Pheretima (genus)

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Pheretima
Pheretima praepinguis, a species up to 50 cm long that is native to Mount Emei in Sichuan (China)

Pheretima praepinguis , a species up to 50 cm long that is native to Mount Emei in Sichuan (China)

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

Pheretima 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 found in the tropics worldwide, with a focus on New Guinea and Southeast Asia .

features

According to Johan GH Kinberg, characteristic features of the genus are a terminal, transverse head flap, which is attached to the upper, front edge of the mouth segment (segmentum buccale), as well as bristles arranged around its equator on each segment (except the first and last) , the number of which is higher on the posterior segments than the anterior, as well as two nodules (papillae) on each of the segments on the ventral side. The genus is also characterized by a pair of blind sacs in a single segment (in most species) and a gizzard in the 8th segment. The animals have 4 pairs of ring hearts from the 10th to the 13th segment, sometimes only 3 pairs from the 10th to the 12th segment.

The giant earthworms of the genus Pheretima have a short clitellum that only extends from the 14th to the 16th segment. Like all girdle worms , they are hermaphrodites , the two female genitals of which are anteriorly on the 14th segment, the two male behind on the 18th segment, whereby genital papillae can also be present. The two pairs of testicles - characteristic of the genus - lie in scrotums, as with other earthworms in the 10th and 11th segment, i.e. in front of the ovaries in the 13th segment. Common, combined paired tubes lead from the four testicles and the grape-shaped prostate to the two male openings and cross several segments, including the ovary-bearing one. The number of receptacula seminis varies. As with most of the Megascolecidae, the exits are located at all or some of the furrows from the transition from the 4th to the 5th to the transition from the 9th to the 10th segment, rarely within a segment, i.e. always in front of the testicle-bearing segments.

Development cycle

Like all girdle worms , the giant earthworms of the genus Pheretima are hermaphrodites and reproduce sexually through mutual copulation, 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. In the genus Pheretima , however, there are numerous pronounced r-strategists who also reproduce through parthenogenesis .

Habitat and way of life

The Pheretima -Regenwürmer as other Crassiclitellaten soil inhabitants and substrate eaters which digest the organic components of the ingested substrate and due to their activity grave for a loosening and ventilation of the forest soils.

Sample species and their distribution

In 1866, Johan Gustaf Hjalmar Kinberg described two species belonging to it at the same time as the genus Pheretima : Pheretima montana , which lives in the mountains of the Pacific island of Tahiti , and Pheretima californica , which is native to the forest floors of California . Since then, over 1000 sub-taxa species or subspecies of this genus have been described, although the status of most of them has not been clarified.

Pheretima darnleiensis (JJ Fletcher, 1886), which grows to considerable sizes and is widespread in Southeast Asia , has also attracted greater attention . Pheretima praepinguis Gates, 1935 , on the other hand, is a species that is native to the Sichuan Province in the People's Republic of China .

species

The following species have been described in the genus Pheretima :

literature