Pagurus Criniticornis Research Articles

Diversity of decapod crustaceans in a neotropical coastal lagoon interconnected with the sea/estuary

Coastal lagoons are aquatic environments that are located at the coast-sea interface. Ecologically important, they harbor a high abundance of macroinvertebrates, especially decapod crustaceans. Therefore, the present study investigated the influence of physical factors on the diversity of decapod macrocrustaceans in a Neotropical coastal lagoon and prepared a list of species, with emphasis on new occurrences for this habitat. The study was conducted from January/2013 to January/2014 in a Neotropical coastal lagoon, seasonally connected to the sea. Ecological indices were estimated to understand biotic diversity; in addition, correlations and type II regression were performed on bivariate combinations to assess the degree of interaction between biotic vs. abiotic variables related to lagoon hydrodynamics. Finally, a partial least squares regression was performed to assess such relationships in the multivariate scenario. Field observations revealed a period of interconnection between the lagoon and the sea/estuary in March and complete isolation in October. The most abundant taxa were Penaeus sp., Callinectes sp., C. danae, Pagurus criniticornis and Clibanarius sclopetarius. In the month before total isolation, greater general abundance was recorded, and in the following month, greater diversity, dominance and equitability were recorded. In the multivariate model, only Maximum Wind Gust, Hourly Wind Speed and Minimum Monthly Astronomical Tide were relevant to explain the biotic variations in the lagoon. These results demonstrate that wind and tide can act as proxies for the hydrodynamic analysis of the lagoon in relation to the biotic factors investigated, since they promote seasonal events of opening and isolation of connectivity, contributing to the transport of individuals by carrying water masses. Still, the coastal lagoon presented itself as a place of shelter and foraging for the biota, with emphasis on the genera Penaeus and Callinectes that use the lagoons to complete their life cycle in the sea-estuary transition. This study indicates that coastal lagoons are essential for the life cycle of coastal crustaceans and should be included in management actions to conserve these areas and Neotropical crustacean species.

The effect of ocean acidification on the intertidal hermit crab Pagurus criniticornis is not modulated by cheliped amputation and sex

Impacts of the interactive effects of ocean acidification (OA) with other anthropogenic environmental stressors on marine biodiversity are receiving increasing attention in recent years. However, little is known about how organismal responses to OA may be influenced by common phenomena such as autotomy and sexual dimorphism. This study evaluated the long-term (120 days) combined effects of OA (pH 7.7), experimental cheliped amputation and sex on physiological stress (mortality, growth, number of molts, cheliped regeneration and startle response) and energy budget (lipid and calcium contents) in the intertidal sexually-dimorphic hermit crab Pagurus criniticornis. Crabs exposed to OA reduced survivorship (46%), molting frequency (36%) and lipid content (42%). Autotomised crabs and males molted more frequently (39% and 32%, respectively). Males presented higher regeneration (33%) and lower lipid content (24%). The few synergistic effects recorded did not indicate any clear pattern among treatments however, (1) a stronger reduction in lipid content was recorded in non-autotomised crabs exposed to low pH; (2) calcium content was higher in males than females only for autotomised crabs under control pH; and (3) autotomised females showed a proportionally slower activity recovery than autotomised males. Although our results suggest an effect of long-term exposure to low pH on the physiological stress and energy budget of Pagurus criniticornis, the physiological repertoire and plasticity associated with limb regeneration and the maintenance of dimorphism in secondary sexual characters may provide resilience to long-term exposure to OA.

Vulnerability of juvenile hermit crabs to reduced seawater pH and shading

Multiple simultaneous stressors induced by anthropogenic activities may amplify their impacts on marine organisms. The effects of ocean acidification, in combination with other anthropogenic impacts (apart from temperature) are poorly understood, especially in coastal regions. In these areas, shading caused by infrastructure development, such as harbor construction, may potentially interact with CO2-induced pH reduction and affect invertebrate populations. Here, we evaluated the effects of reduced pH (7.6) and shading (24h in darkness) on mortality, growth, calcification and displacement behavior to live predator (danger signal) and dead gastropod (resource availability signal) odors using juveniles of the hermit crab Pagurus criniticornis collected in Araçá Bay (São Paulo state, Southeastern Brazil). After a 98 day experimental period, both stressors had a significant interaction effect on mortality, and an additive effect on total growth. No difference in calcification was recorded among treatments, indicating that individuals were able to maintain calcification under reduced pH conditions. When exposed to odor of live predators, crab responses were only affected by shading. However, an interactive effect between both stressors was observed in response to gastropod odor, leading to reduced displacement behavior. This study shows how local disturbance impacts may enhance the effects of global environmental change on intertidal crustacean populations.

