scholarly journals Animal contests and microplastics: evidence of disrupted behaviour in hermit crabs Pagurus bernhardus

2021 ◽  
Vol 8 (10) ◽  
Author(s):  
Eoghan M. Cunningham ◽  
Amy Mundye ◽  
Louise Kregting ◽  
Jaimie T. A. Dick ◽  
Andrew Crump ◽  
...  
Keyword(s):  
Hermit Crabs ◽  
Marine Biota ◽  
Resource Holding Potential ◽  
Cognitive Assessments ◽  
Marine Systems ◽  
Shell Quality ◽  
Animal Contests ◽  
Pagurus Bernhardus ◽  
Negative Impacts ◽  
Vast Range

Microplastics are ubiquitous in global marine systems and may have negative impacts on a vast range of species. Recently, microplastics were shown to impair shell selection assessments in hermit crabs, an essential behaviour for their survival. Hermit crabs also engage in ‘rapping’ contests over shells, based on cognitive assessments of shell quality and opponent fighting ability and, hence, are a useful model species for examining the effects of microplastics on fitness-relevant behaviour in marine systems. Here, we investigated how a 5-day microplastic exposure (25 microplastics/litre) affected the dynamics and outcome of 120 staged hermit crab contests. Using a 2 × 2 factorial design, we examined how microplastics (i.e. presence or absence) and contestant role (i.e. attacker or defender) affected various behavioural variables. Significantly higher raps per bout were needed to evict microplastic-treated defenders when attackers were pre-exposed to control conditions (i.e. no plastic). Also, significantly longer durations of rapping bouts were needed to evict control-treated defenders when attackers were pre-exposed to microplastics. We suggest that microplastics impaired defenders' ability to identify resource holding potential and also affected attackers’ rapping strength and intensity during contests. These impacts on animal contests indicate that microplastics have broader deleterious effects on marine biota than currently recognized.

scholarly journals Ocean Acidification Amplifies the Olfactory Response to 2-Phenylethylamine: Altered Cue Reception as a Mechanistic Pathway?

2021 ◽  
Author(s):  
Paula Schirrmacher ◽  
Christina C. Roggatz ◽  
David M. Benoit ◽  
Jörg D. Hardege
Keyword(s):  
Climate Change ◽  
Ocean Acidification ◽  
Hermit Crabs ◽  
Ecological Interactions ◽  
Ecological Processes ◽  
Mechanistic Pathway ◽  
Sea Lampreys ◽  
Pagurus Bernhardus ◽  
Decreasing Ph ◽  
The Impact

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.

scholarly journals Microplastics disrupt hermit crab shell selection

2020 ◽  
Vol 16 (4) ◽  
pp. 20200030 ◽  
Author(s):  
Andrew Crump ◽  
Charlotte Mullens ◽  
Emily J. Bethell ◽  
Eoghan M. Cunningham ◽  
Gareth Arnott
Keyword(s):  
Hermit Crab ◽  
Information Gathering ◽  
Animal Behaviour ◽  
Hermit Crabs ◽  
Marine Biodiversity ◽  
Crab Shell ◽  
Potential Threat ◽  
Pagurus Bernhardus

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.

scholarly journals The opposite effects of routine metabolic rate and metabolic rate during startle responses on variation in the predictability of behaviour in hermit crabs

Behaviour ◽  
2016 ◽  
Vol 153 (13-14) ◽  
pp. 1545-1566 ◽  
Author(s):  
Mariana Velasque ◽  
Mark Briffa
Keyword(s):  
Metabolic Rate ◽  
Generalized Linear Models ◽  
Startle Response ◽  
Linear Models ◽  
Elevated Temperatures ◽  
Hermit Crabs ◽  
Routine Metabolic Rate ◽  
Intraindividual Variation ◽  
The Mean ◽  
Pagurus Bernhardus

Studies on animal behaviour have suggested a link between personality and energy expenditure. However, most models assume constant variation within individuals, even though individuals vary between observations. Such variation is called intraindividual variation in behaviour (IIV). We investigate if IIV in the duration of the startle response is associated with metabolic rates (MR) in the hermit crabPagurus bernhardus. We repeatedly measured startle response durations and MR during each observation. We used double hierarchical generalized linear models to ask whether among and IIV in behaviour was underpinned by MR. We found no association between the mean duration of the startle responses and either routine MR or MR during startle response. Nevertheless, we found that IIV increased with MR during startle responses and decreased with routine MR. These results indicate that crabs with higher MR during startle responses behave less predictably, and that predictability is reduced during exposure to elevated temperatures.

Size Assessment and Cues: Studies of Hermit Crab Contests

Behaviour ◽  
1985 ◽  
Vol 92 (1-2) ◽  
pp. 22-37 ◽  
Author(s):  
Susan J. Neil
Keyword(s):  
Relative Size ◽  
Apparent Size ◽  
Hermit Crabs ◽  
Defensive Behaviour ◽  
Factors Affecting ◽  
Large Size ◽  
Intermediate Size ◽  
Pagurus Bernhardus ◽  
Major Cheliped

The agonistic behaviour of pairs of hermit crabs (Pagurus bernhardus) was observed in the laboratory. It was found that relative size was a reliable predictor of the outcome of a contest only when the crabs differed by at least 100% in weight. However, weight differences of 10 to 30% could be sufficient to cause differences in behaviour. It was concluded from this that whereas crabs can accurately assess small differences in weight, these differences may not be sufficient to reliably determine the outcome of contests. Other factors affecting RHP are relevant at intermediate size differences. Two possible cues for size assessment were tested: the size of the major cheliped and the size of the opponent's shell. The presence and size of the major cheliped were found to have a strong effect on contest initiation and outcome, and therefore this is likely to be a cue used in RHP assessment. The major cheliped was also found to play an important part in defensive behaviour, crabs lacking this appendage being less successful in defending their shells from attack. However, the apparent size of the opponent's shell did not seem to affect the initiation or outcome of contests. Thus it seems that crabs assess their opponents independently of the shells they occupy. It is concluded that large size differences are sufficient to decide contests. For smaller size differences other factors of RHP are important, and can override size differences. There is no evidence indicating that the defending crab can assess the quality of its oppo- nent's shell and make contest decisions based on this evidence. These data do not support the negotiation hypothesis.

