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UTILIZATION OF SHELL RESOURCES BY THE HERMIT CRABS CALCINUS LATENS AND CALCINUS GAIMARDII AT KENTING, SOUTHERN TAIWAN
Abstract
Shell resource utilization in two common species of hermit crabs, Calcinus latens (Randall) and Calcinus gaimardii (H. Milne Edwards), from intertidal and subtidal zones at Kenting, southern Taiwan, was studied. Field data were compared with laboratory results in shell-selection tests. Shell parameters examined included shell length, shell width, aperture length, aperture width, and weight in sea water. Crab parameters examined included carapace length, shield length, and wet weight. Most intertidal C. latens did not use the most abundant shell type in the field, but showed a strong preference for the most abundant shell type in shell-selection tests. The small size of the most abundant shell type in the field appeared to be responsible for this pattern. The results of shell-fit tests showed that most crabs lived in adequate shells at least in terms of internal volume. Shell-selection tests, however, proved that larger crabs (carapace length > 5 mm) are more shell-limited than smaller ones by SAI (shell adequacy index) values. Larger crabs would select much larger shells if they were available. Differences in shell utilization between the subtidal C. latens and C. gaimardii are discussed.
... In nature, hermit crabs are normally not capable of removing the body of live gastropods to acquire their shells (Laidre, 2011) (but see Rutherford, 1977 for an exception), and consequently, they depend on dead gastropods (Scully, 1979). For this reason, the availability of gastropod shells is a limiting factor for hermit crab distribution (Shih and Mok, 2000). Various other studies have shown that the species, size, abundance and quality (or condition) of gastropod shells commonly influence the population size (Vance, 1972), growth (Fotheringham, 1976; Turra and Leite, 2003), morphology (Blackstone, 1985), fecundity (Childress, 1972; Fotheringham, 1976) and survivorship (Angel, 2000; Lively, 1988) of hermit crabs. ...
... Hermit crabs are the only anomuran decapod crustaceans that use empty gastropod shells (Hazlett 1981), which serve as portable shelters that provide protection for their soft abdomens (Hahn 1998). These shells, in turn, may restrict crab growth and force the animal to search for new and larger shells during its lifetime (Shih & Mok 2000; Turra 2003; Hazlett et al. 2005). The strong association between these crabs and their shelters has profoundly influenced almost all aspects of their biology (Hazlett 1981), and this has contributed to the success of these crustaceans, which are found in almost all marine environments as well as in terrestrial habitats (see Hazlett 1981; McLaughlin 1983). ...
The effect of crab behaviour on shell-use dynamics was analysed, comparing both interference and exploitation behaviours between the hermit crabs Pagurus criniticornis and Pagurus brevidactylus. Although these species exhibited microhabitat separation, with P. criniticornis dominating (100%) in sandy substrates and P. brevidactylus (80%) on rocky shores, they overlapped in the rocky shore/sand interface (P. criniticornis, 53%; P. brevidactylus, 43%). Pagurus criniticornis occupied shells of Cerithium atratum in higher frequencies (84%) than P. brevidactylus (37%), which was hypothesized to be a consequence of competitive interactions combined with their ability to acquire and/or retain this resource. The species
P. criniticornis was attracted in larger numbers to simulated gastropod predation events than was P. brevidactylus, which, on the few occasions that it moved before P. criniticornis, tended to be attracted more rapidly. Interspecific shell exchanges between these species were few, suggesting the absence of dominance relationships. The shell-use pattern in this species pair is thus defined by exploitation competition, which is presumed to be intensified in areas of microsympatry. These results differ from other studies, which found that interference competition through interspecific exchanges shapes shell use, indicating that shell partitioning in hermit crabs is dependent on the behaviour of the species involved in the contests.
Portunid crabs are strong predators in shore ecosystems, and often prey on hermit crabs. In a previous study, we observed the loss of larger individuals of the hermit crab Diogenes nitidimanus during the mid-reproductive season. Therefore, we experimentally investigated predation intensity of the portunid crabs Charybdis japonica and Portunus pelagicus on D. nitidimanus collected from the tidal flat of the Waka River to elucidate the effects of predator body size, prey shell type and shell size, and season. Each predator was given six prey items with a combination of two shell types (Umbonium and Batillaria) and three shell size classes. We replaced eaten prey items daily with identical ones in terms of shell size and type, and recorded the number of prey items eaten over 10 days per predator. However, we were unable to analyze the effect of season for P. pelagicus because of the species’ limited periods of collection. C. japonica preferred prey with small, Umbonium-type shells. The total number of prey items eaten increased in summer, but not with body size. By contrast, P. pelagicus preferred prey with Batillaria-type shells, and predator body size tended to be a more important factor in the context of medium- and small-sized shells. Batillaria-type shells are likely more resistant to crushing pressure than Umbonium-type shells. More smaller prey were eaten during the experiment, which does not explain the loss of larger individuals at the study site.
The gastropod shell utilization pattern of the hermit crab Clibanarius antillensis Stimpson 1862 was studied at Montepio, Veracruz, Mexico. Specimens were collected along the intertidal zone. All gastropod shells were identified, measured, and weighed. Hermit crabs occupied 25 species of gastropod shells; Odostomia sp. was the most occupied shell, followed by Modulus modulus Linnaeus 1758. Hermit crabs were found more frequently in shells that were relatively lighter for their size (lower shell weight/shield length ratio). Males used relatively heavier shell types than females and ovigerous females. The Olmstead-Tukey diagram showed ten shell species as dominant, seven shell species as rare, two shells as occasional, but none as frequent.