Shell use by sympatric hermit crab species in a seasonally open coastal lagoon in Northeastern Brazil

AbstractThere are gaps in what is known about the patterns of gastropod shell use by hermit crabs in Brazilian lagoon areas, especially in Northeastern Brazil. However, this is important because the understanding of selection patterns provides information on life history and eco‐evolutionary conceptions of paguroids. The present study investigated the use of gastropod shells occupied by Pagurus criniticornis and Clibanarius sclopetarius in a coastal lagoon seasonally connected to an estuary and to the sea, correlating eco‐evolutionary aspects and hydrodynamic characters. The study was carried out between February 2013 and January 2014. Hermit crabs and their shells were identified and measured (hermit crabs’ cephalothorax shield length and width, major propodus length and height, weight, shell total length and width, shell aperture length and width). Partial least squares regression was used to analyse the morphometric data. Additionally, a multinomial proportions test was performed to infer patterns (inter‐/intra‐specific) of shells’ occupation. Hermit crab species occupied a total of 13 types of shells, predominantly those of Neritina virginea (67.83%). The shell weight was the most important determinant of shell occupancy in the morphometric model (variable importance in projection >1). The proportions of N. virginea shells used were similar in both species of hermit crabs, except between the sexes of P. criniticornis. Presumably, the high utilization rate of N. virginea shells is related to its abundance and dispersal, and to the shells’ suitability for hermit crabs, which is reflected by the morphometric model, as well as by the hydrodynamics of the lagoon‐estuarine environment. The relative occupation of different types of shells for each species of hermit crabs studied appears to be associated with regulation by inter‐/intra‐specific competition, which fosters the co‐occurrence of those populations. These results endorse coastal lagoons as a refuge and recruitment area for aquatic fauna. In addition, it highlights a challenge in the management and conservation of paguroid species whose population dynamics depend on the resources coming from the Gastropoda community.

Sponge symbioses between Xestospongia deweerdtae and Plakortis spp. are not motivated by shared chemical defense against predators.

The recently described epizoic sponge-sponge symbioses between Xestospongia deweerdtae and two species of Plakortis present an unusual series of sponge interactions. Sponges from the genus Plakortis are fierce allelopathic competitors, rich in cytotoxic secondary metabolites, and yet X. deweerdtae flourishes as an epizoic encrustation on Plakortis deweerdtaephila and Plakortis symbiotica. Our objective in this study was to evaluate the hypothesis that X. deweerdtae grows epizoic to these two species of Plakortis due to a shared chemical defense against predators. We collected free-living individuals of X. deweerdtae and symbiotic pairs from a wide geographical range to generate crude organic extracts and a series of polarity fractions from sponge extract. We tested the deterrency of these extracts against three common coral reef predators: the bluehead wrasse, Thalassoma bifasciatum, the Caribbean sharpnose puffer, Canthigaster rostrata, and the white spotwrist hermit crab, Pagurus criniticornis. While the chemical defenses of P. deweerdtaephila and P. symbiotica are more potent than those of X. deweerdtae, all of the sponge species we tested significantly deterred feeding in all three generalist predators. The free-living form of X. deweerdtae is mostly defended across the region, with a few exceptions. The associated form of X. deweerdtae is always defended, and both species of Plakortis are very strongly defended, with puffers refusing to consume extract-treated pellets until the extract was diluted to 1/256× concentration. Using diode-array high performance liquid chromatography (HPLC) coupled with high-resolution mass spectrometry (LC-MS/IT-TOF), we found two secondary metabolites from P. deweerdtaephila, probably the cyclic endoperoxides plakinic acid I and plakinic acid K, in low concentrations in the associated—but not the free-living—form of X. deweerdtae, suggesting a possible translocation of defensive chemicals from the basibiont to the epibiont. Comparing the immense deterrency of Plakortis spp. extracts to the extracts of X. deweerdtae gives the impression that there may be some sharing of chemical defenses: one partner in the symbiosis is clearly more defended than the other and a small amount of its defensive chemistry may translocate to the partner. However, X. deweerdtae effectively deters predators with its own defensive chemistry. Multiple lines of evidence provide no support for the shared chemical defense hypothesis. Given the diversity of other potential food resources available to predators on coral reefs, it is improbable that the evolution of these specialized sponge-sponge symbioses has been driven by predation pressure.

