Dotted sea slug - Peltodoris atromaculata - Discodoris atromaculata
Peltodoris atromaculata, more commonly known as the dotted sea slug or sea cow, is a species of sea slug, a dorid nudibranch, a marine gastropod mollusk in the family Discodorididae. It dwells in salt water up to the depth of 40m. It is exclusively found in precorralligene and coralligene communities and is very common in such communities. In the wild, Peltodoris is most abundant between June and September. Adults individuals can be found throughout the year, and two separate generations can coexist at the same time.
Dotted sea slugs are found almost exclusively in the Mediterranean Sea from Bay of Biscay to the Azores. Peltodoris atromaculata, is characterized by brown spots distributed randomly on its white mantle, each spot has a border of a darker brown color. The spots are generally darkest around the center of the mantle. Different populations exhibit different amounts of brown spots, and there is a general pattern of increasing coverage from west to east.
Reproduction is restricted during the summer, during which the animal will spawn for 3-4 days, followed by 2-3 weeks without spawning, after which the cycle restarts. Adult individuals that are spawning experience a decrease in body size and weight which continues after oviposition. All individuals of the species are simultaneous hermaphrodites.
During mating, both animals engage each other with their penises, and the one that successfully penetrates the body wall of the other becomes the male. After the eggs hatch they develop into a planktonic larvae. The larvae are chemically attracted to fulvinol-like polyacetylenes produced exclusively by their food sponges Petrosia and Haliclona, which can trigger settlement.
Adults generally grow to an average length of 5 to 7cm, and are able to grow up to 12cm. The sizes of brown spots on the mantle increase proportionally with mantle area as the slug grows. However, coverage of the brown spots never exceeds 50% of the mantle area.
Each individual has a unique pattern of spots which may change with growth but remain distinct from one another. The animals grow fastest around the first 6-7 months of their lifespan, growth rate slows for the following 4-5 months and a final decrease in growth rate occurs 3-4 months before death. In the wild, Peltodoris exhibits an annual life-cycle, but have been observed to live up to 15 months in the laboratory. They generally die a few weeks after reproduction.
(tratto da Wikipedia)