Hesionidae

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Hesionidae
Oxydromus pugettensis

Oxydromus pugettensis

Systematics
Empire : Animals (Animalia)
Trunk : Annelids (Annelida)
Class : Polychaete (Polychaeta)
Subclass : Aciculata
Order : Phyllodocida
Family : Hesionidae
Scientific name
Hesionidae
Pit , 1850
Hesiocaeca methanicola eating bacteria to methane life

Hesionidae is the name of a family that tends to be smaller, mostly predatory or as a scavenger , more rarely free-living polychaeta that feed on bacteria or detritus and can be found in seas around the world.

features

The poly-bristles of the Hesionidae family are up to 5.5 cm long and have up to 80 segments . As a characteristic autapomorphy, they have 2 to 4 fused segments with well developed, cup-shaped cirrophores in which the 4 to 8 pairs of tentacles - cirrus are often supported by aciculae , but otherwise a body that is not divided into sections with consistently similar segments whose parapodia attach the fragile dorsal cirrus directly or with a stunted cirrophore. The prostomium is clearly separated and usually has a pair of antennae , sometimes a single central antenna , rarely two pairs or none, and almost always a pair of articulated palps on the ventral side. The nuchal organs are located in the form of ciliate patches on the posterior processes of the prostomium. The peristomium is reduced to lips around the mouth.

The parapodia are two-branched, the notopodia being always smaller than the neuropodia. Both dorsal and ventral cirrus are always present, the latter often being very long and can also be curled. Aciculae are also always present. The bristles on the notopodia are simple, if present, the bristles on the neuropodia are composed and sickle-bearing. A pair of cirrus is sitting on the pygidium.

The pharynx consists of an anterior and posterior section and can contain jaws , teeth or soft papillae in an end ring. The nephridia are mostly designed as mixonephridia.

habitat

The Hesionidae are distributed in oceans worldwide mostly below the intertidal zone down to the deep sea, with a particularly large number of species and individuals being found on the continental shelves . They live both on hard, rocky ground and on soft sediment and rarely occur in large numbers. Types of the intertidal zone are largely restricted to the sand gap system .

Development cycle

The Hesionidae are generally segregated, but there is protandric hermaphroditism in Hesione pantherina . In the genera Hesionides and microphthalmus , inhabit the sand gap systems, there are simultaneous hermaphrodites. Some species of the Hesionidae actively swim. In larger species, sexual maturity occurs around 2 years of age. The animals can mate several times in their life.

In three species of the Hesionidae in the polluted Oslofjord ( Norway ), the yolkless eggs develop into free-swimming larvae that feed on plankton after they have been fertilized in the open sea . After 1 to 2 months, the larvae sink and metamorphose into crawling animals, whose gonads do not begin to develop until they are two years old.

Asexual reproduction in the Hesionidae is unknown.

nutrition

As far as is known, most of the Hesionidae are carnivores or scavengers . Species of the genus Podarke apparently prefer copepods of the order Harpacticoida as prey. Both predators and scavengers can be found in the genera Ophiodromus and Nereimyra . There are actively hunting as well as species that wait in their caves for prey to come by. This is perceived through chemical sensory cells or contact with the cirrus. Hesiocaeca methanicola , on the other hand, lives on methane ice , where it grazes bacteria from the substrate.

Genera

The approximately 150 species of the Hesionidae family belong to 3 subfamilies with 32 genera :

literature

  • Adolf Eduard Grube: The families of the Annelids. In: Archives for Natural History. Year 16, Volume 1, Verlag der Nicolai'schen Buchhandlung, Berlin 1850, pp. 249–364, here p. 306 ( biodiversitylibrary.org ).
  • Stanley J. Edmonds: Fauna of Australia, Volume 4A. Polychaetes & Allies. In: The Southern Synthesis. 4. Commonwealth of Australia, 2000. Class Polychaeta. Pp. 176-178, ( environment.gov.au PDF), Family Hesionidae.

Web links

Commons : Hesionidae  - Collection of images, videos and audio files

Individual evidence

  1. ↑ Hesionidae Grube, 1850 WoRMS , 2018. Accessed December 12, 2018th