What makes a good home for hermits? Assessing gastropod shell density and relative strength

ABSTRACTThe survival and reproductive success of hermit crabs is intrinsically linked to the quality of their domicile shells. Because damaged or eroded shells can result in greater predation, evaluating shell structure may aid our understanding of population dynamics. We assessed the structural attributes of Cerithium atratum shells through assessments of (a) density using a novel approach involving computed tomography and (b) tolerance to compressive force. Our goal was to investigate factors that may influence decision making in hermit crabs, specifically those that balance the degree of protection afforded by a shell (i.e. density and strength) with the energetic costs of carrying such resources. We compared the density and relative strength (i.e. using compression tests) of shells inhabited by live gastropods, hermit crabs (Pagurus criniticornis) and those found empty in the environment. Results failed to show any relationship between density and shell size, but there was a notable effect of shell density among treatment groups (gastropod/empty/hermit crab). There was also a predictable effect of shell size on maximum compressive force, which was consistent among occupants. Our results suggest that hermit crabs integrate multiple sources of information, selecting homes that while less dense (i.e. reducing the energy costs of carrying these resources), still offer sufficient resistance to compressive forces (e.g. such as those inflicted by shell-breaking predators). Lastly, we show that shell size generally reflects shell strength, thus explaining the motivation of hermit crabs to search for and indeed fight over the larger homes.

Olfactory selectivity in intertidal hermit crabs: aggregation behavior by Pagurus criniticornis (Decapoda, Anomura) in response to simulated predation on the gastropod Cerithium atratum

Hermit crabs respond to sensory cues that guide them toward limiting resources in marine and terrestrial environments. We examined the response of the common intertidal hermit crab Pagurus criniticornis (Dana, 1852) to simulated predation events on: (1) their principal shell donor Cerithium atratum (Born, 1778), (2) conspecifics, and (3) a sympatric bivalve; to test for the prevalence of olfactory specificity (i.e., attraction to a preferred gastropod species) or olfactory generality (i.e., attraction to a range of cues). Results showed that crabs were strongly attracted to gastropod baits but not to conspecifics or bivalves possibly reflecting greater motivation to acquire newly liberated resources than those more widely available (e.g., existing shells or food). We then examined the potential drivers of aggregative behavior by comparing the morphology and shell quality of attending individuals to an unbiased population. Although attending crabs were of a similar size and weight to the general population, their shells were of lower quality (adequacy, damage, and encrustation), suggesting that motivation to procure new shells is modulated by existing shell quality. The findings provide a clearer understanding of how hermit crabs acquire new resources and might have implications for the release and redistribution of other limiting resources within coastal environments.

An integrative approach-using field and laboratory data to characterize shell utilization and selection pattern by the hermit crab Pagurus criniticornis (Paguridae) from Anchieta Island, Brazil

The aim of this study was to characterize the pattern of gastropod shell occupation in the field and selection of shell size and type under laboratory conditions by the hermit crab Pagurus criniticornis (Dana, 1852), inhabiting the infralittoral area of Anchieta Island, Sao Paulo, Brazil. Hermit crabs were obtained monthly during 1999 by SCUBA diving. For experiments under laboratory conditions, samplings were performed in 2002. The hermit crabs occupied 16 species of gastropods shells. Cerithium atratum (Born, 1778) was the most occupied shell (89.31%), followed by Morula nodulosa (4.73%) (Adams, 1845). No difference was observed in the pattern of occupation between males and females. The equations that best demonstrated the relationship between hermit crabs and their shells were those that involved Shell Wet Weight (SWW) and Shell Internal Volume (SIV). The laboratory experiments were in accordance to the pattern of occupation observed in the field; the mean value of SAI (Shell Adequacy Index) recorded to the population studied was 1.13 with a trend to increase this value in the last size classes. The results obtained corroborate with the hypothesis of the occupation process of shells governed not only by availability of shells, but also by its architecture. In addition, the shell stock in the area is one another important condition related to the exhibited pattern of shell occupation by P. criniticornis, and allows the stable coexistence among the island assemblage. The pattern of occupation observed promotes a high reproductive profile for the population studied, maximizing the populational growth.

