Comparative descriptions of some oyster larvae from New Zealand and Chile, and a description of a new genus of oyster,Tiostrea

Abstract

Detailed comparisons of the larvae of four species of New Zealand oyster (Saccostrea glomerata, Crassostrea gigas, Ostrea lutaria, and a new species of Ostrea) and one Chilean oyster (Ostrea chilensis) showed that larvae of species other than O. lutaria and O. chilensis share certain features. One conspicuous feature is a distinct tract, termed here the posterior dorsal sulcus, which runs from the posterior margin of prodissoconch I to the valve margin of prodissoconch II; other characteristic features are an umbonate, inequivalve shell and a provinculum bearing distinct teeth. The larvae of O. lutaria and O. chilensis, in contrast, lack the posterior dorsal sulcus, are non-umbonate, and have nearly equal valves with an edentulous provinculum. These distinctive features, together with other adult features, suggest that the two species are more appropriately included in a separate genus. The name Tiostrea is proposed for the new genus. Certain supraspecific groupings within the Ostreinae need to be re-examined in the light of breeding experiments.

Larvae of the incubatory oysterTiostrea chilensis(Bivalvia: Ostreidae) in the plankton of central and southern New Zealand

“…The larvae of T. chilensis arc readily distinguished from all other oyster larvae found in New Zealand (Chanley & Dinamani 1980). The pediveligcrs are very large at release, between 416 and 514 \im long (Hollis 1963;Chanley & Dinamani 1980) and longer than larvae of any other living species of oyster.…”

“…The pediveligcrs are very large at release, between 416 and 514 \im long (Hollis 1963;Chanley & Dinamani 1980) and longer than larvae of any other living species of oyster. Unlike all other living oyster species, the shell of the pedivcligcr T. chilensis has no umboncs; both valves are equal, are considerably longer than high and oval in shape (slightly broader in the anterior end), and lack teeth along the hinge.…”

“…Unlike all other living oyster species, the shell of the pedivcligcr T. chilensis has no umboncs; both valves are equal, are considerably longer than high and oval in shape (slightly broader in the anterior end), and lack teeth along the hinge. Because of these different larval characteristics, Chanley & Dinamani (1980) erected the genus Tiostrea for the Chilean and Foveaux Strait oysters.…”

“…Stead presented no evidence that this indeed occurred. Although incubating oysters captured in the wild often released larvae at various stages of development when placed in sea water in the laboratory (Hollis 1963;Chanley & Dinamani 1980), Hollis found that such releases seemed to be triggered by environmental changes during handling. She concluded that, in the wild, larvae were released ready to settle but could postpone settlement in the absence of suitable settlement surfaces.…”

Larval shell development of four species of New Zealand mussels: (Bivalvia, Mytilacea)

“…Depth was measured on an additional series of whole larvae, with the total length for reference, viewed in the dorsal or ventral profile. The accuracy with which the larval dimensions can be measured was discussed by Chanley and Dinamani (1980). Slight variations may occur in the measurements because of the orientation of the larvae on the slide and in those larvae with broadly rounded anterior and/or posterior margins the judgment of the position of the extreme anterior or posterior margin and the shoulder height is more subjective.…”