The biology, functional morphology and taxonomic status of Gaimardia (Neogaimardia) finlayi (BivaMa: Gaimardiidae)

Abstract

Gaimardia (Neogaimardia) finlayi Powell 1933 is a member of the little known family Gaimardiidae which collectively have an Australian, New Zealand and sub‐Antarctic distribution. N. finlayi nestles amongst algal holdfasts at the bottom of wave‐exposed beaches in New Zealand. It is a small, weakly heteromyarian dioecious bivalve attached by a relatively stout byssus. The mantle and the siphons are exceedingly simple; mantle fusions, other than anterior and posterior to the internal ligament, are of the inner folds only. The siphons are non‐extensible wide openings with few sensory papillae. Each ctenidium comprises an inner demibranch only with no inter‐lamellar and but a few inter‐filamentar junctions. Within the ctenidium large telolecithal eggs are incubated to a crawling, shelled stage of approximately 0–75 mm in length. Sperm were found in the ctenidium of two mature males. The possible storage of sperm and eggs and the incubation of fertilized eggs have survival value for a small bivalve living in a difficult environment. The modifications which suit N. finlayi to its mode of life are discussed, but major interest centres around the taxonomic position of the Gaimardiidae. It is concluded that the Cyamiidae and Gaimardiidae are very closely related, but more comprehensive studies on representatives of both families are needed.

The functional morphology of Parilimya fragilis (Bivalvia: Parilimyidae nov. fam.) with a discussion on the origin and evolution of the carnivorous septibranchs and a reclassification of the Anomalodesmata

“…It is unlikely that, as in other incubatory species e.g. Corbicula JIuminea or Neogaimardia Jinlayi (Morton, 1977b(Morton, , 1979, the secretion nourishes the eggs themselves because they are already richly endowed with yolk and have a protective capsule. The labial palps and mouth The labial palps of P. fragilis (Fig.…”

Some aspects of the biology and functional morphology (including the presence of a ligamental lithodesma) of Montacutona compacta and M. olivacea (Bivalvia: Leptonacea) associated with coelenterates in Hong Kong

“…The exact function of these glands is unknown, but bearing in mind that non-incubating individuals do not possess them it seems probable that they nourish the developing oligolecithal eggs. Glands also occur in the inter-lamellar and inter-filamentar junctions of Anodontu (Wood, 1974) and Corbicula (Morton, 1977a) which similarly incubate eggs, whereas in Neogaimardia (Morton, 1979) the telolecithal eggs require no nourishment and filamentar glands are absent.…”

Unusual modes of oogenesis and brooding in bivalves: the case of Gaimardia trapesina (Mollusca: Gaimardiidae)

“…In other Gaimardiidae, the brooding of embryos has been reported, but no details on the process have been provided. In Gaimardia finlayi POWELL 1933, Morton (1979) described egg incubation within the inner demibranch, the only demibranch present, with the offspring released as shelled juveniles. Benavides & Cancino (1988), in a study dealing with physiology of the little Southwestern Pacific species Gaimardia bahamondei OSORIO & ARNAUD 1984, reported the incubation of numerous embryos ''adhered to the demibranchs,'' without providing further details.…”