During a visit to the KwaZulu Natal coast, I found some amazing creatures in the tidal pools. One of them was this sea slug which is about 10" (20cm) in body length. It was laying eggs at the time and they are marked in the last picture.
Dwarf Sea Hare (Aplysia parvula) family
Aplysiidae
Although called a Dwarf or pygmy, various
sites list it as growing to about 5cm which is incorrect. This specimen found in
a tidal pool on the beach in South Africa, is about 18cm (7” inches) in length.
This species is found in warm waters worldwide
and will sometimes wander out of the water to feed on plankton and algae.
It opens it wing-like flaps in order to
attract females.
The following info is from a website on sea hares in general:
They are impressive animals growing to 40 cm and
weighing up to 2 kg. Most found in Britain have been smaller, but the specimen
from Poole was a large one of 30 to 35 cm and 1.5 kg.
While called sea slugs they are very different from garden slugs, being some of
the most spectacular and beautiful of molluscs.
The sea hares have a small thin internal shell, largely
covered by the large wing-like body flaps which also protect their gills. These
give it a bat-like appearance when swimming. They vary from bright red to brown
in colour, have a clear head, tiny eyes and have two pairs of tentacles, the
larger of which look like rabbits ears. It is these tentacles along with its
large size and rounded body shape that give it a rabbit-like look and
consequently its common name. When stressed they release a purple ink into the
water which is contains the toxin opaline. The animals are said to be mildly
toxic but are eaten in some areas of the world.
Most sea slugs feed on other animals including
sea anemones, but the sea hares are vegetarians preferring seaweed.
Hermaphrodite
They come inshore to breed, usually in the Spring. Each sea hare is both male
and female being a simultaneous hermaphrodite. They are known to form long
mating chains, with each animal being a male to the one in front of it and
female to the one behind. The penis is on the side of the head just below the
right anterior tentacle. They then lay a pink to orange chain of eggs forming
large spaghetti-like masses at the bottom of the shore or in shallow water. The
young hatch from these, spend some time as a veliger larva in the plankton and
them settle on algae as a tiny 1-2 mm sea hare. They grow rapidly reaching full
size in a year, before breeding and dying.
They are a rare southern species but a
combination of climatic conditions appear to have brought quite a few to our
southern shores this year. This is probably a one-off occurrence, and there is
no reason at present to link it to climate change, though it could be related
to changes in oceanic currents.
