Metabolic levels and microhabitat of an interstitial cephalocarid and micro-isopod

Oxygen consumption rates were assessed for two meiobenthic crustaceans inha biting a subtidal sandflat at Carrie Bow Gay, Barrier Reef of Belize. The m icro-isopod Lightiella incisa Gooding 1963 was confined to the surface subs trate layers. Lightiella incisa Gooding 1963 (Cephalocarida) occurred in de eper substrate strata below the redox potential discontinuity layer. Respiration rates were measured using the "Stoppered Cartesian Diver" metho d at normoxic conditions, The aim was to obtain information on the metaboli c level of a representative of the conservative crustacean taxon, the Cepha locarida, and to cheek whether the hypothesis of lower metabolic levels in benthic animals occurring in anoxic sediment strata is also applicable for this group. The results obtained show that the weight-specific and weight-s caled respiration rates in Lightiella are in the same range as the values o btained for Microcharon. This indicates that under normoxic conditions no " capacity" adaptation in the form of a controlled lower metabolic rate occur s in Lightiella. This is in contrast to the situation in nematodes and gnat hostomulids living in or below the redox potential discontinuity layer.