• Photo by Rantje Allen

  • Photo by William Tan

  • Photo by Rantje Allen

  • Photo by William Tan

  • Photo by Rantje Allen

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Monthly Archives: January 2016

Sacoglossans of Gorontalo

Sacoglossans are vegetarian sea slugs or snails. They bite into algae. Then they suck out the contents. Sometimes they are called sap-sucking sea slugs. Several species are found in Gorontalo’s diverse marine environment.

Blue-spotted bubble snail

Blue-spotted sacoglossans crawling
Blue-spotted sacoglossan

One of the sacoglossans found in Gorontalo is Oxynoe viridis. Although it looks like a simple slug, it is not. It carries a small, white shell on its back. However, the shell is rarely seen. This sea slug has twin side flaps that usually cover the shell.
Sacoglossans like this Blue-spotted bubble snail only eat algae. Typically, they feed on palm-like Caulerpa algae. This bubble snail’s green color helps camouflage it. That makes it hard for predators and divers to spot. For additional protection, this bubble snail produces a sticky, white secretion when disturbed.

If further threatened, it can break off its long tail. The tail wiggles vigorous, giving the snail time to hide. A new tail will grow in time. This bubble snail uses its long tail to hang onto algae. The one in this photo has fallen. It will climb back onto the nearest Caulerpa algae. Watch it feed in the video. Notice the algae to the left has already been munched!

Expansa sap-sucking sea slug

Another sacoglossan found in Gorontalo is Elysia expansa. Its name comes from its expanded twin side flaps. It does not have a shell. Like other sacoglossans, it is strictly vegetarian.

Expansa sacoglossans crawling
Expansa sacoglossan

It seems to prefer eating Caulerpa taxifolia. Ironically, it looks like a discarded piece of vegetation, a great disguise! Watch it rock like a leaf in the video.

Similar Sacoglossans

In Indo-Pacific waters, there are several similar looking sacoglossans. The white-spotted Elysia tormentosa was described by Kathe Rose Jensen in 1997. The Expansa sea slug has noticeably fewer hairs. The thin line that outlines the pinkish edges of the side flaps is black.

Divers never know what unusual marine life will appear. The marine diversity here is incredible. For your chance to watch Gorontalo marine life in action, please book your dive trip with us.

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