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Social context of shell acquisition in Coenobita clypeatus hermit crabs
Abstract
Vacancy chains involve unique patterns of resource acquisition behaviors that determine how reusable resources are distributed
through animal populations. Shell vacancy chains have been described for several hermit crab species, both terrestrial and
marine, but little is known about the ecological and behavioral dynamics of shell choice in social versus solitary contexts.
Here, we present a novel conceptual framework that differentiates 2 types of shell vacancy chain in hermit crabs and discuss
fundamentally distinct predictions concerning the behavioral and ecological costs and benefits associated with synchronous
versus asynchronous vacancy chains. In laboratory studies of the terrestrial hermit crab Coenobita clypeatus, we found support for the prediction that social context alters shell acquisition behaviors. Field observations demonstrated
that both synchronous and asynchronous vacancy chains are common and revealed previously undescribed waiting and piggybacking
behaviors that appear to facilitate synchronous vacancy chains. Additionally, simulation results from an agent-based model
showed that population density and waiting behaviors can both influence the likelihood of synchronous vacancy chains. Together,
these results indicate that better understanding of hermit crab resource acquisition requires studying social behaviors, including
vacancy chain formation.
... Again, we might see several crabs change shells within a vacancy chain. Rotjan et al. (2010) refer to these as asynchronous vacancy chains, and contrast them with synchronous vacancy chains, which have features that indicate a high cognitive ability and forward planning. ...
... The crab will discard its original shell, which then becomes available to the second in line and so on until all the crabs switch shells and the smallest crab discards its very small shell. This behaviour results in all the crabs gaining in shell quality (Rotjan et al. 2010). ...
... This also occurs when a terrestrial hermit encounters an empty shell that is too large. It and other crabs might wait nearby for a large crab to take the shell and discard its original shell, which is smaller than the large new shell (Rotjan et al. 2010;Laidre 2014). That shell is then available to be taken by the largest of the waiting crabs. ...
Hermit crabs have an intimate relationship with gastropod shells and show numerous activities by which they locate, select, and change shells in different contexts. They gather information about new shells and update information about their existing shells. This involves integration of different sensory modalities, memory-formation, and comparison of the overall value of each shell. Crabs also fight to get shells from other crabs, and again they gather information about the shell qualities and the opponent. Attacking crabs monitor their fight performance, and defenders are influenced by attacker activities, and both crabs are influenced by the gain or loss that might be made by swapping shells. Swapping shells involves the defender being naked for a short period. Leaving a shell also occurs if the shell is experimentally fixed in place or buried in sand or if small electric shocks are applied to the abdomen, and the quality of the current shell is traded-off against escaping possible asphyxiation or the aversive shocks. Hermit crabs show remarkable abilities, involving future planning, with respect to recognizing the shape and size of shells, and how they limit their passage through environmental obstructions. They also assess if shells might become available and wait for that to happen. Groups of crabs arrange themselves in size order so that orderly transfer of shells might occur down a line of crabs. These observations are discussed in the light of complex perceptual and cognitive abilities, and the possibility of sentience and awareness is discussed.
... Vacancy chain theory, whereby a single resource propagates through a community, is increasingly recognized as a key component of resource-use behavior in any organism that utilizes discrete, limit- ed, and re-usable resources (Chase, 1991). Hermit crabs are becoming a model system for testing vacancy chain theory (Briffa and Austin, 2009;Friman, 2004;Lewis and Rotjan, 2009;Weissburg et al., 1991;White, 1970), and such chains can occur in a delayed (asynchronous) or immediate (synchronous) fashion (Rotjan et al., 2010). An increas- ing number of studies have addressed shell choice patterns in a social context (3 crabs or more) and/or vacancy chain framework (Briffa and Austin, 2009;Lewis and Rotjan, 2009;Rotjan et al., 2010), but compari- sons of social context across habitat types have yet to be investigated. ...
... Hermit crabs are becoming a model system for testing vacancy chain theory (Briffa and Austin, 2009;Friman, 2004;Lewis and Rotjan, 2009;Weissburg et al., 1991;White, 1970), and such chains can occur in a delayed (asynchronous) or immediate (synchronous) fashion (Rotjan et al., 2010). An increas- ing number of studies have addressed shell choice patterns in a social context (3 crabs or more) and/or vacancy chain framework (Briffa and Austin, 2009;Lewis and Rotjan, 2009;Rotjan et al., 2010), but compari- sons of social context across habitat types have yet to be investigated. ...
... To ensure that shell decisions would be made on physical characteristics rather than site-specific chemical char- acteristics, empty shells were cleaned with a mild bleach-freshwater solution followed by several freshwater rinses; this method also re- moved any living material in or on the shell that might influence hermit crab shell choice. These methods are consistent with previous studies, which have shown that vacancy chains move from larger to smaller crabs ( Briffa and Austin, 2009;Lewis and Rotjan, 2009;Rotjan et al., 2010). To calculate ideal shell size, we developed a series of equations. ...
Both ecological and social contexts are recognized as key variables in hermit crab shell switching behavior, but the impact of site variability on social shell choice has not yet been explored. Pagurus longicarpus marine hermit crabs are common inhabitants of highly variable intertidal habitats where they compete for gastropod shell resources. The goal of this study is two-fold: (1) to assess natural resource (shell) quality and use in the field; (2) to determine how differences in resource quality and ecological context affect social behavioral decisions in the lab. We used vacancy chain theory to analyze the impacts, benefits and consequences of shell choice on the population. Specifically, we quantified movement of shells through a group and described hermit crab shell decision patterns from two different intertidal populations: Beverly (rocky shore) and Nahant, MA (mudflat). Shell damage and shell fit are both known to negatively impact hermit crab fitness and survival; we found that Nahant crabs inhabited poorer quality shells compared to Beverly crabs. Similar-ly, Nahant crabs were more crowded and spent more time investigating shells. Despite the clear motivational and behavioral differences in populations, vacancy chain lengths were extremely similar between Nahant and Beverly populations, and chains always terminated when the vacant shell was highly damaged, suggesting that chain length is mediated most by shell quality. These results suggest that relative (rather than absolute) differences in resource quality may dictate the dynamics of social vacancy chain outcomes in this species.
... The hermit crabs (with smaller shells than the found one) usually wait and aggregate around a hermit crab (with a size closer to the found shell) to occupy its shell. Processes called negotiation and aggression are typical in this regard (Rotjan et al., 2010). In aggression, the dominant (attacker ) (i.e., the bigger crab) exchanges its shell with the subordinate (defender ) (i.e., the smaller crab). ...
... In this process, the gigantic crab leaves its shell behind for the smaller one, as it may discover a more suitable shell from larger crabs. The social search strategy is more common and is called as vacancy chain process because of similarities with humans' behavior when getting promoted and other people acquiring their position (Rotjan et al., 2010). ...
This paper proposes a novel meta-heuristic algorithm (MA), called hermit crab optimizer (HCO), which simulates the swarm intelligence of hermit crabs in nature in finding shells protecting and letting them grow in their lifetime. HCO guides search agents separately and in parallel using new solitary and social search operators. It acts similar to a reinforcement learning process, in which the successful agents and failed ones are treated differently, inspired by the group behavior of hermit crabs and environmental characteristics. Computational experiments with well-known test problems confirm HCO's validity, accuracy, robustness, ability to escape local optima, and balance exploration-exploitation.
... ''Shell switching'' takes place when the crab holds the new shell with the aperture facing upward and releasing its abdominal grip on the old shell, rapidly swings its abdomen over to occupy the new shell. Solitary crabs often retain hold of their original shell and ''reversals'' occur when a crab moves back and forth between shells before finally choosing one (Rotjan et al., 2010). The assessment is done by comparing the resource value of shell already occupied with the encountered shells (Tricarico and Gherardi, 2007;. ...
... Hermit crabs show preference to lighter shells (Herreid and Full, 1986) when compared to heavy shell which otherwise adversely affect the reproduction and growth of hermit crabs (Elwood et al., 1995;Osorno et al., 2005). The length of solitary shell investigations by hermit crabs was highly variable, ranging from 3 to 429 seconds (Rotjan et al., 2010). Present study showed that when the hermit crab was introduced into the tank with other gastropod shells, they preferred shells with larger aperture width and thicker shells like that of Natica vitellus, Turbo intercostalis, Babylonia zeylanica and Purpura bufo. ...
Extensively distributed along tropics and subtropics, terrestrial hermit crabs play critical roles in coastal ecology and they often show preferences towards few gastropod shells in natural ecosystems. The nature of selection of empty gastropod shells as protective 'home' from natural environment for shelter varies with species. In this study the vacant shell search and selection by the terrestrial hermit crab Coenobita rugosus (Coenobitidae; Crustacea) was found to be governed by various parameters including the presence of vacant shells in vicinity, types of vacant shells, and morphometric characters of shells. Laboratory simulation for 72 hours of exposure of hermit crab to different types of vacant host shell combinations followed by statistical evaluation revealed specific relationship in shell selection by hermit crab with morphometric characteristics of vacanthost shells.They also exhibit a greater plasticity in shell selection.
