CONICET | Buscador de Institutos y Recursos Humanos

Ophioplocus januarii is a common brittle star along the Argentinian and Brazilian coasts occurring on both, soft and hard substrates. Based on stomach contents and tooth microstructure analysis and together with field observations, the feeding habit of this species is described. Opposed to previous suggestions, O. januarii appears to be a microphagous species feeding on macroalgal fragments (found in 60.0% of the analyzed stomachs with content), plant debris (28.0%), animal cuticle structures (13.0%), and unidentifiable material (30.7%). Less frequent items found were foraminiferans, ostracods, an amphipod, a juvenile bivalve, and other crustaceans. Small portions of the unidentifiable material were investigated under at the light microscope and with a scanning electronic microscope and revealed digested material, diatoms and small crustacean appendices. Thus, O. januarii is an omnivorous species, feeding mainly on algae, complemented opportunistically with other items. Suspension feeding was observed in the field. Analysis of the microstructure of the tooth stereom revealed an intermediate fenestrated arrangement which is to be positioned between the two so far described types of uniform and compound teeth. Hereby the former have been typically found in macrophagous species whereas the latter generally correspond to microphagous ophiuroids. Here, we propose a new kind of intermediate arrangement in the dental stereo structure of ophiuroidsd.