Nipponomysella subtruncata
| Nipponomysella subtruncata | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Systematics | ||||||||||||
|
||||||||||||
| Scientific name | ||||||||||||
| Nipponomysella subtruncata | ||||||||||||
| ( Yokoyama , 1927) |
Nipponomysella subtruncata is a mussel species from the lentil mussel family(Montacutidae). The species lives commensally with the splashworm Siphonosoma cumanense , which digsin the sediment in the tidal range,on the coasts of southwestern Japan.
features
The equally-hinged case is broadly elliptical in outline and is up to 6.8 mm long. A 5 mm long specimen was 3.2 mm high and 1.8 mm thick. The length / height ratio is thus about 1.6. The housings are clearly unequal, the comparatively small, opisthogyric vertebrae are about a third of the length of the housing from the rear end. The front end is slightly more rounded than the rear end. The anterior dorsal margin is almost straight to slightly convex; it slopes down only slightly towards the front end. The posterior dorsal margin is also almost straight to slightly convex, but slopes much more steeply than the anterior dorsal margin. The ventral margin is curved in a flat convex manner.
The ligament lies internally in an elongated, triangular depression under the vertebrae. There are two lateral teeth in each of the two valves. In the right valve are the two approximately equal lateral teeth, an anterior and a posterior, protrusions of the dorsal edge of the housing. In the left valve, the two lateral teeth are not the same size and diverge from each other.
The whitish shell is thin-walled and semi-transparent. The glossy surface is smooth with coarse stripes parallel to the edge. A weak keel runs from the vertebra to the anterior end of the ventral margin. The surface line is not indented. The Prodissoconch is 360 µm long and 260 µm high. The inside edge of the case is smooth.
Similar species
Nipponomysella oblongata (Yokoyama, 1922) is very similar in overall habit, the shell is longer (in relation to the height), and the vertebrae are even closer to the posterior end (about a quarter to a fifth).
Geographical distribution, habitat and way of life
The distribution area is only partially known. So far, the species is known from Japanese coastal waters and off Phuket, Thailand. It lives there on sandy and sandy-silty soils from the tidal range to about 20 meters water depth.
Nipponomysella subtruncata is attached individually or in groups of up to nine specimens with byssus threads to the burrowing sprayworm Siphonosoma cumanense . They are commensals of the splashworm digging in structures in the tidal range.
The animals are protandric hermaphrodites ; Specimens between 1.4 and 2.5 mm in length are males. When the size is between 2.1 and 3 mm, the sex is reversed and the animals become (and remain) females. Reproduction takes place in summer. The few eggs with a diameter of 84 to 88 µm are retained in the mantle cavity or in the area above the gills, where they develop into Veliger larvae with a D-shaped Prodissoconch. With a housing size of 107 µm in width (or length), they are released into the open water. After a planktotrophic phase of unknown duration, they continued to develop into pediatric learners . With a Prodissiconch size of 360 µm, they move on to soil life and metamorphosis . The young mussels initially prefer to attach themselves to adult mussels of the same species, mostly females. From a size of 1 to 1.6 mm, they peel off and live separately.
The sperm are transferred in the form of sperm packets (spermatophores) and stored in paired, mushroom-shaped sperm pockets. Presumably several clutches are fertilized with it. The seminal containers appear first in larger males, or in individuals who are about to change their sex.
Taxonomy
The species was first described in 1927 by Matajiro Yokoyama as Montacuta subtruncata . 1959 established Yamamoto & Habe, the genus Nipponomysella and assigned Montacuta subtruncata to this genus. Species and genus are accepted as valid taxa by the MolluscaBase.
supporting documents
literature
- Jørgen Lützen, T. Takahashi, T. Yamaguchi: Morphology and reproduction of Nipponomysella subtruncata (Yokoyama), a galeommatoidean bivalve commensal with the sipunculan Siphonosoma cumanense (Keferstein) in Japan. Journal of Zoology, 254: 429-440, London 2001 doi : 10.1017 / S0952836901000929
- Elio Robba, Italo Di Geronimo, Niran Chaimanee, Mauro Pietro Negri, Rossana Sanfilippo: Holocene and Recent shallow soft-bottom mollusks from the Western Gulf of Thailand: Pak Phanang Bay and additions to Phetchaburi fauna. Bollettino Malacologico, 43 (n. Speciale): 1-98, 2007 PDF (Research Gate)
Individual evidence
- ↑ Matajiro Yokoyama: Mollusca from upper Musashino of Tokyo and its suburbs. Journal of the Faculty of Sciences Imperial University of Tokyo (II) 1: 391-437, Tokyo 1927 (not viewed)
- ↑ G. Yamamoto, Tadashige Habe: Fauna of shell-bearing mollusks in Mutsu Bay. Lamellibranchia (2). Bulletin of the Marine Biological Station of Asamuchi, 9 (3): 85-122, 1959 (not viewed)
- ↑ MolluscaBase: Nipponomysella subtruncata (Yokoyama, 1927)