Article

Effect of autotomy and regeneration of the chelipeds on growth and development in Petrolisthes laevigatus (Guérin, 1835) (Decapoda, Anomura, Porcellanidae)

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Abstract

The capacity to discard and regenerate limbs under conditions of vital risk does increase the probability of survival. Eventually, however, this can negatively influence the performance of other aspects of fitness in the organism affected. The influence of autotomy and regeneration of one or both chelipeds on body growth and intermoult period in Petrolisthes laevigatus was studied; individuals in a broad range of sizes were captured and subjected to autotomy treatments in one or both chelipeds, contrasted against a control group without autotomy. Body growth was measured as the increment of the carapace width after a moulting event. At the same time, the duration of the intermoult was considered as the period of time between two succesive moults. Significantly higher values of response in body growth, intermoult duration, and growth rate were observed in the control group with respect to the group with autotomy treatments. In the growth responses, the phenomenon of suboptimal foraging can be discarded and therefore the more probable explanation for growth decrease is related to reduction of the intermoult period or for changes in the allocation of energy from overall growth processes into the limb regeneration process.

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... Anomuran crabs, which belong to the family Porcellanidae Haworth 1825, exhibit a brachyuran crablike body shape; broad and dorsoventrally flattened, relatively large chelipeds for their body size; and a well-developed, symmetrical pleon that is carried bent under the cephalothorax and held against the thorax (Jones 1977;Barría and González 2008;Osawa and McLaughlin 2010). Sexual size dimorphisms of the chelipeds and pleons have been documented in some porcellanid crab species (i.e., males with larger chelipeds and females with wider pleons) (Miranda and Mantelatto 2010;Baeza and Asorey 2012;Wassick et al. 2017); it is therefore likely that the relatively large chelipeds and well-developed pleons of porcellanid crabs are costly to produce and maintain, and that seasonal changes in sexual size dimorphism occur in their chelipeds and pleons. ...
... The chelipeds of the porcellanid crabs are broad, dorsoventrally flattened and large relative to their body size (Jones 1977;Barría and González 2008;Osawa and McLaughlin 2010). These chelipeds are known to be involved in intraspecific agonistic and sexual communications in porcellanid crabs. ...
Article
Decapod crustaceans develop secondary sexual structures, such as large chelipeds for weaponry and/or display in males and a wider pleon for incubating eggs in females. These structures should be costly to produce and maintain; hence, the crustacean reproductive strategy might have adapted to conserve energy for developing secondary sexual characteristics during the reproductive season. However, little is known about seasonal changes in the sexual size dimorphisms of the chelipeds and pleons of decapod crustaceans. Anomuran crabs from the family Porcellanidae exhibit a true crab-like body shape, with relatively large chelipeds for their body size and a well-developed pleon. They also show sexual size dimorphism (i.e., males with larger chelipeds and females with wider pleons); therefore, it was expected that seasonal changes in the sexual size dimorphisms of these organs would occur in porcellanid crabs. We tested this expectation using Petrolisthes japonicus, which is common on the intertidal cobble and boulder shores of the temperate and tropical regions of Japan. We employed allometric growth analyses of the cheliped and pleon dimensions of P. japonicus females and males collected over a year. Our analyses supported our expectation regarding the seasonal changes in the sexual size dimorphisms of the chelipeds and pleons in P. japonicus. Intersexual size dimorphism of the chelipeds and pleons was evident during the breeding season: females allocated more energy to pleon growth, while reducing cheliped growth, and investment in the pleon increased with increasing female body size, whereas males invested their energy in cheliped growth, and the investment in chelipeds increased with increasing male body size. During the nonbreeding season, females and males conserved energy by reducing the size of pleons and chelipeds relative to their respective body sizes. Our results highlighted the sex-specific and season-dependent resource allocation and reproductive strategies of porcellanid crabs.
