Carpet Flatworm – Thysanozoon brocchii
The Carpet Flatworm is a species from the phylum of Platyhelminthes. There are also four recognised subspecies and four recognised variations. Thysanozoon brocchii was first described by Risso in 1818.
Since the species has not yet been thoroughly researched, similar species are summarized as Thysanozoon cf. brocchii.
Description, Anatomy & Characteristics
Thysanozoon brocchii has a flat, elongated and oval body. Its back area is, apart from the edge area, completely equipped with small warts. Two fan-shaped sensors are located at the head end.
The colouring varies from individual to individual. Green, violet, brown, white, orange and other colours are used. The colouration is not uniform and usually there are small, coloured dots. Very striking is a single-coloured stripe, which runs longitudinally along the middle of the body. Sometimes it also has one or two cross stripes of the same colour of the longitudinal strip.
The maximum length of Thysanozoon brocchii is 8cm.
Habitat & Distribution
Thysanozoon brocchii lives on rocky ground in depths down to 80m. I found the flatworm at a depth of 5m in the harbour of La Restinga, El Hierro.
When scuba diving on the Canary Islands, the species can only be observed very rarely. Maybe it’s the size. Furthermore I only discovered Thysanozoon brocchii once during a night dive.
Its distribution range is wide. In Europe, it can be found in the Mediterranean Sea and the adjacent Atlantic areas. It is also represented in North and South America. It is also found on the coasts of Africa, in the Suez Canal, Hawaii and Japan.
Biology, Feeding & Reproduction
They are carnivorous and therefore predators. Their diet consists of sponges, moss animals, tunicates and small crustaceans. They usually recognise the food at a certain distance through their chemoreceptors. Thanks to its well branched digestive system, nutrients can reach all parts of the body. Anything that cannot be digested is excreted through the mouth due to the lack of anus.
Like many other flatworms, Thysanozoon brocchii is a hermaphrodite. That is, every animal has both sexes, the male and the female. With the reproduction, the animals fertilize themselves mutually. After mating, the egg or fertilised eggs form a small cocoon together with some nutrient cells. These are fixed under stones or plants. When the cocoons hatch, the embryos turn into a larva. It lives planktonic for a short time until it sinks to the seabed.