck by the rostral teeth through rapid lateral swipes of the rostrum (Wueringer et al., 2012a). ...
... Such work has shown that the rostrum contains a high density of electroreceptors (Wueringer et al., 2011a) and facilitates the sensing of prey in both the water column and on the substratum (Wueringer et al., 2012a, b). Once detected, prey is then struck by the rostral teeth through rapid lateral swipes of the rostrum (Wueringer et al., 2012a). The rostrum can also be used to move prey into position for consumption once it has reached the substratum (Wueringer et al., 2012a). ...
... Once detected, prey is then struck by the rostral teeth through rapid lateral swipes of the rostrum (Wueringer et al., 2012a). The rostrum can also be used to move prey into position for consumption once it has reached the substratum (Wueringer et al., 2012a). In terms of using the rostrum to uncover buried prey, both the anatomical and behavioural work suggest that this is unlikely. ...
Article
Potential roles of the rostrum of sawsharks (Pristiophoridae), including predation and self-defence, were assessed through a variety of inferential methods. Comparison of microwear on the surface of the rostral teeth of sawsharks and sawfishes (Pristidae) show that microwear patterns are alike and suggest that the elongate rostra in these two elasmobranch families are used for a similar purpose (predation). Raman spectroscopy indicates that the rostral teeth of both sawsharks and sawfishes are composed of hydroxyapatite, but differ in their collagen content. Sawfishes possess collagen throughout their rostral teeth whereas collagen is present only in the centre of the rostral teeth of sawsharks, which may relate to differences in ecological use. The ratio of rostrum length to total length in the common sawshark Pristiophorus cirratus was found to be similar to the largetooth sawfish Pristis pristis but not the knifetooth sawfish Anoxypristis cuspidata. Analysis of the stomach contents of P. cirratus indicates that the diet consists of demersal fishes and crustaceans, with shrimp from the family Pandalidae being the most important dietary component. No prey item showed evidence of wounds inflicted by the rostral teeth. In light of the similarities in microwear patterns, rostral tooth chemistry and diet with sawfishes, it is hypothesised that sawsharks use their rostrum in a similar manner for predation (sensing and capturing prey) and possibly for self-defence.
... It would then promptly swim to the bottom to scrape the food from its rostrum. The feeding behaviour of captive juvenile P. pristis was first described in detail by Wueringer et al. (2012a). The observed P. pristis (n = 19) produced fast lateral swipes with their rostra in order to manipulate food, which sometimes impaled fishes on the rostral teeth. ...
... The observed P. pristis (n = 19) produced fast lateral swipes with their rostra in order to manipulate food, which sometimes impaled fishes on the rostral teeth. Behavioural observations did not support the hypotheses that sawfish use their rostra to search through the bottom sediments for cryptic prey, as P. pristis searching for food held their rostra lifted off the ground (Wueringer et al., 2012a, b). The authors, however, note that P. pristis were observed to scrape their teeth on the bottom, which might sharpen them and that prey was manipulated on the floor with fast lateral swipes of the rostrum aimed at the prey and the floor (Wueringer et al., 2012a, b). ...
... Behavioural observations did not support the hypotheses that sawfish use their rostra to search through the bottom sediments for cryptic prey, as P. pristis searching for food held their rostra lifted off the ground (Wueringer et al., 2012a, b). The authors, however, note that P. pristis were observed to scrape their teeth on the bottom, which might sharpen them and that prey was manipulated on the floor with fast lateral swipes of the rostrum aimed at the prey and the floor (Wueringer et al., 2012a, b). ...
Article
Detailed computational fluid dynamics simulations for the rostrum of three species of sawfish (Pristidae) revealed that negligible turbulent flow is generated from all rostra during lateral swipe prey manipulation and swimming. These results suggest that sawfishes are effective stealth hunters that may not be detected by their teleost prey's lateral line sensory system during pursuits. Moreover, during lateral swipes, the rostra were found to induce little velocity into the surrounding fluid. Consistent with previous data of sawfish feeding behaviour, these data indicate that the rostrum is therefore unlikely to be used to stir up the bottom to uncover benthic prey. Whilst swimming with the rostrum inclined at a small angle to the horizontal, the coefficient of drag of the rostrum is relatively low and the coefficient of lift is zero.
... Like sharks, skates, and rays, sawfish are elasmobranchs. Active predators, sawfish use their rostra to detect, kill, and manipulate prey (Kirkland and Aguillon-Martinez 2002;Wueringer et al. 2009Wueringer et al. , 2012. Known for this unique neurocranial appendage, sawfish are culturally known as a novelty and their rostra have been widely collected (Fig. 1). ...
... The anatomical properties of the sawfish skeleton, including the rostrum, are similar to those of rays, sharks, and skates, including teeth-like modified scales (Hamlett 1999, Fowler et al. 2005). Sawfish rostra are distinct cranial appendages with lateral protruding rostral teeth and are covered in placoid scales, also called dermal denticles (Shellis and Berkovitz 1980, Miyake et al. 1992, Hamlett 1999, Cicimurri 2007, Wueringer et al. 2012). The underlying cartilage structure has both mineralized and nonmineralized areas. ...
... However, a lost tooth is not replaced, and the socket remains empty and eventually closes. Sawfish use the rostral teeth to attack and manipulate prey, which are consumed using rows of true teeth within its mouth located below the rostrum (Aguillon-Martinez 2002, Wueringer et al. 2012, Whitty et al. 2013. ...
Article
Full-text available
Sawfish rostra are commonly found in historic natural science collections, yet there is a scarcity of guidance on their preservation. Rostra are cartilaginous with teeth-like scales. The function and structure of sawfish rostra as well as key mechanical and chemical issues need to be considered for their appropriate care in museum collections. Possible routes of decay are discussed, and methods for the care and conservation of rostra in museum collections are suggested. The species of sawfish can be determined by the morphology of the rostral structure. Physical damage, due to the nature of the material and from handling, often causes deterioration of rostra.
... Sawfish (Pristidae) and sawsharks (Prostiophoridae) have adapted their elongate rostra to bear lateral teeth on the outside. The function of these toothed-rostrums ('saws') has been widely hypothesised (Breder, 1952;Nevatte et al., 2017a;Slaughter & Springer, 1968;Wueringer et al., 2012). The sawfish rostrum bears large, broad, flattened and triangular shaped teeth that grow continuously but are not replaced if lost (Slaughter & Springer, 1968). ...
... The rostrum in sawfish is thought to serve as a tool for prey capture, self-defence and prey manipulation. Sawfish rostral use has been successfully explored through a number of behavioural experiments in aquaria and laboratory settings (Wueringer et al., 2012). The function of the saw in sawsharks is less clear as maintaining them in aquaria has proved difficult (Nevatte et al., 2017a;Wueringer et al., 2020). ...
... We propose that the rostral teeth that continue into the head of the sawshark and on the ventral sides of the saw, possibly in combination with the rostral barbels, may help orientate and manipulate prey for headfirst ingestion. Prey manipulation using rostral or head structures has been observed in sawfish, guitarfishes and shovelnose rays (Wilga & Motta, 1998;Wueringer et al., 2012). For crustaceans, the prey items were well digested, which makes any inferences on foraging difficult though the size and lack of prominent spines may make orientation less problematic. ...
Article
Full-text available
Prey manipulation through headfirst ingestion is a common foraging tactic in predatory taxa. Sawsharks possesses a toothed rostrum that is thought to assist in prey capture, but the process from prey contact to ingestion is unknown. Here we provide evidence of headfirst ingestion and possible prey orientation in situ through the use of cone beam CT scans in the common sawshark (Pristiophorus cirratus). CT scans provide an efficient method for assessing ingestion and proposing plausible behavioural tactics for food manipulation in a species difficult to observe in the wild or maintain in captivity. This article is protected by copyright. All rights reserved.
... A study on three species of sawfish also showed that the majority of ampullae were located along the rostrum and the greatest number occurred on the ventral surface (Wueringer, Peverell, Seymour, Squire, Kajiura, et al., 2011). Kajiura, et al., 2011;Wueringer et al., in review), as well as modelling and behavioural methods that have been successfully applied to sawfish (e.g., Bradney et al., 2017;Wueringer, Squire, Kajiura, Hart, & Collin, 2012). ...
... Others have noted that the consumption of prey appears to be head first (P. Burke, personal communication; R. Nevatte, personal observation), perhaps similar to the behaviours observed in sawfish (Wueringer, Squire, et al., 2012). Morphological asymmetries in the jaws and head angle have been detected across many fish and chondrichthyan taxa, including sawsharks (Hori et al., 2017), and thus suggest that some behaviours exhibited by sawsharks may be lateralized. ...
Article
Sawsharks (Order: Pristiophoriformes, Family: Pristiophoridae) are a highly distinctive group of sharks, characterized by a tapering saw‐like rostrum with a pair of elongate barbels on the ventral surface. Their unusual characteristics should attract attention; however, very few studies have been dedicated to sawsharks. As a result, our understanding of their biology and ecology is limited. However, information on aspects of their biology and ecology can be found in studies not directly focussing on sawsharks. This review provides a synthesis of information pertaining to the 10 recognized sawshark species following a comprehensive search of the scientific literature. We cover their distributions, habitat utilization, life histories, reproduction, trophic dynamics and sensory biology. Current knowledge on their unique rostral structures, the evolutionary history of pristiophorids, taxonomy, behaviour and threats to sawshark populations are also reviewed. This compilation serves as a foundation for sawshark researchers and highlights key knowledge gaps in this unique group of elasmobranchs, thereby beginning the sawshark redemption.
