The reproductive cycle, sex distribution, and gonadal characteristics of the flame scallop, Ctenoides scaber, formerly Lima scabra scabra (Born 1778), collected from Boca Chica Key, FL, were investigated over the 21-mo period from January 1998 through September 1999. Gametogenic cycles were examined using qualitative and quantitative methods, and the relationships between those observations and environmental conditions (e.g., water temperature, salinity and phytoplankton concentrations) were analyzed. The relationships between sex, gonad color and shell height were also examined. Gamete development in both sexes was initiated in winter and was associated with small oocytes and follicles, cool water temperatures and moderate concentrations of food. Growth of gametes occurred throughout spring, as temperature and chlorophyll-a concentrations increased. A partial synchronous spawn occurred in early summer but did not seem to be related to environmental conditions. Maximum gamete ripeness and size occurred in late summer, when water temperatures were at maximum values and food densities were increasing. Decreases in female gamete and follicle sizes and increases in occurrence of partially spawned, spent and early growth gonads in autumn were suggestive of synchronous spawning, which coincided with a rapid decrease in water temperature and maximum measured chlorophyll-a concentrations. Decreases in oocyte size in February coincided with annual water temperature minimums and may represent the conversion of energy from reproduction to survival, and not spawning. The presence throughout the year of juveniles, ripe and partially spawned flame scallops and chlorophyll-a concentrations sufficient to support gamete development suggest a reproductive strategy of continuous spawning, common in tropical marine invertebrates. No relationship was detected between salinity and gonad condition. Flame scallops collected for this study ranged in size from 21–68 mm shell height (SH) and those >25 mm SH had gamete development. The smallest animals were found principally in summer, which suggests a massive synchronous spawning event. Analyzing sex distribution by SH showed that flame scallops are protandric sequential hermaphrodites. Flame scallops <40 mm SH were predominantly male (83%), those ≥40 mm SH were mostly female (71%), and 4% were in sexual transition near 40 mm SH. The sex ratio for the sampled population was 0.63M:1F. Histologic examination of fresh gonadal tissues revealed that female gonads were predominantly purple (96%) and male gonads were predominantly cream-colored (91%). Other gonad colors observed were not reliable indicators of sex nor was there a clearly defined association between color and those animals in sexual transition. Documenting the reproductive cycle of Ctenoides scaber in the existing Florida fishery is the first logical step to understanding its life history. Because flame scallops are important to the marine aquarium industry in the United States and are a potential food source for humans, it is important that we understand the reproductive cycle of this species to ensure proper management policies. This study provides basic information applicable to mariculture of flame scallops for commercial production to supplement the harvest of wild stock for the marine aquarium industry.
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Vol. 24 • No. 2