Category: 3D Anatomy

A new metamorphosis revealed using synchrotron CT

A new lead-authored paper published in Proceedings of the Royal Society B: Biological Sciences reveals a previously undocumented type of metamorphosis exhibited by the deep-sea vent snail Gigantopelta using synchrotron micro-CT.

Press coverage by the New York Times: This Snail Goes Through Metamorphosis. Then It Never Has to Eat Again. by JoAnna Klein.

Metamorphosis, such as the transformation from caterpillar to butterfly or tadpole to frog, is one of the most exquisite phenomena in animal life history, and has been thought to always involve a clearly correlated transformation in both external and internal morphology. We used state-of-the-art 3D reconstruction with synchrotron CT data to reveal that the snail Gigantopelta chessoia from deep-sea hydrothermal vents goes through a further internal transformation in anatomy after settlement, which is not apparent from external morphology. Termed ‘cryptometamorphosis’, this newly discovered phenomenon allows Gigantopelta to switch from ingesting food to relying entirely on symbionts. The possibility of an additional, ‘hidden’, metamorphosis as adults also have a profound impact on understanding the energy flow in ecosystems, as it means we may not be able to tell the trophic role of an animal without detailed anatomical observations. Modelling food webs and the energetic flow in ecosystems is crucial in their conservation, especially in a time of rapid environmental changes, and our results highlight the importance of in-depth knowledge on the life history of animal species in order to model ecosystems accurately.

3D reconstructions of the digestive system in Gigantopelta chessoia, at body lengths (a) 2.2 mm, (b) 3.5 mm, (c)5.1 mm, (d) 7.8 mm, (e) 12.2 mm, and (f ) 23.0 mm. The ‘trophosome’ is indicated by yellow, shades of blue indicate other parts of the digestive system, including buccalmass, oesophagus, stomach, digestive gland, and intestine. Scale bars = 1 mm for all parts.

New paper demonstrates convergent adaptation in vent snails!

New first-authored paper published in BMC Evolutionary Biology! [Link]

In the new paper, we reveal that two neomphaline hydrothermal vent gastropods, Gigantopelta and the ‘scaly-foot’ Chrysomallon, convergently evolved the peculiar adaptation of housing endosymbiotic bacteria in their much enlarged oesophageal gland. We first confirmed the existence of endosymbionts in Gigantopelta using Transmision Electron Microscopy (TEM), and then carried out serial sectioning and 3D reconstruction for a juvenile specimen of Gigantopelta chessoia along with dissections of the adult. These revealed many key anatomical differences with the ‘scaly-foot gastropod’ pointing towards two independent origins of a similar way of life, confirmed by a 5-gene phylogenetic reconstruction clearly showing that the two are not sister within the known members of Peltospiridae. By comparing Gigantopelta and Chrysomallon, we show that metazoans are capable of rapidly and repeatedly evolving equivalent anatomical adaptations and close-knit relationships with chemoautotrophic bacteria, achieving the same end-product through parallel evolutionary trajectories.


The paper is open access and available freely: http://bmcevolbiol.biomedcentral.com/articles/10.1186/s12862-017-0917-z

We also included an interactive 3D anatomical model of Gigantopelta, you only need a PDF reader to play around with it! Have fun! It is available here: https://static-content.springer.com/esm/art%3A10.1186%2Fs12862-017-0917-z/MediaObjects/12862_2017_917_MOESM1_ESM.pdf

 

Chen C*, Uematsu K, Linse K, Sigwart JS (2017). By more ways than one: Rapid convergence in adaptations to hydrothermal vents shown by 3D anatomical reconstruction of Gigantopelta (Mollusca: Neomphalina). BMC Evolutionary Biology, 17:62. DOI: 10.1186/s12862-017-0917-z