... Freshwater is highly resistive to electric currents, and as a result, Atlantic stingrays in have a dramatically reduced sensitivity to prey-simulating stimuli freshwater when compared to seawater (McGowan and . Shovelnose rays and sawfishes, on the other hand, are two groups of batoids with enlarged rostral regions compared to the typical batoid morphology and both groups have been known to use their rostrum in feeding behaviors (Wilga and Motta, 1998;Wueringer et al., 2012b). Electrosensory organs in both groups inundate the enlarged rostrum and help to orient the ray to the prey item for a strike and manipulation into the mouth (Wilga and Motta, 1998;Wueringer and Tibbetts, 2008;Wueringer et al., 2011;Wueringer et al., 2012a;Wueringer et al., 2012b;). ...
... Shovelnose rays and sawfishes, on the other hand, are two groups of batoids with enlarged rostral regions compared to the typical batoid morphology and both groups have been known to use their rostrum in feeding behaviors (Wilga and Motta, 1998;Wueringer et al., 2012b). Electrosensory organs in both groups inundate the enlarged rostrum and help to orient the ray to the prey item for a strike and manipulation into the mouth (Wilga and Motta, 1998;Wueringer and Tibbetts, 2008;Wueringer et al., 2011;Wueringer et al., 2012a;Wueringer et al., 2012b;). Two species of Australian shovelnose rays which both reside in shallow, coastal habitats and have a similar rostral morphology have a four-fold difference in sensitivity to prey-simulating electric fields, which may correlate to differences in diet (Wueringer et al., 2012a); however, this hypothesis remains to be tested and emphasizes the need for future studies to investigate ecological correlates of sensory function. ...
Thesis
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The electrosensory and visual adaptations of elasmobranchs to the environment have been more studied than most other senses, however, work on these senses is mostly limited to descriptive analyses of sensitivity, morphology, and behavior. The goal of this work was to explore electrosensory and visual capabilities in a more ecological context. To gain an understanding of the content of bioelectric signals, the magnitude and frequency of these stimuli were recorded from a broad survey of elasmobranch prey items. Teleosts produced a greater voltage than invertebrates and elasmobranchs and there was no correlation between voltage strength with frequency, mass, or total length as assumed in previous studies. The DC bioelectric field was reproduced in a behavioral assay and the sensitivity of two batoid elasmobranchs, the cownose ray (Rhinoptera bonasus) and the yellow stingray (Urobatis jamaicensis) to these stimuli was quantified. Cownose rays demonstrated a median sensitivity of 107nV cm-1, which was considerably less sensitive than yellow stingrays that demonstrated a sensitivity of 22nV cm-1. Cownose rays may have reduced sensitivity as a mechanism to prevent overstimulation of the electrosensory system by schooling conspecifics. Although it is unlikely that cownose rays use their electrosensory systems to maintain position within a school as hypothesized, their visual adaptations suggest tracking of schoolmates may be primarily visual. Cownose rays had a faster temporal resolution than yellow stingrays, which would support this hypothesis. Color vision adaptations also correlated to the photic environment of each species; cownose rays inhabit turbid, green-dominated waters and had two cone visual pigments that maximize contrast of objects against the green background. Yellow stingrays were trichromatic and likely possess the ability to discriminate colors in their clear, reef and seagrass habitats, which are spectrally rich. Both species showed evidence of ultraviolet sensitivity, which may aid in predator and conspecific detection as an enhanced communication channel. Future studies should investigate the integration of sensory input and sensory involvement in intraspecific communication to gain more insight into ecological adaptations.
... Little is known about the diets or ecology of sawsharks. Research on the critically endangered largetooth sawfish (Pristis microdon) found that the saw-like rostrum is used to disable schools of fish in the water column (Wueringer et al. 2012). Sawfish rostral teeth are permanent and much thicker and smoother than the finer, more jagged sawshark teeth that are frequently replaced (Slaughter and Springer 1968). ...
... This study suggests that the trophic level of P. cirratus is similar to species that prey on benthic primary consumers; consequently, P. cirratus may use their rostrums to sift through substrate in the search of prey. The isotope levels of P. nudipinnis suggest a more piscivorous diet and raise the possibility that they feed in a similar manner as some Pristidae species (Wueringer et al. 2012). Further research into diet, feeding modes, and rostrum use is necessary to elucidate the specifics of feeding in these species. ...
Article
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Despite the global distribution of sawsharks, little is known about their diets or their role in the marine biosphere. As species in higher trophic positions are generally considered to be more at risk to perturbations such as fishing, understanding their role in the food chain will enable better conservation and management strategies for these species. Two sawshark species (Pristiophorus cirratus, Pristiophorus nudipinnis) co-occur in waters off east Tasmania, Australia. This study determined the trophic positions of these sawsharks and whether they avoided competing with each other through resource partitioning. Isotopic analysis of muscle tissue revealed that P. cirratus and P. nudipinnis had significantly different trophic levels, with P. cirratus likely to have a diet of primary consumers and P. nudipinnis likely to have a piscivorous diet. Owing to their different isotopic signatures, it is also likely that the sawshark rostrum has multiple functions. Both species shifted to higher trophic levels during ontogeny. Maternal isotopic signatures were detectable in P. cirratus juveniles. © 2015, National Research Council of Canada. All rights reserved.
... Los peces sierra se distinguen de las otras rayas por poseer un rostro en forma de sierra al ser elongado, comprimido, y equipado con una fila de dientes (escamas modificadas) a cada lado (Faria et al., 2013), lo que les da su apariencia distintiva y su nombre común. El peculiar rostro en forma de sierra puede llegar a ser entre 20-33% de la longitud de su cuerpo (Faria et al., 2013) y lo utilizan para defenderse, detectar y capturar a sus presas (Wueringer et al., 2012). ...
... Esto les ayuda a localizarlas y, seguidamente, pueden capturarlas. Además, al mover la sierra rápidamente, golpean y aturden a sus presas, como peces, antes de comerlos (Wueringer et al., 2012). ...
... Lastly, we considered that any event exceeding 0.75 g to be indicative of a burst (see Fig. 2) based on a simple visual assessment of the ODBA associated with routine swimming. Such burst events likely constitute sawfish attempting to capture prey (see video in Wueringer et al. (2012) for dorsal fin motion during prey strikes in P. pristis) or escape responses from predation or being startled (Gleiss et al., 2009;Wueringer et al., 2012). Following the classification, we resampled the new data to yield hourly mean depth, % time spent active and the number of bursts for every sawfish. ...
... Lastly, we considered that any event exceeding 0.75 g to be indicative of a burst (see Fig. 2) based on a simple visual assessment of the ODBA associated with routine swimming. Such burst events likely constitute sawfish attempting to capture prey (see video in Wueringer et al. (2012) for dorsal fin motion during prey strikes in P. pristis) or escape responses from predation or being startled (Gleiss et al., 2009;Wueringer et al., 2012). Following the classification, we resampled the new data to yield hourly mean depth, % time spent active and the number of bursts for every sawfish. ...
Article
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Circadian rhythms occur widely amongst living organisms, often in response to diel changes in environmental conditions. In aquatic animals, circadian activity is often synchronised with diel changes in the depths individuals occupy and may be related to predator–prey interactions, where the circadian rhythm is determined by ambient light levels, or have a thermoregulatory purpose, where the circadian rhythm is governed by temperature. Here, these two hypotheses are examined using animal-attached accelerometers in juvenile freshwater sawfish occupying a riverine environment displaying seasonal changes in thermal stratification. Across seasons, diel patterns of depth use (shallow at night and deep in the day) tended to occur only in the late dry seasons when the water was stratified, whereas individuals were primarily shallow in the early dry season which featured no thermal stratification. Activity was elevated during crepuscular and nocturnal periods compared to daytime, regardless of the thermal environment. Our observation of resting at cooler depths is consistent with behavioural thermoregulation to reduce energy expenditure, whereas activity appears linked to ambient light levels and predator–prey interactions. This suggests that circadian rhythms in activity and vertical migrations are decoupled in this species and respond to independent environmental drivers.
... The general function of the billfish rostrum is under continued discussion and has been proposed to relate to defence (Fierstine, 1997), locomotion (Kozlov, 1973) and feeding (Shimose et al., 2007). While the billfish rostrum may have multiple functions, similar to the beak of birds (Friedman et al., 2019) or the saw of the sawfish (Wueringer et al., 2012), in I. platypterus and K. audax (Domenici et al., 2014;Hansen et al., 2020) the evidence for rostrum use in prey capture is unequivocal. ...
... Another potential function of lacunae rostralis relates to prey handling. Such a function has been proposed for a rostral structure, i.e. the mandibular canal, in sawsharks Pristiophoriformes, (Wueringer et al., 2012;Wueringer et al., 2021). In Pristiophoriformes, prey handling with the mandibular canal is assumed to aid in swallowing prey headfirst and might thereby prevent injuries from the pointed and venomous spines of some prey species. ...
