Category: Neomphalina

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.

Strange ‘stacking’ behaviour seen in vent snails

A short paper describing the strange behaviour of forming hanging ‘stacks’ exhibited by the vent snail genus Gigantopelta has been published in the journal Plankton and Benthos Research! This behaviour is probably related to reproduction. The paper is open access and available for view here: https://doi.org/10.3800/pbr.13.25“Mating stacks” have been widely documented in calyptraeid slipper limpets, which are protandric and exhibit sequential hermaphroditism. Gigantopelta is a genus of peltospirid snails endemic to deep-sea hydrothermal vents containing two species, one distributed on the East Scotia Ridge in the Southern Ocean and another on the Southwest Indian Ridge in the Indian Ocean. Here, we report the observation that both species form extensive (often >15 individuals) “snail chains”. These chains are potentially analogous to ‘mating stacks’ of calyptraeids, or alternatively, maybe a behaviour to facilitate spermatophore transfer. Both Gigantopelta species apparently have separate sexes and are sexually mature at a small size. However, it remains unclear whether they undergo sex change during their life.

Snail chains formed by Gigantopelta chessoia (left) and G. aegis (right)

  • Chen C*, Marsh L, Copley JT (2018). Is it sex in chains? Potential mating stacks in deep-sea hydrothermal vent snails. Plankton and Benthos Research, 13(1): 25-27.

Two new vent snails from 2.8km deep in the Indian Ocean!

New lead-authored paper, announcing the discovery of two new peltospirid vent snails, has been published in the peer-reviewed Open Access journal Frontiers in Marine Science! Read for free here: https://doi.org/10.3389/fmars.2017.00392

This paper describes two new species of small gastropods, belonging to the hydrothermal vent endemic family Peltospiridae, from the Longqi hydrothermal vent field (~2785 m deep) on the Southwestern Indian Ridge, Indian Ocean; a new genus was erected to house one of them. The descriptions are based on shell (protoconch, teleoconch, periostracum, shell microstructure), radula, as well as anatomical characters.

Lirapex politus Chen et al., 2017 (~4.5 mm shell height) is the first Indian Ocean representative of genus Lirapex which is also known from eastern Pacific and mid-Atalantic vents, and differs from the other known congeners by its lack of obvious axial sculpture (hence ‘politus’, smooth), as well as a narrower umbilicus and the final 0.5 whorl of the teleoconch being less detached.

Lirapex politus n. sp., scale bars = 1 mm.

Dracogyra subfuscus Chen et al., 2017 (~7 mm shell diameter) is a depressed, globular, coiled peltospirid with a dark periostracum; the genus Dracogyra Chen et al., 2017 was established for this species. It is most similar to Depressigyra globulus Warén & Bouchet, 1989 known from the eastern Pacific, but easily separated from it by a lack of basal notch in the aperture and a more depressed shell with narrower umbilicus. Furthermore, the radula of D. subfuscus is highly characteristic with the central tooth being very wide and compressed.

Dracogyra subfuscus n. gen., n. sp., scale bars = 1 mm.

A Bayesian phylogeny using the mitochondrial COI barcoding gene confirmed the placement of the two new species in clade Neomphalina and family Peltospiridae. The two new species co-occur with two giant holobiont peltospirids including the scaly-foot Chrysomallon squamiferum Chen et al., 2015 and Gigantopelta aegis Chen et al., 2015, and are sometimes found on their body surface. The two new species do not host endosymbiotic bacteria and gut contents suggest that they probably feed on microbial film on chimney surfaces, as well as epibionts of the two larger peltospirids.

  • Chen C*, Zhou Y, Wang C, Copley JT (2017). Two new hot-vent peltospirid snails (Gastropoda: Neomphalina) from Longqi hydrothermal field, Southwest Indian Ridge. Frontiers in Marine Science, 4: 392. DOI: 10.3389/fmars.2017.00392

New paper characterises microbes associated with Antarctic vent snail

New co-authored paper published in the peer-reviewed journal “Polar Biology“! The article can be read for free via the following link: http://rdcu.be/tWBe .

In this paper, we characterised microbes associated with the recently discovered Antarctic vent snail Gigantopelta chessoia Chen et al., 2015. It has been known that this snail hosts endosymbionts in an much enlarged oesophageal gland, but the details about the symbiont’s phylogenetic position has not been published. We show that the endosymbiont is a Gammaproteobacteria related to sulfur-oxidising bacteria from cold seeps and other animals living in chemosynthetic ecosystems. Also revealed is a more diverse epibiont community on the gill surface, including members belonging to Gamma, Epsilon and Deltaproteobacteria. Interestingly, the endosymbiont Gammaproteobacteria strain was also found on the gill surface but not in the surrounding water column. Given that juveniles of this species is regularly recovered from within the adults’ mantle cavity, this suggests they may acquire the symbionts directly from the gills of adult snails.

Gigantopelta chessoia and its associated microbial community

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