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Some porcellanid crabs (Decapoda Anomura) are known to escape predator crabs through a hair-trigger autotomy response when they are held by the cheliped only. The porcellanid crab Petrolisthes japonicus autotomizes chelipeds, and the post-autotomy cheliped movement functions like a lizard tail, which may increase predator distraction time, affording the prey more time to escape. However, the predatory encounters between prey and the relevant predators have not been observed to understand the benefits of autotomy in P. japonicus. The present study conducted 140 predation trials to evaluate the effectiveness of cheliped autotomy by P. japonicus in avoiding predation from its potential predator crab Gaetice depressus that commonly co-occurs with P. japonicus under cobble and boulders in intertidal zones. The predator attacked the prey in many trials (84%) and successfully grasped the prey in most attack cases (94%). The prey held by the body was able to escape the predator in a few cases (7%). When the prey was held by the cheliped only, the prey autotomized the cheliped and was able to escape the predator in many cases (75 and 83%, respectively), while the predator was eating the autotomized cheliped. The predator appeared to take a long time to handle the autotomized cheliped with its claws. Thus, our laboratory experiments demonstrated that P. japonicus exhibited high incidences of cheliped autotomy when it was held by the cheliped only, enabling it to escape the predator crab at high probabilities. Furthermore, post-autotomy movements may improve the efficacy of the antipredator defence mechanism of autotomized chelipeds in P. japonicus.
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Population and reproductive information of highly endemic species allow us to understand their underlying conservation problems. Aegla concepcionensis is restricted to a small and intervened Chilean basin, and its conservation status has varied from extinct in nature to endangered. We characterized their life history measuring population, morphological and environmental variables during an annual cycle capturing individuals with a catch and release method based on electroshocking. Although the maximum water temperature was related to the recruitment, it can be physiologically risky for the remaining macroinvertebrate community. The relationship between abundance and narrow pH variations indicates a condition of unstable equilibrium given the environmental deterioration by deforestation. Sex ratio was predominantly male biased during copulatory activity, and sexually dimorphic body size distributions supported the hypothesis of greater natural selection in females and sexual selection in males. The period of ovigerous females was comparatively restricted, late and consistent with an efficient ecophysiological strategy of reproductive investment. Patterns of pubertal moult, onset of morphometric maturity, absence of morphological differentiation in both sexes suggested that A. concepcionensis tends to maximize reproductive performance favouring the recovery of their relict populations.
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... Despite its apparent immediate advantages for survivorship, autotomy can have important negative consequences for the prey. The costs can include impaired locomotion, foraging, survivorship, and/or reproduction, in addition to the long-term energetic costs of replacing the autotomized appendage (Arnold 1988;Juanes & Smith 1995;Barr ıa & Gonz alez 2008). ...
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... Following autotomy, a diaphragm membrane rapidly seals off the wound to prevent blood loss (Paul 1915), and regeneration of autotomized limbs occurs within several molts. Induced autotomy is a commonly used practice in studies on crustaceans and is generally assumed to result in minimal stress to the organism (Allen and Levinton 2007; Barria and Gonzalez 2008; Patterson et al. 2009). The autotomized claw was weighed immediately after separation. ...
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IF an organ serves several functions, two or more of these may conflict at times in their contribution to the immediate fitness of the organism. Among lower invertebrates the tail is commonly used as a defence against predators but it has other functions such as fat storage, locomotion, respiration and courtship. Experiments have shown that tail loss can depress reproductive output in lizards1,2, but this has not been reported for natural populations. Data reported here suggest that loss of the tail frequently depresses reproductive output in natural populations of the plethodontid salamander Batrachoseps attenuatus, which is widespread in California. The dual use of the tail for energy storage and for protection may increase the adaptive flexibility of the salamander for coping with an unpredictable environment.
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Size increase at molt is reduced following multiple limb regeneration in the shore crabs, Hemigrapsus oregonensis and Pachygrapsus crassipes. Limb loss per se does not influence postmolt size. Effect of increasing number of regenerating limbs is additive. Postmolt size is programmed early in the premolt period of the preceding instar and is probably not readily influenced by water uptake mechanics at ecdysis. A simple model for growth, molting, and regeneration in heavily calcified Crustacea is developed from the viewpoint of adaptive strategies and energetic considerations.
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The Hiatt growth diagram relates post-moult to pre-moult size in crustaceans. Size in this context is most frequently defined by a linear measurement of length or width. Linear regression analysis of data on the Hiatt growth diagram is used to define growth constants. This assumes that growth factors (percentage increase in body size) at successive moults remain constant over the length of the line. Growth factors, however, decrease logarithmically at successive moults. Consequently, points on a Hiatt growth diagram are fitted better by a hyperbola than a straight line. The method of fitting an equation for a hyperbola is given. The best growth constant is the moult slope factor which is the factor by which the growth factor decreases at each successive moult. This is comparable with the intermoult period slope factor, the factor by which the intermoult period increases at each successive moult. These constants can be used to determine the moulting and growth sequences throughout the life of a crustacean.