Intra-specific competition drives variation in the fundamental and realized niches of the hermit crab, <I>Pagurus criniticornis</I>

The difference between preferred and available resources within natural environments can be viewed as the disparity between fundamental and realized niches. We employ this concept to examine intra-specific sexual variation in the shell-size relationships of the hermit crab Pagurus criniticornis (Dana, 1852) from two treatments: (1) a natural unbiased population (i.e., realized niche); and (2) a group subjected to free-choice experiments that were able to select a preferred shell from a selection of high-quality shells (i.e., fundamental niche). Crab-shell relationships for both treatments suggest that males and females select shells proportional to their size. The relationships between crab size and preferred shell weight (i.e., fundamental niche) derived from free-choice experiments enabled the calculation of a shell adequacy index (SAI) for all individuals from both treatments. A strong interaction between SAI values across sex and treatment (♂Free choice = ♀Free choice = ♂Population > ♀Population) suggested that non-ovigerous females may experience a considerable niche disparity in their natural habitats while ovigerous females tend to inhabit shells with a greater prevalence of damaged shell apices. Results suggest a competitive hierarchy whereby males out- compete females for access to high-quality shells. Despite niche disparities, P. criniticornis typically occupied shells of good condition (low damage and encrustation), suggesting that resource limitation may not be as severe as that reported for other hermit crab populations. Our data provide insights into intra-specific competition that reflect the ability of individuals to win and hold high-quality resources within resource-limiting environments.

Behavioral trade-off on shell exchange and exploration of the white spotwrist hermit crab <i>Pagurus criniticornis</i> (Crustacea, Anomura, Paguridae)

Behavioral trade-off on shell exchange and exploration of the white spotwrist hermit crab <i>Pagurus criniticornis</i> (Crustacea, Anomura, Paguridae)

Spatial and temporal variation in the predation risk for hermit crabs in a subtropical bay

Comparing the spatial and temporal dynamics of predation in turbid coastal waters can be notoriously difficult. We used a tethering approach to directly assess variation in predation risk for the intertidal hermit crab Pagurus criniticornis and the gastropod Cerithium atratum in a subtropical bay. Predation outcomes were used to test the effects of; (1) microhabitat (i.e., intertidal mud vs. intertidal fringe), (2) season (summer vs. winter), and (3) the type of domicile shell occupied (C. atratum vs. Tegula viridula). Predation varied across microhabitat for both species, with unambiguous cases more prevalent at the intertidal fringe than the mud habitat (20.6% and 11.8% greater for the hermit crab and gastropod, respectively). This pattern related to the abundance of the portunid crab predator Callinectes danae (~2.2 times greater in the fringe vs. mud). There was similar variation among seasons for P. criniticornis, with cases of predation 51.3% more prevalent in summer than winter, again matching the abundance of C. danae (greater in summer than winter). Closer examination of the type of shell damage suggests differences in the way that predators might access prey across spatial and temporal scales. The high prevalence of damaged shell apertures (indicative of peeling) suggests possible targeting of this species by smaller individuals or females. Although there was no seasonal difference in the size of predators, the proportion of males was greater during summer and this may constitute a driver of variable predation pressure. Lastly, the risk of predation was also related to domicile shell morphology, with crabs inhabiting C. atratum shells 27.3% more likely to be predated upon than those inhabiting T. viridula shells. Combining the outcomes of our experiments, we suggest that changes to intertidal habitat configuration (e.g., the proliferation of hard substrates through, erosion or harbor and break wall construction) as well as factors that alter the supply of appropriate domicile shells (e.g., effects of acidification on calcifying organisms) could alter predation risk for hermit crabs and other soft bottom species.

