Range extension and microhabitat of Lightiella incisa (Cephalocarida)

During an intensive meiofauna sampling campaign in intertidal seagrass beds along the Caribbean coast of the Yucatan Peninsula (Mexico), 131 specimens of Lightiella incisa (Cephalocarida, Crustacea) were recovered from the se diment. Two-thirds of the specimens were adults, one-third were pre-adults. This collection is the first record of this minute primitive crustacean in the western part of the Caribbean Sea, and extends the known range 3000 km from the type locality of Hastings Bay, Barbados. A detailed sampling prot ocol and environmental data made it possible to study the microhabitat pref erences of this species, and perhaps for cephalocarids in general for the f irst time. The vertical distribution of L. incisa in the sediment showed a maximum density in deeper layers, i.e. 3-4 and 4-5 cm depth. Nitrate and ni trite concentrations seem to be most closely related to the distribution of L. incisa. It was clear that L. incisa followed polychaetes to deeper sedi ment layers. In this study we state that L. incisa is an endobenthic specie s occupying anoxic sediments oxygenated by bioturbation (e.g. Polychaeta) r ather than being an animal living in the oxygenated top layers.