Nerillidae

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Nerillidae
Nerilla antennata, prostomium

Nerilla antennata , prostomium

Systematics
without rank: Primordial mouths (protostomia)
Over trunk : Lophotrochozoa (Lophotrochozoa)
Trunk : Annelids (Annelida)
Class : Polychaete (Polychaeta)
Order : Orbiniida
Family : Nerillidae
Scientific name
Nerillidae
Levinsen , 1883
Nerilla antennata , Pygidium

Nerillidae is tiny, the name of a family in sand gap system of living and from bacteria and diatoms nourishing polychaete (Polychaeta), which are found in seas or fresh water worldwide.

features

The Nerillidae are about 0.3 to 2 mm long. Most species have nine segments , but some species only have seven segments. The prostomium is fused with the peristomium and has three slender, smooth or articulated antennae and laterally to ventrolaterally a pair of club-shaped palps , but antennae and palps can also be missing. As a rule, all segments have bristles , but these may be missing from the first segment. The bristles are either composed or simply and capillary-shaped. Mostly noticeable cirrus waves are present between the branches of the parapodia , but are sometimes absent on some or all of the segments. In some species, such as Nerilla australis , the cirrus is much longer on the first segment than on the following segments. The pygidium usually carries two anal cirrus. The pharynx lies ventrally and consists of a muscular bulb, a tongue-like, rod-shaped or bridge-shaped structure and a heavily ciliated lower lip. The cells of this tongue have striated intracellular skeletal elements connected with tonofilaments. The nephridia are formed as metanephridia, protonephridia and enteronephridia.

habitat

Most Nerillidae are marine life , where they live in the sand gap system of the beaches and feed on diatoms and bacteria on the grains of sand. Some species live in the intertidal zone or in estuaries , but there are also freshwater inhabitants such as Troglochaetus beranecki , which live in the sand gap system of the groundwater . The animals move forward with the help of the cilia in their eyelash grooves.

Development cycle

The Nerillidae are either separate sexes or protandric hermaphrodites . The eggs are laid in small numbers and fertilized on the outside, for which purpose spermatophores are attached to or next to the eggs in some species . The eggs are attached either individually or in groups in cocoons to a solid substrate or to the outside of the front or rear end of the mother animal. The embryos develop directly into crawling worms and, in the case of brood-care species, do not leave the mother until an advanced stage of youth.

Systematics

The Nerillidae were traditionally counted among the Archiannelida . Due to their molecular genetic work presented Torsten Hugo Struck, Anja Golombek and other 2015 Nerillidae in the clade Orbiniida , a common taxon with the Diurodrilidae , Dinophilidae , Orbiniidae and Parergodrilidae , which according to the authors, in adaptation to the narrow sandy gap systems through Progenese to developed into today's dwarf forms.

Genera

The following genera belong to the family Nerillidae :

literature

Web links

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

Individual evidence

  1. ↑ Nerillidae Levinsen, 1883. WoRMS , 2018. Retrieved November 17, 2018.