Title photo sp. 7 by Ludovic

Costasiella is a genus of sacoglossan sea slugs

Sacoglossons are ‘solar powered sea slugs’ aka ‘sap sucking sea slugs’ which live by ingesting the cellular content of algae. Some will just digest this fluid, others will store the living chloroplasts in their own tissues, which continue to photosynthesize benefiting the sea slug!

Above photo C. kuroshimae by Michaels Bubbles

There are currently 17 different species in the genus, and they are tiny some are only 2mm! The largest can be up to 13mm!

Above photo sp. 2 by Jean-Marie GRADOT

Costasiella kuroshimae was discovered off the coast of the Japanese Island of Kuroshima, and later also found in the sea off Japan, The Philippines and Indonesia. They have 2 dark coloured eyes, and 2 rhinophores (club shaped structures) that look like sheep ears, these have given them the name of ‘leaf sheep’

Above, C. kuroshimae by Anilao~Critters

From the limited information that I could find, C. kuroshimae itself has 7 different types (numbered as sp 1-7) and within each sp there are subtle variations

Above, C. kuroshimae by Todd Aki

Above photo sp. 5 by Anilao~Critters

Above, C. kuroshimae by Vania Kam

Above photo of C. kuroshimae with spiral shaped egg mass, by Kelly McCaffrey

Above ‘family tree’ of Costasiella, with the different types of C. kuroshimae sp 1-7 source

Other species of Costasiella include C. Usagi…

Above, photo by Allen Lee

Above, photo by Allen Lee

Others within the genus…

Above, photo by Ludovic

Above, photo by Patrick Ess

And finally, some more photos of the Leaf Sheep (C. kuroshimae)…

Above, Costasiella sp. #1 photo by Jenna Szerlag

…weeeeeeeeeeeeeee!!

Above, Costasiella sp. #1 photo by unknown

Information via wikipedia- Costasiella and C. kuroshimae, also from here and here

Apologies folks, if this post is a bit patchy and garbled, there really isn’t a lot of information about these nudibranchs…but I thought the photos were really nice!

    • quinacridoneOP
      5·
      7 months ago

      Yep, it’s probably why they were only discovered (relatively) recently and good photos are hard to find, unlike their bigger relations…Having said that I didn’t realise they’d be that tiny!

    • quinacridoneOP
      2·
      7 months ago

      [they] use the chloroplasts of the algae on which they feed, which they keep alive for hours to months after their ingestion…

      Sacoglossans have been known to survive for months living solely on the photosynthetic products of their acquired plastids

      Sacoglossans are able to choose which method of feeding they use. The switch from active feeding to photosynthesis in sacoglossans is triggered by the shortage of food resources, and typically not preferred

      starvation periods (with photosynthesis and no active feeding) vary between species of sacoglossans from less than a week to over four months, and photosynthesis is used as a last-resort mechanism to avoid mortality

      All from wikipedias page on sacoglassa…the whole process is fascinating and worthy of a post in itself, probably one for next week 👍