Saccocirrus

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Saccocirrus
Systematics
Over trunk : Lophotrochozoa (Lophotrochozoa)
Trunk : Annelids (Annelida)
Class : Polychaete (Polychaeta)
Order : Protodrilida
Family : Saccocirridae
Genre : Saccocirrus
Scientific name of the  family
Saccocirridae
Czerniavsky , 1881
Scientific name of the  genus
Saccocirrus
Bobretzky , 1872

In the genus Sacco Cirrus , at the same time the mono generic family Saccocirridae forms, is a group of minute to less than, in the sand gap system of living polychaete (Polychaeta), which are found in seas worldwide. While most species feed on the algae that live on the substrate , there are some predators that prey on small crustaceans.

features

The Saccocirridae have a slender, clearly segmented body and have up to 200 segments with a maximum body length of 2 cm .

At the front of the prostomium there is a pair of palps (" tentacles ") with inner canals that unite behind the brain and are connected by two ampoules, as well as a pair of nuchal organs and usually a pair of pigmented eyes . Some species have an anterior pharynx with a muscular tongue and cilia on the abdomen . The retractable parapodia are single-branched and have various types of simple bristles . The pygidium is bilobed and has adhesive glands. Gonads are located on one side or both sides of the body.

distribution and habitat

The Saccocirridae are found in seas around the world. They live in the intertidal zone and a little below in the sand gap system in coarse sand. They move actively similar to leeches and attach themselves to the grains of sand with the help of their sticky pygidium, the body wall and the palps. Most species feed on microscopic algae , which they bring to their mouths through the cilia of their eyelashes. However, there are saccocirrus species without an eyelash groove that prey on copepods .

Development cycle

The Saccocirridae are separate sexes. There are up to 100 segments with gonads located in the center of the body. Each gonad-bearing segment has a complete genital system with paired gonads and unpaired gonoducts, which include penis-like structures in males and receptacula seminis in females . Because of this, copulation with transfer of the sperm into the female must be assumed, although the sexual act has not yet been observed. The fertilized eggs, as described in the Japanese Saccocirrus uchidai and the Australian Saccocirrus krusadensis , are smaller than 100 μm and develop into free-swimming trochophora larvae within 18 to 36 hours , which start phytoplankton at the age of 2 to 3 days to eat. At 7 to 11 days, the larvae of Saccocirrus krusadensis have three bristle-bearing segments, while the larvae of Saccocirrus uchidae only begin to develop bristles after they sink and metamorphose into a creeping worm with 12 to 14 segments .

species

The following species belong to the Saccocirridae family and its only genus, Saccocirrus :

literature

  • Stanley J. Edmonds: Fauna of Australia, Volume 4A. Polychaetes & Allies. The Southern Synthesis 4. Commonwealth of Australia, 2000. Class Polychaeta. Pp. 319f., Family Saccocirridae.

Web links

Individual evidence

  1. ↑ Saccocirridae Bobretzky, 1872. WoRMS , 2018. Accessed December 5, 2018.