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The dynamics of animal populations are determined, to a greater or lesser extent, by interactions with other organisms in the ecological web within which they are embedded - what is called the functional web. I propose a methodology for determining the structure of the functional web from a series of observations on the densities of constituent populations made over time - a multi-species time series. The approach is based on analysis of the R-function for each species; i.e., the relationship between the per-capita rate of change of each population and (1) the density of the population at different times in the past, providing clues to the order of population regulation, and (2) the densities of all potentially interacting species, providing clues to the inter-specific associations involved in population regulation. The application of the methodology is illustrated by application to a series of observations on Tengmalm's owls and three small mammals in Finland and, in a more cursory way, on spruce needleminers interacting with a guild of parasitoids in a Danish spruce plantation.
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Evolutionary trajectories under hard and soft selection can differ: in hard selection, the environments with the highest initial mean fitness contribute most individuals to the mating pool. In both hard and soft selection, evolution toward the optimum in a rare environment is much slower than it is in a common one. A subdivided population model reveals that migration restriction can facilitate local adaptation. However, unless there is no migration or one of the special cases discussed for panmictic populations holds, no geographical variation in the norm of reaction will be maintained at equilibrium. Implications of these results for the interpretation of spatial patterns of phenotypic variation in natural populations are discussed. -from Authors Dept. of Biol., Iowa Univ., Iowa City, IA 52242, USA.
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To understand the evolution of polyphenism. or adaptive switching between alternative developmental pathways and corresponding phenotypes, environmental factors governing the developmental switch, or cues, must be distinguished from factors affecting relative fitnesses. or selective agents. Under most conditions of purely spatial variation in environment, the maintenance of polyphenism requires adaptive developmental sensitivity to cues, which results in phenotype-environment matching. Other determinants of the maintenance of polyphenism under spatial variation include relative fitnesses of different phenotype-environment combinations, frequencies of alternative environments, and possible costs of polyphenism. Where variation is temporal, polyphenism is affected by the same parameters but is maintained more readily and may be favored without adaptive developmental sensitivity. Even where environmental conditions are sufficient for maintaining polyphenism, its evolution may be precluded by constraints on developmental sensitivity that prevent phenotype-environment matching, costs of developmental switching, or antagonistic pleiotropy that prevents independent evolution of alternative phenotypes. These factors could be highly taxon-specific, which would preclude generalizations concerning the distribution of polyphenism. However, the abundance of seasonal polyphenisms in multivoltine organisms suggests that where environments are favorable. developmental systems are often flexible enough for the establishment of simple polyphenisms. Elaborate polyphenisms may be restricted to circumstances in which the developmental switch occurs during very early development.
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Article
Autotomy, the voluntary shedding of limbs or other body parts in the face of predation, is a highly effective escape mechanism that has evolved independently in a variety of taxa. Crabs are unusual in that the limb that is typically sacrificed during autotomy, the anterior clawed cheliped, can also be used to ward off attack. During an encounter with a predator, an individual must thus decide between two mutually exclusive strategies: flight or fight. We used experimental predation encounters with two species of porcelain crabs (genus Petrolisthes) to examine the factors that influence the decision to flee versus fight and to determine the degree to which this decision is context-dependent. We found that autotomy was highly conditional. The characteristics that best predicted autotomy--smaller body size or female gender--also correlated with a lower escape rate by the alternative escape tactic, struggling and pinching the predator. Variation among individuals in the benefit of autotomy (relative to alternative tactics) appears to drive variation in propensity to autotomize. Porcelain crabs thus demonstrate adaptive flexibility, employing the costly strategy of autotomizing a limb as a last resort, only when their chance at success by struggling is low. Copyright 2005.
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Many environmental pollutants have toxic effects that can alter normal limb regeneration and molting in Crustacea. The most common effect of heavy metals is that of retardation of regeneration of limbs accompanied by a delay in ecdysis; in some cases regeneration is affected without altering the molt cycle. Chlorophenols and dithiocarbamates caused inhibition of regeneration without affecting molting in shrimp. Organic toxicants such as aromatic hydrocarbonsand dioxins also result in a decrease in the growth increment per molt, while DDT was found to accelerate regeneration and molting. A number of toxicants also produce morphological alterations in the regenerated limbs of crabs. These may be relatively minor, such as reduced number of pigment cells, setae, or tubercles in the regenerated limbs (mercury and cadmium), or may be more major deformities, such as abnormal bending in the limb or claw (tributyltin), or defects inchitin formation in the exoskeleton (diflubenzuron).
