HOME | DD

Description
A group of small primitive invertebrates.

Chemosynthesizing organs are marked in red.

The digestive system is marked in dark green.

Photosynthetic organs are marked in bright green.

Violet marked reproductive organs.

The peculiarity of many species is that they do not have a circulatory system. Instead, they have only a small cavity (hemolymph), which performs the function of blood. Breathing takes place over the entire surface of the skin. (for larger representatives, breathing is carried out through the tentacles)

Some individuals do not have gonads, and therefore, like many polychaetes, they spawn eggs and sperm through excretory holes.

Fertilization is external. However, in digging and parasitic forms it has internal fertilization. And some even ovoviviparity observed.

All free-living forms live in the seas. A small number of them are in fresh water. Parasites, depending on the species, either live inside their hosts, or in the adult state live in the soil (but in some groups, on the contrary, the larvae live in the soil, and as adults they begin to lead a parasitic lifestyle).

Description
A group of small primitive invertebrates.

Chemosynthesizing organs are marked in red.

The digestive system is marked in dark green.

Photosynthetic organs are marked in bright green.

Violet marked reproductive organs.

The peculiarity of many species is that they do not have a circulatory system. Instead, they have only a small cavity (hemolymph), which performs the function of blood. Breathing takes place over the entire surface of the skin. (for larger representatives, breathing is carried out through the tentacles)

Some individuals do not have gonads, and therefore, like many polychaetes, they spawn eggs and sperm through excretory holes.

Fertilization is external. However, in digging and parasitic forms it has internal fertilization. And some even ovoviviparity observed.

All free-living forms live in the seas. A small number of them are in fresh water. Parasites, depending on the species, either live inside their hosts, or in the adult state live in the soil (but in some groups, on the contrary, the larvae live in the soil, and as adults they begin to lead a parasitic lifestyle).