... Several hermit crab species use "vacancy chains" to find new shells: when a new, bigger shell becomes available, hermit crabs gather around it and form a kind of queue from largest to smallest. When the largest crab moves into the new shell, the second biggest crab moves into the newly vacated shell, thereby making its previous shell available to the third crab, and so on (Randi et al., 2010). ...
... The energy saved by carrying a light shell may be used to increase growth rate and egg production of intertidal hermit crabs, which ultimately improve fitness (Guillén and Osorno, 1993;. Also, crabs occupying shells large enough that, they can withdraw completely and block the shell aperture with the chelipeds are much harder to extract from their shells than crabs which are too large to withdraw completely, and for this reason they would presumably be less vulnerable to predators (Randi, et al., 2010). ...
... H ERMIT CRABS use the abandoned shells of gastropods as their refuge. Hermit crabs require the protection of the shells in order to shield their vulnerable abdomen (Hazlett 1987) and to avoid predation, cannibalism and desiccation (Rotjan et al. 2010). According to Elwood (1995), most species of hermit crabs have morphological adaptations that allow them to live in gastropod shells including a symmetrically coiled abdomen and a pair of legs that have evolved to grasp their shell. ...
A compilation of Coastal Carolina University undergraduate research project papers conducted as part of the 2014 Ecology of Coral Reefs short-term, study abroad program in Discovery Bay, Jamaica.
... Shell selection is an example of a decision-making process that is affected by external factors (Reese, 1963;Conover, 1978;Bertness, 1981;Hazlett, 1981;McClintock, 1985;Lewis & Rotjan, 2009;Rotjan et al., 2010). The shell utilization data indicates that the type of shells used by C. clypeatus in the protected beach does not vary substantially between seasons, favoring the green star shell (A. ...
The coastal Caribbean is a well-known harbor for biodiversity, yet it is mainly valued for its ample resources and services. Economic interests typically supersede conservation efforts, introducing anthropogenic-related factors such as noise, chemical pollution, and geographical disturbances into the littoral zone, where ecological diversity is abundant. Although human activity is known to be detrimental to biodiversity across habitats, the effect of conservation measures that limit anthropogenic activity on coastal populations remains understudied. To measure the benefit of conservation in the littoral environment, we sampled populations of the hermit crab Coenobita clypeatus (Fabricius, 1787) of highly frequented (non-protected) and protected beaches in northern Puerto Rico. We profiled 1,119 individuals by using transects, describing their size and shell utilization patterns during winter and summer. The C. clypeatus population was larger (P < 0.0001 during both seasons) and more abundant (P = 0.0006 during winter, P < 0.0038 during summer) in the protected beach than in the non-protected beach, with no effect of season. Shell utilization patterns were more consistent in the protected beach, likely due to the greater availability of gastropod shells. These results suggest that the conservation measures implemented in the protected beach promote the survival, reproduction, and growth of hermit crabs in the location. Expansion of protected habitats through governmental and civilian efforts should enhance the conservation of the biodiversity of protected areas.
... While nutrient availability is rarely a limiting factor for hermit crabs (Hazlett, 1981), appropriate shells often are (Bollay, 1964;Vance, 1972;Mantelatto & de Meireles, 2004). Because the probability of finding a shell of proper size and quality is low, the cost of relying on these sporadic resources is high (Rotjan et al., 2010). ...
We examined the prevalence and shell use of two species of hermit crabs ( Pagurus granosimanus and Pagurus beringanus ) in exposed and protected microhabitats at five sites in the rocky temperate intertidal on San Juan Island, Washington, to compare present habitat partitioning and potential interspecific competition to that reported nearly 50 years ago. We found that, in contrast to previous findings, the two species of hermit crabs overlapped extensively at some sites, typically those with less wave action. While the hermit crabs typically inhabited certain types of shells significantly more than others, and that use was congruent across microhabitats and species of hermit crabs at the same site, the dominant domicile differed substantially across sites. We provide a more complete ranking of shell use than previous authors and note site-specific dominant shell use. We conclude that previous habitat partitioning by depth may have weakened at protected sites. We hypothesize that increasing temperatures have caused P. granosimanus to expand its range deeper into the intertidal, which may increase the degree of interspecific competition for shells at the edge of the species’ tidal height range, where they overlap. Whether the habitat shift by this hermit crab is due to recent alterations in climate (particularly elevated temperatures, ocean acidification and lower local open ocean salinity) is unknown, but warrants further study.
... The growing need for new sources of low-cost adsorbent, the increased problems of waste disposal, the increasing cost of synthetic resins undoubtedly make chitosan one of the most attractive materials for wastewater treatment. Treatment of water with chitosan would be a cost effective and safer method over the traditional methods of removal of toxic metal species using chemicals [28]. Tumova [29] researched that egg shell by-product represents about 10 % of the total weight (~average weight of an egg is 60 g) of egg. ...
This study investigated the potential of some agricultural wastes viz; African Star apple seed shell (ASS, plant source), crab shell (CS, animal source) and chicken egg shell (ES, animal source) as eco-friendly and low-cost biological materials for the removal of heavy metals from poultry wastewater. TS, TSS and TDS of the wastewater sample were assayed by filtration methods, chloride content by previously reported method and heavy metal contents (Zn, V, Cd, Fe, Ni, Cu, Co, Pb, Cr and Mn); were analyzed using Microwave Plasma Atomic Emission Spectrometer. The results of the solids and chloride contents of the poultry wastewater were TDS (3100 mg/L), TS (3700 mg/L), TSS (6000 mg/L) and chloride (4.7 g/L); all above the EPA permissible limits. Results of the FTIR analysis showed that ASS is an amide polymer while the CS and ES shells are mixtures of amide and carbonate polymers. Also, results of heavy metal analysis before and after adsorption showed that ASS caused removal of Zn, V, Fe, Cu, Co/ Pb and Mn by 48.27, 32.22, 49.64, 91.44, 100 and 82.39% respectively while Cd, Ni and Cr contents increased by 31, 61 and 48.3% respectively. CS showed removal of Fe, Ni/ Co/ Cr, Pb and Mn by 89.64, 100, 3.51 and 95.96% respectively while Zn, V, Cd and Cu contents increased by 1.7, 61.2, 76.1 and 68.1% respectively. Meanwhile, with ES, the contents of Zn, Fe, Ni, Cu, Cr and Mn increased by 31.56, 86.36, 100, 55.5, 45.80 and 90.33% respectively while the contents of V, Cd, Co and Pb decreased by 78.9, 86.7, 42.5 and 46.2% respectively. This study demonstrated the use of ASS, CS and ES as low- cost and eco-friendly agricultural wastes with significant potential for removal of heavy metals from wastewaters.
... Many animals that compete by interference also display indeterminate growth with no fixed adult size, and form size-structured populations, such as fish (Nakano, 1994(Nakano, , 1995b and hermit crabs (Rotjan et al., 2010). ...
Coexistence of species requires equalizing mechanisms that minimize fitness differences, which are balanced by stabilizing mechanisms that enhance negative intraspecific interactions versus interspecific ones. Here, we develop a simple theoretical framework that allows measuring the relative strength of intraspecific versus interspecific competition in dominance hierarchies. We use it to evaluate mechanisms promoting coexistence between two congeneric charr that compete for foraging positions, which strongly influence density‐dependent growth and survival.
Agonistic interactions (n = 761) among 71 Dolly Varden Salvelinus malma and whitespotted charr Salvelinus leucomaenis were measured by snorkelling in two pools in the sympatric zone of a Hokkaido stream during two summers. Interspecific dominance hierarchies, analysed using three methods, were closely correlated with fish length but the species treated each other equally. Ranks for the most dominant fish in each pool, determined directly by knockout experiments, were also virtually identical to ranks by length.
Similarly, exponential random graph modelling of the social networks provided no evidence that either species was dominant over the other. Instead, larger fish were more likely to win contests, especially over fish of the next lower ranks.
These results demonstrated that the two species were nearly ecological equivalents in accessing key resources in this sympatric zone. Nearly identical growth and stable densities over 4 years further supported this inference, although Dolly Varden were a minority (29% of the assemblage), a sign of some fitness difference.
Detailed foraging observations coupled with two concurrent studies revealed an effective stabilizing mechanism. Dolly Varden shifted to feeding directly from the benthos when drifting invertebrates declined, a behaviour enhanced by morphological character displacement, thereby partitioning food resources and enhancing intraspecific competition while avoiding agonistic encounters with whitespotted charr.
The plurality of evidence indicates that fitness differences between these ecologically equivalent species are small in this local assemblage, and balanced by resource partitioning, a modest stabilizing mechanism that promotes coexistence. The theoretical framework presented here is a useful tool to evaluate the strength of interspecific versus intraspecific competition, which combined with information on trade‐offs in ecological performance can contribute to a mechanistic understanding of species coexistence.