Article
Recent comparative studies of billfishes (Istiophoridae and Xiphiidae) have provided evidence of differences in the form and function of the rostra (bill) among species. Here, we report the discovery of a new structure, lacuna rostralis, on the rostra of sailfish Istiophorus platypterus, which is absent on the rostra of swordfish Xiphias gladius, striped marlin Kajikia audax and blue marlin Makaira nigricans. The lacunae rostralis are small cavities that contain teeth. They were found on the ventral rostrum surface of all I. platypterus specimens examined and dorsally in half of them. Ventrally, the lacunae rostralis were most prominent in the mid‐section of the rostrum. Dorsally, they occurred closer to the tip. The density of lacunae rostralis increased towards the rostrum tip but, because they are smaller in size, the percentage of rostrum coverage decreased. The teeth located within the lacunae rostralis were found to be different in size, location and orientation from the previously identified micro‐teeth of billfish. We propose two potential functions of the lacunae rostralis that both relate to the use of the bill in feeding: mechanoreception of prey before tapping it with the bill, and more efficient prey handling via the creation of suction, or physical grip. This article is protected by copyright. All rights reserved.
... A high ventral: dorsal distribution is also seen in the shovelnose rays (Rhinobatidae) that forage on benthic prey but use their disc to pin and manipulate prey into their mouth (Wueringer, 2012;Wueringer et al., 2009). On the other hand, the pristids are related to rhinobatids but have the derived rostrum with a higher proportion of dorsal pores to facilitate feeding on free swimming prey (Wueringer, 2012;Wueringer et al., 2012b). ...
... Urobatis halleri has a high ventral: dorsal pore ratio, significantly higher ventral pore density near the mouth and a greater percentage of its ventral surface covered by electrosensory pores (Jordan, 2008). A similar series of comparative studies on the freshwater sawfish, P. micrdon, G. typus and A. rostrata, showed that the freshwater pristids had the lowest median sensitivity, the highest number of pores and the largest spread of receptors across the body due to the rostrum (Wueringer et al., 2012a(Wueringer et al., , 2012b). ...
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Electroreception in marine fishes occurs across a variety of taxa and is best known in chondrichthyans. Here, we present an up‐to‐date review of what is known about the biology of passive electroreception and considered how this knowledge can assist in understanding the ecological consequences of responding to electric and magnetic stimuli by electroreceptive fish in the marine environment. The focus is on electroreception in marine Chondrichthyes, the current understanding of the passive mode, ecomorphology of the receptor system and its functional importance in terms of the ecology of this sensory system. The review complements the review of electroreception in freshwater fish in this special issue, which provides a comprehensive state of knowledge regarding the evolution of electroreception. The review concludes that whilst there has been much improved understanding of the biology of electroreception in the marine environment, there are several outstanding gaps in knowledge which limit our full understanding of the sensory ecology of electroreception, particularly in an environment that increasingly is being altered by anthropogenic electric and magnetic fields. This article is protected by copyright. All rights reserved.
... European catfish Silurus glanis L. 1758 locate their prey via wake detection (Pohlmann et al., 2004), and, when hunting pigeons, have their maxillary (upper jaw) barbels erect so that the vibrations generated by bathing pigeons can be detected (Cucherousset et al., 2012). For prey partially buried in sediment, it is hypothesized that sawsharks use the electroreceptive capabilities of their rostrum, similar to sawfishes (Wueringer et al., 2012a, b), in conjunction with the barbels contacting the seafloor and sensing for prey-related changes in surface texture. This action could also be used to locate 'silent' prey (i.e. ...
Article
The internal anatomy of the barbels of the common sawshark Pristiophorus cirratus was examined with light microscopy to clarify their sensory role. No sensory structures such as taste buds (chemoreception), ampullae of Lorenzini (electroreception) or free neuromasts (lateral line mechanoreception) could be located in the barbels. The presence of bundles of nerve fibres, however, indicates a tactile function for the barbels. Conveyance of information regarding potentially damaging stimuli (nociception) and temperature (thermoception) cannot be excluded at this stage. It is hypothesized that the barbels are used by P. cirratus to locate prey in both the water column and on the substratum via wake detection and sensing changes in surface texture. The barbels may also be involved in the detection of water currents for rheotaxis. Regression analyses on P. cirratus morphometric data showed that the width of the rostrum at two sections (the barbels and the rostrum tip) does not significantly correlate with total length. The regression analyses also suggested that the barbels of P. cirratus may be lateralised.
... Sawfishes belong to one of the most distinct and threatened elasmobranch families, with all species listed as Critically Endangered by the International Union for Conservation of Nature (IUCN, 2012). Their uniqueness comes from their large size and rostrum, which is lined with tooth-like denticles and is used to sense and hunt prey (Wueringer et al., 2012). However, it is because of the rostrum that sawfishes are easily entangled in fishing gear. ...
Article
Effective management of critically endangered sawfishes can be a difficult task, in part due to interspecies misidentification. Current methods for identifying sawfishes can be impractical as they are based on morphological features that are often unobservable. Further exploration is required to develop a more reliable means of identification.This study explored the utility of sawfish rostra in determining the species, size and sex of sawfishes, as rostra are commonly the only feature of a sawfish observed by fishers or present in public and private collections.A morphometric and meristic database consisting of over 1100 narrow sawfish (Anoxypristis cuspidata), dwarf sawfish (Pristis clavata), largetooth (or freshwater) sawfish (Pristis pristis; formerly Pristis microdon) and green sawfish (Pristis zijsron) rostra from Australian waters, was statistically analysed.Identification of sawfishes was found to be possible through the use of the variables: inter-tooth spacing, standard rostrum width/standard rostrum length, standard rostrum length/total rostrum length, rostrum tip width/standard rostrum length, and/or rostral tooth count range, although the distinguishing variables were species-dependent.The relationship between standard rostrum length and total length was also observed to vary substantially between most species. Models for estimating total length from standard rostrum length are provided.This study has provided a tool that can be used to identify accurately the species and size of sawfishes by their rostra, and therefore can assist in clarifying historical and contemporary sawfish records, nomenclature and distributions. A better understanding of these issues should allow sawfish conservation strategies to become more focused, and thus more effective. Copyright © 2013 John Wiley & Sons, Ltd.
... Moving into glides at night would also likely increase encounter rates be tween P. pristis and their prey, which are more abundant in shallow waters at night. The lateral striking action of the rostrum of a sawfish (Wueringer et al. 2012) would also be most effective in this vertically re stricted habitat, which contains minimal if any com plex structure (e.g. woody debris or macrophytes) (cf. ...
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Knowledge of how an animal uses its habitat is a fundamental component of effective conservation strategies. The Critically Endangered largetooth sawfish Pristis pristis uses rivers and their estuaries as nursery habitats, where it is likely to be exposed to elevated pressures from anthropogenic-induced stresses including fishing (e.g. bycatch, direct harvest) and instream habitat modification and degradation (e.g. barriers, water extraction, mining). With a paucity of data available on habitat use of P. pristis, we monitored the movements of 32 juveniles (952 to 2510 mm total length; mean ± SE = 1919 ± 64 mm) using acoustic telemetry to explore correlations between sawfish movement and abiotic as well as biotic variables over an 8 year period (2008 to 2015) in the freshwater reaches of the Fitzroy River, Western Australia. Monitored juveniles were least active when they occupied deeper runs and pools in proximity to large woody debris by day and were most active during night-time and twilight hours when inhabiting shallow water such as glides, pool edges, and shallow runs. These shifts in activity and habitat use were primarily mediated by foraging and refuging behaviours, which were coupled to day-night cycling of light availability. Protection of these instream habitats and the understanding of their use by P. pristis are important for aiding in the management of intermittently flowing rivers that are used as nurseries for this species.
... Major differences between sawsharks and sawfishes include non-growing and unequally large rostral spines that are usually arranged in an alternating pattern and only weakly anchored in the tissue rather than being set in sockets of the rostral cartilage, small additional rostral spines on the ventral side of the rostrum, and a pair of long ventral barbels anterior to the nostrils. The rostrum in saw-bearing elasmobranchs both are used to detect electric fields of possible prey and capture prey by stunning or disabling the prey with strikes of the rostral saw (Frazzetta 1994;Wueringer et al. 2012). ...
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The highly fossiliferous Eocene deposits of the Antarctic Peninsula are among the most productive sites for fossil remains in the Southern Hemisphere and offer rare insights into high-latitude faunas during the Palaeogene. Chondrichthyans, which are represented by abundant isolated remains, seemingly dominate the marine assemblages. Eocene Antarctic sawsharks have only been known from few isolated rostral spines up to now, that were assigned to Pristiophorus lanceolatus. Here, we present the first oral teeth of a sawshark from the Eocene of Seymour Island and a re-evaluation of previously described Pristiophorus remains from Gondwana consisting exclusively of rostral spines. The holotype of Pristiophorus lanceolatus represents a single, abraded and insufficiently illustrated spine from the Oligocene of New Zealand. All other Cenozoic rostral spines assigned to this species are morphologically very indistinct and closely resemble those of living taxa. Consequently, we regard this species as dubious and introduce a new species, Pristiophorus laevis, based on oral teeth. The combination of dental characteristics of the new species makes it unique compared to all other described species based on oral teeth. Rostral spines from the Eocene of Seymour Island are assigned to this new species whereas those from other Cenozoic Gondwana localities remain ambiguous. LSID urn:lsid:zoobank.org:pub:7177A373-527B-4315-85F6-25180DB5E087
... Sawfishes (Pristidae) are among the most endangered fishes, and all 5 species are protected by state, federal, and international laws (Harrison & Dulvy 2014). Recent behavioral and sensory research has shown that sawfishes use ampullae on their toothed rostrum to sense prey-like electric fields and capture prey (Wueringer et al. 2012). However, other than anecdotes and some supporting data that suggest sawfish feed on schooling fishes and crustaceans and occasionally use their rostrum for defense (Breder 1952, Bigelow & Schroeder 1953, Thorson 1976, Thorburn et al. 2007, little is known about their diet or their interactions with other predators such as bull sharks Carcharhinus leucas , Thorburn et al. 2014. ...
