The Influence of Salinity on Behaviour and Oxygen Uptake of the Hermit Crab Pagurus Bernhardus L.

Author(s):  
J. Davenport ◽  
P. M. C. F. Busschots ◽  
D. F. Cawthorne

Hermit crabs, Pagurus bernhardus L., are common inhabitants of the littoral zone where they may be found in pools and puddles on the lower and middle portions of rocky shores. Only small specimens are normally found between the tidemarks but large crabs are found sublittorally as deep as 450 m. Unlike many of the animals found at a similar level on the shore, such as mussels, barnacles and winkles, Pagurus does not penetrate estuaries to any great extent. However, the smaller animals found in the littoral zone are likely to encounter reduced salinity levels caused by rainfall and terrestrial runoff.

2020 ◽  
Vol 16 (4) ◽  
pp. 20200030 ◽  
Author(s):  
Andrew Crump ◽  
Charlotte Mullens ◽  
Emily J. Bethell ◽  
Eoghan M. Cunningham ◽  
Gareth Arnott

Microplastics (plastics < 5 mm) are a potential threat to marine biodiversity. However, the effects of microplastic pollution on animal behaviour and cognition are poorly understood. We used shell selection in common European hermit crabs ( Pagurus bernhardus ) as a model to test whether microplastic exposure impacts the essential survival behaviours of contacting, investigating and entering an optimal shell. We kept 64 female hermit crabs in tanks containing either polyethylene spheres ( n = 35) or no plastic ( n = 29) for 5 days. We then transferred subjects into suboptimal shells and placed them in an observation tank with an optimal alternative shell. Plastic-exposed hermit crabs showed impaired shell selection: they were less likely than controls to contact optimal shells or enter them. They also took longer to contact and enter the optimal shell. Plastic exposure did not affect time spent investigating the optimal shell. These results indicate that microplastics impair cognition (information-gathering and processing), disrupting an essential survival behaviour in hermit crabs.


Author(s):  
I. Lancaster ◽  
G.D. Wigham

Dispersion in a littoral population of Pagurus bernhardus in south-west England is shown to be random, with members demonstrating no evidence of site attachment. Movement patterns within the population are shown to be asynchronous and random, and to be dictated by the quantity and quality of each individual's shell contacts. These, in turn, affect the time that individuals spend within the habitat. This implies that population dynamics and residence times are so influenced by the availability of suitable empty gastropod shells that movement and migration in hermit crabs should be regarded as resource-dependent phenomena.


2012 ◽  
Vol 279 (1742) ◽  
pp. 3510-3519 ◽  
Author(s):  
Anna-Sara Krång ◽  
Markus Knaden ◽  
Kathrin Steck ◽  
Bill S. Hansson

The ability to identify chemical cues in the environment is essential to most animals. Apart from marine larval stages, anomuran land hermit crabs ( Coenobita ) have evolved different degrees of terrestriality, and thus represent an excellent opportunity to investigate adaptations of the olfactory system needed for a successful transition from aquatic to terrestrial life. Although superb processing capacities of the central olfactory system have been indicated in Coenobita and their olfactory system evidently is functional on land, virtually nothing was known about what type of odourants are detected. Here, we used electroantennogram (EAG) recordings in Coenobita clypeatus and established the olfactory response spectrum. Interestingly, different chemical groups elicited EAG responses of opposite polarity, which also appeared for Coenobita compressus and the closely related marine hermit crab Pagurus bernhardus. Furthermore, in a two-choice bioassay with C. clypeatus, we found that water vapour was critical for natural and synthetic odourants to induce attraction or repulsion. Strikingly, also the physiological response was found much greater at higher humidity in C. clypeatus , whereas no such effect appeared in the terrestrial vinegar fly Drosophila melanogaster . In conclusion, our results reveal that the Coenobita olfactory system is restricted to a limited number of water-soluble odourants, and that high humidity is most critical for its function.


Author(s):  
I. Lancaster

Hermit crabs use gastropod shells to protect their bodies and developing eggs; an inadequate supply of shells of the appropriate size will, therefore, adversely affect their growth, fecundity and longevity. Since the supply of shells is commonly limited, mechanisms that help to reduce these adverse effects will be selectively advantageous. In Pagurus bernhardus it is suggested that two mechanisms have evolved in this respect: larval settlement is encouraged in the littoral zone where gastropod species are diverse and numerous and where the youngest hermits will find growth potentially unrestricted; and females breed within their first year of life and at a size substantially below that which could be attained in the shells commonly available to them. This ‘precocious’ breeding is suggested to be an adaptation enabling hermits to overcome the problems of shell-limitation, since it frees females of the need to attain a specific age or size before reproducing - a situation which would be perilous when large shells are scarce. Males of a similar age are freed from competition for the larger shells as a result of this strategy, since the growth of the females is suppressed while they are ovigerous.


