Title of the project
Functional morphology of the reproductive organs of viviparous freshwater snails
Management
Prof Dr Matthias Glaubrecht,
Project assistance: Lena SchwingerOrg. categorisation
Department of Animal Biodiversity
Description of the
Small crown snails are born
Most snails (gastropods) lay eggs, they are oviparous. However, some species groups have developed - several times independently of each other - the ability to give birth to small living snails (viviparity). These include the crown snails or Thiaridae, which are native to the world's tropics.
The special feature of this family is a chambered brood pouch in the neck area of the females. There, up to hundreds of embryos equipped with a shell grow into young snails, which in some species are even nourished there before they are released from the brood pouch into the environment.
We are investigating the anatomical characteristics of this brood pouch and the associated female genital tract in different species of thiarids. As an example, histological and 3D visualisation data are available for the crown snail Fijidoma maculata , which is endemic to rivers on the Fiji island of Viti Levu, although its occurrence is restricted to a few fast-flowing headwaters.
Our phylogenetic analyses show that F. maculata is most closely related to freshwater snails that colonise rivers in the neighbouring continent of Australia. Therefore, we are comparatively analysing Australian thiarids, such as currently Stenomelania aspirans and Melasma onca.
3D model helps to clarify the function of the brood pouch
For Fijidoma maculata and M. onca, comprehensive data on reproduction and brood care are available from the field. Thanks to viviparity, the number of young is limited compared to other gastropods, but they have a higher chance of survival at birth due to their advanced stage of development.
It is possible that this strategy is an adaptation to tropical waters, both on islands and on the continent: it could be related to the colonisation of new habitats (annidation), species diversity (speciation) and adaptive radiation.
In order to better understand the particular reproductive mechanism as well as the structure and function of the reproductive organs in viviparous gastropods, a 3D reconstruction of the brood pouch and the genital tract will be created using anatomical-histological examination methods and computer tomography.
How does shape influence the evolution of a species?
The aim of the project is to analyse the structural characteristics and functional morphology of the brood pouch and compare them with those of other limnic and viviparous thiarids. This will also be revised in connection with other species, including some viviparous marine Cerithioidea, such as the Planxidae.
The three snail species modelled so far in this project should help to better understand the role of anatomy in these evolutionary processes, especially in the colonisation of new adaptive zones.
CT scans: The computed tomography images were made possible and produced with the CT system FF20 CT in co-operation with the Hamburg-based company YXLON International GmbH.
