Stereophaedusa (Breviphaedusa) jacobiana (Pilsbry, 1902)

Sulikowska-Drozd, Anna, Hirano, Takahiro, Wu, Shu-Ping & Páll-Gergely, Barna, 2018, High Fecundity, Rapid Development and Selfing Ability in Three Species of Viviparous Land Snails Phaedusinae (Gastropoda: Stylommatophora: Clausiliidae) from East Asia, Zoological Studies 57 (38), pp. 1-11 : 3-6

Stereophaedusa (Breviphaedusa) jacobiana

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Eight F0 individuals placed in the culture were 12.53 mm high (SD = 0.36) and consisted of 7.97 whorls (SD = 0.51) on average. Kept in pairs they released offspring repeatedly during the experiment (total 779 neonates). During a year, they produced from 97 to 159 neonates per pair of snails (median 143.5, n = 4), while during a week, 3.5-5.5 neonates were delivered per pair of snails (median 4.0, n = 4). At the moment of release, the neonates had shells 1.86-2.57 mm high (mean 2.09 mm, SD = 0.15, n = 28) with 2.0- 2.5 whorls ( Fig. 3B ). Time needed for shell growth ranged between 88 and 115 days (n = 10). The first reproduction was recorded 168 days after birth. The reproduction of virgin S. jacobiana was recorded in only one of 10 isolated snails. It delivered 41 juveniles over 6 months.

Stereophaedusa jacobiana (F1 generation), kept under high humidity, contained 5 to 7 eggs and embryos in the reproductive tract (mean 6.2, SD = 0.84, n = 5). Retained progeny had egg envelopes with visible crystals of calcium carbonate ( Fig. 3D, E ). The majority of the offspring (52%) were at the first stage of development (egg without shelled embryo). The stage I egg length varied from 1.67 to 2.53 mm (mean 2.08, SD = 0.28, n = 16). The stage IV embryos still had parts of egg envelope with calcium carbonate crystals. Their shell height varied from 1.57 to 1.96 mm (mean 1.84 mm, SD = 0.12, n = 13) and number of whorls from 1.25 to 2.5. The exposure to 60 days of drought resulted in loss among adults of S. jacobiana (3 dead out of 13), and among retained progeny (in 3 out of 10 surviving adults). In the remaining snails, the mean number of eggs and embryos was 2.3 (SD = 2.98, range 0-7, n = 7). The majority of embryos (87%) were advanced in development and their shell height varied from 1.57 to 2.27 mm (1.84 mm, SD = 0.16, n = 14).

Figures

Fig. 3. Stereophaedusa jacobiana. (A) adult (F1 generation); (B) neonates; (C) clausilium; (D) dissected adult with eggs; (E-F) egg and embryos from dissected adults. Scale bar = 1 mm.