Metaphire posthuma
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| ( Vaillant , 1868) |
Metaphire posthuma (original combination Perichaeta posthuma , common synonym Pheretima posthuma ) is a type of little bristle from the family Megascolecidae (giantearthworms) in the order of Crassiclitellata (earthworms in the broader sense), which iswidespreadin South Asia and reaches a length of 15 cm .
features
The cylindrical, elongated body Metaphire posthuma is usually up to 15 cm long and 3 mm to 5 mm wide, with adult animals having about 100 to 120 ring-shaped segments. The front end of the animal tapers while the rear end is more or less blunted. The skin of the earthworm is colored light brown to dark brown by porphyrin and is thus partially protected from solar radiation. It is darker at the top than at the bottom. The annular clitellum comprises three segments from the 14th to the 16th segment and is not marked by external furrows between the segments. From the furrow between the 12th and 13th segment, there is a dorsal pore at the rear edge of each furrow up to the penultimate one. The head is shaped like a tanylob, a dorsal head flap process runs over the entire peristomium up to the furrow to the following segment. In the middle of each segment, with the exception of the first and last and the clitellum, there are numerous rearward-facing, S-shaped, pale yellow bristles with a thickened section, the nodule , in a ring-shaped row.
A dark center line can be seen on the back of the body, which is the back vessel of the closed blood vessel system located just below it . The back vessel has a pair of flaps in each segment. It collects the blood from the lateral vessels in the segments behind the 14th segment and pushes it forward by contractions, where the blood is taken up by 4 pairs of neurogenic hearts : lateral hearts in the 7th and 9th segment, latero-esophageal heart in the 12th and 9th segments 13th segment, which drives the blood into the abdominal vessel, into the supraoesophageal vessel extending from the 8th to the 13th segment and then into the subneural vessel extending from the 14th to the last segment. From the abdominal vessel, in which the blood flows backwards, an intestinal plexus is also supplied, from which the blood returns to the back vessel.
The foregut has a chewing stomach that comprises up to 2 segments between the 8th and 9th segment. In the 26th segment there are two short, cone-shaped intestinal blind sacs. Between the 26th segment and the segment in front of the last 24 to 25 segments there is a typhlosolis in the intestine, a fold reaching into the intestinal lumen from above, which increases the surface area used for digestion.
In all segments with the exception of the first three there are numerous small nephridia (micronephridia or meronephridia).
The pair of upper pharyngeal ganglia is in the 3rd segment, the pair of lower pharyngeal ganglia in the 4th segment.
Sex organs and development cycle
On the ventral side of the hermaphrodite there is a single female genital opening on the 14th segment and a pair of crescent-shaped male genital openings on the 18th segment. The earthworm has two pairs of testicles , which are located in segments 10 and 11 on the respective front septum in the scrotum. The large prostates flow into the sperm conductors before the male exits. In line with the male genital orifices are paired, circular, raised copulation papillae (penises) on the 17th and 19th segments without an opening, but with a cup-shaped indentation at the tip that acts as a suction cup during copulation. The ovaries are tightly packed as a pair in the 13th segment with strands of ice, while ice sacs are missing. In the segments from the 6th to the 8th segment, there are three pairs of receptacula seminis , each with a large ampulla and a diverticulum, which open outward in paired openings at the rear edge of the respective segment. In contrast to most Crassiclitellates, the sperm taken in during mating are not stored in the ampoule, but in the diverticulum. When the eggs are laid, the sperm of the sex partner are released from the diverticula into the egg cocoon formed by the clitellum at the same time as the own eggs. As with all terrestrial annelids, the fertilized eggs in the cocoon develop directly into crawling worms.
Distribution, habitat and way of life
Metaphire posthuma is native to Southeast Asia and South Asia - including Pakistan , India , Bangladesh , Myanmar , Thailand and Indonesia - but its appearance as an invasive species has also been reported in France , Mexico and Argentina since the end of the 20th century .
The earthworm is common in humus-rich soils in gardens, meadows, pastures, irrigated farmland, next to ponds, lakes and rivers. Metaphire posthuma is most numerous in the uppermost layers of the earth down to depths of 30 to 45 cm, but can penetrate up to 3 m deep into the ground in dry periods in search of moisture. In the rainy season, however , the earthworm can often be found crawling on the surface. During this time the animals mate. The earthworm is nocturnal and, as a substrate eater, swallows both leaf litter and humus-rich soil, from which it digests the organic components - humus, microorganisms and small animals such as rotifers and nematodes - and excretes the mineral components unchanged.
literature
- Léon Vaillant (1868). Note sur l'anatomie de deux espèces du genre Perichaeta et essai de classification des Annélides lombricines. Annales des science naturelles: zoologie 10, pp. 225-256 (description as Perichaeta posthuma ).
- PS Verma, BP Pandey: ISC Biology Book I for Class XI. S. Chand Publishing, Ram Nagar (New Delhi) 1991. pp. 300-320. Pheretima posthuma - The Indian Earthworm.
- A. Ghafoor (2003): Biodiversity of earth worms in Gutwala and Thekriwala Forest at Faisalabad. Pakistan Journal of Zoology 35, pp. 171-173.
Individual evidence
- ↑ Metaphire posthuma (Vaillant, 1869). DriloBASE TAXO, accessed December 1, 2018.
- ↑ Metaphire posthuma (Vaillant, 1868) in the Integrated Taxonomic Information System (IT). Accessed December 1, 2018.