RESUMEN

Plastic is the most pervasive element of marine waste, with harmful impact on wildlife. By using iEcology (i.e., internet Ecology, use of online data sources as a new tool in ecological research), we report on the emergence of a novel behaviour in hermit crabs related to the use of plastic or other anthropogenic materials as protective shells. We analysed images posted on social media to identify 386 individuals with artificial shells - mainly plastic caps (85 %). We report that 10 of the world's 16 terrestrial hermit crabs use artificial shells, a behaviour observed on all of the Earth's tropical coasts. Four non-exclusive mechanisms may drive individual choice for artificial shells: sexual signaling, lightness of artificial shells, odour cues, and camouflage in a polluted environment. Further research is needed to determine the impact of this behaviour on hermit crab evolutionary trajectories.

Asunto(s)

RESUMEN

Heterochely denotes the presence of dissimilarly sized chelipeds on opposite sides of the body, a prevalent occurrence in diverse crustaceans. Conversely, heterometry pertains to the quantifiable disparities in size between these chelipeds. Both chelipeds hold pivotal roles in activities such as foraging, mating, and defense. Consequently, individuals of both genders in heterochelic species exhibit this morphological pattern. Previous studies have identified sexual dimorphism in cheliped size, with males displaying larger major chelipeds compared to females, albeit solely relying on propodus length as a size proxy and focusing solely on the major cheliped. In our study, we meticulously examined 190 specimens of the common European hermit crab Pagurus bernhardus from two collections. We sought to elucidate allometric relationships and assess whether heterometry exhibited sex-based differences when adjusting for body size by using ratios. Our findings revealed that male chelipeds displayed hyperallometric growth relative to females, and all three calculated heterometry indices exhibited significant disparities between the sexes. Consequently, male specimens exhibited larger major and minor chelipeds, even when theoretically matched for body size with females. This phenomenon may be attributed, among other factors, to male-male contests. Should indirect mate selection favor males with larger chelipeds in proportion to their body size, this dynamic could potentiate sexual selection in their favor.

Asunto(s)

RESUMEN

There is currently a strong scientific consensus that recent global change of climate, including the global warming, seriously damage ecosystems of both lands and oceans. Here, I review recent drastic northern expansion of distribution of tropical land hermit crabs (Coenobita) into temperate Japan. Seto Marine Biological Laboratory of Kyoto University has a long history (97 years) and has been conducting various programs of long-term monitoring survey on coastal biota. A part of the results is also introduced here. Seventeen species of land hermit crabs are known from tropical regions worldwide, and seven species are known in Japan, which are mainly distributed in tropical region of Japan. Recent intensive studies on coastal areas of Japan have shown that many juveniles and small individuals of land hermit crabs are found during warm season in temperate regions. The finding of the species that were identified by DNA analysis as Coenobita rugosus and C. purpureus might be an indication for the global warming effect. Further, I here introduce the model of northern limit of distribution proposed by Gorodkov (1986) which explains change of detailed structure of population toward the limit of distribution. Moreover, I here propose the model of stages of adaptation of tropical species to temperate zone through ecological and evolutional times. These two models are useful and helpful to understand the things happen in populations in the limit of distribution and, therefore, useful for conservation of species and biological communities.

Asunto(s)

