Hermit Crab Pagurus Filholi Research Articles

Reason for being single: some males do not guard receptive females in the hermit crab Pagurus filholi

In animals that reproduce sexually, males are often under strong selection to maximize the number of mating opportunities. However, in some iteroparous species, males do not always maximize the allocation of time and energy to the present mating opportunity. Male hermit crabs of the genus Pagurus show precopulatory guarding as a mate acquisition strategy. Although almost all males within this genus guard and compete for receptive females, males of Pagurus filholi differ in how likely they are to do so. To examine the factors explaining the absence of guarding behaviour in P. filholi, a laboratory experiment was conducted that focused on whether either of two receptive females was guarded by solitary males that had been found not paired in the field, had lost a previous male–male contest or had copulated with other females. Solitary males showed a significantly lower frequency of guarding than males with experience of losing or of copulation. In the solitary group, males that moulted within 5 days after the experimental trial did not guard females, and the moulting frequency of nonguarding males was significantly higher than that of guarding males. In further analysis, smaller solitary males were shown to be less likely to guard females. The results of the experiment suggest that males of P. filholi may not always invest as much as possible in the present mating opportunity but may temporarily invest in growth during the 8-month mating season.

Sex‐related differences in size, function and regeneration of the major cheliped in the hermit crab Pagurus filholi

AbstractPagurus hermit crabs have a well‐developed right cheliped (major cheliped) and in some species the major cheliped of males is longer than that of females. This paper describes sex‐related differences in major cheliped length and regeneration pattern of the major cheliped in the hermit crab Pagurus filholi. We also examined the function of the major cheliped in male–male competition. Major cheliped length of males was longer than that of females in P. filholi. Males regenerated larger chelipeds than females at the first molt after experimentally induced autotomy. Body size growth in males of the regeneration group was less than that in intact males of the control group while there was no significant difference in body size growth of females between regeneration and control groups. Major cheliped length was included in the best model to explain the outcome of male–male competition and thus sexual selection appears to be a causative factor in the sex‐related difference of the major cheliped length. Sex‐related differences in the regeneration pattern may reflect differences in evolutionary pressures on males for large major chelipeds and females for large body size.

Guarding males of the hermit crab climb up algae to avoid male–male competition

Abstract Males of the hermit crab Pagurus filholi show precopulatory guarding behavior in which a male grasps the shell of a mature female with his left cheliped before copulation. Hermit crabs were most common in rocky intertidal areas with cobbles and boulders, while many guarding pairs were observed on fronds of brown algae such as Sargassum confusum in Hakodate Bay, Japan. We examined three hypotheses explaining why the guarding pairs were most common on algae; (1) aggregation place for mature males and females to find mates, (2) avoidance of male–male combat, and (3) avoidance of predators. If solitary males and females climbed up algae, then many guarding pairs were observed after pairing, but only guarding pairs climbed up the algae after removing all crabs. Experiments in aquariums showed that the disturbance rate for guarding pairs due to male–male competition was lower on the algae than in boulder and rocky flat areas, and few disturbances were observed by predatory crabs in all habitat types. These results suggest that the guarding males climb up the fronds of algae to sequester guarded females from rival males and avoid male–male combat. This behavior could be considered as a male counter tactic against indirect female choice mediated by sex pheromones in which females release sex pheromones while guarded, attracting many rival males and inducing male–male competition.

Delayed copulation as a means of female choice by the hermit crab Pagurus filholi

Male hermit crabs perform precopulatory mate-guarding behavior during their reproductive season. As females generally cannot reject guarding attempts by males, male guarding prevents females from inspecting and choosing other male mates. However, as guarding males are often replaced by other males through competition for females during the guarding phase, females may be able to select males by delaying their copulation. To examine the possibility of female choice by hermit crabs, we investigated whether female Pagurus filholi that were being guarded in the field were ready to copulate and spawn. We found that about 30% of females guarded in the field were ready to spawn, indicating that guarded females delayed copulation with their current male. Our results suggest that by delaying copulation females may exploit male–male competition to “choose” dominant males. However, delaying copulation reduced the spawning potential of females. Hence, there is a trade-off between waiting for the opportunity to mate with a dominant male and decreased spawning success if females exploit male–male competition.

Size assortative mating by the hermit crab <i>Pagurus filholi</i> (Decapoda: Anomura: Paguridae)

The hermit crab Pagurus filholi shows precopulatory guarding behavior in which males drag the shells occupied by ripe females. It bas been suggested by our previous study on male mate choice in this species that males would adopt a mating strategy of pairing with the first ripe female they encounter. If it is true, we would expect random pairing by size in a field population. However, we observed positive size assortative pairing in the actual field population; larger males tended to mate with larger females and smaller males with smaller females. In this study, field observations and laboratory experiments were conducted to examine the following possible causes of the size assortative mating: 1) mate choice, 2) mate availability, and 3) constraints of size and/or weight of possible partners. The results were: 1) no strong preference for larger females was found in males; 2) males often took over females guarded by smaller males; 3) smaller males could not drag larger females and thus did not pair; and 4) larger females often rejected smaller males. These results suggest that the loading constraint of size and/or weight of the partners and female's rejection of pairing with smaller males explain size assortative mating by P. filholi.

