ROPES ET AL.: SIZE. AGE, AND SEX OF OCEAN QUAHOGS OFF LONG ISLAND. NY. 



(1980a) reported a longevity of about 150 yr. They 

 found that growth was vigorous at old age and that 

 there were no obvious indications of reproductive 

 senility. A small abyssal nuculoid bivalve, Tin- 

 daria call isti for mis, studied by Turekian et al. 

 (1975) seems most exceptional with regard to age 

 and size at sexual maturity They found a longev- 

 ity of about 100 yr for a large specimen (8.4 mm 

 shell length) by radiometric techniques and 

 counts of shell growth bands, but gonadal devel- 

 opment was not recognized until the clams were 

 about 4 mm long and 50-60 yr old. The attainment 

 of sexual maturity about midway in the life span of 

 Tindaria sets it apart from other species that re- 

 produce at a younger age. Nevertheless, all have 

 the potential to reproduce for many years. Repro- 

 duction during a long life span of a species may be 

 an evolutionary strategy in response to uncertain 

 larval and juvenile survival (Krebs 1972). Repro- 

 duction during a particularly long life span is most 

 obvious for Arctica islandica. 



For the 69 gonads containing sexually differen- 

 tiated germinal cells and sparse-to-moderate 

 tubule development, some morphologically ripe 

 sperm were present. In contrast, oogenesis never 

 exceeded an early developmental state. Jones 

 (1981), Loosanoff (1953), von Oertzen (1972), and 

 Mann (1982) reported that mature ocean quahogs 

 spawn each year. Thus, the sperm may be 

 spawned, but the fate of the oocytes remains an 

 enigma. In American oysters, Crassostrea vir- 

 ginica, germinal cells remaining in the gonads 

 after spawning are reabsorbed (Galtsoff 1964), but 

 viable, nearly ripe, or ripe germinal cells may be 

 retained by hard clams throughout the fall, 

 winter, and into the following spring (Loosanoff 

 and Davis 1951). Thus, bivalves appear to differ 

 greatly in this respect. No conclusion can be drawn 

 relative to retention of germinal cells after spawn- 

 ing for ocean quahogs which were intermediate 

 between the immature and mature condition in 

 the absence of collected data. 



Gonadal development in 28 mature clams 

 suggested that many (46% ) were approaching 

 ripeness or were ripe (21% ). Later development 

 probably resulted in a spawning which was begun 

 in late August-September. This seems reasonable 

 based on observations by Mann (1982) of the re- 

 productive cycle of Arctica islandica from sample 

 locations in Block Island Sound. At the beginning 

 of his study in September 1978, most (69% ) were in 

 the partially spent or spent condition and spawn- 

 ing was indicated until mid-November. An exact 

 correspondence of the time and duration of spawn- 



ing may be a hazardous assumption, since the two 

 sample sites are about 110 km apart and some of 

 the samples taken by Mann (1982) were at shallow 

 depths (36 m). 



A disparity in the initiation of gametogenesis 

 was observed between the sexes. Male ocean 

 quahogs began producing germinal cells at a 

 smaller size and younger age than females. This 

 suggests that females require a longer period of 

 development and growth. The later development 

 of female sexuality is a probable explanation for 

 the highly significant difference obtained in tests 

 of the sex ratio of quahogs in the intermediate 

 gonadal condition. The significant difference ob- 

 served for fully mature quahogs may be due to the 

 small number in the sample (Dixon and Massey 

 1957), but Jones (1981) observed a similar dispar- 

 ity (P = 0.008) for quahogs > 75 mm from offshore 

 New Jersey. In his collections 184 were males and 

 136 were females, a ratio of 1:0.74. Mann (1982) 

 examined ocean quahogs that were mostly 80-100 

 mm long and found 185 males and 169 females, a 

 ratio of 1:0.91. These observations suggest that 

 spatial variation may occur in the sex ratio of 

 ocean quahog populations, but that males are 

 more numerous than females. 



Pelseneer (1926) investigated the sex ratio of 

 several mollusc species, including bivalves. He 

 found more females among the older individuals of 

 some populations and the converse among younger 

 individuals. Coe ( 1936) recognized the existence of 

 such disparities in molluscs and proposed the fol- 

 lowing hypotheses as possible explanations: 1) 

 That males have a shorter longevity than females, 

 because of a differential mortality rate or less re- 

 sistance to unfavorable environmental conditions; 

 2) that the development of alternative sexual con- 

 ditions is environmentally determined; and 3) 

 that sex change may occur. Loosanoff (1953), von 

 Oertzen ( 1972 ) , Thompson et al .( 1980b ) , and Jones 

 (1981) all considered the species to be strictly 

 dioecious, as did Mann (1982), although he found 

 two hermaphrodites. These are anomalous, "acci- 

 dental functional hermaphrodites" by the ter- 

 minology of Coe (1943). Although Sastry (1979) 

 hypothesized that a failure in the genetic sex- 

 differentiating mechanism may produce some 

 hermaphrodites, he found no evidence of a 

 phenotypic or genetic basis for sex determination 

 in pelecypods. 



It is unlikely that ocean quahogs are protandric. 

 This condition in a typically hermaphroditic 

 species is characterized by the development of 

 male organs or maturation of their products before 



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