RESUMEN

Trindade and Martin Vaz (TMV) is a highly isolated, oceanic volcanic archipelago located some 1200 km off the Brazilian coast and about 4200 km away from the nearest African coast. For almost 100 years Calcinus tibicen (Herbst, 1791) was the only hermit crab species known from TMV. From 2012 to 2018, 263 daytime SCUBA diving and intertidal samplings conducted at TMV yielded 1075 paguroid specimens in 10 species, three of which are established herein as new species: Iridopagurus martinvaz sp. nov., Nematopagurus micheleae sp. nov., and Pagurus carmineus sp. nov. Iridopagurus margaritensis García-Gómez, 1983, and Phimochirus leurocarpus McLaughlin, 1981, both only known from the northern hemisphere, are recorded for the first time from the southwestern Atlantic. Opportunity was taken herein to include hitherto unreported or little known specimens from along the Vitória-Trindade Seamount Chain, namely, Dardanus venosus H. Milne Edwards, 1848, Nematopaguroides pusillus Forest de Saint Laurent, 1968, Pagurus provenzanoi Forest de Saint Laurent, 1968, and Phimochirus holthuisi (Provenzano, 1961). The lectotype of Pagurus venosus H. Milne Edwards, 1848 is designated as the neotype for the obscure Pagurus arrosor divergens Moreira, 1905, which thus becomes an objective junior synonym of the former. A list of all paguroid species known from the tropical southern-central Atlantic oceanic archipelagoes and islands (Ascension, Cape Verde, Fernando de Noronha, Gulf of Guinea, Rocas Atoll, Saint Helena, Trindade and Martin Vaz) with their gross distribution in the Atlantic Ocean is provided. Investigation on the existence of patterns of geographic distribution for the paguroid fauna of the tropical southern-central Atlantic oceanic islands showed that 70% percent of the paguroids from TMV are western Atlantic in origin and 30% endemic. No amphi-Atlantic paguroid species are known from TMV. Conversely, the affinity of Ascension's (33%) and Saint Helena's (50%) paguroids is with the eastern Atlantic; no western Atlantic paguroids have been reported from these two islands so far. Exploration on the existence of trends of correlation between islands area and species richness through the Spearman's coefficient of correlation showed that the patterns in the number of paguroid species cannot be explained by variation in island area alone (rs = 0.4728; p = 0.28571).

Asunto(s)

RESUMEN

The present study aimed to elucidate the population dynamics of land hermit crabs on the coast of the Boso Peninsula, Chiba Prefecture, Japan, which is the northern limit of their geographical distribution. We conducted monthly field surveys at four sites from April 2012 to December 2014 and visually searched for crabs. Laboratory experiments were also conducted to evaluate the overwintering ability of two species, Coenobita purpureus and C. rugosus, which were detected during the field surveys; adult crabs and laboratory-raised juveniles were exposed to low-temperature conditions that simulated the in situ temperatures during the early overwintering period. Newly landed juveniles first appeared in August. They were identified as either C. purpureus or C. rugosus, with C. purpureus being the dominant species. Early juveniles grew until October. The abundance of early juveniles decreased with decreasing air temperatures, and dead individuals were found during the overwintering period. The low-temperature tolerance ability of C. purpureus was stronger than that of C. rugosus. Some crabs successfully overwintered, and all were identified as C. purpureus. The growth and overwintering success of juveniles varied among the survey sites depending on the local temperature regime. Our results highlight the frontier for expanding the northern geographical distribution of land hermit crab populations by the colonization and overwintering success of C. purpureus.

RESUMEN

Tarantulas and hermit crabs are commonly kept pets and are underappreciated in veterinary medicine. Safe handling, biology and husbandry, diagnostic techniques, anesthesia, fluid therapy, disorders, and euthanasia are covered in this article. Current research is applied to these topics to keep practitioners abreast with the best medicine for these creatures.

Asunto(s)

RESUMEN

The Coenobitidae (Decapoda, Anomura, Paguroidea) is a taxon of hermit crabs that includes two genera with a fully terrestrial life style as adults. Previous studies have shown that Coenobitidae have evolved a sense of spatial odor localization that is behaviorally highly relevant. Here, we examined the central olfactory pathway of these animals by analyzing central projections of the antennular nerve of Coenobita clypeatus, combining backfilling of the nerve with dextran-coupled dye, Golgi impregnations and three-dimensional reconstruction of the primary olfactory center, the antennular lobe. The principal pattern of putative olfactory sensory afferents in C. clypeatus is in many aspects similar to what have been established for aquatic decapod crustaceans, such as the spiny lobster Panulirus argus. However, there are also obvious differences that may, or may not represent adaptations related to a terrestrial lifestyle. In C. clypeatus, the antennular lobe dominates the deutocerebrum, having more than one thousand allantoid-shaped subunits. We observed two distinct patterns of sensory neuron innervation: putative olfactory afferents from the aesthetascs either supply the cap/subcap region of the subunits or they extend through its full depth. Our data also demonstrate that any one sensory axon can supply input to several subunits. Putative chemosensory (non-aesthetasc) and mechanosensory axons represent a different pathway and innervate the lateral and median antennular neuropils. Hence, we suggest that the chemosensory input in C. clypeatus might be represented via a dual pathway: aesthetascs target the antennular lobe, and bimodal sensilla target the lateral antennular neuropil and median antennular neuropil. The present data is compared to related findings in other decapod crustaceans.

