Diploma Thesis

"Feinmorphologie der Larve von Lasaea rubra (Bivalvia, Heterodonta, Galeommatidae), einer brutpflegenden Muschel." *

Larval morphology of the brooding clam Lasaea rubra (Montagu, 1803) (Bivalvia, Heterodonta, Galeommatidae)

The strongly modified mode of development of the small and brooding bivalve Lasaea adansonii (Gmelin, 1791) has been studied by means of transmission and scanning electron microscopy and by fluorescent staining of the muscular system and of various neurotracers (FMRFamide and serotonin). In addition, computer-aided 3D-reconstructions were done on two larval stages before and after metamorphosis.

All larval stages of Lasaea adansonii lack ciliary rings. The apical tuft has been invaginated and is located at the base of a duct that contacts the cerebral ganglia and opens on the preoral region. There are no larval protonephridia. The adult kidneys develop independently of the pericardial cavity and contain a protonephridial part which enables function until the pericard is formed. The muscular system generally consists of smooth muscle fibres only. Posteriorly and immediately below the ligament a paired cell of unknown function is present which contains serotonin and FMRFamide.

In summary the developmental mode of Lasaea adansonii is strongly modified from the general pattern of bivalve ontogeny.

* - Update 08.01.2008: Lasaea rubra (Montagu, 1803) is now Lasaea adansonii (Gmelin, 1791)