Acesta oophaga
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| Scientific name | ||||||||||||
| Acesta oophaga | ||||||||||||
| Järnegren , Schander & Young , 2007 |
Acesta Oophaga is a shell - type from the family of limidae (Limidae). It lives in fauna communities on so-called Cold Seeps in about 400 to 800 meters water depth on the Louisiana Slope in the northern Gulf of Mexico . The mussels filter the yolk-rich eggs of the beard worm Lamellibranchia luymesi from the water and feed on it, hence the species name oophaga = egg-eater.
features
The equally-folded, moderately inflated cases are up to 113 mm in size (high). They are rounded triangular in outline, adult housings have a deep indentation between the vertebra and the front end. The front ear is largely reduced, the rear ear is triangular.
The ornamentation consists of fine, slightly wavy radial ribs that intersect with fine concentric lines. The periostracum is thin and brown in color. The shell is thin and translucent. The soft body is deep orange with long tentacles.
Similar species
Acesta oophaga was first described by Järnegren as Acesta bullisi . After detailed comparisons with the type material, it turned out that it was a new species, which differs through the very specialized way of life and through the strong indentation in the housing. The case of Acesta bullisi is slimmer than Acesta oophaga .
Way of life
Acesta oophaga lives in fauna communities that have established themselves on so-called Cold Seeps in about 400 to 800 meters water depth on the Louisiana Slope in the northern Gulf of Mexico . However, it has no chemoautrophic bacteria in the tissue or on the gills that can fix methane or hydrogen sulfide. Adult specimens Acesta oophaga are always found with byssus attached to the front opening of the tube of the beard worm Lamellibranchia luymesi , but almost only female tube worms. From a certain size of the mussel, even the housing is exactly adapted to the rounding of the tube and has an indentation in the area of the lunula in front of the vertebra. The large mussel tries to keep the tube opening and the tentacle wreath of the tube worm, around three quarters of which is enclosed by the mantle, in the flowing water (for the mussel). The beard worm Lamellibranchia luymesi has neither a mouth, a bowel nor an anus. It gets its food directly from sulfur-oxidizing bacteria in the tissue. It is the dominant species in this community of fauna and forms dense, bush-like stands. The tubes can grow to be over two meters long, and an individual can live to be over 200 years old. The adult specimens of Acesta oophaga have specialized in filtering and eating the yolk- rich eggs of Lamellibranchia luymesi from the water flow, hence the species name oophaga = egg-eater. Lamellibranchia luymesi produces eggs all year round. The eggs measure a little over 100 µm in diameter. On average (out of 22 specimens), one specimen contained over 18,000 eggs per animal, while a single female counted almost 60,000 eggs. So far, however, it is not known at what intervals the eggs are released into the water.
Young specimens of Acesta bullisi , which are not yet able to enclose the tube opening of the beardworm with the coat, are very mobile thanks to their very flexible feet. You can climb up the tubes of the beard worms, but also switch from one tube to the other. Swimming was not observed. They use the height of the tubes above the sediment surface and filter.
literature
- Johanna Järnegren, Craig R. Thomas, Stephen A. Macko, Craig M. Young: Egg Predation Fuels Unique Species Association at Deep-Sea Hydrocarbon Seeps. Biological Bulletin, 209: 87-93, 2005 PDF
- Johanna Järnegren, Christopher Schander, Jon-Arne Sneli, Vera Rønningen, Craig M. Young: Four genes, morphology and ecology: distinguishing a new species of Acesta (Mollusca; Bivalvia) from the Gulf of Mexico. Marine Biology, 152: 43-55, 2007 doi : 10.1007 / s00227-007-0651-y
- Harold E. Vokes: Studies on Tertiary and Recent giant Limidae. Tulane Studies in Geology, 1: 73-92, 1963