Diurodrilus

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Diurodrilus
Drawing of Diurodrilus (just under 0.45mm long)

Drawing of Diurodrilus (just under 0.45mm long)

Systematics
Over trunk : Lophotrochozoa (Lophotrochozoa)
Trunk : Annelids (Annelida)
Class : Polychaete (Polychaeta)
Order : Orbiniida
Family : Diurodrilidae
Genre : Diurodrilus
Scientific name of the  family
Diurodrilidae
Kristensen & Niilonen , 1982
Scientific name of the  genus
Diurodrilus
Remane , 1925

In the genus Diurodrilus that simultaneously the mono generic family Diurodrilidae forms, is a group of tiny, in sand gap system of living and from bacteria nourishing annelids , which are found in oceans worldwide.

features

The Diurodrilidae are always less than 0.5 mm long. On their maggot-shaped body there are neither parapodies nor bristles, but on their pygidium at the end of the body they have a pair of short "anus toes" with adhesive glands and muscles as the only body appendages. The body of the Diurodrilidae is divided into a prostomium , which lacks any appendages, a peristomium , five indistinct trunk segments and a pygidium . Ventrally there is a muscular pharynx , in front of this a prepharyngeal gland and behind this two salivary glands (esophageal glands), while all jaws and teeth are absent. The body is covered with a cuticle , which in some species is thickened in places and thus forms plate patterns that enable species to be identified. There are cilia in the form of individual spots or transverse rows, as well as ciliophores, species-specific, specialized areas with eyelashes. A blood vessel system is missing, but protonephridia are present in segments .

The Diurodrilidae move quickly through the ciliophores on their trunk. Glue glands on the prostomium and on the "anus toes" produce both glue and granules that cancel the glue effect.

Development cycle

The Diurodrilidae are separate sexes, but little is known about their reproductive biology. There is obviously internal fertilization, as numerous sperm have been observed in the largest egg in egg-bearing females. The mating has not yet been observed, but the organs of attachment on the pygidium could also play a role in the sexual act. The sperm of the Diurodrilidae have a huge acrosome and a cell nucleus, which is located in the throat between the mitochondria.

Systematics

The type species Diurodrilus minimus was described by Adolf Remane in 1925 at the same time as the genus Diurodrilus , which was still monotypical at the time . Six species are now known from the Atlantic and Pacific Oceans , two from the coasts of New Zealand and one from the Australian coast of Queensland . The genus was initially placed in the family Dinophilidae by Remane . By Gregory Rouse and Fredrik Pleijel it was with these to the Dorvilleidae counted. Reinhardt Kristensen and Tonny Niilonen elevated the genus to the monogeneric family Diurodrilidae in 1982 without clarifying its phylogenetic status. On the basis of their micro-anatomical investigations, Kristensen and Eibye-Jacobsen in 1995 questioned whether the Diurodrilidae belong to the annelid worms. In their molecular genetic work, Anja Golombek, Sarah Tobergte and others in 2013 and Torsten Hugo Struck, Anja Golombek and others in 2015 came to the conclusion that the Diurodrilidae are very well annelids, and placed them in the Orbiniida clade , a common taxon with the Nerillidae , Dinophilidae , Orbiniidae and Parergodrilidae , which have developed into today's dwarf forms by adapting to the narrow sand gap systems through progenesis .

Genera

The genus Diurodrilus includes the following six species :

literature

Web links

Commons : Diurodrilus  - collection of images, videos and audio files

Individual evidence

  1. ↑ Diurodrilus Remane, 1925. WoRMS , 2018. Retrieved November 17, 2018.