Subjective resource value and shell abandoning behavior in hermit crabs

Understanding the factors that motivate animals to hold or abandon a valuable resource is a central goal of behavioral ecology, the study of which will grow more important in the face of increasingly frequent extreme events. We compared the shell-abandoning behavior of the sympatric hermit crabs Clibanarius antillensis and Pagurus criniticornis in response to simulated burial and entrapment by rocks and other debris. While these hazards are relatively common in dynamic intertidal habitats, the frequency and severity of such disturbance are increasing due to human activity. While both species exhibited shell-abandoning behavior in response to experimental burial, it was far more prevalent for the soft-bottom dwelling species P. criniticornis (90%) when compared to the rocky bottom inhabitant C. antillensis (55%). Simulated entrapment experiments highlighted further differences in species response, with the decision to abandon domicile shells again far more common for P. criniticornis (80%) than it was for C. antillensis (10%). Given the tendency for P. criniticornis to abandon its shell, we subsequently focused on this species to test specific hypothesis about subjective resource value in hermit crabs. There was no difference in the tendency for this species to abandon optimal or sub-optimal (poorly-fitting) shells when faced with the immediate and potentially fatal risk of burial. This contrasted the response seen under conditions of entrapment, whereby individuals inhabiting sub-optimal shells abandoned them more rapidly and in greater numbers than those inhabiting optimal shells. Combining these two outcomes, we suggest that hermit crabs subjectively assess shell-value and respond according to the nature of the disturbance and its associated risks (i.e., high-value shells are abandoned in minutes under conditions of burial; but are held for hours under the less severe conditions of entrapment). In effect, the results show that extrinsic environmental cues can be just as important to decision making processes as those intrinsic cues that govern an animal's physiological condition. The contrasting behavior of the two hermit crabs to the movement of mud and other debris may lead to a higher survivorship of P. criniticornis than C. antillensis where activities such as dredging and harbor construction are intensifying along developing coastlines.

Is shell partitioning between the hermit crabs Pagurus brevidactylus and Pagurus criniticornis explained by interference and/or exploitation competition?

The effect of crab behaviour on shell-use dynamics was analysed, comparing both interference and exploitation behaviours between the hermit crabs Pagurus criniticornis and Pagurus brevidactylus. Although these species exhibited microhabitat separation, with P. criniticornis dominating (100%) in sandy substrates and P. brevidactylus (80%) on rocky shores, they overlapped in the rocky shore/sand interface (P. criniticornis, 53%; P. brevidactylus, 43%). Pagurus criniticornis occupied shells of Cerithium atratum in higher frequencies (84%) than P. brevidactylus (37%), which was hypothesized to be a consequence of competitive interactions combined with their ability to acquire and/or retain this resource. The species P. criniticornis was attracted in larger numbers to simulated gastropod predation events than was P. brevidactylus, which, on the few occasions that it moved before P. criniticornis, tended to be attracted more rapidly. Interspecific shell exchanges between these species were few, suggesting the absence of dominance relationships. The shell-use pattern in this species pair is thus defined by exploitation competition, which is presumed to be intensified in areas of microsympatry. These results differ from other studies, which found that interference competition through interspecific exchanges shapes shell use, indicating that shell partitioning in hermit crabs is dependent on the behaviour of the species involved in the contests.

Are the preference and selection patterns of hermit crabs for gastropod shells species- or site-specific?

Experimental analyses of hermit crabs and their preferences for shells are essential to understand the intrinsic relationship of the crabs' dependence on shells, and may be useful to explain their shell use pattern in nature. The aim of this study was to evaluate the effect of crab species and site on the pattern of shell use, selection, and preference in the south-western Atlantic hermit crabs Pagurus brevidactylus and Pagurus criniticornis, comparing sympatric and allopatric populations. Differently from the traditional approach to evaluate shell preference by simply determining the shell selection pattern ( i.e., the number of shells of each type selected), preference was defined (according to [Liszka, D., Underwood, A.J., 1990. An experimental design to determine preferences for gastropod shells by a hermit-crab. J. Exp. Mar. Biol. Ecol., 137(1), 47–62]) by the comparison of the number of crabs changing for a particular shell type when three options were given ( Cerithium atratum, Morula nodulosa, and Tegula viridula) with the number of crabs changing for this same type when only this type was offered. The effect of crab species was tested at Cabelo Gordo Beach, where P. brevidactylus was found occupying shells of C. atratum, M. nodulosa, and T. viridula in similar frequencies, whereas P. criniticornis occupied predominantly shells of C. atratum. In laboratory experiments the selection patterns of the two hermit-crab species for these three gastropods were different, with P. criniticornis selecting mainly shells of C. atratum, and P. brevidactylus selecting more shells of M. nodulosa. The shell preference was also dependent on crab species, with P. criniticornis showing a clear preference for shells of C. atratum, whereas P. brevidactylus did not show a preference for any of the tested shells. The effect of site was tested for the two species comparing data from Cabelo Gordo to Preta ( P. brevidactylus) and Araçá beaches ( P. criniticornis). The pattern of shell use, selection, and preference was demonstrated to be dependent on site only for P. brevidactylus. The results also showed that the shell use pattern of P. criniticornis can be explained by its preference at both sites, whereas for P. brevidactylus it occurred only at Cabelo Gordo, where the absence of preference was correlated with the similar use of the three gastropod species studied. Finally, the results showed that the shell selection pattern cannot be considered as a measure of shell preference, since it overestimates crab selectivity.

