Redescription of Parophryotrocha isochaeta (Eliason, 1962) and a new species of Parophryotrocha (Polychaeta: Dorvilleidae) from the Skagerrak and North Sea

Abstract

The original description of Parophryotrocha isochaeta (Eliason, 1962; as Ophryotrocha (?) isochaeta) was based on three specimens collected in the deepest part of the Skagerrak in 1933. The species is here redescribed from new material collected at the type locality in 1990. Its most characteristic features pertain to jaw morphology and the presence of only one type of simple chaeta in all parapodia. Several structures, such as prostomial appendages, parapodia and parapodial cirri, were not depicted in the original description, but were found to be present and are here characterised. A new species, Parophryotrocha rhadina n. sp., is described from material collected from the northern North Sea. It differs from P. isochaeta by being smaller and of slimmer size, by lacking ventral cirri and by the shape of the mandibles and maxillae. The genus Parophryotrocha Hartmann-Schröder, 1971 was originally erected for O. (?) isochaeta with lack of antennae, palps, parapodia and composite chaetae as diagnostic features. The generic definition is here emended. The status of the genus is discussed with regard to related genera. The presence of prostomial and parapodial structures implies that the difference between P. isochaeta and the species currently placed in Ophryotrocha is not as great as had previously been considered.