Article

New Species of Troglobitic Catfish of the Genus Prietella (Siluriformes: Ictaluridae) from Northeastern México

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  • University of Florida, Gainesville, United States
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Abstract

Prietella lundbergi, a new species of cave ictalurid and only the second of the genus to be discovered, is described from a single specimen collected in a subterranean thermal spring, Tamaulipas state, México. Morphologically, the new species shares with three previously known troglobitic ictalurids (Prietella phreatophila, Satan eurystomus, Trogloglanis pattersoni) many convergent, paedomorphic characters associated with subterranean life. Prietella lundbergi differs from its nearest relative, P. phreatophila, in retention of the endopterygoid; reduction of the swimbladder; hypural osteology; numbers of principal caudalfin rays, branchiostegals and gill rakers; and in some body measurements. Morphological comparisons support monophyly of the genus Prietella and its recognition as the sister group of Noturus. The new species is found in the El Abra mountains of the Sierra Madre Oriental range, far outside the Río Grande basin and Edwards Aquifer where all other ictalurid troglobites occur. Historical interdrainage connections along the northeast Gulf Coastal Plain of México may have favored a broad distribution of the epigean ancestor of the two extant Prietella species. /// Se describe una nueva especie de bagre ciego ictalurido, Prietella lundbergi, en base a un solo ejemplar capturado en un fuente subterráneo con aguas cálidas en el estado Tamaulipas, México. Antes del este descubrimiento nuevo, el género Prietella se habia conocido por una sola especie, P. phreatophila. Esta especie nueva posee varios carácteres morfológicos convergentes y paedomórficos en común con las otras tres especies de ictaluridos conocidos con hábitos troglobios (Prietella phreatophila, Satan eurystomus y Trogloglanis pattersoni). Prietella lundbergi se distingue de P. phreatophila por la retención de los huesos endopterigoides; la reducción de la vejiga gaseosa; la osteología del base de la aleta caudal; el número de radiales de la aleta caudal; los números de los radios branquiostegios y branquispinas del primer arco branquial; y tambien por varias medidas morfométricas. Una comparación morfológico presenta evidencia que Prietella forman un grupo "sister" monofilético del género Noturus. La localidad tipica de de la especie nueva es una cueva situada en las montañas El Abra de la Sierra Madre Oriental. Esta localidad está ubicado bastante lejos de la cuenca del Río Grande y Edwards Aquifer de donde se encuentran los otros tres ictaluridos adaptados a la vida en las aguas subterráneas. Se proponen que la interconexión histórica entre los varios dranajes en el parte noreste del costo plano del Golfo de México ha permitodo el ancestro de las dos especies de Prietella a tener una distribución posteriormente muy amplia.

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... One vertebrate family containing several troglobitic species is the North American catfishes, Ictaluridae (Lundberg, 1970;Lundberg, 1992;Walsh & Gilbert, 1995;Burr et al., 2020). This monophyletic family occurs from Southern Canada to Guatemala (Fig. 1), inhabiting a wide diversity of lentic and lotic habitats, such as creek riffles, large river channels, lakes, and subterranean pools (Nelson, 2006;Arce H. et al., 2016;Burr et al., 2020). ...
... Fossils extend the historical distribution of ictalurids to the Pacific Northwest of the United States (Lundberg, 1992). Ictaluridae comprises seven genera, including four surface genera (Ameiurus, Ictalurus, Noturus, and Pylodictis) and three cave genera (Prietella, Satan, and Trogloglanis) ( Fig. 1; Walsh & Gilbert, 1995;Wilcox et al., 2004). There are currently 50 recognized extant species in the family, of which four are troglobitic: Prietella lundbergi, Prietella phreatophila, Satan eurystomus, and Trogloglanis pattersoni (Wilcox et al., 2004;Nelson, 2006;Arce H. et al., 2016;Burr et al., 2020). ...
... There are currently 50 recognized extant species in the family, of which four are troglobitic: Prietella lundbergi, Prietella phreatophila, Satan eurystomus, and Trogloglanis pattersoni (Wilcox et al., 2004;Nelson, 2006;Arce H. et al., 2016;Burr et al., 2020). These four troglobitic species exhibit similar morphological adaptations to subterranean life observed in other aquatic cave fauna, such as non-functional eyes, achromatism, reduced swim bladder size, and fragmented lateralline systems (Walsh & Gilbert, 1995;Arce H. et al., 2016). ...
