Pandora inaequivalvis
| Pandora inaequivalvis | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Pandora inaequivalvis | ||||||||||||
| ( Linnaeus , 1758) |
Pandora inaequivalvis is a shell - type from the family of rifle shells (Pandoridae).
features
The unevenly hinged housing is up to 4 cm long. The right flap is flat or even slightly concave. The case is overall flat, the ratio is length: 3.5 cm, height 1.9 cm and thickness 0.6 cm. The case is also asymmetrical, with the small vertebrae sitting in front of the center line. The outline of the case is boat-shaped and trimmed at the rear end. The posterior dorsal margin is long and concave and rises to the angled end or transition to the posterior margin. The rear part of the housing is elongated and pulled out into a "beak". The anterior dorsal margin is slightly convex and also slopes down flat to the rounded anterior end. The ventral margin is very broadly rounded.
The edge of the right flap is only slightly calcified, so the edge is made of periostracum material that fits exactly into the left flap when the housing is closed. The edge of the housing is only slightly calcified in the siphon region. The housing is also rotated in the longitudinal axis. The back two thirds of the ventral margin are twisted so that they cover the dorsal margin of the left valve. The front part of the left flap overlaps the vertebrae of the right flap. The case gaped at the front and rear.
In each valve there is a main tooth in the lock region. The tooth on the right flap is larger and sits at right angles to the lock plate. It fits exactly into a pit in the left flap. The ligament lies inside and is just a thin band. It points backwards at an angle of about 45 ° (seen from the dorsal margin). The lunula is narrow and deepened. The area is narrow and lanceolate. The periostracum of the two valves is fused over the dorsal margin and forms a kind of secondary ligament. The ends of the jacket are largely fused together at the ventral edge. The opening for the foot only takes up about a third of the ventral margin. There is no lock plate. In the right valve there is a tooth-like protrusion in front of the ligament. In the left valve there is a thickening in front of the ligament, which runs over two thirds - but not exactly parallel - to the dorsal edge. In this thickening there is a gap for the ligament. There are two sphincters. However, the posterior sphincter is roughly halfway between the posterior edge and the vertebra, the anterior sphincter at the edge at the anterior end. The surface line is not continuous, but consists of a line of points. It is not indented.
The whitish skin is thin and fragile. It is aragonitic with an inner layer of layered mother-of-pearl, a middle layer of lenticular mother-of-pearl and an outer prismatic layer. The ornamentation consists of growth strips parallel to the edge. On the left flap, two radial ones run from the vertebra to the upper part of the posterior margin ("beak"). The inner edge of the case is smooth. The periostracum is beige to light brown. Grains of sand often attach to the posterior region of the beak.
Geographical distribution and habitat
The distribution area extends from the south coast of the British Isles to North Africa, and into the Mediterranean .
The animals live in sheltered bays on sandy bottoms below the tide line . They lie on their side on the sediment or live half-buried in the sediment.
Way of life
The animals are facultative hermaphrodites . The male and female sex organs mature at the same time. The following observations were made in the laboratory. The eggs have a diameter of 105 to 125 µm. Shortly after the eggs are released into the open water, a gelatinous shell forms around the eggs, increasing the diameter of the eggs to 300 µm. The eggs are heavier than water and lie on the surface. After fertilization, the first cell division was observed after about 1¼ hours, which is very uneven. Gastrulae were formed after approximately 9 hours. After a little over 17 hours the first trochophora larvae appeared, which were then released into the open water by tearing open the surrounding gelatinous shell. Shortly thereafter, a first, organic, disc-like membrane forms. Soon afterwards the bilobed Prodissoconch I forms, the ligament is not yet present and the shell runs over the dorsal margin. After about 24 to 36 hours the velum is formed, but it remains small (compared to the vela of other Bivalvia veligans ). The prodissoconch, which at this stage has the same valve, enlarges and now encloses the body. The ligament was formed after 32 hours. The Prodissoconch measures 175 µm in length, with a height of 120 µm. After about 100 hours (after fertilization) the dissoconch is now formed. After 70 hours the Veliger larvae went over to soil life and metamorphosed . The foot is already fully functional at this stage. The larvae do not yet have gills at this point. These are only formed about 170 hours after fertilization. The larval development is very short compared to the development of many other mussel species.
Taxonomy
The taxon was founded in 1758 by Carl von Linné in the combination Solen inaequivalvis . It is the type species of the genus Pandora Bruguière, 1797. A more recent synonym is Pandora rostrata Philippi, 1836.
supporting documents
literature
- JA Allen: On the Structure and Adaptations of Pandora inaequivalvis and Pandora pinna. Quarterly Journal of Microscopical Science, 95 (4): 473-482, 1954 PDF
- JA Allen: The Development of Pandora inaequivalvis, Journal of Embryonology and Experimental Morphology, 9 (2): 252-268, 1961 PDF
- Paul Chambers: Channel Island Marine Molluscs: An Illustrated Guide to the Seashells of Jersey, Guernsey, Alderney, Sark and Herm. 321 pp., Charonia Media, 2008, ISBN 978-0-9560655-0-6 , p. 283 Preview on Google Books
- Fritz Nordsieck : The European sea shells (Bivalvia). From the Arctic Ocean to Cape Verde, the Mediterranean Sea and the Black Sea. 256 p., Gustav Fischer Verlag, Stuttgart 1969 (p. 157/58)
- Guido Poppe, Yoshihiro Goto: European Seashells Volume 2 (Scaphopoda, Bivalvia, Cephalopoda) . 221 pp., Verlag Christa Hemmen, Wiesbaden 1993 (2000 unc. Reprint), ISBN 3925919104 (p. 136)
On-line
- Marine Bivalve Shells of the British Isles: Pandora inaequivalvis (Linnaeus, 1758) , website of the National Museum Wales, Department of Natural Sciences, Cardiff
Individual evidence
- ^ Carl von Linné: Systema naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata. Pp. 1-824, Holmia / Stockholm, Salvius, 1758. Online at www.biodiversitylibrary.org (p. 673).
- ↑ a b Pandora inaequivalvis (Linnaeus, 1758) on MolluscaBase.org