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This laboratory has previously called attention to the efficacy of loss of a critical number of limbs, either pereiopods or chelipeds, in stimulating precocious molts in Crustacea (Skinner and Graham, 1970 ; 1972) . The underlying mechanism for that stimulation is not yet known. The interval between limb loss and ecdysis is somewht longer than that undergone by animals triggered to molt by loss of eye stalks, which contain the neurosecretory X-organ sinus gland complex, the source of an as yet incompletely characterized molt inhibitory hormone (Bliss, 1956; Passano, 1960 ; Rao, 1965 ) . In most species, animals that have undergone pre cocious molts initiated by eyestalk removal die at or immediately following ecydsis. By contrast, mortality following limb loss is very low (Skinner and Graham, 1972). In recent years, removing a critical number of limbs has become a common means of inducing precocious molts. Although the minimal effective stimulus in the land crab, Gecarcinus lateralis, is five or more limbs, others have shown that loss of four limbs from the freshwater shrimp, Palaenzonetes kadiakensis, at all stages of the molt cycle except the late premolt period decreases the duration of the intermolt period by as much as 40% (Stoffel and Hubschman, 1974). Similarly, the number of animals molting within a given time period is directly correlated with the number of walking legs removed from the edible crab, Cancer pagurus (Bennett, 1973) and from the fiddler crab, Uca pugilator (Fingerman and Fingerman, 1974). The latter authors also showed that in specimens of fiddler crab triggered to undergo precocious molts by loss of eyestalks, subsequent autotomy of walking legs had the converse effect: the dura tion of the premolt period was significantly lengthened in animals from which three or more limbs were autotomized as compared to animals missing eyestalks only or missing eyestalks and one or two limbs. The present paper describes another set of interactions between regeneration and molting: loss of one or more partially regenerated limbs (primary regenerates) before a critical stage in the premolt period temporarily, for 10 to 14 days, decreases both growth and DNA synthesis of other primary regenerates remaining on the animal while the early stage of re-regeneration is initiated at the sites of the missing limbs. (Throughout the paper, we shall designate as primary regenerates those that form after autotomy of limbs and secondary regenerates those that form after autotomy of primary regenerates.) The duration of the premolt period is also
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If the Bermuda land crab, Gecarcinus lateralis, loses numerous walking legs or both chelipeds, it undergoes almost immediate preparations for molting with attendant limb regeneration. Injections of the arthropod-molting hormone, ecdysterone, have no effect in either intact animals or those missing legs.
Article
Molting and limb regeneration are tightly coupled processes, both of which are regulated by ecdysteroid hormone synthesized and secreted by the Y-organs. Regeneration of lost appendages can affect the timing and duration of the proecdysial, or premolt, stage of the molt cycle. Autotomy of all eight walking legs induces precocious molts in various decapod crustacean species. In the land crab Gecarcinus lateralis, autotomy of a partially regenerated limb bud before a critical period during proecdysis (regeneration index <17) delays molting so that a secondary limb bud (2 degrees LB) forms and the animal molts with a complete set of walking legs. It is hypothesized that 2 degrees LBs secrete a factor, termed limb autotomy factor-proecdysis (LAF(pro)), that inhibits molting by suppressing the Y-organs from secreting ecdysone. Molting was induced by autotomy of eight walking legs; autotomy of primary (1 degrees ) LBs reduced the level of ecdysteroid hormone in the hemolymph 73% by one week after limb bud autotomy (LBA). Injection of extracts from 2 degrees LBs, but not 1 degrees LBs, inhibited 1 degrees LB growth in proecdysial animals, thus having the same effect on molting as LBA. The inhibitory activity in 2 degrees LB extracts was stable after boiling in water for 15 min, but was destroyed by boiling 15 min in 0.1 N acetic acid or incubation with proteinase K. These results support the hypothesis that LAF(pro) is a peptide that resembles a molt-inhibiting hormone.
Autotomía de apéndices en el cangrejo estuarial Chasmagnathus granulata Dana, 1851 (Brachyura, Grapsidae) en la laguna Mar Chiquita
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LUPPI, T. A. & E. D. SPIVAK, 1996. Autotomía de apéndices en el cangrejo estuarial Chasmagnathus granulata Dana, 1851 (Brachyura, Grapsidae) en la laguna Mar Chiquita, Buenos Aires, Argentina. Atlantica, 18: 55-68.
Effect of tail loss on sprint speed and growth in newborn skinks, Niveoscincus metallicus
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Why does tail loss increase a lizard's later chances of being consumed by snake predators? Ecology
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Physiological limits to sustainable energy budgets in birds and mammals: ecological implications
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