... Anomuran crabs (infraorder Anomura), including porcelain crabs, mole crabs, squat lobsters, hermit crabs, and king crabs, differ markedly in their morphology, physiology, behavior, ecology, and lifestyle (De Grave et al., 2009;Lozano-Fernandez et al., 2019). While most hermit crabs that use gastropod shells for protection against predators and abiotic stress are marine dwellers, a few have conquered semi-terrestrial environments and exhibit complex social networks (e.g., Coenobita clypeatus Herbst, 1791, family Coenobitidae (Rotjan et al., 2010)). Other anomuran species that do not appear to exhibit major social interactions form remarkable aggregations either underneath rocks in the intertidal zone in temperate rocky shores (e.g., porcelain crabs, Petrolisthes Stimpson, 1858, family Porcellanidae (Rivadeneira et al., 2010)) or in the surge zone on sandy beaches in tropical and temperate environments (e.g., mole crabs, Emerita Scopoli, 1777, family Hippidae (Tam et al, 1996). ...
We present a full description and analysis of the complete mitochondrial genome of a Pacific Ocean specimen of the coconut crab Birgus latro (Linnaeus, 1767), the largest extant terrestrial arthropod in the world. Our de novo-assembled mitogenome has a massive 16,161 times organelle read coverage, a length of 16,411 bp, contains 22 tDNAs (20 unique), 13 protein-coding genes, two rDNAs, and a putative control region of length 1,381 bp. The control region contains three microsatellites and two pairs of inverted repeats. Contrary to the mitochondrial sentinel gene concept, two-dimensional nucleotide analysis reveals higher GC-content in cox gene families than in nadh gene families. Moreover, cox gene families are more conserved than nadh gene families among the species of Coenobitidae selected for comparison. Secondary structure prediction of the 22 tDNAs shows major deviations from the cloverleaf pattern, which points to a relatively high rate of mutation in these genes. We also present a repertoire of mitochondrial variation between our male Okinawan coconut crab and an Indian Ocean specimen that consists of one insertion, one deletion, 135 SNPs, three MNPs and nine complex polymorphisms. We provide confirmatory evidence that the superfamily Paguroidea, to which the coconut crab belongs, is polyphyletic, that all the protein-coding genes of B. latro are under purifying selection, and that a Pacific versus Indian Ocean coconut crab population divergence occurred during the Pleistocene.
... In the most complex cases, when a hermit crab finds an empty shell too big for him or her, the crustacean waits for other conspecifics and an orderly queue, dictated by size, begins to develop. At last, the bigger crab moves into the empty shell and triggers the chain, and all the rest immediately follow and upgrade their current shelters (Rotjan, Chabot, & Lewis, 2010;BBC Earth, 2015). So, according to Chase, as both in human and nonhuman animals what defines vacancy chains is the type of resource involved, it would be possible to vary the characteristics of shells and crabs to optimize the communal improvement, and then to extrapolate the results into human situations. ...
A hermit crab housed in a broken glass bottle or inside a plastic cap is becoming like a polar bear stranded on a tiny, melting iceberg: those pictures are emergent icons of the plight faced by oceans and creatures, caused by human waste excesses and wrongdoings. These inventive crustaceans fulfill a warning role akin to charismatic megafauna, and induce empathy with varied sources, dominated by human projections like the housing crisis metaphor. Crabs emerge like a cluster where many opposed notions collapse, while they stage the frictions of a complex, fractured balance. They are wild animals, and controversial companion animals, and when they live inside human trash, they show resilience that questions the natural-artificial divide. Simultaneously, they remind humans of strains imposed upon them, the oceans, and the planet, becoming tokens of the unbalances with which humans have to deal in their often-misguided attempts to fix the things they are rupturing.
... Furthermore, the hemiellipsoid bodies of some crustacean species are frequently assimiled to particular neuropils present in Hexapoda, namely the mushroom bodies, which are well-known as learning and memory centers , 2017. Wolff and collaborators (2017) pointed out that large hemiellipsoid bodies are found in eumalacostracan groups that evidence memory of exact locations (cleaner shrimp [Limbaugh et al. 1961], land hermit crabs [Rotjan et al. 2010]) and eusociality (pistol shrimp [Duffy 1996]). The welldeveloped hemiellipsoid bodies in M. fortunata could thus eventually be involved in memory processes, particular navigational skills or social interactions. ...
Alvinocaridid shrimp are an emblematic taxon at hydrothermal vents on the Mid-Atlantic Ridge, but how they locate active vents and detect their habitat is still enigmatic. They might use the chemical and thermal signatures of the hydrothermal fluid as orientation cues. The chemo- and thermosensory abilities of the hydrothermal species Mirocaris fortunata and the coastal species Palaemon elegans were investigated using various approaches. Structural features of the peripheral and central nervous system were used as rough estimates of their olfactory abilities. The co-ionotropic receptor IR25a, involved in chemodetection, was identified and located in the antennal appendages. A new electroantennography method was developed to test the detection of hydrothermal fluid chemicals. Several attraction tests were conducted at atmospheric and in situ pressure to investigate the behavior of the vent and shallow-water species when exposed to a food odor, sulfide and warm temperatures. Altogether, these results provide advances in the knowledge of the chemosensory biology of vent shrimp, and a substantial background for future researches on sensory adaptations to the hydrothermal environment.
... The formation of clusters is a common behavior displayed by many hermit crabs of the families Diogenidae and Paguridae, from both tropical and temperate intertidal habitats (Hazlett, 1966;Snyder-Conn, 1980;Gherardi and Vannini, 1989;Gherardi, 1991). For these animals, aggregations are usually attributed to the "shell exchange market" hypothesis (Gherardi andVannini, 1992, 1993), in which animals exchange shells by fighting (Hazlett, 1966;Elwood and Glass, 1981), bargaining (Hazlett, 1978(Hazlett, , 1980, or by a chain reaction caused by a single empty shell (Chase et al., 1988;Rotjan et al., 2010). Hermit crabs must continually obtain new, suitable shells, either because of growth (Hazlett and Herrnkind, 1980;Rittschof, 1980) or alteration in the condition of their current shell (e.g. ...
Clustering is a common behavior displayed by hermit crabs in intertidal environments. Aggregations are reported to occur during low-tide events, and the number of animals present may vary depending on the species. The “shell exchange market” hypothesis suggests that the main function of clustering is to allow animals to acquire new shells by fighting, bargaining, or by a chain reaction caused by a single empty shell. However, the adaptive significance and the factors that trigger this behavior remain unexplained. Here, the hypotheses tested were that both sex of Clibanarius symmetricus are performing this behavior, that clustered animals have poorly fitted shells compared to isolated ones, and that tidal phase is triggering the formation of clusters. Clustered and isolated animals were collected in the field, sexed, and measured for cephalothoracic shield and shell parameters. The Shell Adequacy Index (SAI) was compared among crabs of both sexes in clustered and isolated conditions. Additionally, manipulative experiments were performed in the laboratory, with different tidal-phase conditions. Both sexes were present in clusters, but clustered females showed a lower SAI than isolated females. Furthermore, a higher proportion of crabs were aggregated during ebb-tide than during flood-tide events. Thus, clustering behavior may be related not only to shell exchanges, but also to mating and protection against desiccation. Consequently, the adaptive meaning and function of aggregations in intertidal hermit crabs should be understood as an integrative behavior related to many aspects of the animals' biology.
... Pistol shrimps are the only crustaceans to have evolved eusociality (Duffy, 1996), an attribute requiring memory of position both outside and within the community. And land hermit crabs are known for their navigational skills and memory of sites at which they socially interact (Rotjan et al., 2010). There are, then, valid grounds to suppose convergent evolution of mushroom bodies in certain crustaceans and hexapods. ...
Mushroom bodies are the iconic learning and memory centers of insects. No previously described crustacean possesses a mushroom body as defined by strict morphological criteria although crustacean centers called hemiellipsoid bodies, which serve functions in sensory integration, have been viewed as evolutionarily convergent with mushroom bodies. Here, using key identifiers to characterize neural arrangements, we demonstrate insect-like mushroom bodies in stomatopod crustaceans (mantis shrimps). More than any other crustacean taxon, mantis shrimps display sophisticated behaviors relating to predation, spatial memory, and visual recognition comparable to those of insects. However, neuroanatomy-based cladistics suggesting close phylogenetic proximity of insects and stomatopod crustaceans conflicts with genomic evidence showing hexapods closely related to simple crustaceans called remipedes. We discuss whether corresponding anatomical phenotypes described here reflect the cerebral morphology of a common ancestor of Pancrustacea or an extraordinary example of convergent evolution.
... The well-known sym and hermit crabs in wh associations are mutual protect each other from anemones and 'plant' t another shell, will take th Most frequently herm 281) although the shells pieces of wood and sto alternative shelters for domiciles provided by gastropods, corals, or sp crab species use "vacanc becomes available, herm queue from largest to s new shell, the second bi thereby making its prev (Randi et al., 2010). A h wider choice of shells competition for the avail While unreliable rep capable of removing li essential shell resource, to investigate this pos 261 Fig. 280. ...
The Pakistani coastal area is known to host a high diversity of marine habitats, flora/fauna yet a region that remains understudied in terms of crustacean symbionts as parasites and commensals. It is suggested that apparent rarity of these study of symbionts is probably a spurious phenomenon resulting from inadequate collecting methods. However, there is an infinite variety of associations between different species of aquatic animals like Crustacea and other organisms. The aim of present compendium is to update the information for the 270 symbiotic aquatic Crustacea from Pakistani area, according to recent taxonomic advances. It aims to bring together into one volume the disparate information of Pakistani marine/fresh water species. This study adds the inter-organismal relationships in symbiont taxa living together to 251 species known from Pakistan adding 19 new records and 7 species new to science. Identifications of hosts as cited in older literature are updated to current nomenclature. A result of study of crustacean parasites in the samples of galathoids collected by International Indian Ocean Expedition (IIOE) 1965-66 is added as separate chapter.
