hinge comprises three anterior and two posterior rectangular teeth (see Figure 

 37). The height of each anterior tooth is twice that of the posterior teeth. The 

 space between the anterior and posterior teeth is smooth. The ligament is 

 posterior. Eyes are present; they develop and become distinct at a shell length 

 of 250-270 |j.m. Concentric and radial striations are equally well-developed on 

 both valves. In the umbonal region, the larva has a large black spot that 

 corresponds to the digestive gland. The larva attains the veliconcha stage at a 

 shell length of 100-120 ^im and a hinge line length of 50 ^im. As the veliconcha 

 grows, the length of the hinge line increases to 65 ja.m. 



The larva of C. gigas, like the larvae of C. virginica and of C. angulata, 

 but unlike those of C. glomerata and C. cucullata, has an asymmetrical shell. 

 The umbo is shifted back, the anterior margin more drawn out ventrally and 

 larger, the three anterior teeth are two to three times longer than the posterior, 

 and the entire provinculum is short. 



Ecology 



Along the southern Sakhalin coast (Aniva Bay, Sea of Okhotsk), spawning 

 and development of oyster larvae in the plankton occurs in the warmest period 

 of the year, i.e., July-September, at a water temperature of 16— 22°C. In 

 Vostok Bay, gamete release is observed from the second half of June to the 

 first half of August (Kasyanov et al., 1976, 1980). In Posjet Bay, larvae are 

 found from June to September (Rakov, 1975), becoming maximum m July- 

 August. In Vostok Bay, larvae are mainly found in the plankton in August. The 

 duration of the pelagic phase of C. gigas in Peter the Great Bay is, on average, 

 26-28 days. A similar duration of this stage in the giant oyster has been 

 reported by Thorson (1946) and His and Kriaris (1972) in the North Sea and 

 in experimental culture. 



Many works (Hori, 1926; Funita, 1933; Cahn, 1950; Loosanoff and Davis, 

 1963; Loosanoff e/ al., 1966; Rakov, 1974) have described the structure of the 

 larval shell of C. gigas, size characteristics, and methods of obtaining and 

 culturing larvae. Le Pennec (1980) examined the ontogenetic development of 

 the hinge of oysters. Data on the ecology of larval development are available 

 in the works of Korringa (1957), Thorson (1946), His and Kriaris (1972), and 

 Kulikova (1975, 1979). 



CHLAMYS FARRERI NIPONENSIS KURODA 



(Pectinidae) 



Veliconcha 



The maximum size of the larval shell is 220-230 ^tm with a provinculum 

 100-1 10 |im long. The shape of the shell of the Japanese scallop is typical of 