Article
Insular habitats have played an important role in developing evolutionary theory, including natural selection and island biogeography. Caves are insular habitats that place extreme selective pressures on organisms due to the absence of light and food scarcity. Therefore, cave organisms present an excellent opportunity for studying colonization and speciation in response to the unique abiotic conditions that require extreme adaptations. One vertebrate family, the North American catfishes (Ictaluridae), includes four troglodytic species that inhabit the karst region bordering the western Gulf of Mexico. The phylogenetic relationships of these species have been contentious, and conflicting hypotheses have been proposed to explain their origins. The purpose of our study was to construct a time-calibrated phylogeny of Ictaluridae using first-occurrence fossil data and the largest molecular dataset on the group to date. We test the hypothesis that troglodytic ictalurids have evolved in parallel, thus resulting from repeated cave colonization events. We found that Prietella lundbergi is sister to surface-dwelling Ictalurus and that Prietella phreatophila + Trogloglanis pattersoni are sister to surface-dwelling Ameiurus, suggesting that ictalurids colonized subterranean habitats at least twice in evolutionary history. The sister relationship between Prietella phreatophila and Trogloglanis pattersoni may indicate that these two species diverged from a common ancestor following a subterranean dispersal event between Texas and Coahuila aquifers. We recovered Prietella as a polyphyletic genus and recommend P. lundbergi be removed from this genus. With respect to Ameiurus, we found evidence for a potentially undescribed species sister to A. platycephalus, which warrants further investigation of Atlantic and Gulf slope Ameiurus species. In Ictalurus, we identified shallow divergence between I. dugesii and I. ochoterenai, I. australis and I. mexicanus, and I. furcatus and I. meridionalis, indicating a need to reexamine the validity of each species. Lastly, we propose minor revisions to the intrageneric classification of Noturus including the restriction of subgenus Schilbeodes to N. gyrinus (type species), N. lachneri, N. leptacanthus, and N. nocturnus.
... Both are known only from the deep waters of the Edwards Aquifer below San Antonio. Later, two more blindcat species were discovered in subsurface waters of northeastern Mexico: Prietella phreatophila Carranza (1954) from the State of Coahuila and, remarkably, recently collected north of the Rio Grande in nearby cave waters of Val Verde County, Texas (Hendrickson et al. 2001(Hendrickson et al. , 2017, and P. lundbergi Walsh and Gilbert (1995) in the State of Tamaulipas. ...
... Among the shared features of Pylodictis and Satan are their wide gape, depressed head, expanded branchiostegal and opercular membranes, and anterior extension of epaxial muscle. The species of Prietella resemble epigean Noturus (Taylor, 1969), and the two species are distinct from each other in morphological features including fin shapes and presence or absence of the swim bladder (Walsh and Gilbert, 1995) as well as mitochondrial gene sequences (Wilcox et al., 2004). Hypotheses on the interrelationships of the blind ictalurids are based on incomplete morphological data and, for Prietella only, scant molecular data. ...
... Further, we raise questions about the polarities of paired-fin ray meristic characters in Ictaluridae and we correct five errors in the past literature dealing with misinterpreted characters in these catfishes. The primary literature includes: Hubbs and Bailey (1947), Suttkus (1961), Taylor (1969), Lundberg (1970Lundberg ( , 1975Lundberg ( , 1982Lundberg ( , 1992, Langecker and Longley (1993), Walsh and Gilbert (1995) and Arce-H. et al. (2016). ...
