Descriptions of two loxosomatids (Entoprocta), with emphasis on a relationship between symbiont attachment structures and host cuticle

Abstract

Information is provided on a new species of Loxosomella, L. diopatricola, with unusual characteristics that is symbiotic with tubicolous polychaetes of the genus Diopatra. Plasticity is displayed in the morphology of the attachment organ: the new loxosomatid possesses a stalk terminating in either a persistent pedal gland or an enlarged adhesive disc. An individual animal develops one or other of the two stalk morphologies according to its exact location on the host and the thickness of the underlying cuticle. The host epidermis underlying individuals with an adhesive disc is, in turn, modified, suggesting that these symbionts may negatively affect their hosts. Females possessed a single ovary, nearly always on the left side. The larva lacks eyespots. Buds were borne only by males. A minute species of Loxosomella commensal on polychaetes of the genus Eunice, characterised by 6 tentacles and a very short stalk, is also described. A grooved foot is present in the bud and a pedal gland is retained in the adult. The larva apparently undergoes metamorphosis.