Shell selection behaviour and spatial distribution of three hermit crab species, Diogenes avarus, D. karwarensis, and Areopaguristes perspicax, were studied at six sites along the intertidal zones of Hormuz Island in the Persian Gulf. 1025 specimens were collected occupying altogether 31 shell species (D. avarus 28 species, A. perspicax 22 species, and D. karwarensis 8 species). Diogenes avarus was found to be by far the most abundant of these three crab species, and Cerithidea cingulata the dominant shell occupied by these hermit crabs. The distribution of the hermit crabs significantly varied (p Keywords: Hermit crab; Hormuz Island; Persian Gulf; distribution; shell selection behaviour Document Type: Research Article DOI: http://dx.doi.org/10.1080/09397140.2014.966521 Affiliations: 1: Department of Marine Biology, Faculty of Marine Sciences, Tarbiat Modares University, Noor, Iran 2: Iranian Fisheries Research Organization (IFRO), Tehran, Iran 3: Persian Gulf and Oman Sea Marine Environment Research Center, Hormuz Island, Iran Publication date: October 2, 2014 (document).ready(function() { var shortdescription = (".originaldescription").text().replace(/\\&/g, '&').replace(/\\, '<').replace(/\\>/g, '>').replace(/\\t/g, ' ').replace(/\\n/g, ''); if (shortdescription.length > 350){ shortdescription = "" + shortdescription.substring(0,250) + "... more"; } (".shortdescription a").click(function() { (".originaldescription").slideDown(); return false; }); }); Related content In this: publication By this: publisher By this author: Seyfabadi, Jafar ; Kheirabadi, Nabiallah ; Owfi, Fereidoon ; Mahvary, Alireza GA_googleFillSlot("Horizontal_banner_bottom");
The present work aims to assess the spatial distribution, analyze shell utilization, shell fitness and determine the effect of coexistence of two hermit crabs Calcinus latens and Clibanarius signatus on used shell resources in various habitats on the Red Sea Coast. Also, to determine the choice of shells and investigate the shell species preference of C. latens and C. signatus in the laboratory. The hermit crabs C. latens and C. signatus were found to occupy shells of 39 gastropod species. The most commonly occupied gastropod shells are those belonging to genera Strombus, Nerita, Cerithium and Planaxis. The results showed that crab individuals utilized mainly the shell with elongate aperture. Laboratory experiments showed that two crab species preferred shells of Strombus followed by Cerithium and Nerita when offered shells of nearly similar size (optimal). Crab individuals showed a significant preference for optimal sized shells when given suboptimal shells as an alternative choice. Also, the hermit crabs avoid damaged shells when given a choice of optimal sized damaged shell and optimal sized intact one. In addition, two hermit crab species chose shells of smaller than optimal size when given a choice of damaged optimal sized shells and smaller intact ones. On the other hand, field observations showed that most crab individuals lived in adequate sized shells. The present data conclude that shell selection by hermit crabs C. latens and C. signatus depends mostly on shell internal volume, shell quality and shell aperture size than other factors, because they provide a maximum protection for hermit crabs.
The preference of the hermit crab, Calcinus
californiensis, among six species of shells, was tested by two different experiments. The first experiment used pair-wise trials, analyzing the preference by Chi-square tests using two different constructions of the null hypothesis. One hypothesis was based on a no-preference among shell species, the second on comparing the number of crabs changing for a particular shell species when two options were given versus the changing when no options were offered. The second experiment was a multiple-alternative test based on a rank ordering of the shell preference. This method has both statistical and resource-saving advantages over the traditional pair-wise comparisons. The sequence of shell preference was similarly independent of the procedure used. The preferred shell species are heavy and might be associated with hydrodynamic advantages and with the protection against predation. The shell preference matches with the pattern of shell occupancy indicating that the shell use in nature is determined by the crab’s preference. The information generated may be used for further research on shell preference as a methodological alternative.
Hermit crabs select shells based on size, weight, species of gastropod, and shell condition. However, in many environments, empty, undamaged gastropod shells are in short supply and this shortage may influence hermit crab shell selection behavior. In this study, the effects of isolation, competition, and predation on shell selection behaviors were investigated using Pagurus granosimanus (Stimpson), a hermit crab from San Juan Island, WA. The hermit crabs were provided with a choice between undamaged, slightly damaged, or very damaged Nucella lamellosa (Gmelin) gastropod shells and were subjected to either isolation (control treatment), water infused with the chemical cues of conspecific hermit crabs (competition treatment) or water infused with both predator (Cancer magister, Dana), and dead conspecific chemical cues (predation treatment). In all 3 experimental treatments, after a trial duration of 20 min, hermit crabs preferentially selected the undamaged shell. However, the frequency of shell switches varied significantly between the three experimental conditions. Hermit crabs in the control treatment switched between shells most frequently and hermit crabs in the competition group switched least frequently. Additionally, larger hermit crabs switched shells more frequently than smaller hermit crabs in all experimental conditions. In settings where competition is the primary environmental stress, such as in the San Juan Islands, the reduced frequency of shell switching may have a long-term effect on hermit crab defense against predation, in turn reducing the reproductive success and population size of hermit crabs.
A characterization of the occupied shells by the hermit crab Clibanarius vittatus was carried out. Hermit crabs were collected in the intertidal zone, during the low spring tide monthly from April 2005 to March 2006. They were sexed and their cephalothoracic shield length (CL) was measured. Shells were identified, dried, weighed and the aperture length (AL) and width (AW) were measured. 1187 crabs were collected (949 males, 216 females and 22 intersexes), which occupied 12 species of gastropod shells. Stramonita haemastoma, Olivancillaria urceus and Dorsanum moniliferum made up 96.55% of the total shell species. Male hermit crabs attained significantly larger sizes than females; therefore, males occupied a wider spectrum of shells in size and weight. A stronger correlation ratio was obtained between CL and AW of S. haemastoma. Last whorl with a rounded shape and a spacious inner area is a common feature of all shell species most frequently occupied by this hermit crab where it occurs. The successful establishment of C. vittatus at Baixio Mirim is mainly due to the appropriately shaped and wide range of size of S. haemastoma shells that were most often occupied by the hermit crabs of the studied population.
