Eudrilus eugeniae
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| Kinberg , 1866 |
Eudrilus eugeniae is the name of a oligochaetes - kind from the family Eudrilidae in order Crassiclitellata (earthworms in the broader sense), in West Africa is indigenous, but now widespread in warm regions worldwide.
features
Eudrilus eugeniae has a cylindrical body without dorsal pores, which reaches a length of 9 to 13 cm and a diameter of 6 mm. The back is dark red in front, but becomes paler in the back half of the animal and has a pronounced bluish hue in front of the citellum. The basic color in connection with the layer of the circular muscles is red, the abdomen is unpigmented. The prostomium is epilobic, that is, separated by a groove and overlapped by a tongue-like extension with the subsequent peristomium. From the 2nd segment on there are 4 pairs of S-shaped bristles with short, transverse rows of serrations at the tips, but ventral bristles are missing on the 17th segment. From the 4th segment the exits of the large, well-developed nephridia are visible. The reddish, saddle-shaped clitellum extends from the 14th to the 18th segment. The copulation bags protrude into the coelom space and each contain an approximately 4 mm long penis ; their openings are transverse slits.
The esophagus forms a chewing stomach in the 5th segment , and the midgut has several midgut glands in the area from the 85th to the 130th segment. The closed blood vessel system has ring hearts from the 7th to the 11th segment, and from the 8th to the 11th segment latero-oesophageal hearts with branches to the intestinal canal. The simple back vessel ends at the front with the ring heart in the 7th segment.
Distribution, habitat and way of life
Eudrilus eugeniae is native to equatorial West Africa, but has been transported to other tropical regions by humans, where it is spreading as an invasive species . Like other crassiclitellates, it is a soil dweller and substrate eater , digesting the organic components of the ingested substrate.
Development cycle
Like all belt worms , Eudrilus eugeniae is a hermaphrodite , in which two individuals exchange their sperm to mate. The worms can be quickly grown in the laboratory with cow dung. Under laboratory conditions at 25 ° C, young worms begin to form a clitellum at an age of 25 to 30 days and reach sexual maturity at 25 days in a fully developed clitellum, so that the iridescent testicles become visible as a sign of completed copulation. This usually happens within half an hour if several worms are brought together. To do this, two individuals bring their abdominal sides close together, with the two clitella lying directly opposite each other and no band of mucus is formed. Young worms that weigh less than 2 g are also capable of this. Within 24 hours, the two mated sex partners begin to lay egg cocoons, which they do 300 days later. The laying rate fluctuates and can be less than one cocoon per day, but also over 2 cocoons per day. The cocoons about 6 mm long and 3 mm wide are irregularly oval with fibrous tips at both ends. The initially whitish mucus of the clitellum hardens quickly and takes on an orange-brown color, only to turn dark brown shortly before hatching after an average of 17 days from the oviposition. With a hatching rate of around 84%, an average of 2 to 3 young worms hatch per egg cocoon based on all cocoons, a maximum of 5 observed from one cocoon. The hatchlings are pink to yellow and do not yet have fully differentiated segments at the rear end. They weigh around 6 mg and gain an average of 34 mg per day for the first 50 days of life if they are fed copious amounts of cow dung. Unfertilized worms can form egg cocoons, but young worms hatching from these have not been observed. This speaks against the ability for self-fertilization or parthenogenesis.
literature
- Johan Gustaf Hjalmar Kinberg (1866): Annulata nova. Öfversigt af Kongliga Vetenskaps-Akademiens Förhandlingar 23 (4), pp. 97–103, here p. 98 ( Lumbricus Eugeniæ n.).
- Gordon Enoch Gates (1942): Notes on Various Peregrine Earthworms. Bulletin of the Museum of Comparative Zoology at Harvard College 89 (3), pp. 63-144, here Eudrilus eugeniae (Kinberg) , pp. 137-143.
- Carl Claus: Fundamentals of Zoology: For Scientific Use, Volume 1. NG Elwert, 1880. Eudrilidae, P. 479.
- Reginald William Sims: A classification and the distribution of earthworms, suborder Lumbricina (Haplotaxida: Oligochaeta). Bulletin of the British Museum (Natural History), Zoology Series 39 (2), pp. 103–124, here p. 111.
- Reginald William Sims, Brian M. Gerard: Earthworms: Keys and Notes for the Identification and Study of the Species. Doris M. Kermack, RSK Barnes (Ed.): Synopses of the British Fauna (New Series), No. 31. EJ Brill, London 1985. p. 123.
- Sophie A. Viljoen, AJ Reinecke: Life-cycle of the african nightcrawler, Eudrilus eugeniae (Oligochaeta). South African Journal of Zoology 24 (1), pp. 27-32, doi : 10.1080 / 02541858.1989.11448130