Article
The Widemouth Blindcat, Satan eurystomus Hubbs and Bailey 1947, was the second of four stygobitic species of Ictaluridae discovered in the subterranean waters of southern Texas and northeastern Mexico. The skeletal anatomy of Satan has been scarcely known from a few, dated radiographs. Using additional radiographs and high resolution CT-datasets for two well-ossified specimens, we applied high-resolution X-ray computed tomography (HRXCT) to visualize, illustrate and describe the bony skeleton of Satan. We also provide an online archive of still and animated tomographic images of the skeletal anatomy of this little-known species. The skeleton and soft anatomy of Satan are distinctive. Twelve skeletal autapomorphies are described that singularly distinguish Satan within Ictaluridae and, probably in combination, from all other catfishes. Some of these are reductive losses or simplifications of skull bones (e.g. loss of one infraorbital bone; reduced ornamentation of the pterotic bone) and joint complexity (e.g. simple overlapping frontal-lateral ethmoid articulation; loosely ligamentous interopercle-posterior ceratohyal joint). Some of the autapomorphies are anatomically and perhaps developmentally complex (e.g. a novel series of three midline joints closing a middle span of the posterior cranial fontanel; a deeply excavated temporal fossa and an unusually enlarged interhyal bone). The tiny dorsal-fin spinelet (first lepidotrich) of Satan has a novel peaked and twisted shape. Ten apparent and exclusive synapomorphies within Ictaluridae gathered from this and previous studies suggest that Satan and Pylodictis are closest relatives. Most of these are functionally related to prey detection and suction feeding: fusion of the symphyseal mandibular sensory pores and increase in the number of preoperculo-mandibular canal pores; depressed, flattened heads and wide transverse mouths; prominent posterior process of the lateral ethmoid alongside and below the frontal bone margin; vertical and blade-like supraoccipital posterior process; unique arrangement of the parasagittal and occipital muscleattachment crests on the skull roof; large triangular panel of integument within the operculum framed by the opercle, preopercle and interopercle bones; elongated posterior ceratohyal; and, form of the fourth supraneural and loss of its anterior nuchal plate. In contrast, 15 synapomorphies recovered by Arce-H. et al. 2016, are confirmed suggesting that Satan is one of the four stygobitic ictalurids comprising a "Troglobites" subclade within the family: (Trogloglanis, Satan, Prietella phreatophila, P. lundbergi). These features include three stygomorphic and reductive apomorphies that are exclusive within Ictaluridae: loss of fully developed eyes and pigmentation, and simplification of the fifth vertebra and its joint with the Weberian apparatus. Twelve other synapomorphies shown by the Troglobites are also apparent homoplasies of character states shared with various other ictalurids. These include reductive characters such as shortened lateral line canal, reduced infraorbitals and underdeveloped or incomplete ossifications of the pterotic, supraoccipital, hyoid arch bones and transcapular ligament. Also, the Troglobites and various other ictalurids have: an adnate adiposecaudal fin, foreshortened anterior cranial fontanelle, reduced ventral wings of the frontal bone, replacement of bone by cartilage in hypohyal joints; incompletely ossified transcapular ligament, and consolidation of some hypural bones. Completing a full morphological character dataset across the Troglobites has been impeded by incomplete specimen preparations and study of P. lundbergi and to a lesser extent, P. phreatophila and Trogloglanis. © 2017 by the Academy of Natural Sciences of Drexel University.
... Other species live in typically phreatic waters, such as Phreatobius cisternarum, Satan eurystomus, Trogloglanis pattersoni, Uegitglanis zammaranoi, Phreatichthys andruzzii, Barbopsis devecchii and Taunayia sp. Some of these fishes show miniaturization, probably achieved by paedomorphosis (as proposed by Weitzmann & Vari 1988 for miniature epigean species), as an adaptation to life in small phreatic spaces: S. eurystomus, T. pattersoni (Langecker & Longley 1993), Prietella lundbergi (Walsh & Gilbert 1995), Taunayia sp., and the new heptapterine genus (Trajano & Bockmann 1999). Small size may also be energetically adaptive for hypogean environments (Walsh & Gilbert 1995). ...
... Some of these fishes show miniaturization, probably achieved by paedomorphosis (as proposed by Weitzmann & Vari 1988 for miniature epigean species), as an adaptation to life in small phreatic spaces: S. eurystomus, T. pattersoni (Langecker & Longley 1993), Prietella lundbergi (Walsh & Gilbert 1995), Taunayia sp., and the new heptapterine genus (Trajano & Bockmann 1999). Small size may also be energetically adaptive for hypogean environments (Walsh & Gilbert 1995). ...
