Systematics, Reproductive Biology and Biogeography of an unusual marine invertebrate family (Mollusca, Gastropoda, Planaxidae)

Poecilogony in snails has often been discussed, though it could only rarely be confirmed. Poecilogony (that is the presence of two distinct reproductive modes within the same animal species) has mainly been found in “ophistobranch” gastropods and polychaets. We set out to evaluate the proposed poecilogony in Planaxis sulctatus anew. Former studies only presented two reproductive modes within this species – an ovoviviparous development and a direct development as floating veliger larvae. Exceeding these findings, we evaluate the reproductive modes in P. sulcatus alongside its entire distribution range. We found a discrete transition from one mode to another, contradicting the hypothesis of poecilogony. After reviewing several factors that might have led to the arising of these reproductive modes, we propose sea surface salinity as the major driving force of the phenomenon.

We enabled the study on the reproductive modes of P. sulctatus by conducting a study on the evolutionary systematics of the Planaxidae. Thereby, we revised the seven genera included in this family and its at least eleven species. Our revision is primarily founded on a study of geometric morphometrics of shell parameters and radula morphology. Furthermore, our revision enables a reconstruction of species distributions. This provided us with the data basis to conduct a study on their biogeography and biodiversity patterns. As result of this study, we found the planaxids to underline recent insights in these fields of study. Our results highlight contemporary distribution and biodiversity patterns of marine, costal exothermal organism groups.

Publications

• Talk: Wiggering, B. & Glaubrecht, M. 2016. Snails in Space: Diversity and distribution patterns underlined by an intertidal gastropod family (Planaxidae). – Zitteliana 88: 54.
• Talk: Wiggering, B. & Glaubrecht, M. 2015. Einblicke in die Evolutionssystematik der Planaxidae. in Rüetschi, J. Zusammenfassung der Tagungsbeiträge anlässlich der 54. Frühjahrstagung der DMG vom 22.-25. Mai 2015 in Beathenberg/Schweiz. – Mitteilungen der deutschen malakozoologischen Gesellschaft 94: 33-40.
• Poster: Wiggering, B.; Glaubrecht, M. 2015. Regions, Range and Redundancy — Correlating chorology and taxonomy in marine gastropods. – Frontiers of Biogeography vol. 6, suppl. 1: 132.

 

Research assistants involved in this project: Benedikt Wiggering (2015-2018)