Les taux de croissance du Paguride Clibanarius albidigitus se sont révélés influencés de façon significative par le type de coquille occupé. Le taux est le plus élevé pour les coquilles légères et à volume interne important, et le plus bas pour les coquilles relativement lourdes, à volume interne faible. De même, la dimension des pontes de C. albidigitus, Calcinus obscurus et Pagurus sp. (non décrit) est affectée de façon significative par le type de coquille. Chez les trois espèces, la ponte est plus importante dans des coquilles légères, à grand volume interne que dans les co- quilles lourdes, à volume interne faible. Les observations sur les avantages résultant du choix de certaines coquilles, en ce qui concerne le taux de croissance et la dimension des pontes, montrent l’importance de ce choix et ses consé- quences dans le domaine de l’écologie et de l’évolution de l’utilisation des coquilles par les Pagurides.
Shell utilization patterns of three sympatric hermit crab species from the Bay of Panama are examined. Shell preferences, as shown by laboratory choice experiments and the selective use of empty shells experimentally added to hermit crab populations, are shown to be important determinants of shell utilization under natural conditions.Factors which influence the types and sizes of shells occupied by hermit crabs in separate populations include: (1) the presence and relative abundance of different gastropod species; (2) the specific shell preferences of different hermit crab species; and (3) the presence and relative abundance of sympatric hermit crab competitors for the limited supply of empty shells. Since the size and type of shell occupied by a hermit crab influences its growth rate and reproductive output, these factors appear to have a direct effect on hermit crab fitness and the demographic structure of separate hermit crab populations.
Shell selection by the hermit crab, Pagurus pollicaris (Say), was studied in a natural population and in laboratory experiments. The results indicate that hermit crabs vary their preference for shells of a certain weight and volume, depending upon the species of shell. When the weight of the shell was increased ≈25%, either by its natural epifauna or artificially, hermit crabs continued to occupy shells of the same size and volume, suggesting that shell volume was more important than weight in shell selection.Alterations of the angle of the shell axis and position of the shell's center of gravity often resulted in an aversion to the altered shells by both P. pollicaris and P. longicarpus (Say), indicating that variations in these two shell properties may influence shell selection. These results provide evidence that hermit crabs select shells on the basis of several shell traits that bear on the protection offered by the shell or by the ease with which it can be carried.
The competitive dynamics of a three-species littoral hermit crab assemblage in Panama are demonstrated. Calcinus obscurus is found in the middle to low intertidal habitat, Clibanarius albidigitus occurs in the middle to high intertidal zone, and Pagurus sp. (undescribed) is found exclusively in the low intertidal habitat. When either Pagurus or Clibanarius are sympatric with Calcinus they occupy shells of poorer quality than they do when they occur alone, while the shell supply of Calcinus is not negatively influenced by sympatry. Experimental addition of empty shells to sympatric and allopatric populations of Calcinus and Clibanarius showed that while Clibanarius exploited empty shells better than Calcinus, Calcinus obtained the new shells over time from Clibanarius via active interference competition. The added shells were also found to move from smaller to larger crabs within 4 d of their introduction. Habitat segregation between Calcinus and Clibanarius is facilitated by the active competitive displacement of Clibanarius by Calcinus. The mechanism of this competitive displacement is shown to be an active escape response of Clibanarius to Calcinus individuals. These results indicate that active competition for a limited supply of shells directly influences the shell quality and spatial distributions of these sympatric hermit crabs. Since shell quality regulates growth and reproduction in hermit crabs, active competition ultimately influences growth and reproduction, demonstrating a fitness cost and benefit to competitors.
The reproductive ecology of three sympatric hermit crab species from the Bay of Panama is examined. All three species reveal patterns of size and reproduction mediated by their supply of shells. Shells are demonstrated to be in limited supply. Crabs with shells large enough to allow growth, put effort into growth at the expense of reducing reproductive expenditures, while crabs in shells too small to permit growth allocate more time and effort into immediate reproductive gains. This resource regulated trade-off between growth and reproduction gives these tropical crabs plasticity in important life-history traits. Crabs with a relatively poor supply of shells reproduce at smaller sizes, reproduce more frequently, have larger clutches, and are unable to reach the larger sizes of crabs with a less limiting supply of shells. This flexibility in life-history traits allows these crabs to tailor their reproductive schedules to resource supplies controlled by gastropod mortality, as well as the presence of competitors and predators.
Shell preference patterns of two common hermit crabs from hard bottom reef flats on the Caribbean coast of Panama are examined in relation to the predation pressures and physical stresses of their habitat. Clibanarius antillensis Stimpson lives in the high intertidal habitat and minimizes exposure to predators by seeking refuge during high tides. It prefers high-spired shells which maximize protection from thermal stress. Calcinus tibicen Herbst avoids tidal emersion and prefers low-spired shells which enhance resistance to the predators common on Caribbean reef flats.The results are compared with similar results from the tropical eastern Pacific Bay of Panama. Shell-crushing predation on Caribbean hermit crabs is suggested to differ quantitatively and qualitatively from predation on hermit crabs in the Bay of Panama. Predation on hermit crabs in the Bay of Panama is more intense and effects larger individuals than predation on Caribbean reef flat hermit crabs. In addition, shell-crushing predation on hermit crabs in the Bay of Panama is primarily from teleost fish predators (Diodon spp.), while predation on Caribbean hermit crabs is primarily by bottom-dwelling crustaceans.Differences in predation pressures and tidal regimes between the Caribbean and Pacific coasts of Panama are reflected in the shell preferences and behavior of hermit crabs from the two areas.