... Ridges of fat tissue along the base of adipose and anal fins are present in the troglobitic heptapterines, Rhamdia reddelli, R. zongolicensis and R. macuspanensis (Weber 1996, and P. kronei (Trajano personal observation), but not in their epigean relatives, respectively R. laticauda and P. transitoria. The ictalurids Prietella lundbergi, T. pattersoni and S. eurystomus have large lipid deposits in subcutaneous areas and viscera, associated with mesenteries, and in the place of the reduced gasbladder (Langecker & Longley 1993, Walsh & Gilbert 1995; however, some individuals of T. pattersoni and S. eurystomus showed signs of starvation. Experiments with troglobitic Astyanax from Pachon Cave have shown that these fishes exhibit an improved ability to store fat and build up enormous reserves (Wilkens 1988). ...
Article
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A synthesis of ecological data available for subterranean fishes throughout the world is presented, and comparatively analyzed in an evolutionary context. Methods of ecological research are described, and their potential and limitations for the study of hypogean fishes are discussed. Ecology of troglobitic (exclusively subterranean) fishes is discussed with focus on distribution areas, population densities and sizes, use of habitat and movements, life cycle and feeding. When data are available, these species are compared with their epigean relatives. Putative ecological autapomorphies of troglobitic fishes, including habitat change, adaptations to cope with food scarcity, and precocial lifestyles, are interpreted in ecological and evolutionary contexts. Species interactions among subterranean species, including cases of syntopy and predation are briefly analyzed. Non-troglobitic hypogean fishes, with their ecological importance and evolutionary role, are also addressed. Problems of classification of subterranean fishes according to the Schiner-Racovitza system (troglobites, troglophiles and trogloxenes) are discussed, and a scenario of evolution of subterranean populations is presented.
... Two of these genera are monotypic: single species of Satan and Trogloglanis are found sympatrically in the Edwards Aquifer 300-600 m under the city of San Antonio, Texas, although neither species has been collected in more than two decades (Langecker and Longley, 1993;Longley and Karnei, 1979a,b;Lundberg, 1982). The third hypogean genus is Prietella, with two poorly known, allopatric species from northeastern M exico (Walsh and Gilbert, 1995). Previous morphological studies have indicated the relationships of the genera as Ictalurus(Trogloglanis(Ameiurus((Noturus + Prietella)(Satan + Pylodictis)))) (Lundberg, 1992). ...
... Prietella phreatophila was described in 1954 from a well at the base of the Sierra de Santa Rosa, near M uzquiz, Coahuila, M exico (Carranza, 1954), and was later collected from a few spring caves within about 10 km of the type locality and from one locality about 64 km WNW of the type locality (Walsh and Gilbert, 1995). More recently Hendrickson et al. (2001) reported additional localities that significantly extended the known distribution of this species. ...
... More recently Hendrickson et al. (2001) reported additional localities that significantly extended the known distribution of this species. The Prietella lundbergi description was based on a single specimen collected in 1989 from a subsurface thermal spring in southern Tamaulipas, M exico (Walsh and Gilbert, 1995). Hendrickson et al. (2001) obtained four new specimens referable to this species from an isolated locality about 26 km from the type locality. ...
Article
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Convergence has long been of interest to evolutionary biologists. Cave organisms appear to be ideal candidates for studying convergence in morphological, physiological, and developmental traits. Here we report apparent convergence in two cave-catfishes that were described on morphological grounds as congeners: Prietella phreatophila and Prietella lundbergi. We collected mitochondrial DNA sequence data from 10 species of catfishes, representing five of the seven genera in Ictaluridae, as well as seven species from a broad range of siluriform outgroups. Analysis of the sequence data under parsimony supports a monophyletic Prietella. However, both maximum-likelihood and Bayesian analyses support polyphyly of the genus, with P. lundbergi sister to Ictalurus and P. phreatophila sister to Ameiurus. The topological difference between parsimony and the other methods appears to result from long-branch attraction between the Prietella species. Similarly, the sequence data do not support several other relationships within Ictaluridae supported by morphology. We develop a new Bayesian method for examining variation in molecular rates of evolution across a phylogeny.
... The presence of small globular structures, which are found at various intensities in different individuals, was observed under the skin of P. sanguijuela, with the highest concentration in the posterior region of the body. These globular structures may constitute subcutaneous fat deposits, as observed in P. dracunculus, Prietella lundbergi Walsh & Gilbert 1995, Trogloglanis pattersoni Eigenmann 1919and Satan eurystomus Hubbs & Bailey 1947(Langecker & Longley, 1993Walsh & Gilbert, 1995;Shibatta et al., 2007). These subcutaneous fatty tissues underneath the skin deserve thorough investigation, as they may mitigate the effects of possible shortages of food in the hypogean environment in certain periods of the year (or throughout the year, as a result of the temporal irregularity in the supply of food in the hypogean environment). ...
