Tolerance of low salinity by larvae in six terrestrial hermit crab species (Decapoda: Anomura: Coenobitidae)

Abstract

Tropical shallow-water crinoids offer shelter to a diversity of marine life, including various symbiotic palaemonid shrimp species. In this study, the reproduc- tive features of the shrimps Cristimenes commensalis and Pontoniopsis comanthi in- habiting comatulid crinoids are studied and compared. Ovigerous females were col- lected from the crinoids Anneissia bennetti and Comaster nobilis from Iriomote-jima, Japan. All specimens were examined for the following traits: carapace length, fecun- dity, embryo volume, brood mass volume and dry weight of the females and the eggs. Cristimenes commensalis produced 15–117 eggs with a volume of 0.04 mm3 ±0.00, whereas the smaller-sized species P. comanthi produced 12–57 eggs with a volume of 0.02 mm3 ±0.01. The reproductive output (RO) of C. commensalis was 0.16±0.03, considerably lower than that of P. comanthi at 0.31±0.05. Data is beginning to emerge on the fecundity and reproductive output of symbiotic palaemonid shrimps, although comparisons remain hampered by the general lack of knowledge on their bi- ology in general. Pontoniopsis comanthi has the highest recorded reproductive output so far, despite being the smallest species studied. Our results confirm that inhabiting a sheltered habitat allows symbiotic shrimps to allocate more energy to embryo produc- tion than free-living species. Different reproductive strategies are, however, apparent for these species inhabiting the same host species, implying the existence of differen- tial selective forces. Key