Annual variations of the presence of Nereididae (Annelida: Polychaeta) from intertidal rocky shores along the east coast of Algeria

Four species of nereidid polychaetes, Peri­ner­eis cultrifera, P. macropus, Nereis falsa, and Platy­ner­eis dumerilii, were identified during three years in four intertidal rocky shore sites (El-Kala, Annaba, Skikda and Collo) along the east coast of Algeria during the years 2011–2013. Species' distribution fluctuated according to sites and season. Perinereis cultrifera was observed during most of the year, except in summer. Perinereis macropus was observed at El-Kala, Skikda and Collo mainly in late winter and early spring. Nereis falsa was observed during most of the year in El-Kala and Annaba; this species was also observed in Skikda in 2011 but then disappeared in the last two years of this study. Finally, the presence of P. dumerilii was noticed only in El-Kala for a few months (mainly in March and April). Perinereis cultrifera, P. macropus and P. dumerilii reproduce after acquiring the epitokous form between April and May, when surface seawater temperature starts rising. The largest mature oocytes were about the same for P. cultrifera (279 µm) and P. macropus (278 µm), while this value was smaller for P. dumerilii (166 µm). In contrast to the other three species of nereidid polychaetes, N. falsa reproduces without epitokal modification between July and August when sea temperature was highest. The largest mature oocytes (168 µm) are about the same as P. dumerilii but is much small than those of P. cultrifera and P. macropus