Many sea slugs are brightly coloured, and members of the genus Chromodoris are among the most beautiful. They move slowly and make good photographic subjects.
Genus Chromodoris
The genus Chromodoris contains over 100 species, and they all eat sponges. They are often colourful and attract the attention of divers in the warm waters where they abound.
The bright colours of this genus probably serve to camouflage them against a background of warm-water sponges (which themselves are usually quite gaudy), but it would be a mistake to assume that marine predators see what humans do. To understand how camouflage works it is necessary to look with the eyes of the predator.
Mollusc Common Names and Classification Details
Chromodoris is often called a 'sea slug', but since this non-scientific term refers to many different mollusc groups it is best to stick to the stricter scientific terms:
- the genus Chromodoris is a member of the larger family Chromodoridae. They are Nudibranch molluscs in the class Gastropoda.
- the class Gastropoda (all the slugs and snails) contains a huge number of species – there are nearly as many gastropods as there are insects! In the past this class of mollusc (the Gastropoda) was divided into four smaller groups, and all sea slugs fall into one of these – the Opisthobranchia.
- 'Opisthobranch' is an out of date term, but it is still used by many to include; bubble shells, headshield slugs, saccoglossans, sea hares, sea angels, sea butterflies – as well as the 'nudibranchs' that concern us here.
Amateur Underwater Sea Slug Photographers and Scientific Research
There are not enough marine biologists in the world to begin to gather information about all the creatures that live in the sea.
When amateurs get interested (as many divers do when they see nudibranchs for the first time) they can become a source of valuable information, provided they take the trouble to identify the animal and record the location. Better still if they take a good photograph and make it available to others who share the interest.
All six images used at the end of this article have two things in common – they are well documented in terms of time and location, and they were all taken by the same photographer.
This underwater photographer (Steve Childs) is a good example of a hobbyist who provides useful research information. He started by taking up scuba diving, then progressed to mastering underwater photography. He is now one of many members of Medslugs, where enthusiasts upload their 'opisthobranch' photos. This photo-library is enormous and it helps enthusiasts identify their specimens – add the location to that and it becomes an invaluable research resource.
Such records of current species distribution form an essential 'base line' against which future information will be compared and changes monitored.
Sources:
- 'Opisthobranchs of the Mediterranean Sea and elsewhere', Medslugs.
- Sea Slug Forum, particularly 'a list of species linked to photos'.
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