Effects of shell size fit on the efficacy of mate guarding behaviour in male hermit crabs

Males of the hermit crab Pagurus filholi show pre-copulatory mate guarding behaviour to keep a receptive female from other rival males during the breeding season. Guarding males are often replaced by other males via contest competition. Shell size fit and shell species of males effects were investigated to see if their ability to defend females against rivals depends on their shell. Shell size fit and shell species of guarding males were experimentally manipulated and then, the males were allowed to guard a female and interact with rival males of various sizes. Contest outcomes depended on neither the shell size fit nor shell species of the guarding males, and depended on body size ratio between guarding and rival males. When the body size of guarding and rival males was similar, however, guarding males in large fitting shells defended their female mate significantly more often than those in small fitting shells. For Chlorostoma lischkei shells, small males preferred larger shells during the breeding season than after the breeding season. The plasticity in the shell size preference of small males suggests that they compensate for body size disadvantage in mating versus larger rivals and for higher defence ability of female mates versus similar sized rivals.

Antipredator defence of the hermit crab Pagurus filholi induced by predatory crabs

Hermit crabs have two antipredator tactics: taking refuge in its shell and fleeing. We examined the following two hypotheses using the hermit crab Pagurus filholi: (1) hermit crabs change their preference for shell types that they take refuge in and/or change the timing of fleeing (i.e. the duration of refuge in the shell) when they perceive a predator threat; (2) the type of shell that a hermit crab occupies affects the fleeing tactic of the individual. Under the stimulus of a crushed conspecific, hermit crabs changed neither their preference for shell species nor their refuge duration. On the other hand, under the stimulus of the predatory crab Gaetice depressus, hermit crabs increased their preference for Batillaria cumingi shells, which provide superior protection against predators, and shortened their refuge duration in the shells even when they occupied those effective against predation. Refuge duration was longer in B. cumingi shells than in the more vulnerable shells of Homalopoma sangarense. These results suggest that both antipredator defences (changing shell and timing of fleeing) are induced by the stimulus of a predator, and the timing of fleeing is affected by the shell type occupied.

Fighting Escalation Independent of Cost-Benefit Relationship Based on Shell Resource Quality in the Hermit Crab Pagurus filholi

Fighting Escalation Independent of Cost-Benefit Relationship Based on Shell Resource Quality in the Hermit Crab Pagurus filholi

Sexual difference in shell use in the hermit crab Pagurus filholi (de Man) from northern Japan

The shell use pattern between sexes of Pagurus filholi was described, at Kattoshi, northern Japan. Line transect sampling showed that the shells available to P. filholi in this area were mainly composed of four species, Reticunassa fraterculus, Homalopoma sangarense, Batillaria cumingi and Littorina brevicula. The former three shell species were used by small crabs, and the pattern of shell use significantly differed between sexes. Almost all large crabs of either sex used Littorina brevicula shell. The abundance of empty shells was about 10% of total hermit abundance. Shell size suitability of crabs decreased as crab size increased, suggesting that shell limitation was more severe in large-sized crabs than in small ones. However, this trend differed between sexes. Males used unsuitable-sized shell relative to similar-sized females in Reticunassa and Homalopoma species. The population sex ratio was biased towards females, and showed an anomalous pattern as a function of crab size that was initially from male bias to female bias with increasing size, but was biased towards males again with a further increase in size. Sexual differences in shell preference, competitive ability and growth rate were discussed as causal explanations for the present pattern.

Functional Roles of Gastropod Shells in the Hermit Crab Pagurus filholi: Effects of Shell Size and Species on Fitness

Functional Roles of Gastropod Shells in the Hermit Crab Pagurus filholi: Effects of Shell Size and Species on Fitness

The Effect of Male Size and Sex Ratio on the Duration of Precopulatory Mate Guarding in the Hermit Crab Pagurus filholi

The Effect of Male Size and Sex Ratio on the Duration of Precopulatory Mate Guarding in the Hermit Crab Pagurus filholi

Effect of Male / Female Size Ratio on Mating Behavior of the Hermit Crab Pagurus filholi (Anomura: Paguridae) under Experimental Conditions

Effect of Male / Female Size Ratio on Mating Behavior of the Hermit Crab Pagurus filholi (Anomura: Paguridae) under Experimental Conditions

EFFECT OF MALE / FEMALE SIZE RATIO ON MATING BEHAVIOR OF THE HERMIT CRAB PAGURUS FILHOLI (ANOMURA: PAGURIDAE) UNDER EXPERIMENTAL CONDITIONS

ABSTRACT We studied the mating behavior and clarified the mating sequences of the hermit crab Pagurus filholi under laboratory conditions. The mating sequences differed, depending on the male to female size ratio. Before copulation, larger males relative to potential female mates tended to perform precopulatory guarding behavior, i.e., grasping the rim of the shell of the female with their chelipeds, more frequently than smaller males. On the other hand, smaller males relative to the females appeared to insert their chelipeds and to attempt copulation by pulling the female out of the shell without performing precopulatory mate-guarding behavior. These different behaviors may be conditional strategies that depend on the male/female size ratio.

On the Functions and Causes of Sexual Dimorphism in Breeding Plumage Characters of North American Species of Warblers and Orioles

Previous articleNext article No AccessLetters to the EditorsOn the Functions and Causes of Sexual Dimorphism in Breeding Plumage Characters of North American Species of Warblers and OriolesTerrell H. HamiltonTerrell H. Hamilton Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The American Naturalist Volume 95, Number 881Mar. - Apr., 1961 Published for The American Society of Naturalists Article DOIhttps://doi.org/10.1086/282167 Views: 14Total views on this site Citations: 25Citations are reported from Crossref PDF download Crossref reports the following articles citing this article:Gabriel Macedo, Rafael S. Marcondes, Cibele Biondo, Gustavo A. Bravo, Elizabeth P. 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