Two species of hermit crab, Pagurus acadianus and P. pubescens are distributed sympatrically in offshore waters of Frenchman Bay, Maine. Laboratory and field investigations indicate that smaller sized specimens of P. acadianus have a preference for Littorina shells over Thais shells whereas P. pubescens individuals enter shells of either Thais or Littorina depending on the relative abundance of each type. Larger P. acadianus individuals which usually exceed the size range of P. pubescens principally occupy shells of Buccinum and Polinices. P. acadianus shows a strong preference for mollusc shells colonized by Hydractinia echinata.Isolation increases the level of aggression in P. acadianus individuals, but the low levels of agonistic behavior found in tests with P. pubescens crabs appear not to be affected by changes in crab density. In both species, subjects in shells of too small a size by volume showed a high degree of dominance in trials over crabs occupying normal or large shells; a factor which can b...
Calcinus latens is the hermit crab widely distributed in the Indo-Pacific region. Many authors have reported that C. latens uses gastropod shells having regular whorls and showing regular conical shape, however I found in a coral reef of Guam that many individuals of C. latens used shells of irregular whorls or peculiar shapes, such as the shells of Vermetidae, Cypraeidae, Conidae and they are highly damaged. These shells are significantly heavier than the shells of normal type and sometimes their center of gravity is various. It has been reported that heavier shells influence the growth rate and clutch size of hermit crabs and that unbalanced shells restrict the locomotion ability of hermit crabs. Thus this condition is regarded as worse for C. latens, and may result from the scarcity of normal shells in the reef.
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 importance of the shell resource (availability of appropriately-sized empty shells of gastropod molluscs) is the critical controlling influence affecting all aspects of growth, behaviour and reproduction. -from Author
Pagurus longicarpus (Say) migrates in autumn from a shallow estuary to deeper waters of Narragansett Bay, Rhode Island, when ambient water temperature are between 10@? and 4@? C. Critical thermal minimum experiments indicated that crabs ceased locomotor activity at approximately 3@?C and righting response at 1.5@?C. When presented with different substrates, crabs used their walking legs and, occasionally, their chelae to scoop a depression in the substrate. They were not able to construct a proper depression in gravel and, although they succeeded in burying themselves in both mud and sand, they remained only in sand. Winter dredging seaward of an estuary in which hermit crabs were found in fine sand. No crabs were found several meters away at 20 m on a silty mud bottom. The water temperature was less than 2@?C in all areas sampled. It is hypothesized that, as environmental temperatures decrease, hermit crabs move into deeper water and bury themselves in regions of sandy bottom. Overwintering in this manner might decrease the predation of hermit crabs by benthic organisms while the crabs are in a state of torpor.
Three series of experiments were conducted on Pagurus longicarpus and Clibanarius vittatus at Beaufort, North Carolina. The first series showed that the preferred species of shell by either species of crab is determined by the size of the crab and that certain species of shells are not available in preferred numbers for the hermit crab species. This affects C. vittatus more than P. longicarpus. The second series showed that shell fighting is not an important factor in determining which species occupies which kind of shell while the third series showed that a substrate preference for mud by P. longicarpus may limit it from obtaining a preferred species of shell that occurs naturally on sand.
Clibanarius tricolor overlaps strongly in shell utilization with the other common species of intertidal hermit crabs found in the Florida Keys. Laboratory observations indicated C. tricolor can dominate Clibanarius antillensis in shell fights, while Calcinus tibicen dominates C. tricolor. In micro-areas of sympatry with C. antillensis, C. tricolor's shell fit is better and egg production parameters not affected when compared to adjacent areas where only C. tricolor occurs. Sympatry with Calcinus tibicien in a poorer shell fit, a smaller shell size for a given size crab, a smaller mean size of crab, and a disruption of the relationship between clutch size and crab size:shell weight ratio. A strong effect of shell species on the probability of @V @V being ovigerous was noted. It is suggested that the ecological separation which characterizes these species over most of their ranges was an evolutionary response, in part, to the effects of interspecific shell competition.
Studies made of specimens of Pagurus bernhardus kept for six months in shells of different sizes showed that they grew appreciably faster in shells which were large relative to their body size than they did in shells which were too small. This difference was especially marked in the increase per molt but less so in the number of days per molt. A new standard of measurement, the length of the front (hard) portion of the carapace, is proposed for these crabs. The reasons for this choice and a conversion factor between the new standard and that frequently used, the whole carapace, are presented. A formula relating size to instar number is derived for this species, but the molt frequency was too variable to permit a determination of an age-size relationship. Finally, observations were made on the weight-to-volume ratios of some of the gastropod shells inhabited by this species in the Øresund and on the ratios of the weights and volumes of the shells to the crabs which bear them.
Certain aspects of the behavioral ecology of the tropical hermit crab, Calibanarius abidigitus, can be analyzed more fully with the use of fitness set theory. Building on the premise that an optimum shell weight/body weight ratio (termed @'weight index@') confers maximum fitness to individual crabs, two independent estimates of fitness, clutch size and percentage aggressive dominance, were plotted against a wide range of weight indexes. These measures were made for individuals of C. albidigitus inhabiting two environments (represented as two species of gastropod shells) and behavioral and reproductive fitness sets were constructed. The dissimilarities of the predicted optimum weight indexes for the two fitness sets, combined with the fact that suitable gastropod shell present a limiting resource, indicate a behavioral strategy by which larger shells than necessary for maximum reproductive fitness are utilized. This strategy, termed the "optimal ratios strategy," has definite advantages to individual hermit crabs and has probably evolved in response to severe competition for shells.
