Morphological characteristics of the hinge edge of the shells of Magallana gigas (Thunberg, 1793) (Bivalvia: Ostreidae) larvae obtained from Black Sea spawners

The morphological features and ultrastructure of the hinge margin of the giant oyster Magallana gigas larvae, which were obtained from a nursery with the Black Sea broodstock and grown under optimal conditions, were studied. The paper presents scanning electron micrographs of disarticulated larval valves at different stages of development. In larvae at the D-veliger stage (2 days old, shell dimensions: 72×62 μm), as well as at the veliger stage (shell dimensions: 84×96 μm), the provinculum of the right and left valves consists of two anterior and two posterior teeth. We noted 2 to 3 teeth on the provinculum in both ”uneyed“ (H: 140–182 μm) and ”eyed“ velikonch larvae (H: 200–230 μm) on the anterior and posterior edges of the right and left valves. In pediveligers (H: 338–358 μm) there are two anterior teeth in the hinge margin of the right and left valves; the posterior teeth are reduced. We also determined logarithmic dependences of the hinge margin length (l, μm) on the length (L, μm) of the shell [ ; R2=0.904] and the maximum provinculum width on the shell height [ ; R2=0.8993] of larvae ranging in size from 72×62 to 322×358 μm. The morphological characteristics and provinculum ultrastructure of the reared larvae were compared with those of M. gigas larvae of Atlantic and Pacific origin. The article discusses the potential hybrid nature of the Black Sea broodstock.