2020 ◽  
Vol 40 (2) ◽  
pp. 152-155 ◽  
Author(s):  
Akihiro Yoshikawa ◽  
Ryutaro Goto ◽  
Chiaki I Yasuda ◽  
Akira Asakura

Abstract Many species of the hermit crab Clibanarius (Diogenidae) live on rocky shores of tropical and warm temperate regions. Some of these species are known to climb out from tidal pools onto rock surfaces exposed to air during low tide. The ecological significance of this behavior, however, remains unclear. We investigated the differences between air-exposed and non-air-exposed Clibanarius virescens (Krauss, 1843) in relation to their body size, sex, and infestation by three species of parasitic bopyrid isopods. Our generalized additive model (GAM) analyses showed a significant effect of the “smoothing factor” of the interaction between body size and sex for the occurrences of the “air-exposure behavior.” The presence of the ectoparasitic isopods did not affect the air-exposure behavior. Females of C. virescens showed a more distinct trend than in males, whereas air-exposure in both sexes had a peak in approximately 3.0–4.0 mm shield size (comparatively larger size in females, and middle-size in males) and decreased after this size range. Intraspecific and/or interspecific competition for shells may be intense in hermit crabs of this size range because of size overlap, and the individuals that carry suitable shells may avoid such competition by actively escaping from tide pools at low tide.


Behaviour ◽  
2006 ◽  
Vol 143 (10) ◽  
pp. 1281-1290 ◽  
Author(s):  
Mark Briffa ◽  
Rebecca Williams

AbstractChemical communication is likely to play an important role during agonistic encounters in aquatic crustaceans but the use of chemical signals is difficult to observe. An alternative approach to direct observation is to collect water that has contained fighting animals and then expose a focal animal of the same species to the cue water and monitor its behaviour. Here we investigate the possibility of the use of chemical cues during 'shell fights' in the hermit crab Pagurus bernhardus. Focal crabs exposed to the fighting cue spent more time withdrawn into their gastropod shell, less time on locomotion and less time searching for food than did those exposed to cues from non-fighting hermit crabs or those treated with plain sea water. At the end of the observation period we used a novel stimulus to induce a startle response in order to probe the focal crab's motivational state for this exploratory behaviour. Those exposed to the fighting cue water took longer to recover than crabs in the other groups, indicating that their motivation was lower. These findings provide clear evidence that chemical cues are a feature of these contests.


Author(s):  
Paula Schirrmacher ◽  
Christina C. Roggatz ◽  
David M. Benoit ◽  
Jörg D. Hardege

AbstractWith carbon dioxide (CO2) levels rising dramatically, climate change threatens marine environments. Due to increasing CO2 concentrations in the ocean, pH levels are expected to drop by 0.4 units by the end of the century. There is an urgent need to understand the impact of ocean acidification on chemical-ecological processes. To date, the extent and mechanisms by which the decreasing ocean pH influences chemical communication are unclear. Combining behaviour assays with computational chemistry, we explore the function of the predator related cue 2-phenylethylamine (PEA) for hermit crabs (Pagurus bernhardus) in current and end-of-the-century oceanic pH. Living in intertidal environments, hermit crabs face large pH fluctuations in their current habitat in addition to climate-change related ocean acidification. We demonstrate that the dietary predator cue PEA for mammals and sea lampreys is an attractant for hermit crabs, with the potency of the cue increasing with decreasing pH levels. In order to explain this increased potency, we assess changes to PEA’s conformational and charge-related properties as one potential mechanistic pathway. Using quantum chemical calculations validated by NMR spectroscopy, we characterise the different protonation states of PEA in water. We show how protonation of PEA could affect receptor-ligand binding, using a possible model receptor for PEA (human TAAR1). Investigating potential mechanisms of pH-dependent effects on olfactory perception of PEA and the respective behavioural response, our study advances the understanding of how ocean acidification interferes with the sense of smell and thereby might impact essential ecological interactions in marine ecosystems.


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