... The downside of this strategy of minimal information sampling is the risk of ending up with an inferior option. Nature provides a good example of this exploration exploitation tradeoff 8,10,11 . Hermit crabs habitually outgrow the shell they live in and have to find a new one. ...
Without competition, organisms would not evolve any meaningful physical or cognitive abilities. Competition can thus be understood as the driving force behind Darwinian evolution. But does this imply that more competitive environments necessarily evolve organisms with more sophisticated cognitive abilities than do less competitive environments? Or is there a tipping point at which competition does more harm than good? We examine the evolution of decision strategies among virtual agents performing a repetitive sampling task in three distinct environments. The environments differ in the degree to which the actions of a competitor can affect the fitness of the sampling agent, and in the variance of the sample. Under weak competition, agents evolve decision strategies that sample often and make accurate decisions, which not only improve their own fitness, but are good for the entire population. Under extreme competition, however, the dark side of the Janus face of Darwinian competition emerges: Agents are forced to sacrifice accuracy for speed and are prevented from sampling as often as higher variance in the environment would require. Modest competition is therefore a good driver for the evolution of cognitive abilities and of the population as a whole, whereas too much competition is devastating.
... Many hermit crab species occur in large groups (Barnes 1997;Burggren and McMahon 1998;Gherardi and Vannini 1993;Laidre 2010). Hermit crab behavior has been studied by authors exploring aggressive behavior (Briffa and Elwood 2001, 2002, 2007Courchesne and Barlow 1971;Hazlett 1966;Tricarico et al. 2008), use of shells (Billock and Dunbar 2011;Chase et al. 1988;Laidre et al. 2012;Rotjan et al. 2010;Turra and Gorman 2014), scrounging based upon cues of group foraging (Laidre 2010(Laidre , 2013, communication and signaling costs (Arnott and Elwood 2010;Doake et al. 2010;Laidre 2009), and behavior in the context of threatening stimuli (Chan et al. 2010). Researchers have also assessed influences of isolation on hermit crab activity levels (e.g., Courchesne and Barlow 1971;Van Zerr 2008). ...
Isolation increases activity in individuals of some species, whereas it decreases activity in individuals of other species. Furthermore, as the length of isolation increases, behavioral changes can become more pronounced. Here, we examined effects of short-term isolation on latencies for individuals to emerge from their shells in two species of terrestrial hermit crab (Coenobita rugosus and Coenobita brevimanus) over a 4-week period. Within each species, crabs were housed individually (isolate context) or socially in groups of four (social context). In each week, crabs were exposed to an emergence test, which measured the latency to emerge from the shell following a potentially threatening stimulus. We obtained a significant context × week interaction. Although socially housed crabs showed no change in emergence over the 4 weeks of the study, isolate crabs took longer to emerge from their shells as the period of isolation increased. Our study corroborates findings in other invertebrate species, as well as in vertebrate species, that isolation generally decreases activity levels and may increase fear levels, in individuals.
... However, when a group of crabs simultaneously encounters an empty shell, each individual crabs' search process is dramatically truncated. In this competitive situation, the crab nearest to the shell will make a split-second decision on whether or not to take it based on a brief visual inspection alone (Rotjan, Chabot, & Lewis, 2010). ...
... In spite of the ecological importance of land hermit crabs in the marine and terrestrial environments, relatively few studies concern C. clypeatus. Most of these have addressed its physiological adaptation to terrestrial life (De Wilde, 1973;McMahon & Burggren, 1979;Harzsch & Hansson, 2008), larval development (Provenzano, 1962), shell acquisition behaviour (Rotjan et al., 2010), massive migrations and spawning (Nieves-Rivera & Williams, 2003), estimations of population density (Morrison & Spiller, 2006), and ecological interactions with ants, Acari, and even snails (Morrison, 2002(Morrison, , 2006Barun et al., 2007;Palacios-Vargas, 2007). However, to our knowledge, relative growth and morphometric relationships of this species remain as yet unknown. ...
Information on growth in hermit crabs is very scarce, possibly due to the inherent difficulties of extracting them from their shells. In this work we document the relative growth, sexual size dimorphism, and level of chelae asymmetry of the land hermit crab Coenobita clypeatus (Fabricius, 1787) collected on a coral reef island in the National Park Arrecife Alacranes, southern Gulf of Mexico, during December 2009 and September 2010. Specimens examined were anaesthetized in a clove oil-water solution to avoid unnecessary crab mortality. A total of 387 individuals was measured on six external variables: cephalothorax length and width, and both chelae in length and width. Taking the cephalothorax length as the reference dimension, the remaining measurements were fitted to a power function to examine the degree of allometry in growth and make comparisons between sexes. For each sex, an asymmetry index (AI) was calculated to determine the degree of heterochely, and the significance of its value was evaluated by means of null models. Numerically, males dominated the crab population in the largest size classes (>12.6 mm CL) in both seasons. As in most anomurans, C. clypeatus males attained larger body sizes than females, but their relative growth was most similar. For both sexes, the growth of chela width was positively allometric (t-test, p < 0.05). Also, AI values showed a heterocheleous condition, with the left chela significantly higher (p < 0.001) than the right. Regarding our own results and previous reports, we propose that heterochely could be triggered during the glaucothoal and juvenile stages. Numerical dominance of males in the larger size classes is probably due to the segregation of ovigerous females from the main crab group, searching suitable areas for egg deposition, but also to a better condition of males to carry heavier shells than females, which in their turn have to invest a considerable amount of energy in reproduction.
Trilobites are one of the most important invertebrate clades in the Palaeozoic, with significant disparity in morphology and behaviour, the latter including intriguing instances of queueing. Previous studies employed Computational Fluid Dynamics (CFD) to investigate queuing behaviour in the Devonian trilobite Trimerocephalus chopini and found drag reduction effects. Novel calculations that define a ratio between drag force and Apparent Gravity (W), along with the Submerged Froude Number (Fr_sub), however, reveal that the obtained drag force was practically negligible in terms of the underwater mobility of trilobites. A trilobite would start to experience difficulty in forward walking only when the relative flow speed was over 42cm/s, which is inconsistent with the interpreted palaeoenvironment or the predicted moving speed of trilobites. Nevertheless, according to the proposed cantilever model, a trilobite had the ability to sense very minute change in fluid velocity (>7.16μm/s). High-sensitivity mechanical sensors distributed along the body, either on the exoskeleton or limbs, empowered queuing individuals to discern the fixed self-similar pattern of the wake generated by their predecessors in the queue. In general, if a trilobite were out of the wake, the asymmetrical velocity and pressure field would aid in repositioning itself, facilitating the maintenance of migratory queues. This permitted blind trilobites to securely sense their companions, compensating for lack of long-range visual capability. This paradigm of force assessment is suitable to Computational Fluid Dynamic analyses in other extinct animal-environment interactions, offering a framework to evaluate whether drags and wakes impact more on organism's mobility (W≫0.1,Fr_sub≫1) or their mechanical sensors, and provides a unique cross-scale insight into animals’ adaptation to palaeohydrodynamic variation.
Social organisms form groups with diverse configurations. While the dynamics within social groups have been explored extensively, the perspective of individuals outside of groups has been considered less. Here, we studied social hermit crabs ( Coenobita compressus ) and experimentally tested the perspective of “outsiders”—individuals that were not yet part of a group but were actively searching for a group to join. Using architectural arrays of shells, we simulated a natural social structure—a “social chain”—in which all group members piggyback in sequence. We then tested how outsiders perceived experimentally simulated social chains, which we varied in orientation (horizontal vs. vertical) and which we arranged to be either socially ordered or disordered (i.e., all members arranged in order of size vs. randomly). Outsiders were more attracted to horizontally vs. vertically oriented chains, consistent with a specialization for detecting groups along the horizon. Outsiders were also more attracted to the long rather than the short side of horizontally oriented chains, consistent with the greater perceptual salience of the long side. Finally, outsiders were only marginally capable of determining where they belonged within groups—in terms of size matching—for ordered chains; and they showed no such capability for disordered chains. Broadly, our experiments suggest that a group's configuration, including both its orientation and social ordering, influences outsiders' perceptions and decisions.
Although sexual segregation (sexual difference in resource use) is versatile in many animal taxa, studies have mostly concentrated on vertebrates. To observe sexual segregation in marine invertebrates, I focused on the sexual differences in shell utilization patterns of hermit crabs. I first reviewed hermit crab biology mainly relating to shell use, including shell acquisition, competition, shell preferences, and influences on fitness components (growth, survival, and fecundity).Then, I considered ecological and evolutionary factors for different shell utilization patterns between sexes observed in Pagurus filholi inhabiting Kattoshi, Hakodate Bay. I integrated the reports on shell species preferences, competitive abilities, and the effects of different shell species on fitness components in P. filholi. Competitive ability for the shells showed no sexual difference. The different shell preferences between sexes were consistent with the field pattern of shell use of the sexes. Females preferred shells which provided them with high fecundity and survival from predators, whereas males preferred shells with high growth potential. As body size is important to males to acquire female mates, high growth is significant for male fitness. Conversely, female fitness greatly depends on the number of eggs produced during their lifetime. In summary, the sexual difference in shell use of P. filholi is mainly determined by different shell preferences by sex, which are ultimately driven from different priorities between sexes to maximize fitness.