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Growing concerns about the conservation of elasmobranchs have prompted a surge in research because scientific studies are needed that can support management actions. Sawfishes are among the most threatened fishes worldwide and epitomize the challenge of conserving widely distributed, large-bodied marine fishes. A comparative approach was used to provide data on the trophic ecology of the smalltooth sawfish Pristis pectinata in the western Atlantic coastal waters of southwest Florida, USA. Specifically, we applied (1) stable isotope techniques to fin tissues of smalltooth sawfish and 2 sympatric elasmobranch species that have well-documented diets (i.e. bull shark Carcharhinus leucas, cownose ray Rhinoptera bonasus), and tissues from a variety of known and potential prey species; (2) an 18S rRNA gene sequencing technique to identify prey taxa in sawfish fecal samples. These analyses provided evidence that the smalltooth sawfish feeds primarily on teleost and elasmobranch fishes at all life stages even though sawfish move from estuarine to coastal habitats during their ontogeny. Although both sawfish and bull sharks occupy estuarine waters as juveniles and are piscivorous, the results also indicate that these species partition habitat. The cownose ray has been thought of as migratory throughout its range, but these data indicate that non-migratory, estuarine populations exist at lower latitudes. Collectively, these results will aid in the development of management decisions regarding these species and in improving long-term recovery planning for the smalltooth sawfish.
... Extended bills can also be found in non-billfish species (e.g. paddlefishes and sawfishes) where they are believed to be used primarily for sensory detection and prey manipulation [17,18] rather than direct capture. In some instances, posterior extensions of the body in a number of vertebrates (e.g. ...
Article
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The istiophorid family of billfishes is characterized by an extended rostrum or 'bill'. While various functions (e.g. foraging and hydrodynamic benefits) have been proposed for this structure, until now no study has directly investigated the mechanisms by which billfishes use their rostrum to feed on prey. Here, we present the first unequivocal evidence of how the bill is used by Atlantic sailfish (Istiophorus albicans) to attack schooling sardines in the open ocean. Using high-speed video-analysis, we show that (i) sailfish manage to insert their bill into sardine schools without eliciting an evasive response and (ii) subsequently use their bill to either tap on individual prey targets or to slash through the school with powerful lateral motions characterized by one of the highest accelerations ever recorded in an aquatic vertebrate. Our results demonstrate that the combination of stealth and rapid motion make the sailfish bill an extremely effective feeding adaptation for capturing schooling prey.
... A potential test of this is represented by the notably tooth-like denticles on the extended rostrumsaw of sawfish (Pristidae; Batoidea), fossil sclerorhynchids (Sclerorhynchoidea; Batoidea) and sawsharks (Pristiophoridae; Selachii). These 'saw-teeth' (previously described as 'saw-tooth scales' [10]) are arranged in lateral rows and are believed to be used for prey capture and feeding [11][12][13]. They extend caudally for the length of the rostrum from its tip, and in sawsharks and sclerorhynchids, are continuous with other tooth-like structures in the skin lateral to the chondrocranium. ...
Article
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Origins of the vertebrate dentition, as a patterned, functional unit associated with the jaws, remain contentious. Hypotheses suggest dentitions evolved from external placoid scales, or alternatively, from denticles within the oropharyngeal cavity, with no input from external dermal structures. The latter hypothesis suggests that oral dentitions and scales derive from separate developmental systems, while the former suggests they share a common developmental system. The latter hypothesis implies that oral dentitions are restricted to the oropharygeal cavity, while the former implies heterotopic migration of dermal structures into the mouth. To test these hypotheses, we examined the elongate rostrum (‘saw’) and associated oral dentitions in three chondrichthyan groups: Pristiophoridae (Selachii), Pristidae (Batoidea) and the fossil Sclerorhynchoidea (Batoidea). The rostrum saw of adult and embryonic individuals was investigated via 3D-rendered, volume density models from x-ray computed tomography, revealing data on topographic position, series size differences, growth stages, progressive mineralization, timing and mode of replacement of the tooth-like structures, all co-located with mineralized embayments of prismatic rostral cartilage. We suggest these structures lack the patterning and replacement characteristic of oral dentitions and instead represent dermally-derived neomorphic structures on the rostrum modified from placoid scales, independent of oral teeth.
... Data of capture distance from the bottom are currently not available, but these data could help prevent future sawfish catches through indication of how far sawfishes travel into the water column. For example, sawfishes are considered to be benthic, but analysis of the food capture behaviour of captive P. pristis indicates that they can use the whole water column for prey manipulation (Wueringer et al. 2012). Importantly, data from surface-set gillnets are likely to underestimate local relative abundances of sawfishes. ...
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Within the Great Barrier Reef World Heritage Area in Queensland, Australia, lack of information on the distribution of sawfishes presents difficulty for informed management of their habitats and populations. This study aims to provide insights into the historical and current distributions through analysis of sawfish by-catch records from the Queensland Shark Control Program (QSCP), which has protected bathers since 1963 by targeting large sharks. Sawfishes have been caught in 8 of the 10 areas where the QSCP has been active. A total of 1450 captures of sawfishes (all 4 species known from Australia) were reported from 1963 to August 2016, with most ( > 99%) in the 4 most northern areas; Cairns, Townsville, Mackay, and Rockhampton. Sawfishes were mainly captured in gillnets. Most (95.4%) animals were alive when the gear was checked. In Townsville and Rockhampton, standardised sawfish captures have declined over the years. No sawfish captures in QSCP gear have been recorded in 3 areas (Cairns, Townsville, Rockhampton) since gillnets were banned there, but in Mackay, where gillnets are still used, only 4 animals have been caught since 1999. It is recommended that QSCP contractors take more detailed data of future sawfish captures, and that contractors and fishers receive training on releasing sawfishes swiftly and with minimal damage. Moreover, as the use of gillnets in the QSCP has been decreasing over the years, fisheries-independent studies of current sawfish distributions are required.
... A potential test of this is represented by the notably tooth-like denticles on the extended rostrumsaw of sawfish (Pristidae; Batoidea), fossil sclerorhynchids (Sclerorhynchoidea; Batoidea) and sawsharks (Pristiophoridae; Selachii). These 'saw-teeth' (previously described as 'saw-tooth scales' [10]) are arranged in lateral rows and are believed to be used for prey capture and feeding [11][12][13]. They extend caudally for the length of the rostrum from its tip, and in sawsharks and sclerorhynchids, are continuous with other tooth-like structures in the skin lateral to the chondrocranium. ...
Article
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A well-known characteristic of chondrichthyans (e.g. sharks, rays) is their covering of external skin denticles (placoid scales), but less well understood is the wide morphological diversity that these skin denticles can show. Some of the more unusual of these are the tooth-like structures associated with the elongate cartilaginous rostrum ‘saw’ in three chondrichthyan groups: Pristiophoridae (sawsharks; Selachii), Pristidae (sawfish; Batoidea) and the fossil Sclerorhynchoidea (Batoidea). Comparative topographic and developmental studies of the ‘saw-teeth’ were undertaken in adults and embryos of these groups, by means of three-dimensional-rendered volumes from X-ray computed tomography. This provided data on development and relative arrangement in embryos, with regenerative replacement in adults. Saw-teeth are morphologically similar on the rostra of the Pristiophoridae and the Sclerorhynchoidea, with the same replacement modes, despite the lack of a close phylogenetic relationship. In both, tooth-like structures develop under the skin of the embryos, aligned with the rostrum surface, before rotating into lateral position and then attaching through a pedicel to the rostrum cartilage. As well, saw-teeth are replaced and added to as space becomes available. By contrast, saw-teeth in Pristidae insert into sockets in the rostrum cartilage, growing continuously and are not replaced. Despite superficial similarity to oral tooth developmental organization, saw-tooth spatial initiation arrangement is associated with rostrum growth. Replacement is space-dependent and more comparable to that of dermal skin denticles. We suggest these saw-teeth represent modified dermal denticles and lack the ‘many-for-one’ replacement characteristic of elasmobranch oral dentitions.
... Sawfishes are shark-like rays best known for their long, toothed rostra ("saws"), which they use for defense and feeding (Breder 1952, Wueringer et al. 2012. Smalltooth Sawfish ( Figure 1A) can grow to 5 m in length (Brame et al. 2019). ...
