• 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: April 2021

Bornella anguilla Spotted in Gorontalo

Bornella anguilla is an unusual nudibranch that sports a mosaic pattern on it skin. Numerous branches grow from its body. Its colors include brown, orange, and tan.

A Rare Find

Bornella anguilla eating
Bornella anguilla ready to eat hydroids

At the end of a dive at Gorontalo’s Otje Garden dive site, a dive master showed guests a most unusual nudibranch. It was busy munching on hydroids, its mouth parts clearly open. Eager underwater photographers took their chance to take shots. Miguel’s Diving staff confess they see this nudibranch less than once a year.

Bornella anguilla, the Eel Bornella nudibranch  

In 1984, this unusual nudibranch received its official name when Johnson submitted his research. Its scientific name reflects its distinct ability to swim like an eel. Anguilla means eel in Latin. Other Bornella species of nudibranch can swim as well. However, they flex their bodies from side to side to generate motion. In this way, they swim sideways. Bornella anguilla creates a muscular wave that moves down its body. In this way, it swims head first in an eel-like manner. While swimming, its rhinophores and cerata lay down for better streamlining.

Bornella anguilla is found throughout the Indo-West Pacific region. However, divers have also seen it in the Indian Ocean. It can grow up to eight centimeters in length. That means it can be rather large for a nudibranch.

Unusual Body Structure

This species of nudibranch has an unusual body structure.

Below the twin rhinophores on its head are its eyes. Although the eyes of most nudibranchs are hard to see, those of this nudibranch are distinct. They look blue or black, depending on the angle. Can you spot the eye in the close-up photo? Rhinophores are sensory organs that detect chemical scents in the water. The eyes measure light and darkness.

Most remarkable are the numerous branches growing from the body. These are called cerata. A pair of them grow around the brown rhinophores. This helps protect the sense organs from predators that can nibble a replaceable cerata instead.

Bornella anguilla close up
Close-Up of Bornella anguilla

Another unusual feature of this nudibranch are its gills. Most nudibranchs sport a cluster of gills near its dorsal rear and look like a small tree. On this nudibranch, the gills are distributed along the dorsal side of the body and protrude from the various branches that grow there. They look like mostly transparent feathers that poke from a cerata. These are visible in the close-up photo.

To dive in Gorontalo with dive masters skilled at spotting unusual marine life, please make your dive reservations with Miguel’s Diving.

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