RESUMEN

Hermit crabs (Anomura: Paguroidea) distribution patterns in the Colombian Caribbean Sea. Hermit crabs represent the marine life in the Colombian Caribbean, and are important for the dynamic equilibrium maintenance in ecosystems, the ecological interactions and their impact on food web stability. Generally, in order to come up with some conservation strategies, strong bio-geographical information is needed for policies definition. With this aim, this study analyzed the distribution patterns of hermit crabs in the Colombian Caribbean Sea, through classification and spatial ordination multivariate analyses, using historical records from years 1916 to 2006. Besides, the world distribution of Colombian species and their geographic affinity in the Caribbean and Western Atlantic were identified. The results show deep differences between coastal and continental slope faunas, and latitudinal differences in the assemblages, with the identification of three groups: Northeast, Center and Southwest. The differences in faunal composition that support these three groups were determined. Based on maps of the Colombian marine ecosystems, it was found that the main factors affecting the distribution of hermit crabs were the Caribaná slope (depth), water-mass temperature, Guajira sea-grass beds, and particular conditions of “Coralline Archipelagos” and “Darién” eco-regions. Colombian hermit crab fauna is more related to the North Atlantic and the Antilles, than to the South Atlantic and the Gulf of Mexico. Additionally, geographical sub-provinces in which Colombia is included, these were found as transition zones among Northern and Austral subprovinces of the Greater Caribbean.

Los cangrejos ermitaños son un grupo representativo de la fauna marina del Caribe colombiano, además, son importantes en el mantenimiento del equilibrio dinámico, en los ecosistemas por sus interacciones ecológicas y también por el impacto en la estabilidad de las redes tróficas. Sus patrones de distribución se identificaron mediante análisis multivariados de clasificación y ordenación espacial, se usaron registros históricos desde 1916 hasta el 2006. Los resultados indican diferencias por profundidad entre la fauna costera y la del talud continental y diferencias en la distribución latitudinal, en donde se encontraron tres grupos: Noreste, Centro y Suroeste, sustentados por diferencias en la composición faunística. Con base en los mapas de ecosistemas marinos de Colombia, se determinó que los principales factores que afectan su distribución son la influencia del talud Caribaná (profundidad), la temperatura de las masas de agua, las praderas de pastos marinos de la Guajira y las condiciones particulares de las ecorregiones Archipiélagos coralinos y Darién. Se identificó la distribución mundial de las especies colombianas y su afinidad geográfica, y se encontró mayor afinidad con el Atlántico norte y las Antillas que con el Atlántico sur y el Golfo de México, asimismo, las subprovincias geográficas que incluyen a Colombia son zonas de transición dentro de la subprovincias septentrionales y australes del Gran Caribe.

Asunto(s)

RESUMEN

Coexisting hermit crabs may competitively interact for shells and microhabitats, mainly when shell availability is habitat-related. Three species of Clibanarius (C. antillensis, C. sclopetarius, and C. vittatus) coexist in the intertidal region of Pernambuco Islet, Araçá Region, São Sebastião Channel, southeastern Brazil. This study evaluated crab preferences for four substrate types used by these species in nature (rocky shore, pebbles, sand, and mud) in allopatric (single species) and sympatric (three species) treatments in simulations of high tide and low tide. The substrate preference of the three hermit crabs did not vary between low and high tide situations. At low tide the crabs either moved into holes in the highly complex rocky substrate or buried themselves in mud. Substrate selection may explain the patterns of substrate use in nature only for C. vittatus. Clibanarius antillensis and C. sclopetarius showed closer similarities in the pattern of substrate selection in the sympatric treatment with the substrate use in nature than in allopatric treatment, indicating a positive influence (dependence) of the presence of one species on the presence of another. Use of sub-optimal substrates, mainly by C. antillensis, may be caused by other factors such as its low desiccation tolerances. If competition for space takes place among these species, it would be more intense between C. sclopetarius and C. vittatus given their higher overlap in substrate preference than between them and C. antillensis.