Article
The Smalltooth Sawfish (Pristis pectinate), a critically endangered species of ray, is in urgent need of strong legal protection and conservation action in the Wider Caribbean Region, particularly in Cuba. Cuba has a long history of conservation initiatives for other marine species and is a signatory to multiple multinational agreements that direct the country to protect sawfish. Nevertheless, sawfish are only just beginning to be a species of concern on the island. Here we review existing domestic laws relevant to biodiversity and endangered species protection in Cuba, with a focus on safeguarding sawfish. We offer specific recommendations to improve sawfish protection in Cuba through clear prohibitions on killing and harassment, as well as safe release requirements for incidentally captured individuals.
... They are distributed across coastal areas, estuaries, and freshwaters from tropical to subtropical regions -especially in shallow, sandy, or muddy bottoms. The saw is used mainly for feeding purposes, such as to scour the bottom for benthic prey or to capture free-swimming ray-finned fishes (Wueringer et al. 2012, Poulakis et al. 2017. However, rostral ex pansion is also the main cause of entanglement in fishing nets (Dulvy et al. 2016). ...
Article
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Sawfishes are the most endangered cartilaginous fishes on the planet. Their external morphology facilitates entanglement in fishing nets and their K-selected life history hinders the recovery of exploited populations. The Eastern Amazon coast (EAC) is known to be an area where sawfishes occur in Brazil, but few studies have been conducted in the area to better understand their biology and ecology. The present study reports sawfish captures along the coast of Brazil’s second largest state. Data were collected from interviews with fishermen, a literature review, and media reports. In total, 23 captures were recorded between 1984 and 2016. Records include adults, a pregnant female with near-term embryos, juveniles, and young-of-the-year specimens. Most catches were reported in the Canal do Navio, an area under strong human pressure. Sawfish saws are valuable items and, for many anglers in precarious economic and social situations, high market prices eclipse the fishing prohibitions laid down under federal laws. Urgent research is required to understand sawfishes’ life history, identify their critical habitats, and effectively manage and conserve these species along the EAC.
... Analogies in function between Edestus tooth whorls and the toothed rostrum of the extant sawfish Pristis were proposed soon after the discovery of Edestus (Hitchcock, 1856;Leidy, 1857). The rostrum of Pristis microdon is used both to sense and to capture prey, by stunning or impaling them or by pinning them to the substrate (Wueringer et al., 2012). Observations of microwear on rostral teeth of the sawshark Pristiophorus cirratus suggest that it also uses its rostrum to capture prey, though not necessarily to impale them (Nevatte et al., 2017). ...
Article
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The symphyseal tooth whorls of the Carboniferous chondrichthyan Edestus consist of files of teeth having sharply-pointed, serrated crowns, joined at their bases. A single tooth whorl was present in each jaw. How these tooth whorls functioned is unclear, since their convex curvature allows only a few of the most lingual crowns of opposing tooth whorls to occlude. Rather than working in opposition, like scissors, the more labial teeth might have been used to cut and disable prey with a vertical motion of the anterior part of the body. Provided the scratches observed on the surface of Edestus teeth can be inferred to have been generated in the process of feeding, their orientation might be used to distinguish whether the teeth were used mainly in occlusion, to cut prey trapped between the jaws, or mainly to cut prey situated outside the oral cavity. Edestus minor teeth having unusually good surface preservation were examined for microwear. The teeth are from the Strawn Group (Desmoinesian, Middle Pennsylvanian) of San Saba County, Texas, USA. The best-preserved crown surfaces display scratches 50 to 500 micrometers long. The scratches are oriented predominantly transversely to the basal-apical axis. This observation appears to support the vertical slashing hypothesis. However, the possibility that interaction with the substrate contributed to the observed wear cannot be discounted.
... The elongated rostrum of sawfshes, which is lined with teeth along either side (Figure 18.1b), is used for both detecting electric felds and capturing prey (Wueringer et al. 2012). The diet of the Largetooth Sawfsh has been examined through limited stomach contents. ...
... The unique rostrums of paddlefish (Polydontidae), sturgeon (Acipenseridae), and sawfish (Pristidae) are all used as sensory organs, containing electroreceptors, lateral line canals, and even barbels for detecting prey items (Miller, 2006;Wueringer et al., 2012). The novel nasal protrusion of the durophagous pupfish may also be a sensory organ, but whether the nasal protrusion has an increased number of superficial neuromasts is still unknown. ...
Article
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Dietary specialization on hard prey items, such as mollusks and crustaceans, is commonly observed in a diverse array of fish species. Many fish consume these types of prey by crushing the shell to consume the soft tissue within, but a few fishes extricate the soft tissue without breaking the shell using a method known as oral shelling. Oral shelling involves pulling a mollusk from its shell and may be a way to subvert an otherwise insurmountable shell defense. However, the biomechanical requirements and potential adaptations for oral shelling are unknown. Here, we test the hypothesis that a novel nasal protrusion is an adaptation for oral shelling in the durophagous pupfish (Cyprinodon brontotheroides). We first demonstrate oral shelling in this species and then predicted that a larger nasal protrusion would allow pupfish to consume larger snails. Durophagous pupfish are found within an endemic radiation of pupfish on San Salvador Island, Bahamas. We took advantage of closely related sympatric species and outgroups to test: 1) whether durophagous pupfish shell and consume more snails than other species, 2) if F1 and F2 durophagous hybrids consume similar amounts of snails as purebred durophagous pupfish, and 3) to determine if nasal protrusion size in parental and hybrid populations increases the maximum diameter snail consumed. We found that durophagous pupfish and their hybrids consumed the most snails, but did not find a strong association between nasal protrusion size and maximum snail size consumed within the parental or F2 hybrid population, suggesting that the size of their novel nasal protrusion does not provide a major benefit in oral shelling. Instead, we suggest that nasal protrusion may increase feeding efficiency, act as a sensory organ, or is a sexually selected trait, and that a strong feeding preference may be most important for oral shelling.
... The unique rostrums of paddlefish (Polydontidae), sturgeon (Acipenseridae), and sawfish (Pristidae) are all used as sensory organs, containing electroreceptors, lateral line canals, and even barbels for detecting prey items (Miller, 2006;Wueringer et al., 2012). The novel nasal protrusion of the durophagous pupfish may also be a sensory organ, but whether the nasal protrusion has an increased number of superficial neuromasts is still unknown. ...
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Dietary specialization on hard prey items, such as mollusks and crustaceans, is commonly observed in a diverse array of fish species. Many fish consume these types of prey by crushing the shell to consume the soft tissue within, but a few fishes extricate the soft tissue without breaking the shell using a method known as oral shelling. Oral shelling involves pulling a mollusk from its shell and may be a way to subvert an otherwise insurmountable shell defense. However, the biomechanical requirements and potential adaptations for oral shelling are unknown. Here, we test the hypothesis that a novel nasal protrusion is an adaptation for oral shelling in a durophagous pupfish ( Cyprinodon brontotheroides ). We first demonstrate oral shelling in this species and then predicted that a larger nasal protrusion would allow pupfish to consume larger snails. Durophagous pupfish are found within an endemic radiation of pupfish on San Salvador Island, Bahamas. We took advantage of closely related sympatric species and outgroups to test: 1) whether durophagous pupfish shell and consume more snails than other species, 2) if F1 and F2 durophagous hybrids consume similar amounts of snails as purebred durophagous pupfish, and 3) to determine if nasal protrusion size in parental and hybrid populations increases the maximum diameter snail consumed. We found that durophagous pupfish and their hybrids consumed the most snails, but did not find a strong association between nasal protrusion size and maximum snail size consumed within the parental or F2 hybrid population, suggesting that the size of their novel nasal protrusion does not provide a major benefit in oral shelling. Instead, we suggest that nasal protrusion may increase feeding efficiency, act as a sensory organ, or is a sexually selected trait, and that a strong feeding preference may be most important for oral shelling. Significance Statement Specialization on hard-shell prey items (i.e. durophagy) is a common dietary niche among fishes. Oral shelling is a rare technique used by some durophagous fish to consume prey items like snails; however, adaptations for oral shelling are still unknown. Here, we document the first evidence of oral shelling in a cyprinodontiform fish, the durophagous pupfish ( Cyprinodon brontotheroides ), and experimentally test whether its novel nasal protrusion is an adaptation for oral shelling using hybrid feeding trials.
... Sawfishes (Family Pristidae) are a group of threatened marine fish that illustrate the critical need for evaluations of captive wildlife displays, and can be used to model a multi-disciplinary evaluation of conservation benefits. Sawfishes are large shark-like rays (possibly reaching over 7 m in length) (Carpenter & Niem, 1999), with a distinctive saw-like appendage that is used to hunt prey (Wueringer, Squire, Kajiura, Hart, & Collin, 2012) (Figure 1). Sawfish populations are at greater extinction risk than most other sharks or rays, due to a high susceptibility to capture in fishing nets, strong associations with widely impacted habitats such as mangroves and seagrass beds, and slow intrinsic population growth rates (Dulvy et al., 2014(Dulvy et al., , 2016. ...