In this article I draw on Jakob von Uexküll and a number of thinkers who engage, extend or otherwise resonate with his work to argue for a theory of meaning as dynamic process. Uexküll enables a view of meaning as something an embodied subject does rather than something possessed or accessed. The ongoing life of an organism – relations to self, to environment, to past experience and to anticipated future events – forms an experiential context within which any encounter must take place. It is this broader context which I refer to as dynamic meaning-making processes. I discuss some recent experiments and observations on hermit crabs to illustrate how a view of meaning as dynamic process informs relations of interspecies care. Interspecies care is conceived here as the modulation of human meaning-making practices: spinning out, folding in and strengthening meaningful relations across forms of life, in anticipation of better futures.
In this chapter I survey key theories and concepts that provide substance to the workings of Transformative Social-Ecological Innovation (TSEI). A number of relevant theories and concept have already been mentioned in the previous chapters, such as Social Contract theory (Sect. 10.1007/978-3-030-67130-3_3#Sec1 ), and in Sects. 10.1007/978-3-030-67130-3_3#Sec8 and 10.1007/978-3-030-67130-3_3#Sec13 , including resilience theory and social-ecological systems (Sect. 10.1007/978-3-030-67130-3_3#Sec8 ), quintuple helix innovation model (Sect. 10.1007/978-3-030-67130-3_3#Sec13 ), as well as institutional change and the structure-agency debate (Sect. 10.1007/978-3-030-67130-3_3#Sec13 ), and several economic theories (Sects. 10.1007/978-3-030-67130-3_3#Sec2 and 10.1007/978-3-030-67130-3_3#Sec3 ). In this chapter I will start with providing a conceptual discussion and definition on Transformative Social-Ecological Innovation (Sect. 4.1), and devote more attention to various theories and approaches that are relevant for TSEI, such as transition studies (Sect. 4.2), institutional design principles for governing the commons (Sect. 4.3), design principles from nature (Sect. 4.4), complex adaptive systems (Sect. 4.5), adaptive, reflexive, and deliberative approaches to governance, management, and planning (Sect. 4.6), social learning, policy learning, and transformational learning (Sect. 4.7), shared value, multiple value creation, and mutual gains approach (Sect. 4.8), effective cooperation (Sect. 4.9), transdisciplinary cooperation, living labs, and citizen science (Sect. 4.10), and the art of co-creation: approaches, principles and pitfalls (Sect. 4.11).
This open access book states that the endemic societal faultlines of our times are deeply intertwined and that they confront us with challenges affecting the security and sustainability of our societies. It states that new ways of inhabiting and cultivating our planet are needed to keep it healthy for future generations. This requires a fundamental shift from the current anthropocentric and economic growth-oriented social contract to a more ecocentric and regenerative natural social contract. The author posits that in a natural social contract, society cannot rely on the market or state alone for solutions to grand societal challenges, nor leave them to individual responsibility. Rather, these problems need to be solved through transformative social-ecological innovation (TSEI), which involves systemic changes that affect sustainability, health and justice. The TSEI framework presented in this book helps to diagnose and advance innovation and change across sectors and disciplines, and at different levels of governance. It identifies intervention points and helps formulate sustainable solutions for policymakers, administrators, concerned citizens and professionals in moving towards a more just and equitable society.
Body size structure, abundance and gastropod shell use by the local population of the land hermit crab Coenobita brevimanus were investigated in the abandoned village of Amitori on Iriomote Island, Okinawa, Japan. Amitori was inhabited by a maximum of 200 people between the 17th century and 1971 and is now used as a research center of Tokai University. Results of mark-recapture experiments showed higher recapture rates than previous studies and an estimated population size of > 1000 crabs. The hermit crabs in Amitori, which use shells of edible marine gastropods such as Turbo (Marmarostoma) argyrostomus likely discarded by the former residents, grow to be larger than crabs living on an adjacent uninhabited island and an inhabited village without shell middens. The proportion of abraded and broken shells used by the crabs in Amitori is higher than that of crabs in another village on an adjacent island where edible gastropod shells continue to be discarded by residents. The crabs in Amitori use either small shells with little damage, or relatively large shells with more damage. Since the growth and abundance of C. brevimanus individuals depend on the continued supply of new marine gastropod shells, the proportion of large crabs in the uninhabited village of Amitori will likely decrease in the future.
Mathematical Models for Society and Biology, 2e, is a useful resource for researchers, graduate students, and post-docs in the applied mathematics and life science fields. Mathematical modeling is one of the major subfields of mathematical biology. A mathematical model may be used to help explain a system, to study the effects of different components, and to make predictions about behavior. Mathematical Models for Society and Biology, 2e, draws on current issues to engagingly relate how to use mathematics to gain insight into problems in biology and contemporary society. For this new edition, author Edward Beltrami uses mathematical models that are simple, transparent, and verifiable. Also new to this edition is an introduction to mathematical notions that every quantitative scientist in the biological and social sciences should know. Additionally, each chapter now includes a detailed discussion on how to formulate a reasonable model to gain insight into the specific question that has been introduced.
Animal personality has been investigated in a variety of contexts but few studies have investigated the effects of individual‐level traits on processes that occur at the group or population level. Vacancy chains describe sequences of linked vacancy moves in systems where individuals use discrete and reuseable resource units. When a new resource unit becomes available, this can cause a cascade of moves between resource units, beyond the first individual that encounters the new unit. Thus, vacancy chains can drive the distribution of resources through a population. Here, I investigate the effect of variation in boldness on movements between vacant gastropod shells in the hermit crab Pagurus bernhardus. Boldness was quantified using the duration of a startle response, which varied consistently between individuals. In groups of five crabs, introduction of a single new shell led to aggregate benefits, in terms of improving shell quality, across all group members. Boldness did not influence the extent of these benefits or the extent to which they were distributed between crabs of different sizes. Initially, vacancy chains were longer, indicating that more individuals moved between shells, for bold groups compared with shy groups. After 24 h, however, the chain length was longer for shy groups. Thus, although participation in a vacancy chain may lead to similar benefits, these could be more widespread for groups comprising shy individuals that show long startle responses, low inquisitiveness and low aggression. Similar effects on resource acquisition could be present in other examples of animals that utilise reusable resource units and show consistent between‐individual differences in behaviour.
Hermit crabs are critically dependent upon gastropod shells for their survival and reproductive fitness. While anecdotal reports have suggested that hermit crabs may be capable of removing live gastropods from their shells to access the essential shell resource, no systematic experiments have been conducted to investigate this possibility. This paper reports experiments on both marine (Pagurus bernhardus) and terrestrial (Coenobita compressus) hermit crabs in which crabs were paired in the laboratory with the gastropods whose shells they inhabit in the field. Pairings included both shelled and naked crabs and spanned the full range of the gastropod life cycle. Neither marine nor terrestrial hermit crabs were successful at removing live gastropods from their shells. Furthermore, only a small fraction of the crabs (5.7%) were capable of accessing shells in which the gastropod had been killed in advance, with its body left intact inside the shell. Finally, although hermit crabs readily entered empty shells positioned on the surface, few crabs (14.3%) were able to access empty shells that were buried just centimeters beneath them. These results suggest that hermit crabs are constrained consumers, with the shells they seek only being accessible during a narrow time window, which begins following natural gastropod death and bodily decomposition and which typically ends when the gastropod's remnant shell has been buried by tidal forces. Further experiments are needed on more species of hermit crabs as well as fine-grained measurements of (i) the mechanical force required to pull a gastropod body from its shell and (ii) the maximum corresponding force that can be generated by different hermit crab species' chelipeds.
Exposure to pollution and environmental change can alter the behaviour of aquatic animals and here we review recent evidence that exposure to elevated CO₂ and reduced sea water pH alters the behaviour of tropical reef fish and hermit crabs. Three main routes through which behaviour might be altered are discussed; elevated metabolic load, 'info-disruption' and avoidance behaviour away from polluted locations. There is clear experimental evidence that exposure to high CO₂ disrupts the ability to find settlement sites and shelters, the ability to detect predators and the ability to detect prey and food. In marine vertebrates and marine crustaceans behavioural change appears to occur via info-disruption. In hermit crabs and other crustaceans impairment of performance capacities might also play a role. We discuss the implications for such behavioural changes in terms of potential impacts at the levels of population health and ecosystem services, and consider future directions for research.
