As we know, Nudibranchs come in come in various shapes and sizes.
Today, let’s delve into the world of cerata, dorsal outgrowths that decorate select sea slugs. Within the vast realm of sea slugs, only two significant orders have cerata: Nudibranchia and some Sacoglossa.
Firstly:
Nudibranchs, commonly known as sea slugs, are classified into two significant clades: Doridoidea (the dorids) and Cladobranchia (the cladobranchs). Dorids do not have cerata. That is our first step in identification and clarification. There is a lot of information regarding nudibranchs and classifying them. I’m going to keep it as simple as possible. Are you ready to get into the science? Grab a cup of tea and get ready to channel your inner marine biologist.
Secondly:
Cerata are visible dorsal appendages that find their home in the cladobranchs, particularly within three major groups. Cerata are the flowy decorations that make nudibranchs so dynamic in the water.
Aeolidina – The Aeolids:
The commonly sighted members are Fionidae, Facelinidae, Flabellinidae, Samlidae, and Aeolidiidae families. The Aeolids showcase the beauty of cerata as they move around the reefs and tidal pools. They are the nudibranchs who wear cerata that look like flowing hair. Or Justin Timberlake in the 2000s; we all remember that hairstyle!
Aeolidina uses their cerata for defence, digestion, and even respiration. Their cerata replace the ‘gills’ we see on a dorid nudibranch.
Dendronotina – The Dendronotinids:
Dendronotina brings together species with lateral appendages, which we know as cerata. Members of Bornellidae, Dendronotidae, Hancockiidae, Lomanotidae, Tethydidae, Tritoniidae, and Dotidae families are among the commonly sighted dendronotinids, each displaying unique cerata variations. Usually, wearing padel-like cerata or cerata that are segmented and spaced out over the body.
The snakey Bornella (Bornella Anguilla) is one of the most well-known nudibranchs in this grouping. Have you ever seen one swim? If not, head to YouTube and search for it; you will be satisfied they are unique swimmers of the nudibranch world.
Arminina – The Arminids:
Another grouping within Cladobranchia, the arminids, includes species with cerata. Janolus, Caldukia, Madrella, and Dirona genera house most cerata-bearing species. Some arminids, like Armina and Dermatobranchus, adopt a dorso-ventrally flattened form with ridges or tubercles on the dorsum.
These cerata are seemingly sporadic and carry many shapes, sizes and configurations.
Sacoglossa – The Sap-Sucking Sea Slugs:
Diverging from the nudibranchs, sacoglossans represent the only non-nudibranch sea slugs with cerata. Three families within the Superfamily Limapontioidea showcase this intriguing feature.
1) Caliphyllidae:
Examples like Cyerce, Mourgona, Sohgenia, Caliphylla, and Polybranchia belong to this family, all adorned with cerata.
2) Limapontiidae:
Members such as Placida, Stiliger, Ercolania, and Costasiella are part of this family, exhibiting the beauty of cerata in diverse forms.
3) Hermaeidae – Hermaea:
The final family, Hermaeidae, hosts species like Hermaea, completing the trio of sacoglossan families with cerata.
In the world of sea slugs, the presence of cerata adds a touch of dynamic. From the cerata-rich aeolids and dendronotinids among the nudibranchs to the unique cerata-clad sacoglossans, these marine wonders showcase the diversity of life on our reefs.
References:
Nudibranch Expert. (2024, February 21). Cerata Part 2: The Multiple Functions. Nudibranch Domain. https://nudibranchdomain.org/cerata-part-2-the-multiple-functions/