The ecology of an assemblage of gonodactylid stomatopods and pygmy octopus in shallow sea grass beds in Belize, Central America.

摘要

The ecology and population biology of three species of gonodactylid stomatopod (Neogonodactylus oerstedii, N. austrinus, and N. bredini) and a previously undescribed species of pygmy octopus were studied in shallow sea grass beds of Thalassia testudinum along the barrier reef of Belize in Central America. These organisms were initially collected from cavities in dead coral rubble at mangrove and reef-associated sites within areas of seven by seven meters. Thirty-six artificial cavities were subsequently placed at each of the sites where the rubble had been collected and were sampled regularly over the 29 months of the study.;In addition to observing the stomatopod and octopus populations, a variety of physical and biotic parameters were measured at each of the nine sites, including temperature, salinity, water height, coral rubble density, prey abundance, and presence of predators. Sites with a high density of dead coral rubble had more stomatopods. Mangrove sites had a greater diversity of stomatopod species and larger and more numerous adults. Octopods, on the other hand, were extremely rare in the mangroves and may have limited the numbers of stomatopods at the reef sites. Crab abundance was correlated with stomatopod density and increased at the mangrove sites over the course of the study in a similar way to the stomatopods.;The introduction of artificial cavities enhanced the number of stomatopods at the mangrove sites but decreased the number at the reef sites. Octopus density increased at the reef sites with the introduction of the artificial cavities. Stomatopods at the mangrove sites were cavity limited, while at the reef they seemed to be limited by competition and predation.;By uniquely marking individual stomatopods, the growth rate and molting frequency could be determined. The most abundant species N. oerstedii was found to molt an average of 3.5 times a year and grew 2.4 mm per molt. At this rate, the largest individuals (64 mm total length) were five and a half to six years old. Population estimates of stomatopods were made using the Jolly-Setier mark-recapture model. Populations in the mangroves were larger than at the reef.