Like people, hermit crabs and other animals trade up by treasuring what others leave behind
A number of resources important to humans such as jobs in bureaucracies, houses and apartments are allocated through a mechanism known as a vacancy chain. In a vacancy chain process an initial, vacant resource unit entering a population of users is taken by a first individual who leaves his/her previous resource unit behind, which is taken by a second individual, and so on. In this process an initial resource unit works both directly and indirectly to provide opportunities for several individuals to gain new and better resources. Vacancy chains are hypothesized to be important in resource distribution for a variety of non-human animals, and it is documented, in particular, that the hermit crab Pagurus longicarpus gets the gastropod shells in which it lives through this mechanism. The direct and indirect effects of vacancy chains on hermit crabs and the systematic ways in which chains flow through groups of crabs and their resources are indicated. In systems where they occur, it is further hypothesized that vacancy chains have unique implications for the ecology of resource users. Several of these hypotheses are explored using the example of hermit crabs.
Terrestrial hermit crabs (Coenobita compressus (H. Milne Edwards)) on Isabel island, México, prefer Nerita (Ritena) scabricosta (Lanark 1822) over other species of shells. Nerita scabricosta, the lightest species of shell, has the highest internal volume/weight ratio (IV/W ratio) of all species available at the island. Heavier shells (low IV/W ratio) are more costly to carry and may restrain growth. We hypothesized that crabs will search for shells with high IV/W ratios to save energy, and predicted that in every individual shell-exchange crabs will prefer a shell with a higher IV/W ratio. Observations of spontaneous aggressive shell-exchange interactions in nature between crabs carrying preferred shells (with high IV/W ratio) and crabs using less preferred species of shells (low IV/W ratio) support this idea. By inducing individual shell exchanges in the field, we experimentally confirmed the preference for shells with high IV/W ratio, and we also showed that crabs prefer larger shells over those they were bearing. Moving to a larger but not heavier shell may facilitate growth though saving energy that would otherwise be spent in locomotion. High growth rates seem to be advantageous because size is a correlate of fertility, since large males apparently have more access to females, and large females produce larger clutches, thus indicating the possible reproductive benefits for preferred light and large shells.
Gastropod shells are limited resources for most hermit crab species, acting as primary factors in various aspects of their
biology. To investigate the efficacy of different behavioral tactics adopted for their acquisition (locomotion, attendance
at shell-supplying sites, interactions with conspecifics in aggregation) we conducted observations and experiments at a salt
marsh in New England (USA). Locomotion, fast and meandering, significantly increased the chances of encountering empty shells
and conspecifics. However, shell exchanges were rare. Simulated gastropod predation sites quickly attracted a larger number
of hermit crabs than the other shell-supplying sites tested (live and dead conspecifics, live snails) and induced the rapid
occupancy of all the empty shells offered, usually by the first crabs arriving at the site. Aggregations seemed not to function
as shell exchange markets, as previously suggested for several other species. In the short run, exploitation seems to be more
efficient for the acquisition of new shells by Pagurus longicarpus. In the long run, it is the density of nondestructive gastropod predators that regulates the availability of new shells of
good quality in the pool available to this hermit crab species.
A vacancy chain is a unique type of resource acquisition process composed of an interconnected series of events in which the gaining of a particular resource unit by one individual depends directly on prior acquisition events by other individuals. Taken from the sociological literature, vacancy chains may also describe the distribution of many types of animal resources such as burrows, dwellings and shelters. Using data on hermit crabs, we present a Markov model simulating a vacancy chain process, and test the model against field data. Our results show that a simple Markov model adequately describes shell acquisition in hermit crabs, and that models combining shell size and crude estimates of quality fit the data extremely well. We illustrate in detail how to generate vacancy chain models from ecological data, how to determine the number and size of organisms gaining new resource units from resource introductions of specific sizes, and how to statistically evaluate the accuracy of Markov models. Not recognizing the presence of a vacancy chain system may lead to serious errors in estimating resource dynamics and therefore in demographic and competition models based on these dynamics. Finally, we suggest some ways in which vacancy chain models can aid studies of competition, population dynamics, life histories, and conservation in species using this type of resource acquisition process.
This paper presents an algorithm for task allocation in groups of homogeneous robots. The algorithm is based on vacancy chains, a resource distribution strategy common in human and animal societies. We define a class of task-allocation problems for which the vacancy chain algorithm is suitable and demonstrate how reinforcement learning can be used to make vacancy chains emerge in a group of behavior-based robots. Experiments in simulation show that the vacancy chain algorithm consistently outperforms random and static task allocation algorithms when individual robots are prone to distractions or breakdowns, or when task priorities change.
Land hermit crab responses to volatile shell-investigation cues from land hermit crabs and from marine hermit crabs are analogous to the responses of marine hermit crabs to shell-investigation cues from marine crabs and from snails. Land hermit crabs attracted to shell cues are in worse-fitting shells and are more likely to investigate conspecifics' shells than are crabs attracted to feeding cues. Moving land hermit crabs from worse shells to better shells decreases the number of crabs investigating shells, while moving crabs from better shells to worse shells increases the number of crabs investigating shells. Gravid females have better-fitting shells than nongravid females or males. Crabs from two different populations in Panama have different shell fits and show different levels of responses to shell-investigation cues. Land hermit crabs respond to volatile shell-investigation cues from both land and marine hermit crabs, but marine hermit crabs do not respond to cues from land hermit crabs. A cue detection system for volatile cues most likely evolved in land hermit crabs during their transition from a marine to a terrestrial existence. Thus, the cues found in land hermit crabs and marine hermit crabs may be chemically similar. Volatile compounds collected from hermit crabs onto Tenax columns can be eluted with ethanol and act as shell-investigation cues in field assays. Peer Reviewed http://deepblue.lib.umich.edu/bitstream/2027.42/44885/1/10886_2005_Article_BF02059873.pdf
A series of experiments at two tropical locations tested the ability of land hermit crabs Coenobita perlatus (H. Milne Edwards) and Coenobita compressas (H. Milne Edwards) to detect and respond to odors of dead conspecifics. An attraction array compared numbers of crabs attending hidden food odors and dead conspecific odors. Pit experiments tested crab shell-acquisition behaviors at different hidden odors. Bucket experiments confined crabs collected from various categories (feeding crabs, wandering crabs and crabs aggregated at dead conspecific odors) and tested behavioral responses to odors and an empty shell. Land hermit crab behavior at both sites was similar. Crabs were attracted to dead conspecific odors up to 10 times more than to food odors. Crabs attracted to dead conspecifics displayed significantly more shell-acquisition behaviors: touching other crab's shells in an exploratory manner and switching shells if an empty shell was available. In buckets, crabs from each category switched into shells. Results are compared to previous reports of similar shell-seeking behaviors by marine hermit crabs in response to dead conspecific odors. It is suggested that responding to dead conspecific odors for shell source location is an evolutionarily conserved behavior developed before hermit crabs became terrestrial. Peer Reviewed http://deepblue.lib.umich.edu/bitstream/2027.42/31261/1/0000167.pdf
Social scientists have long used ‘chain’ metaphors, yet their methodological justification remains somewhat hazy. This paper offers a rationale for using chains to measure changes in economic welfare in urban and regional contexts. In contrast to the Marshallian surplus, which well describes situations in which price changes generate rents in a single market, chains are especially useful in markets where changes lead to the transmission of demand or supply through a series of markets characterized by sticky prices and markups. This argument is illustrated by reference to chain-driven analyses of local production, labor, and housing markets. The institutional structures that underpin chain models are stressed.
Linear hierarchies, the classical pecking-order structures, are formed readily in both nature and the laboratory in a great range of species including humans. However, the probability of getting linear structures by chance alone is quite low. In this paper we investigate the two hypotheses that are proposed most often to explain linear hierarchies: they are predetermined by differences in the attributes of animals, or they are produced by the dynamics of social interaction, i.e., they are self-organizing. We evaluate these hypotheses using cichlid fish as model animals, and although differences in attributes play a significant part, we find that social interaction is necessary for high proportions of groups with linear hierarchies. Our results suggest that dominance hierarchy formation is a much richer and more complex phenomenon than previously thought, and we explore the implications of these results for evolutionary biology, the social sciences, and the use of animal models in understanding human social organization.
Part 1 Assessments, decisions and hermit crabs: assessments and decisions the behavioural ecology of hermit crabs "pagurus bernhardus" in Northern Ireland. Part 2 Non-competitive assessment: assessment of unoccupied shells assessment and motivational change. Part 3 Competitive assessment: agonistic behaviour assessments during shell fights assessment strategies and the duration of fights motivational change during aggressive encounters.
In Pagurus bernhardus, the relative sizes of the crabs and shell quality of the larger crab influenced the probability of occurrence of a shell fight. These two factors along with the quality of the smaller crab's shell influenced the probability of an escalated fight occurring. During a shell fight, the attacker was able to assimilate information concerning the defender's shell and to compare it with the shell in possession. On the basis of this comparison the attacker decided whether or not to evict the defender and effect a shell change. The defending crab did not have access to information about the attacker's shell and therefore could only estimate the quality of its own shell. This asymmetry of information experienced by the crabs ensured that the attacker decided the outcome of a shell fight.-from Authors
The social interactions of Coenobita clypeatus resemble those of marine hermit crabs in many ways. Stereotyped movements of the chelipeds and ambulatory legs were often executed as two crabs approached each other. Idividuals also have a repertoire of shell fighting behavior patterns, including rotating movements by the attacker and production of a chirping sound by the defender.
