Giants of Taiwan – comparative analysis of life history traits in four land snail species Changphaedusa horikawai, Formosana swinhoei, F. formosensis, and Formosana sp. (Stylommatophora: Clausiliidae: Phaedusinae)

ABSTRACT

Family Clausiliidae (door-snails), which includes oviparous, embryo-retaining and viviparous species, can be a model group for studies on the evolution of reproductive modes in land snails. Yet, for understanding of evolutionary drivers leading to repeated changes of reproductive strategy, the identification of life history traits in phylogenetic lineages and geographical regions is fundamental. In this paper, we identified reproductive modes of clausiliid species endemic to Taiwan: Changphaedusa horikawai, Formosana formosensis, F. swinhoei, and an undescribed new species Formosana sp. Observations were conducted under laboratory conditions. Among Formosana species, oviparity predominated but embryo-retention was also recorded. The size of eggs and egg clutches differed between studied taxa. In contrast, C. horikawai was viviparous and delivered neonates. Anatomical examination of the fresh material allowed for unique observation of a large podocyst in embryos kept in the genital tract. This flattened structure may enable respiration or nutrient transfer between an embryo and a parent. In the regularly sampled wild population from Dawulun (N. Taiwan), gravid individuals were collected between April and November. The number of embryos reached three to nine per gravid individual. None of the species reproduced by self-fertilisation. Results of our study may support implementing conservation measures for malacofauna of Taiwan.

KEYWORDS:

• Eastern Asia
• embryo retention
• fecundity
• oviparity
• phenology
• podocyst
• reproductive strategy
• selfing
• viviparity

Acknowledgements

We are grateful to Ewa Janowska and Karolina Chaniecka, Department of Invertebrate Zoology and Hydrobiology, University of Lodz, for their help in maintaining the laboratory cultures and processing photographs for the manuscript. We are most grateful to the anonymous reviewers for their valuable suggestions which helped to improve the manuscript. We are much obliged to Dr Piotr Duda, University of Silesia in Katowice, for conducting X-ray photography.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Narodowe Centrum Nauki (2016/21/B/NZ8/03086) for A.S.-D., and by the Bolyai Research Scholarship of the Hungarian Academy of Sciences and the Hungarian Research Fund (OTKA FK 135262) to B.P-G.