The nearshore hermit crabs Clibanarius vittatus, Pagurus pollicaris, and Pagurus longicarpus have broadly overlapping shell utilization patterns along the Texas coast. Effects of shell stress resulting from this overlap and from an overall shortage of shells on the reproductive potentials of the crabs were examined. Regression analyses indicate that shell weight and internal volume affect the clutch sizes of C. vittatus and P. pollicaris but not P. longicarpus. Clibanarius vittatus maintained in shells smaller than preferred grew more slowly than crabs maintained in shells of preferred size. Clutch size was highly correlated with crab size in this species. Several commensal animals, including polychaetes, gastropods, a hydroid, and a xanthid crab, consumed hermit crab eggs and/or zoeae in the laboratory. These egg predators were encountered in large shells occupied by @M @M more frequently than in shells in the size range utilized by ovigerous @V @V. These results indicate that shell size may limit hermit crab clutch size through a variety of mechanisms.
Field studies have suggested that the intertidal hermit crabs of the San Juan Islands of Washington normally occupy snail shells smaller than preferred. In this study the effects of shell size on protection from predation and on hermit crab shell fighting were studied in the laboratory. A predator (Cancer) presented with two hermit crabs (Pagurus granosimanus), identical except in size of occupied shell, preyed upon the hermit in the smaller shell first in 15 out of 16 trials. This results suggests that large shell size confers a selective advantage on the occupying crab. Shell fights involving two hermit crabs (P. hirsutiusculus) of unequal size were observed in which replicates differed only in the shell size of the larger crab. The probability of the larger crab effecting a shell exchange through fighting was shown to increase as the size of its shell decreased. However, shell size was shown to have no effect on the level of aggressiveness as measured by four criteria. The mechanism underlying the former result thus appears to involve a continual high level of general aggressiveness together with an increased tendency associated with occupancy of an inadequate shell by the dominant crab for that crab to evoke a shell exchange during an aggressive interaction.
During monthly intervals over a 1-year period, 12,000 empty snail shells were added to a small, isolated, rocky intertidal reef in the San Juan Islands of Washington. The shells added were species normally used by the high intertidal hermit crab, Pagurus hirsutiusculus, and were placed in locations accessible to that species. The shell additions resulted in an increase in density of P. hirsutiusculus at the experimental reef, whereas no density change occurred at a nearby control reef, indicating the importance of shells as a limiting resource. To establish the generality of shell limitation, the hermit crab populations of four unmolested rocky intertidal sites (three of which are typical hermit crab habitats) were quantitatively samples to obtain species compositions and size distributions of hermit crabs, their shells, and unoccupied shells. Shell preference experiments determined the preferred shell sizes and species for each hermit crab species. Except for small size classes, empty shells were rate at the three typical areas. In addition, hermit crab size distributions followed shell size distributions, and all but small hermit crabs of three species occupied shells smaller than the preferred size. These results support the conclusion that empty shells are a limiting resource for these hermit crabs. Since shells constitute a common, necessary resource in short supply, these hermit crabs are in competition for available shells. The fourth area, chosen for its unusual shell-availability characteristics, exhibited a different pattern of shell utilization not suggesting shell limitation. Shell occupancy at the three representative intertidal sites was examined to determine the strength of the relationship between hermit crab species composition and resource availability. Though resource partitioning was demonstrated, the presence and numbers of each hermit crab species and its preferred shell types were poorly correlated. Differences in hermit crab species composition are explained by differences in the physical habitat, and collections from other areas show that the same shell species can support different hermit crab species in different but adjacent habitat types. Thus, the mechanism allowing coexistence apparently involves both resource and habitat partitioning.
A typical hermit crab protects its soft parts by enclosing them in a gastropod shell. Empty shells are often durable enough that one could provide protection for a crab's entire lifetime. However, crabs choose shells that fit their bodies closely, and crabs cannot continue to grow unless they have a continuous supply of shells [except Pagurus prideauxi (Pike and Williamson, 1959) P. bernhardus (Jensen, 1975), and numerous other species (Nyblade, 1974) whose shells support colonial organisms that grow continuously forward from the lip of the shell]. If hermit crabs require a continuous supply of shells, then the shell supply rate may influence crab numbers. An opportunity to test this hypothesis arose during long-term studies of snail populations on a rocky shore area, Shady Cove, 0.5 mile north of Friday Harbor Laboratories, San Juan Island, Washington. Between August 1967 and August 1970, 4272 specimens of Thais lainellosa and 582 of T. eniarginata from the 200 m2 study area were given individually num bered tags (Spight 1974) . About 40% of the snails died each year, and as snails died, their tagged shells were acquired by the hermit crabs of the vicinity. The first crab with a tagged shell was found during May, 1968, and progressively more were found in succeeding months. Since the crabs used many of the tagged shells, the crabs provided a valuable means to verify snail deaths, and deliberate censuses of tagged crabs were undertaken. These census data will be examined here for correlations between changes in the rate of shell supply and changes in the portion of the crab population using shells of Thais.
