瘤蜷
Ecology > Life cycle

Tarebia granifera is both 单性生殖 and 卵胎生, although males have been reported. These are characteristics which are undoubtedly key to its success as an invader. For example, no males have been found amongst hundreds dissected from KwaZulu-Natal, it is probable that a few are present. Males were found in most (6/7) populations examined in 波多黎各 but were generally uncommon at up to 22.7% of the population (mean 4.6%). Live sperm were present in the testes of these males but the genitalia（英语：） were apparently non-functional. R. Tucker Abbott (1952) failed to find sperm in the gonads of male Tarebia granifera from Florida. Most Tarebia granifera are therefore 克隆 of the female parent.
胚胎s develop in a brood pouch. This pouch is a compartmentalized structure lying immediately above the oesophagus（英语：） and develops only after the snail has reached maturity. Its size expands as the number of embryos increases. Tarebia granifera has 1–77 embryos in its brood pouch.
Tucker Abbott (1952), Chaniotis et al. (1980) and WHO (1981) cite the same statistic that females can give birth to one juvenile every 12 hours. Young snails emerge through a birth pore on the right side of the head. The newborn shell is <1–2 mm in height with between 1.5 and 4.8 whorls. The size of juveniles at birth is 0.7–2.1 mm. According to Chen (2003) these newborns have a high survival rate in the field.
Attainment of 性成熟 in Tarebia granifera is generally indicated by the size of the smallest snail observed to give birth rather than a histological assessment of the development of the gonad and associated reproductive structures. Appleton & Nadasan (2002) estimated onset of maturity at 10–12 mm shell height but unpublished data suggest a height closer to 8 mm in line with other published studies. Tucker Abbott (1952) estimated sexual maturity at between 5.5 and 8.0 mm at different stations over a short stretch of river in Florida. Chaniotis et al. (1980) gave a similar estimate of 6.0–7.0 mm from a cohort of laboratory-bred snails in Puerto Rico.
Appleton et al. (2009) extrapolated data by Yong et al. (1987), Ferrer López et al. (1989) and by Fernández et al.(1992) and they resulted that sexual maturity is reached at an age of about five months. Reported variation in maturation period varies from 97–143 days (3.2–4.8 months) under the laboratory conditions to 6–12 months, also from laboratory data. It is difficult to relate shell size at the onset of maturity to age since the size structure of populations vary over time and from one locality to another.
Dissection of Tarebia granifera showed 囊胚 stage embryos in the brood pouches of snails as small as 8 mm shell height. Small numbers of shelled embryos, including veliger（英语：）s, were found in snails of 10–14 mm but became more plentiful in snails >14 mm and especially those >20 mm. Importantly, unshelled embryos (blastula, 原腸胚形成 and 担轮幼虫 stages) were not found in snails >16 mm and the numbers of shelled embryos themselves decreased in the largest snails, >24 mm. This suggests that differentiation of 生殖细胞 in the ovary and their subsequent arrival in the brood pouch as blastulae is not a continuous process over a breeding season but occurs as one or more 'cohorts' or 'pulses' which stop before the birth rate of young snails reaches its maximum. So it seems that while the first birth may occur in snails as small as 8 mm, these are few and most juveniles are born to snails >14 mm. The size of the shell of the parent at peak release of juveniles is 24.0 mm.
The reproductive biology（英语：） of Tarebia granifera needs to be investigated in detail before its population dynamics（英语：） can be properly interpreted from quantitative sampling.