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Shell Quality And Crowding in Caribbean Hermit Crabs (Coenobita clypeatus ) Allison Caldwell Under the Direction of Dr. Renee Godard and Dr. Morgan Wilson St. John, USVI, J-Term 2017 Abstract Encountered crabs were measured for size (weight – gms, chelea length –tip to joint mm), shell size (width and height), shell quality (see below), and crowding (total score was number of pereiopod and pereiopod segments exposed when retracted + visible antennae, eyes, and abdomen.) Shell quality was recorded on a scale of 0-3. 0 = indicated an intact shell, 1= low damage (1 hole or erosion), 2= medium damage (1 hole + erosion, 2 holes, etc…), 3 = high damage (multiple holes and/or erosion). 75 crabs were assessed at VIERS (Virgin Islands Environmental Resource Station) and 22 were assessed at other locations near water. Introduction Acknowledgments I would like to thank Dr. Renee Godard and Dr. Morgan Wilson for their assistance in making this project come to life and for making the trip to St. John a success. I am very thankful for the opportunity and for the lessons I learned whilst on the island, both about myself and about research. This trip was an important part of my undergraduate education and the memories I will carry with me for a lifetime. Thank you! C. clypeatus across the island were crowded regardless of proximity to water/shell source. Smaller shells showed less damage than did larger shells. C. clypeatus were found to acquire available shells of greater quality than their current shell when presented with the choice. Further research should include adding more locations to the assessment regarding crabs close to a water source. Objective: To compare shell crowding and quality of Coenobita clypeatus in crabs at different distances from new shell sources (the ocean). Distant Site : Virgin Island Environmental Resource Station (VIERS) Sites with nearby wa ter: Blue Cobblestone Beach, North Haulover, Salt Pond, Little Lameshur, Big Lameshur As Coenobita clypeatus grow over their lifetime, they require larger shells to better protect themselves from predators and weather. Without availability of new, larger shells, C. clypeatus growth and fitness are compromised. In this study, crowding and shell quality of C. clypeatus were assessed in crabs located near beaches as well as those at a field station further from the sea. While crowding was commonplace in crabs of all sizes and location did not have an impact on level of crowding, shell quality was good. The limited data on shell change suggests that crabs are limited by shell availability. Further research on the crowding and shell quality should include measuring chela width as well as length and an effort to increase sample size of crabs that are located near water (potential source for shells). Table 1: Shells were placed at specific, varied sites across VIERS. Shells were recollected and catalogued the following day. All remaining shells indicate a better quality shell was ultimately chosen. There is the possibility that a ”conga-line” took place in #5. Field Locations Results Conclusion C. clypeatus are omnivorous, opportunistic feeders and can live as long as 30 years in captivity. • Crabs in shells that are crowded (unable to retract fully), damaged, too heavy, or too large are more susceptible to predation and potential desiccation. • Hermit crabs in shells that are damaged or crowded often take part in a local vacancy chain (or “conga line”) when a new shell is available to them or to a larger crab (Rotjan et al., 2010). Figure 1: Average crowding (+/- 1 SE) of crabs at VIERS and other locations based on chela length in mm. Sizes of the crab impact the crowding of crabs (Kruskal Wallis, p<.001). Crabs were crowded regardless of location. Figure 2: Shell quality of crabs of varying chela lengths. Small crabs appear to have the highest quality shells. More shells catalogued were intact than with medium or high damage. Citations Laidre, M. E. (2012). Niche construction drives social dependence in hermit crabs. Current Biology, 22(20). doi:10.1016/j.cub.2012.08.056 Lewis, S. M., & Rotjan, R. D. (2009). Vacancy Chains Provide Aggregate Benefits ToCoenobita clypeatusHermit Crabs. Ethology, 115(4), 356- 365. doi:10.1111/j.1439-0310.2009.01626.x Morrison, L. W., & Spiller, D. A. (2006). Land hermit crab (Coenobita clypeatus) densities and patterns of gastropod shell use on small Bahamian islands. Journal of Biogeography, 33(2), 314-322. doi:10.1111/j.1365-2699.2005.01399.x Rotjan, R. D., Chabot, J. R., & Lewis, S. M. (2010). Social context of shell acquisition in Coenobita clypeatus hermit crabs. Behavioral Ecology, 21(3), 639-646. doi:10.1093/beheco/arq027 Photographs taken by Allison Caldwell and Jessica Michael. “Conga-line” formation Least crowded crab found on the island Weighing crab + shell Examining shell crowding High damage shell Placed shell Annaberg

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Shell Quality And Crowding in Caribbean Hermit Crabs (Coenobita clypeatus)Allison Caldwell

Under the Direction of Dr. Renee Godard and Dr. Morgan Wilson St. John, USVI, J-Term 2017

Abstract

• Encountered crabs were measured for size (weight – gms, chelea length –tip to joint mm), shell size (width and height), shell quality (see below), and crowding (total score was number of pereiopod and pereiopod segments exposed when retracted + visible antennae, eyes, and abdomen.)