... The presence of small globular structures, which are found at various intensities in different individuals, was observed under the skin of P. sanguijuela, with the highest concentration in the posterior region of the body. These globular structures may constitute subcutaneous fat deposits, as observed in P. dracunculus, Prietella lundbergi Walsh & Gilbert 1995, Trogloglanis pattersoni Eigenmann 1919and Satan eurystomus Hubbs & Bailey 1947(Langecker & Longley, 1993Walsh & Gilbert, 1995;Shibatta et al., 2007). These subcutaneous fatty tissues underneath the skin deserve thorough investigation, as they may mitigate the effects of possible shortages of food in the hypogean environment in certain periods of the year (or throughout the year, as a result of the temporal irregularity in the supply of food in the hypogean environment). ...
Article
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The subterranean fish Phreatobius sanguijuela, originally described from Bolivia, was captured in different wells near São Francisco do Guaporé, Rondônia State, Brazil. Thirty wells were investigated in April and July 2012, and September 2013. These surveys resulted in the capture of 58 individuals from eight wells and comprised three to 14 individuals per well. The capture of the individuals allowed a detailed evaluation of their colours in life, behaviour in the field and in captivity, aspects of their biology, confirmation of the species identification and provided new diagnostic characteristics to distinguish between P. sanguijuela and Phreatobius dracunculus. Cannibalism, territorialism, agonistic interactions and phototaxis behaviour were not observed. Phreatobius sanguijuela exhibited cryptobiotic habits and two behaviours under stressful conditions. The analysis of stomach contents reveals that this species apparently feeds on invertebrates, almost exclusively on earthworms. The sex ratio was 1:1. The absence of opercular movement during the resting period associated with intense blood irrigation of the skin indicates a possible cutaneous respiration as an alternative form of gas exchange. Local people often mistake P. sanguijuela for helminths and have the habit of releasing non-native fishes into the wells or to use chemicals to eliminate them. The consequence of this habit for the conservation of the species requires further evaluation.
... However, none of them have extant epigean conspecifics. These catfishes are most likely the remnants of once widespread epigean species because, while the three regions (where the troglobitic catfishes occur) have separate underground drainage systems there is evidence of past epigean interdrainage between them (Walsh and Gilbert, 1995). ...
Thesis
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Tree roots which grow into cave waters constitute an important source of nutrition and shelter for aquatic invertebrates. This substantial and reliable food source has enabled the development of diverse and abundant faunas in the groundwater streams of a number of caves in mid-Pleistocene syngenetic karst of southwest Australia. Evidence is presented for a multiplicity of sources of the southwestern cave faunae: (1) ancient freshwater forms, (2) marine interstitial habitats, (3) interstitial groundwaters (freshwater), (4) ‘lake crawl outs’, (5) wet soil and litter habitats including root feeding species, and (6) winged epigean insects with aquatic larvae which may be trogloxenes or troglophiles. The two cave areas, Yanchep National Park and Leeuwin-Naturaliste Ridge, are subject to significant threats to their long-term maintenance due to their propinquity to human activity. The major threat to the persistence of the aquatic cave ecosystems is the progressive lowering of the water table, mainly due to groundwater abstraction for urban, rural and industry needs. The human populations and consequently the demand for water are growing rapidly, both in the Leeuwin-Naturaliste and Perth regions.
... Cave divers have not seen the cavefish in the nacimientos on the eastern face of the Sierras. A small, blind catfish, Prietella lundbergi (Walsh and Gilbert, 1995), was found in two springs on the eastern face by Hendrickson et al. (2001) (Table 1.2), hinting at a different history of isolation and evolution than Astyanax, which is found only in the western, swallet caves or in large sinkhole caves that penetrate to groundwater. ...