Field studies with three common local species of hermit crabs,Clibanarius vittatus, Pagurus longicarpus, andPagurus pollicaris, showed that these crabs responded behaviorally to chemicals originating from crushed conspecifics. Hermit crabs are attracted specifically and in a manner similar to previously reported crab responses to odors from dead gastropods. Responses byC. vittatus to both kinds of odor are of three types: (1) aggregation/shell investigation responses (previously reported for odors from dead gastropods), characterized by increased locomotor activity, investigation of shells in the vicinity, and switching into empty shells; (2) alarm responses, in which crabs flee the area; and (3) withdrawal responses, in which crabs pull into their shells and do not come out. Studies withC. vittatus showed that the stimulatory chemicals originate from hemolymph, are less than 500 D, adsorb to octadecyl silica, and are recovered by elution with 20% methanol. Responses ofC. vittatus are dependent upon crab size, type of shell occupied, and shell fit. Chemicals originating from dead conspecifics provide a forum for shell acquisition by crabs in relatively small shells and alarm by crabs in relatively large shells.
During fights animals are expected to make a series of strategic decisions that involve interactions between information about the contest and the individual's nervous system that produce a change in behaviour. Biogenic monoamines such as serotonin ('5-HT') and dopamine are thought to prime decision-making centres for appropriate responses during aggressive interactions in crustaceans, and circulating levels vary both between individuals and during agonistic encounters. Aminergenic systems operate in diverse animal taxa and in this study we assayed circulating levels of 5-HT and dopamine following shell fights in the common European hermit crab, Pagurus bernhardus. The two roles in these fights, attacker and defender, perform different activities but, in both, 5-HT increased and dopamine declined in response to engaging in a fight. In defenders but not attackers, giving up was correlated with low 5-HT and dopa- mine. In attackers, motivation to initiate a fight was positively correlated with dopamine levels. Circulat- ing monoamines are therefore involved in decision making during these aggressive encounters.
The focus of this report is on the predictive accuracy of residential vacancy chain models. There are two objectives. The first is to define the mathematical structure of a pair of multisectoral residential vacancy chain models. These models simulate the intersectoral transfer of vacant housing opportunities in response to either the creation of new opportunities or the absorption of existing ones. Residential mobility is given as an analytical by-product. The second objective is to calibrate these models and gauge the accuracy of their projections. Models with six housing sectors each are calibrated with 1975-80 data from three different Swedish municipalities (Gävle, Jönköping and Vasteras). Calibrations are used for projections into the proximate 5-year period. Projections of intersectoral residential mobility for 1980-85 are compared statistically with observed moves for the period. Coefficients of determination range between 0.93 and 0.97. Log-linear analysis shows projection error ranging from 3 to 12 per cent. The projective accuracy of these models exceeds that of any known alternative. The empirical success of these models points to their value in understanding processes affecting the formation and change of urban residential structure.
Hermit crabs fight for ownership of shells, and shell exchange may occur after a period of shell rapping, involving the initiating or attacking crab bringing its shell rapidly and repeatedly into contact with the shell of the noninitiator or defender, in a series of bouts. The temporal pattern of rapping contains information about the motivation and/or relative resource holding potential (RHP) of the initiator and acts as a repeated signal of stamina. Here we investigated the role of the force with which the rapping is performed and how this is related to the temporal pattern of rapping by rubberizing the external surface of shells. Initiators that are prevented from rapping with their usual level of force persist with the activity for longer over the whole encounter but use fewer raps per bout and are less likely to effect an exchange than those supplied with control shells. The fact that the force of rapping affects the likelihood of a crab being victorious suggests that either the force of rapping contains information about motivation or RHP or that force directly affects noninitiators, reducing their ability to maintain an adequate grip on their shells. The data suggest that shell rapping is an agonistic signal rather than one that provides information useful to the noninitiator, as has been suggested by the negotiation model of shell exchange. Key words: aggression, agonistic behavior, communication, hermit-crabs, signal. (Behav Ecol 11:288-293 (2000))
Residential vacancy chain models simulate the transfer of vacant housing opportunities among sectors of an urban housing market. The Markov model simulates forward-reaching chains in response to vacancy initiations. The Leontief model simulates backward-reaching chains in response to vacancy absorptions. Each simulates residential mobility among housing sectors as a by-product. The accuracy of these models was assessed in earlier work by the authors, using 1975-80 data from Gävle, Jonkoping and Vasteras, Sweden, to project intra-urban residential mobility in each town during the 1980-85 period. Using log-linear analysis to compare projected moves with observed moves, they found projection errors ranging from 3-12 per cent. In this paper, data from the 1985-90 period are used first to repeat these assessments over the subsequent time-period and then to extend the projection period from 5 to 10 years. Projection errors range from 5-11 per cent for the 5-year period and from 8-18 per cent for the 10-year period. Both the Markov and the Leontief models perform equally well. Models with more homogeneous housing sector definitions produce more consistent results.
This report examines the relationship within urban housing markets between residential mobility and housing opportunity, The basic unit of analysis is neither households nor housing units but rather vacant housing opportunities. Objectives are three-fold, The first is to clarify concepts about opportunity and mobility within housing markets. Clarification begins with the observation that mobility is limited to a set of currently vacant housing opportunities, continues through reasons for the existence of opportunity differentials and proceeds toward the development of historically and structurally based theories of intraurban residential mobility. The second objective is to define the mathematical structure of a pair of multisectoral residential vacancy chain models that operationalise these concepts. These models simulate the transfer of vacant housing opportunities among housing sectors in response to either the creation of new opportunities or the absorption of existing ones. Residential mobility is given as an analytical by-product. The third objective is to calibrate these models and gauge the accuracy of their projections. The accuracy of these models exceeds that of any known alternative. Vacancy transfer models are shown to be useful in housing programme assessment, in the assessment of regional housing needs and in the design of local housing programs. Their core matrices are useful in tracing chains of opportunities among housing sectors, in determining whether opportunities filter down to those who cannot afford newly constructed units and in defining the ways in which in-migrants and newly formed household support residential mobility among existing residents.
The concept of vacancy chains, originally developed in Harrison White’s pioneering analysis of organizational mobility processes, has been extended to phenomena as diverse as national labor and housing markets, the historical development of professions, gender and ethnic group discrimination in job and housing markets, organizational demography, and the mobility of hermit crabs to empty snail shells. In all populations in which they occur—whether human or animal—vacancy chains appear to organize a variety of social processes in nearly identical ways. This chapter provides a broad and relatively nonmathematical review of the vacancy chain literature covering basic definitions and formulations, main theoretical ideas and assumptions, comparisons of social processes in different vacancy chain systems, and several conceptual and methodological extensions to vacancy chain analysis. The review concludes by discussing a number of outstanding problems, present limitations, and promising areas for future research ...
Vacancy chain theory describes a unique mechanism for the sequential distribution of animal resources across multiple individuals. This theory applies to any resources, such as shelters or nest sites, that are discrete, reusable, and limited in use to single individuals or groups at one time. Hermit crabs rely on gastropod shells for shelter, and a single vacant shell can initiate a chain of sequential shell switches that distributes new resources across many individuals. Using the terrestrial hermit crab Coenobita clypeatus, we examined the previously untested theoretical prediction that this process will yield trickle-down resource benefits to vacancy chain participants (aggregate benefits). In laboratory experiments, we measured improvements in shell quality when a single vacant shell was provided to groups of eight crabs. We found that crabs participating in vacancy chains (averaging 3.2 individuals) gained significant reductions in their shell crowding. In addition, vacancy chains terminated early when experimental groups included a single crab occupying a damaged shell, because damaged vacancies always remained unoccupied. Hermit crabs in damaged shells were more likely to win resource contests for high quality shells against size-matched hermit crabs in crowded shells. Finally, field additions of many new shells to an island population of C. clypeatus hermit crabs reduced average shell crowding for crabs of all sizes, possibly from propagation of benefits through vacancy chains. These results provide empirical support for the theoretical prediction that vacancy chains should provide benefits distributed across many vacancy chain participants. Since shelter-based vacancy chains likely occur in other animals, additional studies of vacancy chain processes should provide new insights into resource acquisition behaviors in diverse animal groups.
Aim To examine patterns of abundance, density, size and shell use in land hermit crabs, Coenobita clypeatus (Herbst), occurring on three groups of small islands, and to determine how these variables change among islands.
Location Small islands in the Central Exuma Cays and near Great Exuma, Bahamas.
Methods Land hermit crabs were captured in baited pitfall traps and were separately attracted to baits. A mark–recapture technique was used in conjunction with some pitfall traps monitored for three consecutive days. The size of each crab and the type of adopted gastropod shell were recorded, along with physical island variables such as total island area, vegetated area, island perimeter, elevation and distance to the nearest mainland island.
Results Relative abundances, densities and sizes of crabs differed significantly among the three island groups. Densities of land hermit crabs were as high as 46 m−2 of vegetated island area. In simple and multiple linear regressions, the only variable that was a significant predictor of the abundance of hermit crabs was the perimeter to area ratio of the island. Patterns of gastropod shell use varied significantly among the island groups, and the vast majority of adopted shells originated from gastropod species that inhabit the high intertidal and supratidal shorelines of the islands.