Article
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Zoos and public aquaria globally display numerous wild harvested, threatened species. To validate conservation credentials, displays are often associated with research projects, educational interpretation, or conservation-related activities. However, accompanying conservation benefits are rarely assessed. In this study, an approach to evaluate conservation benefits of captive wildlife experiences is modelled by assessing four Australian aquarium displays of the Critically Endangered largetooth sawfish Pristis pristis. Conservation impact scores were calculated for research, education, and conservation-related activities. In a novel approach, sawfish-related education (gaining knowledge, changing attitudes, and intentions to change behaviours) was evaluated using a before and after study design (n = 2 229), and conservation impact scores were calculated using effect sizes. Although visitors to all aquariums demonstrated significant positive attitudinal changes, and at one site gained knowledge, no significant change in behavioural intentions were detected. Educational messages addressing attitudes and behaviours were mostly generalised and untargeted. Formative and ongoing evaluations are needed to develop and maintain targeted and relevant messages. With one exception, research projects and conservation activities were unlikely to contribute substantially to sawfish conservation due to limited support from the aquaria. We recommend that increased support is directed to projects that are targeted towards impactful conservation goals.
... Previous comparative work on fishes with toothed rostra (common sawshark (Pristiophorus cirratus), largetooth sawfish (Pristis pristis) and knifetooth sawfish (Anoxypristis cuspidata)) examined rostrum function through an analysis of rostral tooth microwear and stomach analysis [27], and related research explored the feeding strategy of captive sawfish via examination of the transitional probabilities between behavioural states [28]. Our study builds upon this illuminating work and suggests that matching the physical properties of rostra to behavioural strategies in the wild is a productive methodology, especially when capture success can be quantified. ...
Article
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Linking morphological differences in foraging adaptations to prey choice and feeding strategies has provided major evolutionary insights across taxa. Here, we combine behavioural and morphological approaches to explore and compare the role of the rostrum (bill) and micro-teeth in the feeding behaviour of sailfish (Istiophorus platypterus) and striped marlin (Kajikia audax) when attacking schooling sardine prey. Behavioural results from high-speed videos showed that sailfish and striped marlin both regularly made rostrum contact with prey but displayed distinct strategies. Marlin used high-speed dashes, breaking schools apart, often contacting prey incidentally or tapping at isolated prey with their rostra; while sailfish used their rostra more frequently and tended to use a slower, less disruptive approach with more horizontal rostral slashes on cohesive prey schools. Capture success per attack was similar between species, but striped marlin had higher capture rates per minute. The rostra of both species are covered with micro-teeth, and micro-CT imaging showed that species did not differ in average micro-tooth length, but sailfish had a higher density of micro-teeth on the dorsal and ventral sides of their rostra and a higher amount of micro-teeth regrowth, suggesting a greater amount of rostrum use is associated with more investment in micro-teeth. Our analysis shows that the rostra of billfish are used in distinct ways and we discuss our results in the broader context of relationships between morphological and behavioural feeding adaptations across species.
... Armaments such as saws and swords in fish (e.g. see Fig. 4 in Emlen, 2008) have been related to feeding and defence against predators (Wueringer et al., 2012;Domenici et al., 2014;Habegger et al., 2015;Nevatte et al., 2017) but never to intraspecific fights. Our methods allowed us to exclude exaggerated structures that were previously considered as weapons (cf . ...
Article
We propose a practical concept that distinguishes the particular kind of weaponry that has evolved to be used in combat between individuals of the same species and sex, which we term intrasexually selected weapons (ISWs). We present a treatise of ISWs in nature, aiming to understand their distinction and evolution from other secondary sex traits, including from ‘sexually selected weapons’, and from sexually dimorphic and monomorphic weaponry. We focus on the subset of secondary sex traits that are the result of same‐sex combat, defined here as ISWs, provide not previously reported evolutionary patterns, and offer hypotheses to answer questions such as: why have only some species evolved weapons to fight for the opposite sex or breeding resources? We examined traits that seem to have evolved as ISWs in the entire animal phylogeny, restricting the classification of ISW to traits that are only present or enlarged in adults of one of the sexes, and are used as weapons during intrasexual fights. Because of the absence of behavioural data and, in many cases, lack of sexually discriminated series from juveniles to adults, we exclude the fossil record from this review. We merge morphological, ontogenetic, and behavioural information, and for the first time thoroughly review the tree of life to identify separate evolution of ISWs. We found that ISWs are only found in bilateral animals, appearing independently in nematodes, various groups of arthropods, and vertebrates. Our review sets a reference point to explore other taxa that we identify with potential ISWs for which behavioural or morphological studies are warranted. We establish that most ISWs come in pairs, are located in or near the head, are endo‐ or exoskeletal modifications, are overdeveloped structures compared with those found in females, are modified feeding structures and/or locomotor appendages, are most common in terrestrial taxa, are frequently used to guard females, territories, or both, and are also used in signalling displays to deter rivals and/or attract females. We also found that most taxa lack ISWs, that females of only a few species possess better‐developed weapons than males, that the cases of independent evolution of ISWs are not evenly distributed across the phylogeny, and that animals possessing the most developed ISWs have non‐hunting habits (e.g. herbivores) or are faunivores that prey on very small prey relative to their body size (e.g. insectivores). Bringing together perspectives from studies on a variety of taxa, we conceptualize that there are five ways in which a sexually dimorphic trait, apart from the primary sex traits, can be fixed: sexual selection, fecundity selection, parental role division, differential niche occupation between the sexes, and interference competition. We discuss these trends and the factors involved in the evolution of intrasexually selected weaponry in nature.
... The toothed rostrum of Pristis microdon is known to be used both to sense prey and to capture prey (by stunning or impaling prey, or by pinning and manipulating them on the substrate) (Wueringer et al. 2012 The Aetobatus dentition: another example of post-occlusal retention of teeth: The dentition of the extant batoid Aetobatus provides an example of a chondrichthyan in which teeth are retained after the time when they occlude with the teeth of the opposite jaw, similarly to Edestus. While its diet varies regionally, Aetobatus narinari appears to be a hard-prey specialist, feeding mainly on shelled gastropods and bivalves and on hermit crabs (Schluessel, Bennett and Collin 2010). ...
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Edestus is a Middle Pennsylvanian chondrichthyan possessing symphyseal tooth whorls in both the upper and lower jaws. The curvature of the tooth whorls prevents most of the crowns of the opposing whorls from occluding with each other. For that reason, it has recently been hypothesized that the tooth whorls were used to slash prey with a vertical motion of the anterior part of the body, not to cut prey caught between them. A tooth of Edestus minor having a truncated, smoothly worn apex has been reported previously. Here, a partial tooth whorl of a different species, Edestus heinrichi, is described. The apices of the crowns are worn, so that the crown heights are reduced by about one third. The more labial (older) of the two preserved crowns shows more wear than the more lingual (younger) one. In contrast to the previously reported E. minor tooth, wear is observed to the serrations as well as to the apices of the crowns. The observed wear on both the E. minor tooth and on the E. heinrichi tooth whorl supports the recent hypothesis on the function of the tooth whorls. In both cases, the apices might have been abraded by attempted predation on or scavenging of large fish having skin covered with denticles or scales.
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The evolutionary history of feeding biomechanics in fishes is a spectacular story of change in the structure and function of highly kinetic vertebrate skulls. From ratfishes to wrasses there is a spectacular diversity of skull form and feeding mechanisms among fishes, from sit-and-wait predators that use high suction forces to engulf their prey, to species that chase their prey during an attack, and fishes that cut or crunch their food using a biting strategy. Major feeding guilds among fishes include piscivores, herbivores, planktivores, detritivores, and molluscivores, with many more specialized modes of dietary preference such as scale eating, winnowing, and parasitism. Here we review recent advances in our understanding of fish feeding anatomy, behavior, and function, with a focus on progress in cranial biomechanics in fishes. Fish feeding science is a diverse and active discipline, with major advances in structure, mechanics, and evolution continuing to emerge.
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Large fish rostra without data of origin or determination are present in many museum collections or may appear in customs inspections. In recent years the inclusion of fish species on national and international lists for the protection of wildlife resulted in increased trading regulations. Therefore, useful identification tools are of growing importance. Here, we present a practical key for large fish rostra for the families Pristidae, Pristiophoridae, Xiphiidae and Istiophoridae. This key allows determination on species level for three of four families. Descriptions of the rostrum characteristics of the respective taxa are given.
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Incidental capture, or bycatch, in fisheries represents a substantial threat to the sustainability of elasmobranch populations worldwide. Consequently, researchers are increasingly investigating elasmobranch bycatch reduction methods, including some focused on these species' sensory capabilities, particularly their electrosensory systems. To guide this research, we review current knowledge of elasmobranch sensory biology and feeding ecology with respect to fishing gear interactions and include examples of bycatch reduction methods used for elasmobranchs as well as other taxonomic groups. We discuss potential elasmobranch bycatch reduction strategies for various fishing gear types based on the morphological, physiological, and behavioural characteristics of species within this diverse group. In select examples, we indicate how an understanding of the physiology and sensory biology of vulnerable, bycatch-prone, non-target elasmobranch species can help in the identification of promising options for bycatch reduction. We encourage collaboration among researchers studying bycatch reduction across taxa to provide better understanding of the broad effects of bycatch reduction methods.