The availability of gastropod shells to hermit crabs in the Newport River Estuary, Beaufort, N.C. has been assessed by determining the numbers of usuable shells occurring in characteristic subtidal habitats and by measuring shell size adequacy. The proportion of useable shells occupied by hermit crabs ranged from 58–99 % and many of the shells not used by hermit crabs were judged unavailable because they were occupied by sipunculids or only uncovered by the dredge. The shell adequacy index (shell size occupied/shell size preferred) was significantly below 1.0 for the largest species (Pagurus pollicaris Say) in the one location where sufficient numbers were collected and for the next largest species (P. longicarpus Say) in three of the four locations where it was collected. The shell size adequacy index for the smallest species (P. annulipes Stimpson) did not differ significantly from 1.0 in either of the two locations in which it was found. These observations suggest that the availability of gastropod shells plays a significant rôle in limiting the abundance of at least the larger hermit crabs.
Shell selection and utilization in two sympatric species of hermit crabs from the Natal coast, namely Clibanarius virescens (Krauss, 1843) and Calcinus laevimanus (Randall, 1840) were investigated. Shells of 23 gastropod species were occupied by C. virescens while 13 species were utilized by C. laevimanus. Shells of 11 gastropod species were inhabited by both crabs but, of these only two shell species were used in significant numbers. The results showed a close correlation between the morphometric data of the crabs and the utilized shells. Clibanarius virescens preferred high spired shells whilst C. laevimanus showed preference for shells with low spires. As C. laevimanus possesses a large cheliped it was restricted in the choice of shells in the natural habitat as it had to select shells with large apertures. Differential shell utilization has been advanced as the most important factor permitting coexistence of the two species. Clibanarius virescens inhabited a succession of shell species as the crabs grew in hard carapace or shield length whereas C. laevimanus showed preference mainly for two shell species namely Nerita albicilla Linnaeus, 1758 (carapace length less than 5 mm) and Turbo coronatus Gmelin, 1791 (carapace length more than 5 mm). Calcinus laevimanus may not be at a disadvantage by occupying Nerita shells as the large cheliped may be effectively used in sealing the aperture of the shell, and thereby minimizing water loss. Females of both species occupying lighter shells with large internal volumes were found to produce larger clutches as compared to females of similar carapace lengths occupying the heavier shell species.
SYNOPSIS. AS an ecotone, the littoral environment is often complex and is generally rich in numbers and species of organisms. The disadvantages of the biotope in terms of exposure to physical factors of both the marine and terrestrial environments are patent, but the advantages are not so evident. The continual replenishment of food brought from the sea, particularly for detritus-feeding animals such as hermit crabs, coupled with the possibility and ability to establish microhabitatswith microclimatic conditions may constitute the principal advantage. Escape from specialized predators may also be important. Hermit crabs have successfully exploited most intertidal environments. As members of the "benthic detritus-feeding guild" food is abundant, and by utilizing their shells in conjunction with movements within the littoral zone they have met successfully most of the rigors of the environment. The shell also provides some protection from predation, particularly from non-specialized predators.Indeed, the behavioral patterns associated with living in shells which permit the shell to serve as a microhabitat constitute the major adaptation enabling the hermit crabs to exploit the intertidal environment so successfully.
Factors which influence decisions by hermit crabs concerning whether to approach, investigate and enter another shell have been investigated by systematically varying the size of the shell in possession and the size of the shell being offered. The probability that a crab will approach or enter the shell depends on both variables. Investigation after contact, however, depends only on the size of the shell in possession. Durations of each stage of the sequence are negatively correlated with the numbers of crabs in each experimental group performing the next stage. For the final sequence of aperture investigatory activities, the fewer crabs entering the offered shell, the greater the number of investigatory acts performed by those crabs. In addition to variation in number of acts and duration of investigation, specific use of appendages varies according to the experimental situation. Thus naked crabs use the minor cheliped to investigate shells in preference to the major cheliped, which is normally used by housed crabs, with the major cheliped being reserved for defence by naked crabs. These data are discussed in terms of information collection and decisions made on the basis of that information.
Hermit crabs attracted to simulated sites of predation upon gastropods, a source of empty shells, were more likely to inhabit shells of worse condition than crabs collected by visual searches, suggesting that shell condition affects shell choice behavior. Laboratory tests showed that Pagurus pollicaris Say inhabiting shells with lip damage, hydroid colonies, and pitting by boring organisms exchanged shells more frequently than crabs in unmodified shells. Shell fit also affected laboratory shell exchange; i.e., crabs in relatively small shells exchanged significantly more than crabs in relatively large shells. The shell conditions inducing the highest observed rates of shell exchange were those potentially increasing the risk of predation: lip damage, relatively small shells, and shells weakened by boring organisms. The active shell exchange behavior induced in crabs inhabiting damaged, pitted, and fouled shells explains the overrepresentation of these shell conditions at predation events where the probability of shell exchange is high.
Growth rates of the hermit crabs Pagurus longicarpus Say and P. pollicaris Say maintained in preferred shells and in shells smaller than the preferred size have been compared. Changes in wet weight, shield length, and duration of the molt cycle were determined. Crabs in preferred shells grew significantly faster than those in small shells. P. pollicaris molted at approximately the same rate in both cases but grew more each molt in preferred shells. Von Bertalanffy growth curves were fitted to changes in shield length among crabs in preferred shells. These curves indicate that P. longicarpus may mature four months after settling from the plankton and reach its asymptotic size within the next eight months while P. pollicaris also matures four months after leaving the plankton but does not reach its asymptotic size for approximately three years. The rapid growth of P. longicarpus may enable it to preempt shells which are required for the successful brooding of a large clutch before these shells are required by more aggressive competitors, such as P. pollicaris and Clibanarius vittatus.
