Mating success of male hermit crabs in shell generalist and shell specialist species

The reproductive behavior of two species of diogenid hermit crabs was studied in Hawaii. In the shell generalist, Clibanarius zebra , male reproductive success varied little with size, although the largest males were less successful in obtaining copulations than were medium-large males. Male and female size were positively correlated, in successful pairs, thus larger males had the potential to fertilize more eggs when they were successful in obtaining a copulation. Female fecundity in C. zebra was not affected by species of gastropod shell inhabited once female size was taken into account. Male copulatory success was very strongly influenced by the species of gastropod shell inhabited. Males in Trochus or Nerita shells had greatly reduced reproductive success compared to males in Turbo or Nassarius shells. This result was due both to (1) males in Trochus especially dropping and otherwise poorly handling females during precopulatory behavior and (2) females not responding to precopulatory behavior patterns executed by males in Trochus and Nerita . Transferring males from “good” to “bad” shapes of shells and vice versa showed that male success was a function of shell type inhabited and not some correlated feature of the crabs. In the shell specialist, Calcinus seurati , which is found primarily in Nerita shells as an adult, males in Nerita shells were quite successful in obtaining copulations.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46893/1/265_2004_Article_BF00302928.pd

Acanthaster planci Outbreak: Decline in Coral Health, Coral Size Structure Modification and Consequences for Obligate Decapod Assemblages

Although benthic motile invertebrate communities encompass the vast majority of coral reef diversity, their response to habitat modification has been poorly studied. A variety of benthic species, particularly decapods, provide benefits to their coral host enabling them to cope with environmental stressors, and as a result benefit the overall diversity of coral-associated species. However, little is known about how invertebrate assemblages associated with corals will be affected by global perturbations, (either directly or indirectly via their coral host) or their consequences for ecosystem resilience. Analysis of a ten year dataset reveals that the greatest perturbation at Moorea over this time was an outbreak of the corallivorous sea star Acanthaster planci from 2006 to 2009 impacting habitat health, availability and size structure of Pocillopora spp. populations and highlights a positive relationship between coral head size and survival. We then present the results of a mensurative study in 2009 conducted at the end of the perturbation (A. planci outbreak) describing how coral-decapod communities change with percent coral mortality for a selected coral species, Pocillopora eydouxi. The loss of coral tissue as a consequence of A. planci consumption led to an increase in rarefied total species diversity, but caused drastic modifications in community composition driven by a shift from coral obligate to non-obligate decapod species. Our study highlights that larger corals left with live tissue in 2009, formed a restricted habitat where coral obligate decapods, including mutualists, could subsist. We conclude that the size structure of Pocillopora populations at the time of an A. planci outbreak may greatly condition the magnitude of coral mortality as well as the persistence of local populations of obligate decapods

The osmoregulatory capacity of the Ostracoda.

All ostracods that inhabit inland waters are osmoregulators. Freshwater ostracods must be hyperosmotic regulators while ostracods that live in hyperhaline water are hypoosmotic regulators. Some euryhaline species are hypoosmotic regulators in salinities above 8 g·l-1 and hyperosmotic below. Hyperosmotic regulation in ostracods is partly dependent on salt consumed in the food but hypoosmotic regulation is dependent on the excretion of salt brought about by special cells located on the inside of the carapace