Book
This book informs readers on the ecology, ecosystem services, and management of Sundaland wetland ecosystems, discussing the concepts and tools necessary to conserve these imperiled habitats. Sundaland is a biogeographically defined area of South East Asia characterised by an exceptional concentration of endemic species. The unprecedented loss of wetland habitats within Sundaland warrants urgency in implementing conservation actions. The authors are both researchers who have witnessed the ongoing losses of wetland habitats in Sundaland. The first chapter introduces fundamental concepts of ecosystems, ecological processes and ecosystem services of coastal and inland wetlands. The second chapter provides an overview of the global and regional conservation status of these ecosystems. The third chapter advances the importance of wetlands management at the landscape level (drainage basins), and proposes to adopt the concept of Ecotonal Networks (ENTs) as a sustainable management method, within the theoretical framework of Resilience Theory. The fourth chapter showcases potential flagship species that can aid in raising awareness on these endangered but poorly-known ecosystems. The fifth chapter discusses sustainable ecotourism as a viable and profitable industry to manage non-urban wetland areas of Sundaland, while providing specific suggestions for future developments. The book is written for ecosystem managers, conservation scientists, ecologists, and nature enthusiasts. It consists of a coherently arranged set of scientifically accurate tools that consider societal, cultural, and economic factors to succeed in the conservation of the Sundaland wetlands, as well as other wetland habitats in the world.
Book
Multisensory perception is emerging as an important factor in shaping current lifestyles. Therefore, computer scientists, engineers, and technology experts are acknowledging the comparative power existing beyond visual explanations. Perceptions of Knowledge Visualization: Explaining Concepts through Meaningful Images discusses issues related to visualization of scientific concepts, picturing processes and products, as well as the role of computing in the advancement of visual literacy skills. By connecting theory with practice, this book gives researchers, computer scientists, and academics an active experience which enhances the perception and the role of computer graphics.
Chapter
Sensory messages are examined as electromagnetic waves clearly identified by our senses, consisting of interacting electric and magnetic currents or fields and having distinctive wavelengths, energy, and frequency. Further text discusses modes of gathering information and communication that include sensory responses to electromagnetic waves, visible vibrations exemplified by cymatics, the pitch response, the senses of vision, smell, touch, and taste, all of them further expanded by the developments in current technologies. The sense of numbers is examined next, involving numerical and verbal cognition and communication with the use of numerals. Sensitivity, spatial abilities, and the threshold of sensory information make a part of the issues about biology-inspired computational solutions for enhancing our particular or synesthetic abilities, and the role of imagination in biology-inspired research and technology, learning, and teaching. The role of the sensory input in art, which pertains in some extent to individual curiosity and sensibility, concludes the chapter.
Chapter
Reports of marine injuries have increased in recent years as water sports and recreation grow in popularity. Eels, wolf-herring, barracuda, triggerfish, and ribbonfish frequently cause trauma. Sharks play an important role in the animal–human attack game and can render land-based, bipedal primates easy prey. The term shark attack has been considered to be any forceful or injurious exchange between a human and any shark. This frightening incident has always been one of the more thoroughly examined issues of the challenge between human and shark. Because of their feeding mechanisms, including sharp teeth and powerful jaws, and because they can attain very large sizes, sharks are considered to be the top predators of the marine world. Regardless of its size, any shark having both opportunity and physical capacity for injuring humans can be considered dangerous. The incidence of shark attacks in the world could not be said to merit the degree of apprehension or antipathy often expressed towards sharks, but when a shark attack does occur, it is often with an impressive efficiency.
Article
This chapter explores the existing and potential possibilities of exchanging information through the means that exceed those relating only to a text. Discussion entails knowledge visualization and the verbal and nonverbal ways of communication in the physical and online settings. After giving some consideration to the ways we communicate, cognitive activities are discussed by examining notions of cognitive thinking, cognitive science, and cognitive learning. Then follow some remarks on cognitive learning with knowledge visualization, whether occurring in a classroom and online with the use of computer technology, carried out through the social networking, or conducted with the use of educational games. Descriptions of the visual/verbal approach to learning with communication media and a discussion about criticism and assessment with respect to digital art and graphics conclude the chapter.
Technical Report
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Portuguese translation (abridged) of: Harrison, L.R. & Dulvy, N.K. (eds). 2014. Sawfish: A Global Strategy for Conservation. Published by the IUCN Species Survival Commission’s Shark Specialist Group, Vancouver, Canada. ISBN: 978-0-9561063-3-9 Editor/ project manager for Portuguese translation: Ruth H. Leeney
Article
How did the zebra really get its stripes, and the giraffe its long neck? What is the science behind camel humps, leopard spots, and other animal oddities? Such questions have fascinated us for centuries, but the expanding field of evo-devo (evolutionary developmental biology) is now providing, for the first time, a wealth of insights and answers. Taking inspiration from Kipling's ‘Just So Stories’, this book weaves emerging insights from evo-devo into a narrative that provides startling explanations for the origin and evolution of traits across the animal kingdom. Held's unique and engaging style makes this narrative both enlightening and entertaining, guiding students and researchers through even complex concepts and encouraging a fuller understanding of the latest developments in the field. The first five chapters cover the first bilaterally symmetric animals, flies, butterflies, snakes, and cheetahs. A final chapter surveys recent results about a menagerie of other animals.
Chapter
This chapter examines our modes of imparting or exchanging facts and opinions. After discussion of the role of electromagnetic waves in our sensory perception, further text describes the ways we and other living beings gain information through the senses, especially when enhanced with technology. Finally, communication between people, with computers, and with other living things is described, especially when animal communication involves senses unavailable to human beings. Emphasis is put on visual communication, some basic notions about semantics, and also visualization techniques and domains. Basic art concepts, elements of design in art, and principles of design in art serve as background information, followed by learning projects.
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The foundation of food web analysis is a solid understanding of predator-prey associations. Traditional dietary studies of fishes have been by stomach content analysis. However, these methods are not applicable to Critically Endangered species such as the smalltooth sawfish (Pristis pectinata). Previous research using the combination of stable isotope signatures from fin clips and 18S rRNA gene sequencing of fecal samples identified the smalltooth sawfish as piscivorous at low taxonomic resolution. Here, we present a high taxonomic resolution molecular technique for identification of prey using opportunistically acquired fecal samples. To assess potential biases, primer sets of two mitochondrial genes, 12S and 16S rRNA, were used alongside 18S rRNA, which targets a wider spectrum of taxa. In total, 19 fish taxa from 7 orders and 11 families native to the Gulf of Mexico were successfully identified. The sawfish prey comprised diverse taxa, indicating that this species is a generalist piscivore. These findings and the molecular approach used will aid recovery planning for the smalltooth sawfish and have the potential to reveal previously unknown predator-prey associations from a wide range of taxa, especially rare and hard to sample species.
Technical Report
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Version francaise du rapport complet: Harrison, L.R. and Dulvy, N.K. (eds). 2014. Sawfish: A Global Strategy for Conservation. IUCN Species Survival Commission’s Shark Specialist Group, Vancouver, Canada. ISBN: 978-0-9561063-3-9 Version francaise: Traduction par Céline Graciet/ Naked Translations; Bernard Séret. Édité par par Ruth Leeney.
Chapter
Passive electroreception has evolved independently at least three times and is found in both vertebrates (fishes, amphibians and some mammals) and invertebrates (crustaceans and insects). Specialized receptor organs provide the ability to detect weak electric fields produced either in nature (by prey or predators) or anthropogenically. Localized within the epithelium, the receptor organs are numerous and often non-homogeneously distributed over the body, providing information about the electric field’s intensity, its spatial configuration and the direction of its source. The high sensitivity of the receptors aids in localizing prey when other senses are not functional. Electroreception also aids in complex behaviors such as migration, orientation and navigation.
Chapter
Flagship species are key to conservation, and can act as umbrella taxa to represent entire ecosystems. The fourth chapter of the book presents a selection of potential flagship species that will help raise awareness to the imminent threats to Sundaland wetland ecosystems.
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The Freshwater Sawfish Pristis microdon was captured in marine waters of King Sound, and estuarine and fresh waters of the Fitzroy and Robinson rivers, in the Kimberley region of Western Australia. In light of the IUCN listing of the species as critically endangered, non-destructive means, including lagging-recapture data and information from specimens found dead on the banks, were utilised. Observations of sexual maturity, annuli present on vertebrae, recaptures of tagged individuals and length-frequency data suggested that the freshwaters of the Fitzroy River are a nursery for this species where immature individuals (up to 2800 mm total length) remain for a maximum of four or five years. Morphology and counts of the number of rostral teeth indicated that, in most cases, the rostral tooth morphology can be used to differentiate male and female P. microdon and also are useful in distinguishing this species from the congeneric and sympatric Pristis clavata. Furthermore, differences in the relationship between rostrum length and total length between the sexes may provide an effective diagnostic tool for the collation of historical distribution and sex ratio data from rostrums held in private collections. Rostral tooth counts and length at age data also suggest that the synonymisation of P. microdon, Pristis zephyreus and Pristis perotteti is not warranted.
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The ability of sharks to orient to weak electric fields is well documented, but a detailed analysis of orientation pathways is lacking. Digital video analysis was used to quantify the behavioral response of naıe neonatal bonnethead sharks, Sphyrna tiburo, to prey-simulating weak electric fields. Sharks less than 24 h post-parturition failed to demonstrate a positive feeding response to the electrodes whereas vigorous biting at the electrodes was observed in all sharks greater than 32 h post-parturition. Orientation behaviors were classified as one of five types: ''straight'' approach, ''single turn,'' ''overshoot,'' ''spiral tracking,'' and ''orient without biting.'' One-third of all orientations were elicited at stimulus intensities of less than 20 nV cm)1 . The median electric stimulus threshold for initiation of orientation was 47 nV cm)1 and the minimum was less than 1 nV cm)1 . Most orientations to the dipole were from a dis-tance of less than 10 cm with a maximum orientation distance of 22 cm. The innate feeding response to elec-tric stimuli is demonstrated for the first time in a chon-drichthyan fish.
