Offadesma angasi
| Offadesma angasi | ||||||||||||
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![Offadesma angasi (from Crosse & Fischer, 1865: Plate 11, Fig. 1, holotype. [1])](https://de.wikipedia.org/wiki/Datei:Crosse%26Fischer1865_pl11_fig1_Offadesma_angasi.png)
Offadesma angasi (from Crosse & Fischer, 1865: Plate 11, Fig. 1, holotype.) |
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Offadesma angasi | ||||||||||||
| ( Crosse & P. Fischer , 1864) |
Offadesma angasi is a type of mussel from the family of the spoon clams (Periplomatidae). It is found in the coastal waters of southern and eastern Australia and New Zealand .
features
The unevenly hinged housing reaches a length of over nine centimeters. The right flap is more arched and slightly larger. It is also clearly unequal, with the vertebrae sitting behind the center line in relation to the length of the case. The two vertebrae each have a slot that is closed again in the adult housing. The outline is egg-shaped. The ratio of width to length is about 1 to 1.4. The anterior dorsal margin is longer than the posterior one, and is also significantly higher. It is convexly rounded and merges into the broadly rounded front edge without a noticeable edge or kink. The posterior dorsal margin is straight and almost horizontal. The transition to the slightly convex, sloping rear edge is slightly angled. The rear edge also merges at a slight angle into the broadly rounded, strongly upwardly curved ventral edge. The housing gapes at the front and rear.
The lock is toothless, but has a spoon-shaped extension that acts as the attachment of the ligament . The external ligament is more or less a secondary ligament, as it is formed from the periostracum layer.
The whitish shell is very thin-walled and fragile. The ornamentation consists of fine concentric pits and lines. The inside edge of the case is smooth. The posterior end of the periostracum is studded with grains of sand that are held in place by mucus. The mucus is produced by glands in the middle fold of the mantle. In old age the foot is reduced. The labial palps are very long.
Geographical distribution and habitat
Offadesma angasi occurs in the coastal waters off the Australian states of South Australia , Victoria , New South Wales , Queensland , Northern Territory and Tasmania as well as around the North and South Islands of New Zealand, Stewart Island and the Chatham Islands .
The mussel prefers sandy silt or silty sand below the low water line in sheltered, low-energy bays. It lies on the left flap, buried seven to eight centimeters deep in the sediment. The siphons are stretched out towards the sediment surface. Because the foot is reduced with age, the mussels cannot bury themselves again if they are exposed by currents or storm waves. They are adapted to areas with a high intake of very fine sediment. The cilia therefore produce a powerful return current from the mantle cavity.
The animals are simultaneous hermaphrodites that produce large, yolk-rich, encapsulated eggs.
Taxonomy
The taxon was first described by Hippolyte Crosse and Paul Henri Fischer as Periploma angasi . It is the type species of the genus Offadesma Iredale, 1930.
supporting documents
literature
- S. Peter Dance, Rudo von Cosel (arrangement of the German edition): The great book of sea shells. 304 pp., Verlag Eugen Ulmer, Stuttgart, 1977 ISBN 3-8001-7000-0 (p. 274)
- Miguel Griffin, Guido Pastorino: The Genus Offadesma Iredale, 1930 (Bivalvia: Periplomatidae) in the Miocene of Patagonia. The Veliger, 48 (2): 75-82, 2006 PDF
- Brian Morton: The biology and functional morphology of Periploma (Offadesma) angasi (Bivalvia: Anomalodesmata: Periplomatidae). Journal of Zoology, 193 (1): 39-70, 2009 abstract at ResearchGate
Individual evidence
- ^ A b Hippolyte Crosse, Paul Henri Fischer: Diagnoses Molluscorum Australiae meridionalis. Journal de Conchyliologie, 12: 346-350, Paris 1864 Online at www.biodiversitylibrary.org (p. 349) Journal de Conchyliologie, 13: Plate 11, Fig . 1 Online at www.biodiversitylibrary.org .
- ↑ MolluscaBase: Offadesma angasi (Crosse & P. Fischer, 1864)