Main conclusions Although densities of land hermit crabs varied, they were relatively high on many islands, and land hermit crabs may play an important role in these insular food webs. Patterns of shell use may be strongly restricted by island geomorphology: irregular shorelines provide relatively more habitat for the gastropod species that account for the majority of adopted shells and the steep sides of the islands prevent the accumulation of marine gastropod shells. The size of adult hermit crabs appears to be limited by the relatively small gastropod shells available, while the abundance of hermit crabs may be limited by the number of shells available.
Recent studies add to the large body ofliterature on residential mobility bypresenting a fresh view of the residentialmobility process. At the micro level, newresearch sheds light on the jointdecision-making by members of a householdregarding a residential move, and clarifies thelink between place of residence and place ofwork. There are also many new studies onfinding an alternative dwelling if the mostpreferred house is unavailable. Householdrelocation is strongly embedded in housingmarket conditions at the local and nationallevel. Recent studies analyse variations in themobility process over space and time.
To address the question of hermit crab clustering, 11 clumps composed of Clibanarius laevimanus were studied in the mangal of Mida Creek, Kenya in 1988. Hermit size and sex were analyzed, as well as the type, dimensions, and status of their shells. Empty gastropod shells constituted a limiting factor on the population studied; the architectural traits which seemed to be favored by the hermits were those associated with a defence against crab predators (high weight and narrow apertures). Differences in either the availability of adequate shells or in the services provided by the housing in question explained the observed diversity in both the type and the mass of shells occupied among the examined population categories. Furthermore, each clump showed homogeneity with respect to the dimensions of the hermits participating in it, and immature and adult specimens were partitioned among three cluster types. It is suggested that clustering might be classified as a social phenomenon, becaus hermits are attracted by similarly sized conspecifics, interact through an elaborate communication system, and because most benefit from a chain process in shell exchange.
Drawing on ethnic succession and vacancychain approaches, I argue that lawenforcement efforts targeted at establishedcriminal enterprises can lead to unintendedvacancy chains in criminal economies. Theextent and impact of these chains onmobility varies, however, depending on theextent to which amputation, decapitation,or eradication enforcement strategies areused. To illustrate this argument, Iexplore crime control policies, vacancychains and mobility in drug markets in thecities of Chicago and Osaka.
Simulated gastropod predation sites were observed in the gulf intertidal near the Edward Ball Marine Laboratory, Sopchoppy, Florida,Fundulus similis, Callinectes sapidus, Melongena corona, Clibanarius vittatus, andPagurus longicarpus were attracted to the sites by small molecules released passively from the flesh of wounded or dead animals. Flesh consumers (F. similis, C. sapidus, andM. corona) were attracted to molecules released from the flesh of bivalves, gastropods, and crabs. Shell users (C. vittatus andP. longicarpus) were attracted only to small molecules from gastropod flesh, withP. longicarpus attendingP. duplicatas sites whileC. vittatus preferentially attendedM. corona, Busycon contrarium, andBusycon spiratum sites. Flesh consumers and shell users may be attracted to the sites by different sets of small molecules. The addition of proteolytic enzymes to the flesh increased the attendants at a site, indicating that the attractant molecules might be amino acids or small peptides. Flesh consumers were attracted to the sites primarily in the first 12 hr while the shell users were attracted from 2 hr to several days postinitiation. New shells were attractive to hermit crabs up to 12 hr after entry by a hermit crab. The shell species of the attendantC. vittatus were in different proportions than the generalC. vittatus population, and the shell fit of theP. longicarpus attendants was not as good as the general population ofP. longicarpus. Significantly moreC. vittatus attended than P. longicarpus, and it was speculated that there were moreC. vittatus in the area with a poor shell fit thanP. longicarpus.
A study was conducted to determine whether asymmetries in both resource-holding potential (RHP) and resource value (RV) influence
dominance and fighting behavior in the hermit crab Pagurus longicarpus. A total of 120 groups of three crabs were observed for 10min in four experiments that tested all diverse combinations of
equal/different RHP (i.e. ‘body size’) and equal/different RV (i.e. ‘shell size’ and ‘shell quality’). In a fifth experiment,
dominant and subordinate individuals of the same size category (26 groups) were forced to enter shells of opposite quality
than those previously occupied, and then the behavior of the reconstituted original groups was observed for additional 10min.
As expected, crabs in lower quality shells were more willing to initiate and to escalate fights. However, their attacks were
directed to any crab of the group, independently of the defender's shell quality, and the fight duration did not vary with
the different value of the resources at stake. This may indicate that P. longicarpus is unable to assess the quality of the shells available in its social environment but bases its tactical decisions during
fights solely on its own resource. This suggestion was confirmed by the change in the fighting behavior of crabs whose shell
quality was experimentally altered. This manipulation induced an overall increase in the intensity of aggression, drastic
modification of crab behavior, and inversion of the hierarchy even though these crabs have had previous experiences of wins/losses
and were familiar to the other members of the group. In this species, large crab size and/or the occupancy of adequate (and
oversized) shells appeared to be the most likely determinant of contest resolution. Individuals seemed to retain a memory
of the previously held resource and behaved accordingly.
Freilandbeobachtung des Erwerbs von Schalen einer durch Raubschnecken frisch getteten Schnecke durch Einsiedlerkrebse.
The proximate and ultimate factors of the clustering behavior in the mangal-dwelling hermit Clibanarius laevimanus have been studied at Mida Creek, Kenya. First, field experiments showed that the hermits correctly oriented towards their clustering sites after deprivation of references from the sky, landscape, and substrate. Second, the pros and cons are weighed of various hypotheses on the adaptive significance of clustering; the most plausible is that aggregations may serve as “shell exchange markets”. Although shell exchange is rare, most hermits in the group could benefit from such a chain process, and the adaptive significance of clustering could be “magnified”.
The importance of physical resources in influencing life chances makes the study of resource allocation processes and rules especially pertinent and this leads naturally to the question: who gets what and why? This article focuses on the significance of housing construction for residential mobility and addresses the vital question: who will gain from new construction? It examines whether it is possible to build directly for well-resourced households and hope that it indirectly also supports lower income households. It also examines the possibility that changes in the way in which the housing market operates with market-driven construction, geared at a post-modern housing lifestyle, have changed the situation for less well resourced households, compared to traditional housing construction. The study is based on a unique longitudinal database that covers the total population in Sweden over the period 2000-2002. The data are analysed using a Markov chain model that provides a way of analysing the relationship between vacancies in the housing market and household mobility. Tentative answers to questions on the length of the vacancy chains that are created when different types of dwellings become vacant in Stockholm city and what type of households are involved and not involved, are given. These answers have important implications for urban planning.
Agonistic interactions between animals are often settled by the use of repeated signals which advertise the resource-holding potential of the sender. According to the sequential assessment game this repetition increases the accuracy with which receivers may assess the signal, but under the cumulative assessment model the repeated performances accumulate to give a signal of stamina. These models may be distinguished by the temporal pattern of signalling they predict and by the decision rules used by the contestants. Hermit crabs engage in shell fights over possession of the gastropod shells that they inhabit. During these interactions the two roles of signaller and receiver may be examined separately because they are fixed for the duration of the encounter. Attackers rap their shell against that of the defender in a series of bouts whereas defenders remain tightly withdrawn into their shells for the duration of the contest. At the end of a fight the attacker may evict the defender from its shell or decide to give up without first effecting an eviction; the decision for defenders is either to maintain a grip on its shell or to release the shell and allow itself to be evicted. We manipulated fatigue levels separately for attackers and defenders, by varying the oxygen concentration of the water that they are held in prior to fighting, and examined the effects that this has on the likelihood of each decision and on the temporal pattern of rapping. We show that the vigour of rapping and the likelihood of eviction are reduced when the attacker is subjected to low oxygen but that this treatment has no effect on rates of eviction when applied to defenders. We conclude that defenders compare the vigour of rapping with an absolute threshold rather than with a relative threshold when making their decision. The data are compatible with the cumulative assessment model and with the idea that shell rapping signals the stamina of attackers, but do not fit the predictions of the sequential assessment game.
Understanding the costs of signals used in fights is the key to understanding decisions made by contestants. Hermit crabs use shell rapping. This is a clearly defined agonistic signal, which can be quantified in temporal terms and in the power of the key shell-rapping signal component. We examine the relationship between the power expended by attacking hermit crabs and their consequent lactate levels. High power expenditure over the whole fight leads to high lactate, and attackers give up when lactate is high. Some defenders give up early in fights, particularly if the power of raps in early bouts they receive is high. These defenders and those not allowed to fight have low glucose, but those that successfully resist eviction have high glucose. Glucose is mobilized in an attempt to resist; nevertheless, some defenders that attempt resistance are still evicted by persistent attackers. Thus, early power of the signal is a major determinant of success for attackers, albeit at a cost. These data show the link between power, repetition of a signal, metabolic consequences and decisions of contestants in fights. The different activities, decisions and costs of the two roles are not adequately described by existing models of contests.