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The distribution and density of the ampullary electroreceptors in the skin of elasmobranchs are influenced by the phylogeny and ecology of a species. Sensory maps were created for 4 species of pristid sawfish. Their ampullary pores were separated into pore fields based on their innervation and cluster formation. Ventrally, ampullary pores are located in 6 areas (5 in Pristis microdon), covering the rostrum and head to the gills. Dorsally, pores are located in 4 areas (3 in P. microdon), which cover the rostrum, head and may extend slightly onto the pectoral fins. In all species, the highest number of pores is found on the dorsal and ventral sides of the rostrum. The high densities of pores along the rostrum combined with the low densities around the mouth could indicate that sawfish use their rostrum to stun their prey before ingesting it, but this hypothesis remains to be tested. The directions of ampullary canals on the ventral side of the rostrum are species specific. P. microdon possesses the highest number of ampullary pores, which indicates that amongst the study species this species is an electroreception specialist. As such, juvenile P. microdon inhabit low-visibility freshwater habitats.
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Sclerorhynchids (extinct sawfishes, Batoidea), pristids (extant sawfish, Batoidea) and pristiophorids (sawsharks, Squalomorphi) are the three elasmobranch families that possess an elongated rostrum with lateral teeth. Sclerorhynchids are the extinct sawfishes of the Cretaceous period, which reached maximum total lengths of 100 cm. The morphology of their rostral teeth is highly variable. Pristid sawfish occur circumtropically and can reach maximum total lengths of around 700 cm. All pristid species are globally endangered due to their restricted habitat inshore. Pristiophorid sawsharks are small sharks of maximum total lengths below 150 cm, which occur in depths of 70–900 m. Close examination of the morphology of pectoral fin basals and the internal structure of the rostrum reveals that sclerorhynchids and pristids evolved independently from rhinobatids, whereas pristiophorids are squalomorph sharks. The elongation of the rostrum may be an adaptation for feeding, as all marine vertebrate taxa that possess this structure are said to use it in the context of feeding.
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The kinematics and muscle activity pattern of the head and jaws during feeding in the Atlantic guitarfish Rhinobatos lentiginosus are described and quantified using high-speed video and electromyography to test hypotheses regarding the conservation and modulation of the feeding mechanism. Prey is captured by the guitarfish using suction. Suction capture, bite manipulation and suction transport behaviors in the guitarfish are similar to one another in the relative sequence of kinematic and motor activity, but can be distinguished from one another by variation in absolute muscle activation time, in the presence or absence of muscle activity and in the duration of muscle activity. A novel compression transport behavior was observed that is strikingly different from the other feeding behaviors and has not been described previously in elasmobranchs. The mechanism of upper jaw protrusion in the guitarfish differs from that described in other elasmobranchs. Muscle function and motor pattern during feeding are similar in the plesiomorphic cranial muscles in the guitarfish and the spiny dogfish probably because of their shared ancestral morphology. Modulation in recruitment of jaw and hyoid depressor muscles among feeding behaviors in the guitarfish may be a consequence of duplication of muscles and decoupling of the jaws and hyoid apparatus in batoids.
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The unique head morphology of sphyrnid sharks might have evolved to enhance electrosensory capabilities. The 'enhanced electroreception' hypothesis was tested by comparing the behavioral responses of similarly sized carcharhinid and sphyrnid sharks to prey-simulating electric stimuli. Juvenile scalloped hammerhead sharks Sphyrna lewini and sandbar sharks Carcharhinus plumbeus oriented to dipole electric fields from the same maximum distance (approximately 30 cm) and thus demonstrated comparable behavioral-response thresholds (<1 nV cm(-1)). Despite the similarity of response threshold, the orientation pathways and behaviors differed for the two species. Scalloped hammerheads typically demonstrated a pivot orientation in which the edge of the cephalofoil closest to the dipole remained stationary while the shark bent its trunk to orient to the center of the dipole. By contrast, sandbars swam in a broader arc towards the center of the dipole. The different orientation patterns are attributed to the hydrodynamic properties of the cephalofoil, which enables the hammerheads to execute sharp turns at high speed. The greater trunk width of the sandbar sharks prevented them from demonstrating the same degree of flexibility. Therefore, although the sphyrnid head morphology does not appear to confer a greater sensitivity to prey-simulating dipole electric fields, it does provide (1). a greater lateral search area, which may increase the probability of prey encounter, and (2). enhanced maneuverability, which may aid in prey capture.
Article
An estimate of the amount of additional sampling needed in order to add a given number of new behaviour types (distinguishable acts) to an existing catalogue of types can be valuable in studies of behaviour. Estimation of the size of the repertory, i.e. the total number of behaviour types that a given animal or species is capable of expressing in a given class of situations, is also of interest. Practical solutions to these problems are presented and data from four species (domestic cats, human children, rhesus monkeys, and workers of the ant Leptothorax curvispinosus) analysed.
Article
Pristis microdon, P. zijsron, P. clavata and Anoxypristis cuspidata are distributed throughout the Queensland section of the Gulf of Carpentaria, Australia. In a survey of the four species, Anoxypristis cuspidata was the most abundant and was recorded in both the inshore and offshore set net fisheries. The size distribution and catch locations of A. cuspidata suggest that the inshore area to a depth of 10m may be the preferred habitat for juveniles of this species, while adults primarily occur offshore. Pristis microdon, P. zijsron and P. clavata were recorded only in the inshore fishery with catches dominated by immature animals. Pristis microdon was caught in the inshore fishery late in the monsoonal wet season (February to April) and inhabited both freshwater and estuarine environments. Pristis zijsron occurred only on the sand and mud flats outside river mouths whilst P. clavata inhabited both the sand and mud flats and upstream estuarine habitats. Observations on reproductive staging and the capture of neonate specimens suggest that in all four pristids, pupping occurred through the wet season until the beginning of the dry season in May. A seasonal set net closure for the barramundi, Lates calcarifer and shark fisheries, which has been in place since 1980 in Queensland Gulf waters, therefore offers a measure of protection to breeding female sawfish and their offspring.
Article
Sharks, skates, and rays receive electrical information about the positions of their prey, the drift of ocean currents, and their magnetic compass headings. At sea, dogfish and blue sharks were observed to execute apparent feeding responses to dipole electric fields designed to mimic prey. In training experiments, stingrays showed the ability to orient relative to uniform electric fields similar to those produced by ocean currents. Voltage gradients of only 5 nanovolts per centimeter would elicit either behavior.
Sa�fish (Pristi�ae) �f the Gulf �f Car�entaria
  • � S C Peverell
  • Queenslan�
  • Australia
Peverell,� S.C. (2009). Sa�fish (Pristi�ae) �f the Gulf �f Car�entaria,� Queenslan�,� Australia. MSc Thesis (James C��k University).
The ec�l��y an� functi�nal m�r�h�l��y �f fee�in� �f N�rth American stur�e�ns an� �a��lefishes
  • � M J Miller
Miller,� M.J. (2005). The ec�l��y an� functi�nal m�r�h�l��y �f fee�in� �f N�rth American stur�e�ns an� �a��lefishes. In Stur�e�ns an� Pa��lefish �f N�rth America,� G. LeBret�n,� F. Beamish,� an� R. McKinley,� e�s. (Klu�er Aca�emic Publishers),� ��. 87–102.
The bi�l��y �f extinct an� extant sa�fish (Bat�i�ea: Scler�rhynchi�ae an� Pristi�ae). Rev. Fish Bi�l. Fish
  • � B E Wuerin�er
  • � L J Squire
  • � S P C�llin
Wuerin�er,� B.E.,� Squire,� L.J.,� an� C�llin,� S.P. (2009). The bi�l��y �f extinct an� extant sa�fish (Bat�i�ea: Scler�rhynchi�ae an� Pristi�ae). Rev. Fish Bi�l. Fish. 19,� 445–464.
On the utility �f the sa� �f the sa�fish
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Bre�er,� C.M. (1952). On the utility �f the sa� �f the sa�fish. C��eia. 2,� 90–91.
Sens�ry systems in sa�fishes: Part 1 the am�ullae �f L�renzini
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  • � S C Peverell
  • � J E Seym�ur
  • � L J Squire
  • � S M Kajiura
  • � S P C�llin
Wuerin�er,� B.E.,� Peverell,� S.C.,� Seym�ur,� J.E.,� Squire,� L.J.,� Kajiura,� S.M.,� an� C�llin,� S.P. (2011). Sens�ry systems in sa�fishes: Part 1 the am�ullae �f L�renzini. Brain Behav. Ev�l. 78,� 139–149.
Evi�ence f�r use �f the bill by blue marlin,� Makaira nigricans, �urin� fee�in�
  • � T Shim�se
  • � K Y�ka�a
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Shim�se,� T.,� Y�ka�a,� K.,� Sait�,� H.,� an� Tachihara,� K. (2007). Evi�ence f�r use �f the bill by blue marlin,� Makaira nigricans, �urin� fee�in�. Ichthy�l. Res. 54,� 420–422.