Amynthas

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Amynthas
Amynthas aspergillum or Amynthas robustus, Sai Kung West Country Park, Hong Kong

Amynthas aspergillum or Amynthas robustus , Sai Kung West Country Park, Hong Kong

Systematics
Trunk : Annelids (Annelida)
Class : Belt worms (Clitellata)
Order : Little bristle (Oligochaeta)
Family : Megascolecidae
Genre : Amynthas
Scientific name
Amynthas
Kinberg , 1866

Amynthas is a genus of little bristles from the family of Megascolecidae (giantearthworms) in the order of Crassiclitellata (earthworms in the broader sense), the several hundred species of which are widespreadin East Asia , Southeast Asia and Oceania in particular.

features

The giant earthworms of the genus Amynthas have cylindrical bodies and, depending on the species, reach different lengths between a few centimeters and about three meters.

According to Johan GH Kinberg, characteristic features of the genus Amynthas are a head lobe that is seated on the upper side at the front end, not through the rear edge , but only through the side edges, which is formed by the upper, front part of the narrow and short mouth segment, compared to the rear segments front segments twice as long, plus numerous tiny bristles arranged regularly around each segment , the number of which on the rear segments is higher than the number in front.

A pair of blind sacks in the 27th segment and a chewing stomach in the 8th and 9th segment are characteristic of the genus. The giant earthworms of the genus Amynthas have a ring-shaped clitellum that extends from the 14th, rarely from the 13th to the 16th segment. Like all girdle worms , they are hermaphrodites , the unpaired female genitals of which are anteriorly on the 14th segment, the two male behind it on the 18th, rarely 19th segment. As with other earthworms, the one or two pairs of testes are in the 10th and 11th or only 11th segment, i.e. in front of the ovaries in the 13th segment. The prostates are grape-shaped. The receptacula seminis are usually paired, rarely numerous or unpaired and open into paired, rarely numerous or unpaired small or large openings - as in other Megascolecidae - at all or some furrows from the transition from the 4th to the 5th to the transition from the 9th to the 10th segment outwards, i.e. always in front of the testicle-bearing segments. There are no copulatory bags.

Development cycle

Like all girdle worms , the giant earthworms of the genus Amynthas are hermaphrodites and reproduce sexually through mutual mating, with the sperm of the respective sex partner being stored in the receptacula seminis . With the help of the short clitellum , cocoons are formed, in which both mothers lay their eggs and inseminate them with the sperm of their sex partner. The embryos develop into finished earthworms in the cocoon.

Habitat and way of life

The Amynthas earthworms, like other Crassiclitellates, are soil-dwellers and substrate- eaters , which digest the organic components of the ingested substrate and, through their burial activity, ensure that the forest soil is loosened and aerated.

Sample species and their distribution

In 1866, Johan Gustaf Hjalmar Kinberg described the type species Amynthas aeruginosus, native to the Pacific island of Guam, at the same time as the genus Amynthas (he also wrote Amyntas at one point ) . Since then, over 400 species of this genus have been described, although the status of most of them has not been clarified.

Perhaps the largest species of this genus, as well as of the giant earthworm family, is Amynthas mekongianus ( Synonym Megascolex mekongianus Cognetti, 1922 ), native to the Mekong Valley , which can reach lengths of almost 3 m.

species

The following species have been described in the genus Amynthas :

literature