<i>Aristonerilla</i>:: a new nerillid genus (Annelida: Polychaeta) with description of <i>Aristonerilla</i> (<i>Micronerilla</i>) <i>brevis</i> comb. nov from a seawater aquarium

Abstract

A nerillid polychaete is described from the organic-filter system of a marine aquarium in the AquaZoo (Dusseldorf, Germany). The body comprises the prostomium, seven segments and the pygidium. With two large, ventrolateral palps and three long, threadlike antennae, the species possesses the maximal number of prostomial appendages present in this taxon. Two small eyes are visible. The first segment (buccal segment, peristomium) contains a pair of small parapodia without cirri but with a few, relatively long chaetae. Segments 11 to VI possess parapodial cirri, increasing in length posteriorly. In segment VII the cirri are reduced. Each trunk segment has one dorsal and one ventral bundle of chaetae, which are slightly longer than the parapodial cirri. All chaetae are compound; some possess very long blades. The pygidium carries two threadlike anal cirri. Apart from minor morphometrical and anatomical differences, the animals resemble Micronerilla brevis. However, the type species Micronerilla minuta, does not possess seven but eight segments and because the number of segments is considered a stable character in nerillid genera, the species brei,is, with seven segments, has to be placed in a new genus, Aristonerilla, and named Aristonerilla brevis (new comb.).