Observations sur l'écologie de Lingula reevei Davidson (Brachiopoda:Inarticulata)

Abstract

In Kaneohe Bay (Oahu, Hawaii), Lingula reevei Davidson inhabits infralittoral sandy bottoms. Its distribution appears to be related mainly to the nature of substratum, the presence of predators and diggers, and the food supply. The meiofauna is studied and compared between the stations in which L. reevei occurs. The stomach and intestinal contents are analysed, for the first time in Lingula: the nutrients arise mainly from the superficial fauna and flora. L. reevei filters continuously; the arrange- ment of the anterior mantle ciliation forming the three characteristic siphons is described more precisely. No preferential orientation to prevailing currents could be established; however, this cannot be excluded. The depth of the burial and anchorage conditions depend on the nature of the substratum. L. reevei, if removed from the substratum, is unable to re-establish itself or to change its burrow. But this species is capable of upward burrowing through a sediment layer, even if the animal has to autotomize the pedicle (a new one then regenerates). A growth rate curve for estimating the age length in relation to the shell length is proposed and compared to that of L. anatina. L. reevei does not survive more than a few days exposure to adverse environmental conditions: in extremely diluted salinities (<15‰), after several days, Lingula emerging from the sediment dies, and after body putrefaction the valves dislocate and fall onto the substratum. In high salinities (>40‰) or after substratum emersion, the animal dies within the burrow. Tolerance to desiccation does not ever reach 3 days.