Hermit Crab Clibanarius Vittatus Research Articles

Chemically Stimulated Visual Orientation and Shape Discrimination by the Hermit Crab Clibanarius vittatus (Bosc)

Chemically Stimulated Visual Orientation and Shape Discrimination by the Hermit Crab Clibanarius vittatus (Bosc)

CHEMICALLY STIMULATED VISUAL ORIENTATION AND SHAPE DISCRIMINATION BY THE HERMIT CRAB CLIBANARIUS VITTATUS (BOSC)

ABSTRACT Orientation of the hermit crab Clibanarius vittatus (Bosc) to black geometric shapes of equal surface area was measured in a circular arena. This study tested the hypotheses that crabs can visually discriminate between different shapes and that attraction is related to the potential habitability of gastropod shells represented by the shapes. Test crabs were untrained and exhibited chemically induced shell-seeking behavior. This behavior indicated that they inhabit suboptimal gastropod shells (small relative to their body size). When presented with single silhouettes, crabs were significantly attracted to a horizontal rectangle, horizontal diamond, square, semicircle, and triangle, but not to a vertical rectangle or a vertical diamond. When exposed to pairs, the most and least attractive shapes were the horizontal rectangle and vertical diamond, respectively. Since responses were a complex function of the dimensional characteristics of the shapes, it was concluded that attraction was based on shape recognition. The hypotheses were further supported because crabs oriented poorly to the shape of the suboptimal shell which they inhabited (triangle), but oriented very well to shapes (horizontal rectangle, horizontal diamond, square, and semicircle) that represented more optimal gastropod shells.

Offshore escape response and directional orientation of the striped hermit crabclibanarius vittatus(BOSC)

The involvement of ground slope, waves and celestial cues in y‐axis orientation was studied for the striped hermit crab Clibanarius vittatus. This crab commonly lives subtidally along sheltered shorelines and displayed an escape response oriented in the offshore direction at the home beach. Laboratory studies indicated that crabs moved downslope at angles of 7° and greater. In a wave tank, they moved into approaching waves. As for celestial cues alone, crabs tested under clear skies in both the morning and afternoon displayed directional distributions significantly oriented in the same direction as crabs on the home beach. Crabs displayed random movements under cloudy skies. Thus, C. vittatus can use ground slope, waves and celestial cues for offshore orientation during its escape response.

Orientation of the hermit crab Clibanarius vittatus (Bosc) to visual cues: effects of mollusc chemical cues

Orientation of the striped legged hermit crab Clibanarius vittatus (Bosc) to black horizontal areas of different sizes was studied in a circular arena. Crabs were tested either in the presence or absence of chemicals that signal the potential availability of a gastropod shell. The chemical cue was generated by freezing and thawing muscle tissue from the gastropod Busycon carica Gmelin. Upon pre-experimental exposure to the chemical cue, crabs could be differentiated into two categories: those showing investigative interest in gastropod shells (Investigating), and those with no evident interest (Non-Investigating). The chemicals stimulated increased activity in the Investigating groups but not in the Non-Investigating groups. Clibanarius vittatus exhibited a uniform circular distribution when exposed to an all white horizon, independently of the presence of the chemical cue. Both crab categories showed little interest in black sectors subtending angles of 5, 10, 20 and 30° when the chemical cue was not present in the experimental arena. However, Investigating crabs were attracted to these sectors in the presence of the chemical cue. This response ceased once the dark sector exceeded ≈40° in size and both groups showed an avoidance response, with increasing number of crabs moving towards the white section of the arena as the dark sector increased in size. The attraction towards the small black sectors was interpreted as a shell investigating response, for which the visual cue seems to be activated by the chemical cue. The avoidance of increasingly larger black sectors was interpreted as predator avoidance reaction, which was not affected by the chemical cue. These interpretations were verified as Investigating crabs were attracted to a gastropod shell and both groups generally avoided a large blue crab.

Site specific constraints on shell selection behavior in the hermit crab,Clibanarius vittatus

Site‐specific constraints on shell selection behavior in the hermit crab Clibanarius vittatus were studied with both laboratory and field experiments at two sites along the Louisiana coast. At both sites, crabs selected larger Stramonita haemastoma shells in field experiments. Although discarded shells were often no smaller than selected shells, they did show heavy damage by predators. Crabs in both populations inhabited shells that were on average larger than those of living 5. haemastoma as well as those discarded in experiments. Although these results suggest that larger, undamaged shells may be a limiting resource, crabs collected from a site with few intermediate sized 5. haemastoma actually selected smaller shells in the laboratory. Clibanarius vittatus also selected the stronger, higher spired shell of S. haemastoma over Polinices duplicatus in both laboratory and field experiments, suggesting predation risk plays a role in shell choice. Although crabs in P. duplicatus shells were no more vulnerabl...

Osmoregulation in larvae of the striped hermit crab Clibanarius vittatus (Bosc) (Decapoda: Anomura; diogenidae)

Osmoregulatory capabilities were determined for the larval stages of the striped hermit crab, Clibanarius vittatus (Bosc). For changes of 5 ‰ salinity, larvae were able to re-establish osmotic equilibrium after 1 2 - h exposure to the new medium. Basically, the osmoconcentration response patterns were very similar for all larval stages. The hemolymph from all larval stages, Zoea I–V and Megalopa, hyperosmoconformed to external osmocencentrations over the entire salinity range tested, from 5 to 35‰. Larvae never showed the adult response of being able to hyperosmoregulate at low salinities.

The larval development of Cliban vittatus (Bosc) (Crustacea: Decapoda; Diogenidae) reared in the laboratory.

1. A table of previous descriptions of larvae of Diogenidae is given. 2. Larvae of the hermit crab Clibanarius vittatus were reared on a diet of Artemia nauplii. Five, rarely four, zoeal stages and megalopa were obtained. Duration, mortality and sizes of larvae from two hatches are listed. 3. Detailed descriptions and figures for each larval stage are presented.

Population Consequences of Shell Utilization by Hermit Crabs

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 ♂ ♂ more frequently than in shells in the size range utilized by ovigerous ♀ ♀. These results indicate that shell size may limit hermit crab clutch size through a variety of mechanisms.

Structure of seasonal migrations of the littoral hermit crab Clibanarius vittatus (Bosc)

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.

Effect of Commensal Hydroids on Hermit Crab Competition in the Littoral Zone of Texas

IN Galveston Bay, Texas, the hermit crab Clibanarius vittatus is the dominant animal on many shallow mud and sand flats. During the winter the hermits Pagurus longicarpus and Pagurus pollicaris migrate into the region dominated by Clibanarius and remain there until the following spring. Hermit crabs engage in ritualized fights1 in competition for gastropod shells which are a necessary protection from predators. In both laboratory and field encounters, Clibanarius are very aggressive in competition for shells and are usually able to win shell fights with Pagurus, even if exceeded in size. As suitable unoccupied shells are extremely rare, Pagurus are at a potential disadvantage in competition with Clibanarius for this resource.