Gonadal maturation, fecundity, spawning and timing of reproduction in the mud snail, Cerithidea cingulata, a pest in milkfish ponds in the Philippines
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Gonadal maturation, spawning, fecundity and timing of reproduction of the snail Cerithidea cingulata in a brackish water pond in Molo, Iloilo, Philippines, are described. Snails 4–41 mm in shell length were sampled monthly from May 1997 to May 1998; 25% were <25 mm, 67% were 20–30 mm, and 8% were >30 mm. The sexes are separate and could first be distinguished at 15 mm. Males are aphallic, have narrower shells than females of the same length, and have bright yellow-orange testes overlying the digestive gland deep inside the shell. Females have more robust shells, an ovipositor at the right side of the foot, and yellow-green ovaries overlying the digestive gland. The sex ratio was one male to two females in the pond population studied. Gonadal maturation was monitored by means of gonadosomatic index (GSI, gonad weight as a percent of visceral weight); maturation stages were based on the gonad appearance (immature, developing, mature) and histology (immature, developing, mature, redeveloping). GSI increased with snail size, and reached 16% in a 33-mm female. The smallest mature males and females were 18–19 mm, and most snails >20 mm were mature, spawning, or redeveloping. Histological sections showed all stages of gametogenesis in mature male snails. The oocyte size-frequency distributions in mature females showed mostly mature oocytes and secondary oocytes, but also oogonia and primary oocytes. GSI and the frequency of snails at different maturation stages varied over the year. Both GSI and the frequency of mature snails were highest during the summer months, April to August. Nevertheless, mature snails occurred throughout the whole year, as did mating and egg-laying. Fecundity (= number of oocytes >70 pμ) increased with size in mature females 2041 mm; an average 25-mm female produced about 1,500 oocytes and larger females produced a maximum of about 2,500 oocytes. Eggs strings laid on the pond bottom were 45–75 mm long; an average 64-mm string contained 2,000 eggs 210+20 pm in diameter. The density of eggs strings was highest (80–120/m2) during March-September. Eggs hatched after 6–7 d into planktonic veligers, which in turn settle on the pond bottom 11–12 d later as juveniles. Juveniles 2–6-mm long were most abundant in the pond during August-October.
CitationLantin-Olaguer, I., & Bagarinao, T. U. (2001). Gonadal maturation, fecundity, spawning and timing of reproduction in the mud snail, Cerithidea cingulata, a pest in milkfish ponds in the Philippines.
PublisherTaylor & Francis
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Conference paperAD Munro & TJ Lam - In CL Marte, GF Quinitio & AC Emata (Eds.), Proceedings of the Seminar-Workshop on Breeding and Seed Production of Cultured Finfishes in the Philippines, Tigbauan, Iloilo, Philippines, 4-5 May 1993, 1996 - SEAFDEC Aquaculture DepartmentDespite their great variety of reproductive strategies, a general characteristic of most teleosts is that (where known) natural reproduction shows a long-term periodicity, even in tropical habitats (e.g. see contributions in Munro et al. 1990a). Typically, gonad development from puberty leads to fully-grown gonads by the advent of the spawning season; if conditions are appropriate, then final gonad maturation leads to the production of viable gametes during one or more breeding bouts. Subsequently, in those larger species which spawn over more than one season, the gonads regress and the individual returns to a phase where any growth is somatic. However, there is wide interspecific variability in the pattern of gonad development (Wallace and Selman 1981, de Vlaming 1983, Billard 1986, Selman and Wallace 1989).
Induced gonadal maturation and rematuration in milkfish: Limited success with chronic administration of testosterone and gonadotropin-releasing hormone analogues (GnRH-A) Nine experiments were conducted to investigate the influence of chronic administration of testosterone (T) and gonadotropin-releasing hormone (GnRH) analogues on first maturation of 4- to 6-year-old fish and rematuration of 6- to over 9-year-old spent/regressed fish. Implantation of T or T in combination with luteinizing hormone-releasing hormone analogue (LHRH-A) had no marked effect on maturation rate of 4-year-old milkfish. The percentage of maturing fish was low and similar to controls in Experiment 1 (T, 31–35%; control, 35%) and Experiment 3 (T, 13%; T plus LHRH-A, 28%; control, 22.2%). Most of the 4-year-old maturing fish were males; maturing females were obtained only from the T-implanted groups in Experiment 1. In Experiment 3, T-implanted maturing females were able to retain yolky eggs whereas maturing control females did not, indicating that testosterone may have enhanced vitellogenesis and maintained the integrity of vitellogenic oocytes. Tank-reared maturing 4-year-old females, about half the size of older first maturing females, were induced to spawn. This is the first case of maturation and spawning of 4-year-old milkfish reared in tanks. As in Experiments 1 and 3, the percentage maturation of spent fish in Experiments 7 and 8 was similar for T-implanted and controls. On the other hand, the 4-year-old immature fish in Experiments 2 and 4, the 5- and 6-year-old immature fish in Experiments 5 and 6, and the spent 6-year-old fish in Experiment 9 were immature or regressed throughout. The factors which may have influenced the results of these experiments include age and reproductive history of the fish, timing of hormone implantation, experimental and holding conditions, and stress.
The effect of micro algal diet and rearing condition on gonad maturity, fecundity and embryonic development of the window-pane shell, Placuna placenta Linnaeus. Immature Placuna placenta (Linnaeus) broodstock were given the micro algae Isochrysis galbana (T-ISO) Parke and Tetraselmis tetrahele (G.S. West) at different combinations and density levels and reared in tanks with or without mud substrate. The animals were also reared in the estuary and fed on available natural food. Monthly examination of gonad histology showed a significantly higher gonad index in broodstock reared in tanks with mud substrate than without (P < 0.05). In addition, those given a high-density algal diet (200,000 cells ml−1, 3:1 mixture of I. galbana and T. tetrahele) had a significantly faster gonad development than the low-density diet (100,000 cells ml−1, 1:1 mixture) fed broodstock reaching sexual maturity and gonad index of 330±14 after 1 month (P < 0.0001). P. placenta given the low-density algal diet attained gonad maturity after 3 months and estuary-reared animals after 2 months. Seawater irradiated by ultraviolet light (925–1395 mW h/l) induced spawning of all mature P. placenta. Estuary-reared animals had a higher fecundity and larger eggs and a higher percentage of fertilized eggs developed to straight-hinged larvae than those reared under other condition. Animals given a low-density algal diet released low number of small eggs which did not fertilize. Natural spawning also occurred in the estuary 2 months after stocking.