Evolution of colour and vision in marine invertebrates

Four pink and red and white shells against a white background

King Scallop Pecten maximus. Painted thorny oyster, Spondylus pictorum. Green snail, Turbo marmoratus. Close up of spire of Strawberry Top Shell, Clanculus pharaonius. Shell pigments responsible for colour have been identified for Clanculus pharaonius (Williams et al. 2016) and Turbo marmoratus (Tixier, 1952) and to class for Spondylus pictorum (Wade et al. 2019) and Pecten maximus (Williams et al. in prep.). Pigments for Clanculus pharaonius and Pecten maximus have also been linked to a molecular pathway (Williams et al. 2017; Williams et al. in prep) images © Natural History Museum.

The evolutionary history of colour and vision has been closely intertwined over the last 500 million years, leading to a dazzling diversity of colours and visual systems in marine invertebrates. 

Colour and marine invertebrates

The fabulous and diverse colours and patterns of molluscan shells and brightly coloured echinoderms are widely recognised, however their function for the animal is sometimes less clear and has been the focus of many ecological and evolutionary studies. Despite these studies, almost nothing is known about the evolution of colour in these groups.

My lab is working with international collaborators to identify shell pigments in a range of molluscan species using methods such as high-performance liquid chromatography and resonance Raman spectroscopy.

We are building on that information to identify the molecular pathways responsible for the biosynthesis of pigments in molluscs and echinoderms using transcriptomics and differential gene expression.

Our ultimate aim is to determine the effect of colour on adaptation, ecology, geographical range and speciation.

Two rows of coloured shells on a black background

Raman studies have shown that partially methylated carotenoids are responsible for these shell colours in the scallop genus Mimachlamys (Wade et al. 2019) images © Natural History Museum

Publications – evolution of colour

Wade, J., Pugh, H., Nightingale, J., Kim, J. S. and S. T. Williams. (2019). Colour in bivalve shells: Using resonance Raman spectroscopy to compare pigments at different phylogenetic levels. Journal of Raman Spectroscopy 50: 1527–1536.

Grant, E. H. & S. T. Williams. (2018). Phylogenetic distribution of shell colour in Bivalvia (Mollusca). Biological Journal of the Linnean Society 125: 377–391. doi.org/10.1093/biolinnean/bly122

Williams, S. T., Lockyer, A. E., Dyal, P., Nakano, N., Churchill, C. K. C. and D. I. Speiser. (2017). Colourful seashells: Identification of haem pathway genes associated with the synthesis of porphyrin shell colour in marine snails. Ecology and Evolution 7: 10379-10397. 

Williams, S. T. (2017). Molluscan shell colour. Biological Reviews 92: 1039-1058. 

Williams, S. T., Ito, S., Wakamatsu, K., Goral, T., Edwards, N. P., Wogelius, R. A., Henkel, T., de Oliveira, L. F. C., Maia, L. F., Strekopytov, S., Jeffries, T., Speiser, D. I. and J. T. Marsden. (2016). Identification of shell colour pigments in marine snails Clanculus pharaonius and C. margaritarius (Trochoidea; Gastropoda). PLoS One 11(7): e0156664

Williams S.T., J.A.H. Benzie. (1998). Evidence of a biogeographic break between populations of a high dispersal starfish, congruent regions within the Indo-West Pacific defined by colour morphs, mtDNA and allozyme data. Evolution 52: 87-99

A green mussel against a black background

Green mussel, Perna viridis ©NHM 

Principal investigator

Dr Suzanne Williams

Project summary

Focus: Evolution of colour

Funding: National Geographic Society, NERC London DTP

Have you seen this starfish?

Calling all snorkellers and divers 

Image: Tropical starfish, Linckia laevigata (royal blue morph) © Suzanne Williams

Current students

Hugh Carter 

PhD student at the Natural History Museum and University College London

External collaborators

Dr Jessica Wade

Previous lab members

Emily Noone (NHM/IC MSc student)

Eleonora Rossi (Torno Subito Fellowship)

Sophie Sykes (NHM/UCL MRes student)

Hazel Pugh (NHM/IC MRes student)

Heather Grant (NHM/IC MRes student)

Molluscan vision


A land snail and a conch shell with eyes visible

Vision in shelled molluscs, like the landsnail on the left, is usually poor. However, our studies are showing that conch shells, like Lentigo lentiginosus, right, image ©David Massemin, have surprisingly good vision for marine snails and we are investigating using CT scanning to look at the eye in more detail.

Nearly all molluscs are thought to be colour blind and most have poor visual acuity, yet they showcase the greatest diversity of eye types in the animal kingdom. 

My lab is working to investigate the loss of eyes in dark environments, in particular the deep-sea family Solariellidae (with Dr Lauren Sumner-Rooney).

While it may come as no surprise to find that some solariellids living in the deep sea have lost their eyes, it is surprising that vision has been lost at least seven times in this family of detritovores.

Even more surprisingly, their pigment-cup eyes have degenerated via more than one evolutionary pathway (loss of pigment, degeneration of vitreous body obstruction of aperture), making solariellids an ideal system to look at repeated evolution of vision loss.

My lab has also started looking at the evolution and diversification of eyes in the iconic gastropod superfamily Stromboidea.

A CT scan on a mollusc eye

We are investigating using CT scanning to look at the eye in more detail (Sumner-Rooney et al. 2019; Irwin et al. in prep) image © Alison Irwin

Publications – molluscan vision

Sumner-Rooney, L., Kenny, N. J., Ahmed, F. and S. T. Williams. (2019). The utility of micro-computed tomography for the non-destructive study of eye microstructure in snails. Scientific Reports 9: 15411.

Sumner-Rooney, L. H., Sigwart, J. D., Smith, L. and S. T. Williams. (2016). Repeated eye reduction events reveal multiple pathways to degeneration in a family of marine snails. Evolution 70(10): 2268-2295. 

Principal investigator

Dr Suzanne Williams

Project summary

Focus: Molluscan vision

Funding: NERC Doctoral Training Partnership, NERC DTP GW4+

Current students

Alison Irwin

PhD student Natural History Museum/ University of Bristol

Invertebrates division

Invertebrates are extraordinarily diverse, accounting for 95% of animal species. They can be found almost everywhere, including some of the most extreme environments on Earth.