Ecology 



In Busse Lagoon (southern Sakhalin), spawning of M. yessoensis and 

 development of larvae in the plankton are observed from early July to early 

 August. In Peter the Great Bay, larvae are found in the plankton for two 

 months, from June to July, at a water temperature of 8-18°C. Their number 

 is maximal from mid- June to mid- July. Duration of the pelagic stage of devel- 

 opment of the scallop varies from 20-40 days. 



The morphology of M. yessoensis larvae has been described by Yamamoto 

 (1964), Maru (1972), and Kulikova, Medvedeva and Guida (1981). Data on the 

 ecology of larval development of this species along the coast of Japan and in 

 Mutsu Bay are available in Yamamoto's work (1951). The ecology of the 

 larvae of this scallop along the southern Sakhalin coast was described by 

 Kulikova and Tabunkov (1974) and for Peter the Great Bay by Belogrudov 

 (1973, 1974). 



HIATELLA ARCTICA LINNE 

 (Hiatellidae) 



Veliconcha 



The shell of the veliconcha is triangular. The anterior, posterior, and 

 ventral margins are roundish, with the anterior margin more stretched than the 

 posterior. The shoulders are straight, long, and slope steeply toward the ventral 

 surface. The umbones are high and round. One tooth each is present on the 

 right and left valves. The ligament is posterior (see Figures 48 and 58). The 

 maximum shell length of the pelagic larva is 380-400 ^im. 



Ecology 



In Busse Lagoon (southern Sakhalin), pelagic larvae of this species are 

 found from early September to early October at a water temperature of 15- 

 18°C. In Vostok Bay, larvae of H. arctica occur in the plankton in September. 

 In the southern Adriatic (Poggiani, 1968), H. arctica reproduces from January 

 to Junen-July at temperatures ranging from 6.0-23.5°C. Reproduction is maxi- 

 mum in March — first half of May at temperatures of 11-16 °C. In the 

 northern Adriatic (Brenco, 1971), larvae of//, arctica are found in the plank- 

 ton year-round, but are maximum in May-June. In Plymouth (La Mancha 

 Strait), H. arctica larvae have been found in the plankton from early summer 

 to December (Lebour, 1938). In Danish waters, according to J0rgensen (1946), 

 pelagic larvae of this species are abundant from July to September-November. 

 Along the eastern coast of Greenland (Ockelmann, 1958), this species repro- 

 duces from May to June. 