... The nacimientos (large springs) may be considered yet another biogeographic subregion with some similarities to the El Abra and Guatemala caves, but with unique fauna. A tiny blind catfish, Prietella lundbergi (Walsh and Gilbert, 1995), inhabits two small nacimientos on the eastern face of the region, Cueva del Nacimiento del Río Frío and Nacimiento de San Rafael de los Castro, along with two new species of Troglomexicanus shrimp not found in the Astyanax caves (Hendrickson et al., 2001;Villalobos et al., 1999). Cave divers have not found Astyanax cavefish in the nacimientos, which receive "type-A waters" from the local ranges, as well as "type-B waters," with hydrogen sulfide and dissolved salts, from deeper circulation (Fish, 1977(Fish, , 2004; therefore, these zoogeographic patterns suggest that ancestral cavefishes did not invade the karst through springs, but rather were isolated through stream capture. ...
Chapter
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The general ecology and biodiversity of fish caves in the Sierra de El Abra region is discussed with details about the ecology of four examples. Sótano de Yerbaniz is a deep, violently flooding swallet (stream-capture cave) with the largest catchment area in the El Abra region, 16 km2. Yerbaniz is hydrologically related to two other caves nearby. Cueva Chica, the original cave in which the Mexican cavefish was found in 1936, is a shallow walk-in cave with a series of four pools containing hybrid cavefishes, then more and more river fishes toward the end; Chica is sometimes backflooded by the Río Tampaón. Cueva de Los Sabinos is a large system hydrologically connected to Sótano del Arroyo and Sótano de la Tinaja. Sótano de Soyate is a deep fissure with a large, deep lake reaching below the regional base level. The potential prey of the hardy cavefishes include swimming crustaceans, but the cavefish subsists mainly on bat guano, other fishes, floating animals, and flood debris. Large populations of cavefishes thrive in some of the 29 known, semi-isolated caves, while small populations subsist in shallow pools. Conservation of the cavefishes must begin, perhaps by including their caves in the two major biosphere reserves in the region.
... Cave divers have not seen the cavefish in the nacimientos on the eastern face of the Sierras. A small, blind catfish, Prietella lundbergi (Walsh and Gilbert, 1995), was found in two springs on the eastern face by Hendrickson et al. (2001) (Table 1.2), hinting at a different history of isolation and evolution than Astyanax, which is found only in the western, swallet caves or in large sinkhole caves that penetrate to groundwater. ...
Chapter
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Knowledge about the Mexican cavefish, Astyanax mexicanus, was advanced by biologists, geologists, and cavers over three periods of work: 1936-1954, 1963-1998, and 2009 to present. Hundreds of caves in the Sierra de El Abra region were discovered on the ground or from the air, and explored by Mexican, American, Canadian, and European teams, many participating in the Association for Mexican Cave Studies (AMCS). Twenty-eight of 29 cavefish sites have been mapped. Caving and cave diving techniques advanced over the years, along with cave mapping and cartography. Now the maps and GIS are helping our understanding of the hydrogeological nature of the caves and where they may drain to, thus informing geneticists and their work. Some of the cavefish populations have not been sampled genetically. In the future, dye tracing studies could reveal groundwater flow paths to the region’s springs (nacimientos), which may have very long-distance connections to the caves.
... The minnow family, nearing its southern distributional limit, also is represented by numerous endemics, especially in the genus Dionda (Pánuco minnow, bicolor minnow, chubsucker minnow, lantern minnow, flatjaw minnow, blackstripe minnow), which includes several sympatric species pairs (Mayden et al. 1992). An extremely rare and endan-gered blind cave catfish, the phantom blindcat, recently discovered in the Rio Guayalejo in southernmost Tamaulipas (Walsh andGilbert 1995, Hendrickson et al. 2001) presents an interesting evolutionary enigma (Willcox et al. 2004). Many caves of this region harbor the blind form of Mexican tetra, which may well be one of the most studied nongame fishes of North American (e.g., Mitchell et al. 1977, Langecker et al. 1995, Borowsky 1996, Jeffrey 2001, Dowling et al. 2002. ...
