Distribució en l'espai i en el temps dels opistobranquis ibèrics, amb especial referència als del litoral català


  • Joandomènec Ros i Aragonès


Some data on the geographic, bathimetric and annual distribution of the Opisthobranchs inhabiting the Iberian coasts are presented. These data come from a previous fouryear survey (ROS, 1975) and are the basis for publications dealing on the ecology of these Gastropods (ROS, 1976b, 1978). The more thoroughly prospected area is the Catalonian coast, from where the main data came, and, in decreasing order, the Basque, Balearic, Canarian, Galician and southern Iberian littorals. The sampling stations have been described in ROS (1975), where the sampling methods (mainly by scuba-diving) are also discussed.
Some species of Opisthobranchs have a very wide geographical distribution; others are, «tipically» Atlantic or Mediterranean, and some of these extend in other regions. Not previously recorded are the presence of the Mediterranean Glossodoris tricolor , G. krohni, G. luteorosea and Peltodoris atromaculata in the Cantabric, and the occurrence of the Atlantic Limacia clavigera, Coryphella pedata and others in the Northwestern Mediterranean. The distribution tables also show the richness in species of the more heterogeneous stations and the poorness of the more uniform ones.
The bathimetric range of some species extends to very deep levels, while others appear limited to narrow littoral fringes. Some distributions are uncommon: Umbraculum Mediterraneum (which «rises» in bottoms of cold waters), Archidoris tuberculata (of which one individual, bathial in the Mediterranean, appeared in the shallow waters of the Blanes harbour); others depend on the degree of illumination reaching the bottom.
The annual distribution of the majority of species reflects their annual cycles and their marked abundance in the spring-summer months. All these data agree with those of other authors (HAEFELFINGER, 1960; VICENTE, 1967; SCHMEKEL, 1968; etc.), which have worked in the Western Mediterranean. Historical factors play an important role in the actual distribution of the Iberian Opisthobranchs, as play the environmental ones, but all the species of this group seem to be strictly linked to one or few food species (ROS, 1974, 1978), and it is the distribution of these prey species, in space and time, what in the last instance determines that of the Opisthobranchs.