Reproductive ecology of Bouvierella curtirama (Amphipoda: Eusiridae) from chemically distinct vents in the Lucky Strike vent field, Mid-Atlantic Ridge

Abstract

Populations of the vent amphipod Bouvierella curtirama were compared from two sites in the Lucky Strike vent field on the Mid-Atlantic Ridge. The two sites (Sintra and Eiffel Tower) are chemically distinct, fed by different hydrothermal sources, but separated by only about 400 m. Both sites are characterized by dense beds of the mussel Bathymodiolus azoricus, though the proportion of methanotrophic and thiotrophic endosymbionts supported by the mussel and its isotopic composition vary significantly between the sites. Such differences presumably reflect the availability of primary resources and would be expected to impinge on other members of the mussel bed community, such as B. curtirama, which was abundant at both sites. A detailed comparative study of the amphipod showed that, although the overall population structure (in terms of growth stages) was similar at the two sites, reproductive output was significantly greater at Sintra, a result of females maturing at a smaller body size and producing more broods of a greater size. The reproductive output at both sites was relatively low, with a proportion of surviving females failing to mature. The plasticity of response of the two populations is discussed in relation to food availability (quantity and quality). Grazing predation, resulting in loss of antennal flagellum articles, was high at both sites. Such damage is discussed in terms of predation impact. Damage to the antennae of the holotype has resulted in an inaccurate species description, which is remedied here.