• Shell quality was recorded on a scale of 0-3. 0 = indicated an intact shell, 1= low damage (1 hole or erosion), 2= medium damage (1 hole + erosion, 2 holes, etc…), 3 = high damage (multiple holes and/or erosion).

• 75 crabs were assessed at VIERS (Virgin Islands Environmental Resource Station) and 22 were assessed at other locations near water.

Introduction

AcknowledgmentsI would like to thank Dr. Renee Godard and Dr. Morgan Wilson for their assistance in making this project come to life and for making the trip to St. John a success. I am very thankful for the opportunity and for the lessons I learned whilst on the island, both about myself and about research. This trip was an important part of my undergraduate education and the memories I will carry with me for a lifetime. Thank you!

• C. clypeatus across the island were crowded regardless of proximity to water/shell source.

• Smaller shells showed less damage than did larger shells. • C. clypeatus were found to acquire available shells of greater

quality than their current shell when presented with the choice.• Further research should include adding more locations to the

assessment regarding crabs close to a water source.

Objective: To compare shell crowding and quality of Coenobita clypeatus in crabs at different distances from new shell sources (the ocean).

Distant Site: Virgin Island Environmental Resource Station (VIERS)

Sites with nearby water: Blue Cobblestone Beach, North Haulover, Salt Pond, Little Lameshur, Big Lameshur

As Coenobita clypeatus grow over their lifetime, they require larger shells to better protect themselves from predators and weather. Without availability of new, larger shells, C. clypeatus growth and fitness are compromised. In this study, crowding and shell quality of C. clypeatus were assessed in crabs located near beaches as well as those at a field station further from the sea. While crowding was commonplace in crabs of all sizes and location did not have an impact on level of crowding, shell quality was good. The limited data on shell change suggests that crabs are limited by shell availability. Further research on the crowding and shell quality should include measuring chela width as well as length and an effort to increase sample size of crabs that are located near water (potential source for shells).

Table 1: Shells were placed at specific, varied sites across VIERS. Shells were recollected and catalogued the following day. All remaining shells indicate a better quality shell was ultimately chosen. There is the possibility that a ”conga-line” took place in #5.

Field Locations

Results

Conclusion• C. clypeatus are omnivorous, opportunistic feeders and can

live as long as 30 years in captivity. • Crabs in shells that are crowded (unable to retract fully),

damaged, too heavy, or too large are more susceptible to predation and potential desiccation.

• Hermit crabs in shells that are damaged or crowded often take part in a local vacancy chain (or “conga line”) when a new shell is available to them or to a larger crab (Rotjan et al., 2010).

Figure 1: Average crowding (+/- 1 SE) of crabs at VIERS and other locations based on chela length in mm. Sizes of the crab impact the crowding of crabs (Kruskal Wallis, p<.001). Crabs were crowded regardless of location.

Figure 2: Shell quality of crabs of varying chela lengths. Small crabs appear to have the highest quality shells. More shells catalogued were intact than with medium or high damage.

Citations Laidre, M. E. (2012). Niche construction drives social dependence in hermit crabs. Current Biology, 22(20). doi:10.1016/j.cub.2012.08.056

Lewis, S. M., & Rotjan, R. D. (2009). Vacancy Chains Provide Aggregate Benefits ToCoenobita clypeatusHermit Crabs. Ethology, 115(4), 356-365. doi:10.1111/j.1439-0310.2009.01626.x

Morrison, L. W., & Spiller, D. A. (2006). Land hermit crab (Coenobita clypeatus) densities and patterns of gastropod shell use on small Bahamian islands. Journal of Biogeography, 33(2), 314-322. doi:10.1111/j.1365-2699.2005.01399.x

Rotjan, R. D., Chabot, J. R., & Lewis, S. M. (2010). Social context of shell acquisition in Coenobita clypeatus hermit crabs. Behavioral Ecology, 21(3), 639-646. doi:10.1093/beheco/arq027Photographs taken by Allison Caldwell and Jessica Michael.

“Conga-line” formation

Least crowded crab found on the island

Weighing crab + shell

Examining shell crowding

High damage shell

Placed shell

Annaberg