Ariolimax columbianus
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Ariolimax columbianus |
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| ( Gould , 1851) |
Ariolimax columbianus , also called banana snail a) because of its mostly bright yellow color, is a land-dwelling slug from the family of Ariolimacidae in the suborder of land snails (Stylommatophora). It occurs only on the Pacific coast of North America. In addition to the yellow-colored specimens from which they are named, there are regionally also brown or green varieties. Brown spotted animals are also common. With a length of up to 26 cm, it is the largest species of the genus Ariolimax .
features
Ariolimax columbianus reaches up to 26 cm in length ( Mead ) when stretched out . The basic color varies from olive green, dark yellow green, ocher colored, ocher yellow to gray green with all the shades in between. The animals can have dark brown to black spots, but the spots can also be completely absent. The density of spots ranges from a single central spot on the mantle to many small spots, irregularly shaped large spots that can combine with each other to almost completely black (darkened) animals.
In the hermaphroditic genitalia, the club-shaped, robust penis is permanently slightly everted. The penis sleeve is thin-walled and internally provided with longitudinal folds. The apex is flatly rounded, the diameter decreases to less than half towards the opening into the atrium (atrium of the genital opening). The spermatic duct is comparatively short, in the lower part the spermatic duct is very thin; the diameter increases in the upper part to about twice the thickness. The spermatic duct ends at the top of the apex. The rather band-shaped penis retractor muscle also attaches precisely and very broadly to the top of the apex. It surrounds the entry of the spermatic duct into the penis. The vagina is short and fairly straight. The lower part is thin-walled, the upper part thin-walled up to the confluence of the seminal vesicle conductor. The two parts of the vagina are separated from each other by a small, powerful sphincter muscle. A retractor muscle attaches to the upper part of the vagina and the lower part of the fallopian tube. The seminal vesicle ( spermathec ) is comparatively small with a very short stalk. The free fallopian tube is long and very wide and forms a number of loops. The atrium is very flat.
Similar species
The sexual apparatus of Ariolimax columbianus and Ariolimax stramineus show some similarities, but also some clear differences. The other kinds of the genus Ariolimax differ very clearly in the sexual apparatus. The types of banana snails are difficult to differentiate based on their external characteristics. With Ariolimax columbianus the penis is somewhat thicker, the penile retractor muscle is broadly attached to the top of the apex and encloses the entrance of the seminal duct into the penis. In Ariolimax stramineus , the spermatic duct enters the penis next to the retractor muscle. The vagina is a little wider in Ariolimax columbianus , especially the upper and lower parts are separated by a small, powerful sphincter muscle, which is missing in Ariolimax stramineus . The stem of the seminal vesicle is shorter in Ariolimax columbianus . With Ariolimax stramineus the free fallopian tube is much shorter and because of this shortness it cannot be put in loops.
Geographical distribution and habitat
The distribution area of Ariolimax columbianus extends on the North American west coast from the Salinas Valley in the south, Tuolumne County further inland on the Sierra Nevada to Sitka in Alaska . In the Sierra Nevada, they rise to over 1000 m above sea level.
They live primarily on the ground and up to about 20 m above the ground on trees in the moist sequoia forests that stretch along the coast of North America.
Way of life
The animals feed on fruits and mushrooms. Many seeds and spores can survive the digestive tract unscathed; the snails thus contribute to the spread of plants. Occasionally they also eat carrion and animal droppings. They are usually nocturnal. They can only be found during the day on rainy days in the cooler winter months.
Sexually mature animals leave behind messenger substances with the mucus track that signal potential sexual partners that they are sexually mature. The animals then only need to follow the slime trail and meet a sexual partner. Before the actual sexual act, the partners nibble on each other's mucus layer. Mating then usually takes place at night. On the coast, the animals mate all year round. The pairing can take over twelve hours. The penis is everted from both partners and inserted into the vagina of the other. The muscles of the vagina are usually very strong and can virtually hold the penis in the vagina. The sperm is transferred in the form of balls. At the end of the pairing, the penis is withdrawn and everted again. Strange behavior on the part of a sexual partner can be observed in around five percent of cases. With the help of the rasp tongue (radula), after the transfer of the semen packages, he nibbles off the other partner's penis, which is still in the vagina (also called apophallation) and eats it up. The penis cannot be regenerated.
The sperm can be stored in the seminal vesicle for a while, which means that the eggs that ripen later can still be fertilized with the sperm after weeks. Up to 30 eggs are laid in a clutch under dead wood, leaves, etc. The eggs are translucent with a thin chalky shell. They are approximately round and measure about 7 mm in diameter. The young hatch after about three to eight weeks. At the time of hatching, the young are colorless and already 15 to 20 mm long. They are sexually mature after about a year. They live to be one to seven years old.
In times of drought can Ariolimax columbianus a dry rest hold. The animals dig themselves deep into the leaf litter, but remove a thick, protective layer of mucus and become inactive. They also hibernate when temperatures are very low.
Taxonomy
The taxon was first described in 1851 by Augustus Addison Gould in 1851 as Limax Columbianus . The kind is the type of the genus Ariolimax Mörch, 1860 by monotype . Synonyms are:
- Ariolimax columbianus maculatus Binney, 1890
- Ariolimax Columbianus forma niger Cockerell, 1891
- Ariolimax Columbianus forma typicus Cockerell, 1891
- Ariolimax steindachneri Babor, 1900
The genus Ariolimax is divided by some authors into two sub-genera Ariolimax (Ariolimax) Mörch, 1860 and Ariolimax (Meadarion) Pilsbry, 1948. In this structure, Ariolimax columbianus is placed in the subgenus Ariolimax .
supporting documents
literature
- Mead, Albert R. 1943: Revision of the Giant West Coast Land Slugs of the Genus Ariolimax Moerch (Pulmonata: Arionidae) . American Midland Naturalist, 30 (3): 675-717, Notre Dame, Indiana, JSTOR 2421208 .
- Pilsbry, Henry Augustus 1948: Land Mollusca of North America: (north of Mexico) . Vol. 2 Part II. The Academie of Natural Sciences of Philadelphia, Monographs, 3: XLVII S., pp. 521–1113, online at Google Books (p. 710)
- Alice B. Harper: The Banana Slug: A Close Look at a Giant Forest Slug of Western North America. 32 pp., Bay Leaves Press, Aptos, CA 1988.
Individual evidence
- ↑ Jennifer A. Gervais, Anna Traveset, Mary F. Willson: The potential for seed dispersal by the banana slug (Ariolimax columbianus). American Midland Naturalist, 140: 103-110, 1998, JSTOR 2426993
- ↑ Amos Binney, (Ed. Augustus Addison Gould): The terrestrial air-breathing mollusks of the United States, and the adjacent territories of North America. Described and illustrated by Amos Binney. Edited by August A. Gould. Vol. 2, 362 S., Boston, Little and Brown, 1851 Online at www.biodiversitylibrary.org (p. 43, plate 66, fig. 1)
- ↑ John Pearse and Jane Leonard: All About Banana Slugs. University of California, Santa Cruz Banana Slug Genomics class, April 23, 2010 PDF (175 MB!)