Espécies de ermitões coexistentes podem realizar interações competitivas por conchas e microambientes, principalmente quando a disponibilidade de conchas está relacionada aos microambientes. Três espécies de ermitões do gênero Clibanarius (C. antillensis, C. sclopetarius e C. vittatus) coexistem na região entremarés da Ilha de Pernambuco, região do Araçá, Canal de São Sebastião, Sudeste brasileiro. Este estudo avaliou a preferência dos ermitões por quatro tipos de substrato (costão, seixos, areia e lodo) utilizados por eles na natureza em tratamentos alopátricos (uma espécie) e simpátricos (três espécies) em situações simuladas de marés alta e baixa. A preferência por tipos de substrato não variou entre as simulações de marés alta e baixa. Na maré baixa, os ermitões deslocaram-se para buracos e fendas ou enterraram-se no lodo. A seleção de substratos pode explicar o padrão de uso de substratos na natureza apenas para C. vittatus. Clibanarius antillensis e C. sclopetarius apresentaram maiores similaridades na seleção de substratos no tratamento simpátrico e no uso na natureza que no tratamento alopátrico, indicando influência positiva (dependência) da presença de uma espécie em função da outra. O uso de substratos subótimos no campo, principalmente por C. antillensis, pode ter sido causado por outros fatores, como suas baixas tolerâncias à dessecação. Se houver competição por substratos entre as três espécies, ela será mais intensa entre C. sclopetarius e C. vittatus, dada a maior sobreposição na preferência por substratos entre essas espécies que entre elas e C. antillensis.

RESUMEN

In the sessile hermit crab Discorsopagurus schmitti, four different feeding techniques are described: antennary beating, body-trap feeding, feeding on wafting particles, and scraping. This species' potential for being a generalist in its diet and opportunistic in its foraging behavior certainly opened the way for a sedentary life, allowing occupation of the unusual microhabitat provided by attached polychaete tubes. Nonetheless, deposit-feeding and/or browsing are the most conspicuous foraging strategies, when both the percentage of behavioral acts performed and the quantity of potential food collected are estimated. The question still remains of whether species' reliance on benthos as the main food source should be regarded as an efficient strategy for a sedentary life, or simply as the heritage of its not-so-remote past as a mobile, and shell-dwelling hermit crab.

RESUMEN

The paleobiogeographic histories of three North Atlantic hermit crab lineages were compared with a single-copy DNA-DNA hybridization phylogeny of their symbiotic hydroid genus Hydractinia to test hypotheses of shared history between these host and symbiont lineages. A survey of the geologic literature suggests that two vicariance events in the Quaternary are responsible for existing range disjunctions of the host hermit crab lineages. The Hydractinia phylogeny revealed two distinct clades, one with a primarily northern and the other with a primarily southern distribution. In two of three cases, hydroids associated with closely related hermits on both sides of the range disjunction appear as sister taxa in the phylogeny. A linear scaling between a measure of hydroid sequence divergence and independent geologic estimates of the timing of the vicariant events believed to have established the hermit crab range disjunctions is consistent with the claim of temporal coincidence of cladogenic and vicariance events. These findings provide evidence for shared history of symbiotic associations in two of the three cases.

RESUMEN

Two populations (salt marsh and seagrass bed) of the hermit crab Pagurus longicarpus were sampled to examine associations between shell characteristics and egg production. Multivariate statistical analyses controlled for crab size and time of year, variables that otherwise could be confounded with shell effects. Although correlations between shell characteristics and reproduction existed in both populations, generalizations could not be made because associations varied within and between populations. Shell species was not associated with a female's reproductive state (i.e., whether or not she was barren when sampled) in either population. In the seagrass population, medium-large and large females occupying severely damaged or fouled shells were half as likely to be reproductive as females occupying other shell conditions. However, there was no association between shell condition and reproductive state for small and small-medium females in the seagrass population or among all females in the salt marsh population. In the seagrass population, small through medium-large reproductive females occupied shells more similar to their predicted shell size, regardless of whether the occupied shell was relatively small or large, than nonreproductive females. In contrast, relative shell sizes of reproductive and nonreproductive females were similar for large females in the seagrass population and all females in the salt marsh population. Clutch sizes were enhanced for females occupying Polinices duplicatus shells or shells larger than their predicted shell size in the seagrass population. Relative shell size also was associated with clutch size in the salt marsh population, but crabs occupying shells similar to their predicted shell size had the largest clutches.