Natalina
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Housing by Natalina cafra , Amsterdam Zoological Museum |
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| Pilsbry , 1893 |
Natalina is the name of a genus predatory living snails from the family Rhytididae in the subordination of terrestrial snails (gastropod) that in southern Africa are widespread. The South African species Natalina cafra is particularly known as the herbivorous snail that is undesirable to humans.
features
The clearly open bifurcated, conical-hemispherical, mostly rib-striped shell of the snails in the genus Natalina has a strong greenish to greenish-brown periostracum that protrudes over the edge of the shell mouth. However, the lime layer is very thin and therefore the shell is fragile. The snail shell is moderately large to very large and can reach up to 75.5 mm in diameter. The protoconch, which is over 4 mm in size , typically consists of 1.25 whorls and is often separated from the subsequent teleoconch by an irregularity .
The tooth formula of the radula in the genus Natalina is 1+ (5–9) + (10–30), with adult snails having fewer than 3.5 rows of teeth per millimeter. For example, Natalina cafra has 80 transverse rows of teeth on an approximately 58 mm long radula. The outermost lateral teeth are very large, but all marginal teeth are stunted, while there are no medium-sized teeth between the lateral and marginal teeth.
The labial palps are well developed. The long and cylindrical penis is to the right of the retractor muscle of the right eye feeler. The epiphallos is well developed and makes up a quarter to half the length of the penis. The epiphallos and lower vas deferens are connected to the penis by connective tissue. The vagina is long, the caecum of the fallopian tube well developed. The long suprapedal gland is tangled distally with an end vesicle.
Distribution and occurrence
The snails of the genus Natalina are common in southern Africa . All species are ground dwellers and do not climb trees. They live in humid forests of southeast Africa under leaf litter and dead wood, while in fynbos they hide under shrubs, perennials and rocks. In the mountain grassland ( Tussock ) they live under tufts of grass and fern plants, in Karoo and similar habitats, however, under fallen aloe plants, under Euphorbia bushes and other undergrowth. In non-forested areas, the snails prefer crevices with vegetation. In dry seasons, the snails seek out even better protected areas and, if possible, dig themselves underground. However, these snails do not form an epiphragm . They are almost exclusively nocturnal in humid, warm weather. Different species of the genus Natalina do not appear sympatric .
Life cycle
Like other snails are the Natalina snails hermaphrodite who exchange their sperm during mating. In Natalina cafra , the only species that has so far been studied with regard to mating behavior, sexual intercourse, including foreplay, lasts less than an hour. One sexual partner crawls onto the other's house and strokes the other's neck with his mouth, who is holding his head towards him. The roles can be swapped after a short sexual act of barely 10 minutes. However, since these predatory snails do not mate from sole to sole of foot, unlike Roman snails and most other lung snails, only one-sided mating and fertilization with male and female roles is assumed as a rule, but mutual penetration of the shell is also fundamentally in the sex position on the shell Penises in the partner's vagina possible.
Soon after mating, both partners ideally lay their eggs, which have a thin shell with tightly packed lime crystals and, depending on the species, 10 to 16 mm long and 8 to 12 mm wide ( Natalina cafra ) or about 7.2 mm long and 5 , 5 mm wide ( Natalina quekettiana ). The firmness of the eggshell also seems to vary. When the young snails hatch, in addition to the protoconch of the snail shell, a quarter of the teleoconch has already been formed.
nutrition
The snails of the genus Natalina prefer as carnivorous snails in particular other housing-bearing worm as prey, but also eat slugs and earthworms . The victim is grasped with the radula extended out of the mouth and held and crushed with the help of the radula teeth. Smaller shell snails such as from the genus Sheldonia Ancey, 1888 (family Urocyclidae ) are pulled out of the shell and pulled as a whole into the mouth of the predatory snail. Nudibranchs and earthworms are also swallowed whole very quickly, only to be grated in the foregut with the radula. Larger snails, on the other hand, are eaten more slowly, with the predatory snail tearing off pieces of meat from the victim with its radula and penetrating further and further into its shell. The prey's lime shell is used by the predatory snail inserting its tail tip into the eaten shell or wrapping it around the entire house. So the snail drags the prey house to a safe place to consume. The calcium carbonate is dissolved and absorbed. In a similar way, however, other lung snails are also able to resorb limestone.
Due to their predilection for snails as prey, the Natalina predators in South Africa are colloquially referred to as cannibal snails (" cannibal snails "). Natalina cafra ( common cannibal snail ) and other representatives of the genus are popular as predators of introduced herbivorous snails .
Systematics
The genus Natalina was first described in 1893 by the American malacologist Henry Augustus Pilsbry , as was the family Rhytididae to which it belongs. The snail species previously included in this genus were classified in 2010 by DG Herbert and A. Moussalli in the now reduced genus Natalina and the new genera Afrorhytida and Capitina . Natalina is divided into the subgenus Natalina (Natalina) and Natalina (Tongalina) .
The genus Natalina , which is restricted to Herbert and Moussali, includes the following species:
Natalina (Natalina)
Natalina (Tongalina)
Individual evidence
- ^ O. von Möllendorff: Agnatha Moerch. Predator snails. 4. Genus Natalina Pilsbry , pp. 19f. In: O. von Moellendorff and Wilhelm Kobelt: Die Raublungenschnecken (Agnatha). Systematic Conchylia Cabinet by Martini and Chemnitz. Verlag von Bauer and Raspe (Emil Küster), Nuremberg 1905.
- ^ A b D. G. Herbert, A. Moussalli (2010), p. 22.
- ↑ DG Herbert, A. Moussalli (2010), pp 15f.
- ↑ DG Herbert, A. Moussalli (2010), p. 6
- ↑ DG Herbert, A. Moussalli (2010), p. 10
- ↑ DG Herbert, A. Moussalli (2010), p. 11
- ↑ DG Herbert, A. Moussalli (2010), p 7f.
- ^ David Herbert, Dick Kilburn: Field Guide to the Land Snails and Slugs of Eastern South Africa. Natal Museum, Pietermaritzburg 2004. p. 217.
literature
- DG Herbert, A. Moussalli: Revision of the Larger Cannibal Snails (Natalina sl) of Southern Africa - Natalina ss, Afrorhytida and Capitina (Mollusca: Gastropoda: Rhytididae). African Invertebrates 51 (1), pp. 1-132. KwaZulu-Natal Museum, Pietermaritzburg 2010.
