Black-faced blennies

July 23rd, 2008

Several Black-faced blennies have been found in Dorset and the Nudibranch, Favorinus blianus, was sighted during a dive on Scylla.

The Black-faced blenny, Tripterygion delaisi, is fairly uncommon having been recorded in only three locations on the south coast of Britain. It can reach 9 cm long. Its colouring varies. Both males and females are grey-brown in colour with vertical dark bars. However, in mating season, the males have bright yellow bodies with blue-edged fins and a black head. Males court the females by swimming in a figure of eight.

Photo: Steve Trewhella

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Favorinus blianus reaches 30mm long and has a very pale yellow body. It feeds on the hydroids, Tubularia, and on opisthobranch eggs.

Photo: Douglas Herdson

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The celtic sea slug

May 9th, 2008

The Celtic sea slug (Onchidella celtica) has been sighted on a rocky outcrop at St. Martins Point, Guernsey. Onchidella celtica is a small oval slug with a fleshy body or mantle that is dark green to black in colour and is covered in tubercles. It is about 12mm in length and 6mm in width. When motionless, the mantle covers the head and the foot. The head is only visible when the slug is mobile.

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Sightings of sea hares on Guernsey

April 10th, 2008

There have been a number of sightings of the sea hare Aplysia depilans on Belle Greve Bay, Guernsey from January-April. Aplysia depilans grows to about 30cm long and is brown to green in colour often with pale spots or speckles. As with all species of sea hare, Aplysia depilans has an internal shell and releases ink when disturbed. It is also a herbivore and feeds on seaweeds.

Photo of Aplysia depilans found here.

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Sea hares and thresher sharks

November 22nd, 2007

An uncommon Sea Hare, Aplysia fasciata, has been discovered in September, October and November in the UK. Another unusual and exciting find was a large common Thresher Shark, found in Cornwall.

Aplysia fasciata, rarely seen in the UK, is larger than the common species Aplysia punctata, reaching up to 40cm long (rugby ball sized!) and can weigh up to 2kg! It is usually found on the Atlantic coasts of France, Spain, Portugal and West Africa. Sea hares are large herbivorous sea slugs, feeding on a wide variety of seaweeds. They have a small internal shell and when disturbed, release a cloud of purplish ink. Aplysia fasciata is very dark brown to black in colour. As well as the sea hares themselves, large egg masses, up to 30cm have also been found on the Devon coast.

A skipper, while fishing in the English Channel, south of Land’s end, hauled up a large, female common thresher shark (Alopias vulpinus). It was found to weigh 510 kg (1122 lb) and was 475 cm (15’ 58”) long, although thresher sharks are known to grow to 573 cm (18’8”). Thresher sharks are one of the largest of the approximately 28 sharks found in British water. Thresher sharks have long tails, the same length as their bodies and use these tails to move the fish, usually pilchards, herring and mackerel into tight shoals before attacking. There have been other thresher shark findings recently in Cornwall such as the large shark found in Charlestown which was approximately 400kg (881lb) and 463 cm (15’ 20”) long.

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