Influence of prior experience on shell selection by the white spotwrist hermit crab Pagurus criniticornis (Crustacea: Paguridae)

Individuals of Pagurus criniticornis in a free-choice situation were experimentally tested under different laboratory conditions. In order to assess the effect of recently occupied shells on the size- and type-preference by hermit crabs, individuals were held for 30 days under one of the following two conditions: (1) excess of shells and (2) absence of shells. The crabs were then allowed to select shells from a wide array of empty gastropod shells of the two most-occupied species, as observed previously in the field: Cerithium atratum and Morula nodulosa. Preferred shell type (species) and size (shell aperture width and length) were correlated with hermit-crab size. The crabs showed a strong (100%) preference for C. atratum shells, demonstrating that recent and past experience did not influence either shell-type or shell-size preferences in this pagurid.

Population and reproductive features of the western Atlantic hermit crab Pagurus criniticornis (Anomura, Paguridae) from Anchieta Island, southeastern Brazil

The population of the hermit crab Pagurus criniticornis (Dana, 1852) was studied based on seasonal abundance, size frequency distribution, sex ratio, reproductive period, fecundity and shell relationship. Specimens were collected monthly by SCUBA diving in the infralittoral area of Anchieta Island, Ubatuba. A total of 1,017 individuals was analyzed. Animal size (minimum and maximum shield length, respectively) was 0.7 and 2.9 mm for males, 0.6 and 2.8 mm for non-ovigerous females, and 1.0 and 2.5 mm for ovigerous females. The sex ratio was 1:1.29. Sexual dimorphism was recorded by the presence of males in the largest size classes. Ovigerous females were captured during all months along the year, with percentages varying from 8% (July) to 84.3% (February) in relation to the total females collected. Mean ± SD fecundity was 168 ± 125 eggs and tended to increase with increasing hermit size. Shells of four gastropod species [Cerithium atratum (Born, 1778), Morula nodulosa (Adams, 1845), Anachis lyrata (Sowerby, 1832) and Modulus modulus (Linnaeus, 1758)] were occupied by ovigerous females of P. criniticornis but fecundity was not significantly different in relation to the different shell types. The profile showed continuous and intense reproduction of P. criniticornis probably related to strategies developed to compensate for interspecific competition in the studied insular area.

Parasitization of the white spotwrist hermit crab, Pagurus criniticornis (Dana, 1852) (Decapoda, Anomura), by the rhizocephalan barnacle Peltogasterella socialis (Müller, 1863) (Cirripedia, Rhizocephala) from southeastern Brazil

AbstractHermit crabs of the species Pagurus criniticornis (Dana, 1852) parasitized by the poorly known colonial rhizocephalan Peltogasterella socialis (Müller, 1863), were collected in the infralittoral rocky/sandy area of Anchieta Island (São Paulo), Brazil. We report the presence and pattern of occurrence of this rhizocephalan in the P. criniticornis population. The hermit crabs were obtained monthly during 1999 by two people using SCUBA methods. A total of 992 hermit crabs were captured and examined for rhizocephalans. The studied population showed non-normal size distribution and only 2.11% of the sample specimens carried externae of P. socialis. The parasite occurrence was seasonal and varied with host size. Some signs of feminization were observed on P. criniticornis pleopods (elongation of the endopod and reduction of the exopod of pleopods for males and reduction in the size of endopods for females). This is the first report on this parasite/host relationship for this South American host species. This is the first record of P. socialis (Müller, 1863) subsequent to the species' description, and possible occurrence of the parasite on hermit crabs in the Bahamas is also reported.