Shell fighting behaviour of the hermit crab Pagurus bernhardus was investigated. Analysis of fights between crabs in which there was little or no asymmetry in potential benefit for the two crabs from a shell exchange suggested that the duration of the fight increased as the potential benefit increased. Further experiments indicated that a naked crab was capable of evicting a housed crab by a process of direct aggression. Analysis of fights in which there was a slight asymmetry in potential gains from shell exchange indicated that the result of the fight was primarily determined by the large of the two crabs. These results are contrary to the proposal of Hazlett (1978) that the interactions represent a process of negotiation rather than aggression.
From 1960 through 1967 hermit crabs belonging to three species were collected in Kaneohe Bay, Oahu, Hawaiian Islands. The species are sympatric, with some variation in their distribution throughout the littoral zone. The breeding seasons were determined for each species. The term breeding is used here to mean the period when the females were ovigerous. Calcinus laevimanus (Randall) breeds from February into October with over 80% of the females carrying eggs during the warm summer months. Calcinus latens (Randall) has a bimodal breeding pattern with one peak in February and March, when about 60% of the females were ovigerous, and a secondary peak in late summer, August, when over 50% of the females in the population were carrying eggs. Clibanarius zebra Dana shows a similar pattern. About 20 % of the females were ovigerous from February to mid-April, and in August there is a second period of activity with about 60 % of the females carrying eggs. Data from other species of hermit crabs and related anomurans are discussed, and it is suggested that adaptations to local ecological conditions result in such a degree of variation in reproductive activity that generalizations on the temporal patterning of breeding seasons on the basis of any single factor such as temperature are not valid.
Seven spp. of pagurids from Bermuda shallow waters are listed and discussed. The status of Calcinus verrilli (Clibanarius verrilli Rathbun) as endemic to Bermuda is confirmed. Clibanarius hebes Verrill (in part) and C. brachyops Bouvier are probably referrable to C. tricolor (Gibbes). Clibanarius antillensis Stimpson and Pagurus miamensis Provenzano are new to Bermuda. Availability of gastropod shells is probably a limiting factor in abundance of hermit crabs in this locality. The three most abundant species occupy different ecological niches.
The mating system of the hermit crab, Diogenes nitidimanus, was observed. The male guards the female before copulation. This behavior is often observed in their natural habitat, the tidal flat. The mean size of males is larger than that of females in the population, and the paired male is also larger than his mate. In the field only larger males succeeded in mating, despite the fact that all males in the population are considered to be mature, whereas in the case of paired females size was irrelevant. Laboratory experiments also showed that larger males always won the competition for mature females.
A seasonal migration in the hermit crab Clibanarius vittatus (Bosc) is described and its structure examined for size-related or sexual differences that might lead to differential mortalities. The largest crabs, which were nearly all males, began to leave the shore in early summer, but the smaller females stayed until late autumn. The smaller crabs also returned to the shore at least one month in advance of the large crabs in the spring. No size-related or sexual differences were found in the abilities of the crabs to regulate their volumes when moved from 34.5%. to 10.5%. salinity which is the observed salinity range in their usual habitat.
This article uses a method developed previously (Abrams 1980) to estimate the relative intensities of inter- and intra-specific competition between pairs of species in a highdiversity intertidal hermit crab community in the tropical Indo-Pacific. The community could be separated into two sub-communities, with relatively weak interactions between members of different sub-communities. The average amount of inter-specific competition experienced by the members of this community was greater than that for the species in a less diverse community in Panama (1980). Average competition ratios for the species in the Indo-Pacific community were still less than competition coefficients calculated from overlap data for other taxa of animal.
This article describes the intertidal hermit crab species assemblage at One Tree Island, Great Barrier Reef, Australia. Competition for shells between the two most abundant species, Clibanarius virescens and Calcinus latens, is studied in more detail. Competition appears to be primarily exploitative. The relative intensities of inter- and intra-specific competition between this pair of species are estimated using two different methods. The first is based on habitat overlap data in conjunction with a mathematical model of shell population dynamics described in Abrams (1980). The second method is more direct, and is based on following the fate of marked empty shells. Results of the two methods are very similar. This supports the validity of assumptions made in applying the first method. The relative amount of interspecific competition between these two species appears to be greater than that for other hermit crab species pairs studied previously.
Shell utilization and shell selection studied in the tropical terrestrial hermit crab, Coenobita compressus (H. Milne Edwards). Three major shell related variables are examined; shell size, shell species, and shell condition. Nerita scabricosta (Lamarck) is the most commonly occupied shell, and it is also preferred over other shell species. Coenobita in the field are usually found in smaller than the preferred size of shell, and the difference between utilized and preferred shells is most pronounced in relatively small individuals. Shell size preference differs significantly between similarly sized crabs collected at different sites. There is also a preference for shells which have previously been used by other Coenobita individuals. This preference is due to shell modification by Coenobita, which increases the effective size of the shell. It is argued that the fitness of most sexually mature individuals is probably unaffected by the supply of new shells, since these are too small to be utilized. It is possible that the interaction of adult Coenobita for shells may be better described as mutualism than as competition. This illustrates the fact that a significant difference between utilized and preferred resources need not imply competition for those resources. Results indicate that the nature of intraspecific competition and population regulation in at least this terrestrial hermit crab is significantly different from these processes in marine hermit crabs.
Three shell variables were deemed to be important in the selection of a shell by the hermit crab Pagurus bernhardus (L.). These were the weight, volume and aperture width of a shell. Each of these variables were used in multiple regressions against crab weight for 25 Littorina littorea and 25 Thais lapillus shells chosen when both shell species were together in a tank, and for a further 25 L. littorea and 25 T. lapillus when the two shell species were separate. Principal component analysis was performed on the four groups of 25 shells selected, and multiple-regression equations were calculated using the principal components as the new variables. It was found that crabs chose a shell of suitable general dimensions rather than solely on the basis of one shell variable. The advantages of using statistical techniques developed in this paper over previous approaches to shell selection are discussed.