Influences on movement and migration in the hermit crab Pagurus bernhardus

1990 ◽  
Vol 70 (3) ◽  
pp. 483-491 ◽  
Author(s):  
I. Lancaster ◽  
G.D. Wigham
Keyword(s):  
Population Dynamics ◽  
Hermit Crab ◽  
Movement Patterns ◽  
Hermit Crabs ◽  
Residence Times ◽  
South West ◽  
Pagurus Bernhardus ◽  
And Migration ◽  
South West England

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.

scholarly journals Transition from sea to land: olfactory function and constraints in the terrestrial hermit crab Coenobita clypeatus

2012 ◽  
Vol 279 (1742) ◽  
pp. 3510-3519 ◽  
Author(s):  
Anna-Sara Krång ◽  
Markus Knaden ◽  
Kathrin Steck ◽  
Bill S. Hansson
Keyword(s):  
Hermit Crab ◽  
Olfactory System ◽  
Response Spectrum ◽  
Opposite Polarity ◽  
Water Soluble ◽  
Hermit Crabs ◽  
Larval Stages ◽  
Terrestrial Life ◽  
Pagurus Bernhardus ◽  
Chemical Groups

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.

scholarly journals Validation of an ecological momentary assessment to measure processing speed and executive function in schizophrenia

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Cecelia Shvetz ◽  
Feng Gu ◽  
Jessica Drodge ◽  
John Torous ◽  
Synthia Guimond
Keyword(s):  
Cognitive Impairments ◽  
Cognitive Test ◽  
Future Research ◽  
Validity And Reliability ◽  
Cognitive Assessments ◽  
Subjective Sleep Quality ◽  
Trail Making ◽  
Negative Impacts ◽  
Test Retest Reliability ◽  
Ecological Momentary

AbstractCognitive impairments are a core feature of schizophrenia that have negative impacts on functional outcomes. However, it remains challenging to assess these impairments in clinical settings. Smartphone apps provide the opportunity to measure cognitive impairments in an accessible way; however, more research is needed to validate these cognitive assessments in schizophrenia. We assessed the initial accessibility, validity, and reliability of a smartphone-based cognitive test to measure cognition in schizophrenia. A total of 29 individuals with schizophrenia and 34 controls were included in the analyses. Participants completed the standard pen-and-paper Trail Making Tests (TMT) A and B, and smartphone-based versions, Jewels Trail Tests (JTT) A and B, at the single in-lab visit. Participants were asked to complete the JTT remotely once per week for three months. We also investigated how subjective sleep quality and mood may affect cognitive performance longitudinally. In-lab and remote JTT scores moderately and positively correlated with in-lab TMT scores. Moderate test-retest reliability was observed across the in-lab, first remote, and last remote completion times of the JTT. Additionally, individuals with schizophrenia had significantly lower performance compared to controls on both the in-lab JTT and TMT. Self-reported mood had a significant effect on JTT A performance over time but no other significant relationships were found remotely. Our results support the initial accessibility, validity and reliability of using the JTT to measure cognition in schizophrenia. Future research to develop additional smartphone-based cognitive tests as well as with larger samples and in other psychiatric populations are warranted.

scholarly journals Get off my back: vibrational assessment of homeowner strength

2019 ◽  
Vol 15 (4) ◽  
pp. 20180819 ◽  
Author(s):  
Louise Roberts ◽  
Mark E. Laidre
Keyword(s):  
Hermit Crabs ◽  
Social Conflicts ◽  
Empty Shell ◽  
Resource Holding Potential ◽  
External Structure ◽  
Strength Based ◽  
Sensory Modalities ◽  
Key Variables ◽  
Substrate Vibrations ◽  
Different Levels

Animals may use a variety of sensory modalities to assess ownership and resource-holding potential (RHP). However, few studies have experimentally tested whether animals can assess these key variables through a purely vibrational modality, exclusively involving substrate-borne vibrations. Here we studied social terrestrial hermit crabs ( Coenobita compressus ), where competitors assess homeowners by climbing on top of a solid external structure—an architecturally remodelled shell home, inside of which the owner then produces vibrations. In the field, we used a miniature vibratory device, hidden within an empty shell, to experimentally simulate a ‘phantom owner’, with variable amplitudes of vibration representing different levels of homeowner strength. We found that assessors could use these vibrations to deduce the owner's RHP: for strong vibrations (indicative of a high RHP owner) assessors were least likely to escalate the conflict; for weak vibrations (indicative of a low RHP owner) assessors showed intermediate escalation; and in the absence of vibration (indicative of an extremely weak or absent owner) assessors were most likely to escalate. These results reveal that animals can assess homeowner strength based solely on substrate vibrations, thereby making important decisions about whether to escalate social conflicts over property.

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