Chapter
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The existence of cavernicolous sculpin (here allocated to Cottus carolinae, banded sculpin, and referred to as grotto sculpin), in the karst regions of Perry County, Missouri, first came to our attention in 1991. Examination of 35 caves in Missouri, 96 in Illinois, 17 in Tennessee, two in Indiana, and 11 in Arkansas revealed that banded sculpin are common in cave habitats; however, grotto sculpin are limited to two karst areas of Perry County, Missouri, where they are known from only six cave systems. These caves and their streams are extensive and apparently provide a unique habitat compared to other karst systems; this may be a critical factor in the present restricted distribution of the grotto sculpin. Grotto sculpin occupy pools and riffles of cave streams, and occur over a variety of substrates, from sediment to breakdown. Density estimates in Mystery and Running Bull caves were 0.29 and 0.63 individuals m-2, respectively. Grotto sculpin have small eyes (1–6% SL vs. 6–10% SL in epigean samples), significantly reduced pigmentation (including nearly complete loss of dorsal saddles), a reduction in pelvic fin ray number (from 4+4 elements to often 4+3 , or 3+3), and enlarged cephalic lateralis pores (e.g., mandibular pores of cavernicolous samples are 2–3 times those of epigean stream samples). Multivariate analyses of body shape revealed statistically significant separation of epigean and hypogean samples, with eye size highly variable, but smallest in the Running Bull Cave population. We interpret these results as representative of losses associated with long-term cave habitation. Caves of Perry County provide ample habitat for grotto sculpin, but because the caves are located downgradient of the city of Perryville and an intensively farmed landscape, point and non-point source pollution threaten their continued existence. Escape of farm-pond fishes through the extensive sinkhole network in Perry County has increased potential predation pressure on grotto sculpin by channel catfish, Ictalurus punctatus, and other species normally excluded from cave environments.
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There are at least 86 species of troglomorphic fishes belonging to 18 families. Some of those families are characterized by features that can be labeled as preadaptations to the hypogean life; others are not. The level of structural reduction in eye development and pigmentation is highly variable, even within some populations. Reduction in number and complexity of scales does occur but has yet to be fully documented. Reduction in the size and structure of the swim(gas)bladder may be another troglomorphic feature. There is considerable doubt on the taxonomic position of many species of troglomorphic fishes given that a number of them have been described solely on the basis of morphology while genetically they may be very closely correlated to genera different from those they have been assigned to. Geographically speaking there are no evident patterns since many of those species are not found in karstic areas but in phreatic waters. These fishes represent an excellent example of convergent evolution.
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Previous literature has suggested the absence of an effective barrier between the nasal mucosa and the brain for compounds administered via the nasal route. These experiments were conducted to elucidate the role of the blood-brain barrier efflux transporter P-glycoprotein (P-gp) in attenuating delivery of P-gp substrates to the brain after nasal administration in mice. Brain uptake of several radiolabeled P-gp substrates, was measured in P-gp-deficient and P-gp-competent mice following nasal instillation. Additional experiments were performed to assess the potential for enhancing brain uptake by inhibiting P-gp with intranasal rifampin. All substrates examined were measurable in brain tissue within 2 min. Substrate accumulation in P-gp-deficient mice was higher than in P-gp-competent animals; the degree to which P-gp attenuated brain uptake after nasal administration was similar to that during in situ brain perfusion. Co-administration of rifampin enhanced brain uptake of relevant substrates, and resulted in complete elimination of P-gp-mediated transport for 3H- verapamil. P-gp attenuates brain accumulation of intranasally-administered P-gp substrates. Thus, biochemical components of the blood-brain barrier, such as efflux transporters may influence brain penetration after nasal administration. Co-administration of a P-gp inhibitor enhances the brain uptake of relevant substrates, suggesting that the transporter barrier functions may be reversible.
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The American Fisheries Society herein provides an update of their now decade-old list of rare North American fishes. The 1989 list adds 139 new taxa to the list developed by Deacon et al. (1979) of 251 fishes and removes 26 for a total of 364 fishes in Canada, United States, and Mexico that warrant protection because of their rarity. The 26 taxa removed from the 1979 list include 16 removed because of better information on their taxonomy or status and 10 because they have become extinct. Not a single fish warranted removal from the list because of successful recovery efforts. In addition, 49 fishes have changed in status but remain on the list: 7 have improved in status, 24 have declined, and 18 have been reclassified because new information revealed that they were either more common or rarer than was earlier believed and, therefore, were incorrectly classified in 1979. Comparison of the 1979 and 1989 lists indicates that recovery efforts have been locally effective for some species, but are clearly lagging behind deterioration of the overall fish fauna. The health of aquatic habitats in North America continues to decay. A major commitment to conservation of entire ecosystems, rather than the inconsistent recovery efforts for individual species, is needed to reverse this trend.