Shell preferences were examined inPagurus longicarpus Say, collected from Wakulla Beach, Florida, USA in 1987. Relative shell size was a more important shell characteristic in shell selection than either shell species or shell damage. Hermit crabs rarely selected relatively large shells but often selected relatively small shells over damaged shells. Preferences for a particular shell species were offset by varying the relative size or condition of the preferred shell species. Because specific environmental pressures are linked to particular shell characteristics, an assessment of the importance of various shell features may indicate which environmental pressures are ameliorated via the gastropod shell. Predation and desiccation are linked to relatively small shells and particular shell species; these stresses may be minimized by alternative behavioral mechanisms.
The spatial distribution, reproduction, and shell utilization patterns of three species of common intertidal hermit crabs Pagurus geminus McLaughlin, Pagurus lanuginosus De Haan and Clibanarius virescens (Krauss) on a rocky shore of Kominato, Boso Peninsula, Japan, are described. Although the distribution of each species greatly overlapped, Pagurus geminus mainly inhabited the middle intertidal zone, with Clibanarius virescens occupying a lower and Pagurus lanuginosus the lowest zone. This pattern was maintained over a 1-yr period with a few minor changes. Female Pagurus geminus generally inhabited a lower zone than males, ovigerous female Clibanarius virescens were distributed slightly lower than males, whereas a distinct sexual difference in the distribution was not seen in Pagurus lanuginosus. The ovigerous period of Pagurus geminus extended from October to August and is the longest reproductive season reported for a rocky intertidal decapod in Japanese waters. Pagurus lanuginosus became ovigerous from December to May and Clibanarius virescens, from April to December. The sex ratio was biased toward females in each case. Shell utilization patterns differed significantly between the three species, with Clibanarius virescens using the greatest variety of shells (33 species). Within species, sexual differences in shell utilization were seen in Pagurus geminus and Clibanarius virescens.
Animal contests usually concern ownership or access to a single resource. Asymmetries in the resource holding power and the value of the resource to each of the contestants may be assessed by the animals and these assessments used to determine the winner of the encounter (Parker, 1974). Hermit crabs, however, may exchange resources (shells) at the end of an encounter. This feature has led to the proposal of alternative hypotheses that these encounters are a process of (a) negotiation (Hazlett, 1978) and (b) aggression (Elwood & Glass, 1981). In the present study we have examined data on hermit crabs within the framework of theory on asymmetric contests with incomplete information (Hammerstein & Parker, 1983). A slight modification of this model provides a good fit with the data and will still allow its use in more conventional contests. The model of negotiation, however, provides a poor fit with the data.
Principal components analysis of morphometric data from snail shells occupied by hermit crabs enables the important dimensions of the shell to be described and quantified. A high correlation of the first principal component with crab size shows this component to be a better estimator of overall shell size than any of the original morphometric variates. Principal component II separated the shells utilized by adjacent populations of Coenobita and Calcinus according to shape.
Typescript. Thesis (M.S.)--Florida State University, 1984. Includes bibliographical references (leaves 34-39).
Interspecific competition is often difficult to measure due to the lack of a definitive limiting factor for the two (or more) species. The gastropod shell inhabited by a hermit crab represents a very discrete, definable portion of the ecological needs of every animal. A hermit crab must have protection for its soft abdomen or it will rather quickly be eaten. In addition, the ritualized shell fighting behavior patterns of hermit crabs (Hazlett, 1966a, 1966b, 1967) offer an easily observed specific behavioral parameter which reflects the extent of interspecific vs. intraspecific competition for this ecological factor.
Marine gastropods of Taiwan (1) Taiwan Museum
- K-Y Lai
Lai, K-Y. 1986. Marine gastropods of Taiwan (1). Taiwan Museum, Taipei, Taiwan. 49 pp. [In Chinese.].
Marine gastropods of Taiwan (2) Taiwan Museum
- K-Y Lai
Lai, K-Y. 1987. Marine gastropods of Taiwan (2). Taiwan Museum, Taipei, Taiwan. 116 pp. [In Chinese.].
Gastropods. Tuchia Publishing, Taipei, Taiwan. 197 pp
- K-Y Lai
Lai, K-Y. 1988. Gastropods. Tuchia Publishing, Taipei, Taiwan. 197 pp. [In Chinese.].
- S Miyake
- M Imafuku
Miyake, S., and M. Imafuku. 1980. Hermit crabs from
Kii Peninsula I.-Nankiseibutu 22: 1-7. [In Japanese.]
The behavioral ecology of competition and resource utilization among hermit crabs
- E P Scully
Scully, E. P. 1983. The behavioral ecology of competition and resource utilization among hermit crabs. Pp.
23-55 in S. Rebach and D. W. Dunham, eds. Studies
in adaptation: the behavior of higher Crustacea. Wiley-Interscience, New York.
Identity of two hermit crabs, Calcinus vachoni Forest, 1958, and Calcinus seurati Forest, 1951, from the coral reefs of Taiwan (Crustacea: Decapoda: Anomura)
- H Shih
- S-C Lee
Shih, H-T. and S-C. Lee. 1997. Identity of two hermit crabs, Calcinus vachoni Forest, 1958, and Calcinus seurati Forest, 1951, from the coral reefs of Taiwan (Crustacea: Decapoda: Anomura). Journal of Taiwan Museum 50: 21-31.