Echinoderm

The effects of ultraviolet radiation on the covering behavior of the sea urchin Tripneustes ventricosus

Recent studies have indicated that levels of solar ultraviolet radiation (UVR) are increasing globally as ozone is depleted. Ultraviolet radiation often has negative effects on organism survival; in sea urchins, UVR has been found to reduce sperm motility (reducing fertilization success) and to increase the occurrence of abnormal embryonic development (decreasing embryonic survival). Several species of sea urchins cover themselves with rubble; this study examined how this behavior was affected by UVR in situ. Three types of treatment boxes were placed over Tripneustes ventricosus specimens: a control box, a UVR-blocking box, and an opaque box. Specimens were photographed before and after treatment and percent change in rubble cover was calculated for each individual. The mean change in percent rubble cover presented significant reduction under opaque conditions relative to other treatment conditions (p = 0.005, p = 0.010). There was no significant difference between the latter two treatment groups (p = 0.980). The data suggest that covering behavior in T. ventricosus is not a response specific to UVR, but is a response to light. Further studies of how UVR affects T. ventricosus and as well as how other species cover themselves in response to sunlight and UVR are needed to understand the benefits of covering behavior in elevated UVR climate conditions. Further study on the costs and benefits of covering behavior as well as studies on the covering and sheltering behaviors of other sea urchins is needed to gain a full understanding of how increasing UVR will affect sea urchins.

This student research was retrieved from Physis: Journal of Marine Science XVIII (Fall 2015)19: 27-33 from CIEE Bonaire.

Date
2015
Data type
Other resources
Theme
Research and monitoring
Geographic location
Bonaire
Author

Genetic evidence supports larval retention in the Western Caribbean for an invertebrate with high dispersal capability (Ophiothrix suensonii: Echinodermata, Ophiuroidea)

Abstract The brittle star Ophiothrix suensonii is a com- mon coral reef sponge commensal with high dispersal potential. Here, we utilize COI sequence data from 264 O. suensonii individuals collected from 10 locations through- out Florida and the Caribbean to investigate dispersal dynamics and demographic history. Locations separated by up to 1,700 km lacked genetic differentiation, confirming the ability for long-range dispersal. However, significant differentiation was detected among other regions. Samples from Utila, Honduras showed the greatest differentiation, suggesting that the circulation of the Mesoamerican gyre could be a significant factor restricting gene flow in this region. Demographic analyses provided strong evidence for a population expansion, possibly out of Florida, through the Caribbean, and into Honduras, which commenced in the early Pleistocene. However, the presence of a clade of rare haplotypes, which split much earlier (mid-Pliocene), indi- cates that O. suensonii persisted long before its recent expansion, suggesting a cyclic history of population con- traction and expansion. Finally, patterns of gene flow are not concordant with contemporary surface currents; rather, they reflect historical movements possibly linked with changes in circulation during periods of Pleistocene climate change. 

Date
2015
Data type
Scientific article
Theme
Research and monitoring
Journal
Geographic location
Curacao