Embryonic development and duration of incubation period of tropical intertidal hermit crabs (Decapoda, Anomura)

The description of the embryonic development of the hermit crabs Clibanarius antillensis Stimpson, 1859, C. sclopetarius (Herbst, 1796), C. vittatus (Bosc, 1802), and Pagurus criniticornis (Dana, 1852) and preliminary observations on the development of Pagurus brevidactylus (Stimpson, 1858) and Paguristes tortugae Schmitt, 1933 were done. The analysis of the external morphology of the embryos of the studied species allowed the identification of seven stages: Stage 1, Zygote and cleavage; Stage 2, Homogeneous mass (advanced cleavage and gastrulation); Stage 3, Initiation of the germinal disc (yolk-free area); Stage 4, Percentage of yolk-free area from 5% to 50-70%; Stage 5, Eye pigmentation (comma-shape) and heart beating; Stage 6, Percentage of yolk-free area from 70-80% to 95%) and eye development to a darkened irregularly-rounded shape; Stage 7, Zoea visible and hatching. Despite all stages were recorded in all species, interespecific differences were recorded in relation to zygote size and embryo color; cleavage, absolute and relative developmental time, and moment eye pigmentation appeared. Such morphological differences may be associated to variations in the yolk amount and composition and reveal different reproductive strategies at least between P. criniticornis and all studied species of Clibanarius.

Reproductive behavior of intertidal hermit crabs (Decapoda, Anomura) in southeastern Brazil

The reproductive behavior of four intertidal hermit crab species [Clibanarius antillensis Stimpson, 1859, C. sclopetarius (Herbst, 1796), C. vittatus (Bosc, 1802), and Pagurus criniticornis (Dana, 1852)] was studied in São Sebastião Channel, southeastern Brazil. The overall behavior followed previous descriptions for Diogenid and Pagurid hermit crabs but some particular differences were recorded. Male to male agonistic encounters over females and guarding behavior were more common to C. sclopetarius, C. vittatus, and Pagurus criniticornis. During guarding, males clearly grasped females' chelipeds, eyestalks, and the margins of their shell apertures. This oblique guarding and, simultaneously, accessing behavior (OGAP) has never been described for hermit crabs and was more common to C. sclopetarius and C. vittatus. Pagurus criniticornis did not present the typical jerking behavior of pagurids. Multiple copulations between a single pair were recorded in all species while in only one occasion a female of C. vittatus was observed copulating with two males. In the post-copulatory behavior males held females for some time and, after that, they were left inactive and sometimes totally to partially buried in the substrate. In mating pairs of all species males were larger than females and two individuals (out of 23) of C. antillensis, one (out of 5) of C. sclopetarius and one (out of 3) of C. vittatus, which courted successfully as males fertilizing females' eggs, were demonstrated to be intersex, with both male and female gonopores.

Predation on gastropods by shell-breaking crabs: effects on shell availability to hermit crabs

This study addressed the effect predation on gastropods by shell-breaking crabs has on shell availability to hermit crabs. (1) Variable rates of predation on the gastropod Cerithium atratum were recorded within and among the crab species Menippe nodifrons, Panopeus occidentalis, Eriphia gonagra, and Callinectes danae. Predation rate was more dependent on crab size than on crab species, and all predators consumed the largest individuals of C. atratum available. Comparison of M. nodifrons and C. danae predation of the rocky shore gastropods Stramonita haemastoma, Morula nodulosa, and Tegula viridula revealed that only M. nodifrons consumed M. nodulosa, while both crabs preyed more heavily upon S. haemastoma than on T. viridula. M. nodifrons crushed larger individuals of Stramonita. (2) Prey subjected to M. nodifrons and C. danae presented different criti- cal sizes (S. haemastoma > T. viridula = M. nodulosa. (3) The investment in shell material varied among gastropod species (M. nodulosa > T. viridula > S. haemastoma) and was inversely related to their consumption rate by M. nodifrons. (4) M. nodifrons generally crushed its prey, C. danae and E. gonagra used both peeling and crushing, and P. occidentalis generally peeled. Crushing was usually lethal, while peeling attempts resulted in higher prey survival. Predatory strategy was dependent on relative prey size: small shells were crushed, medium-sized were peeled, and large ones were non- destructively preyed upon through the aperture. (5) Most shells used by the hermit crab Pagurus criniticornis (68%) in nature presented damage very similar to that recorded for gastropods preyed upon experimentally, indicating that this kind of predation makes new shells available to hermit crabs. (6) M. nodifrons showed a clear preference for the gastropod C. atratum over the hermit crab P. criniticornis, suggesting differential predation pressures in nature. In conclusion, shell availability to hermit crabs was demonstrated to be dependent on predator species and size, gastropod architec- tural defenses, and on the relative predator-prey size, which determined the predatory strategy and the damage inflicted on the shells.