Thyca ectoconcha
| Thyca ectoconcha | ||||||||||||
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Thyca ectoconcha sucks on Linckia multifora |
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| Scientific name | ||||||||||||
| Thyca ectoconcha | ||||||||||||
| Sarasin & Sarasin , 1887 |
Thyca ectoconcha is the name of a worm - type from the family of eulimidae (genus Thyca ), as Ectoparasite the comet star lives.
features
As with Thyca crystallina and other representatives of the subgenus Bessomia , the snail shell of Thyca ectoconcha is about 8 to 12 mm in females, and less than a fifth as large in males, and very slightly rolled up and very low with a wide mouth, giving it the shape of a Phrygian Hat or upside down in a shallow bowl. Typical of the very bulbous housing of Thyca ectoconcha are the numerous ribs on the surface, each of which has a number of small nodules. The maximum diameter of the case mouth is about two thirds of the maximum diameter of the entire shell.
The snail has a fully developed mantle cavity with a gill . The eyes and other sense organs are also fully developed. The animal has a short, very strong snout and a muscular pharyngeal head (esophageal bulb) that penetrates between the calcareous plates of the starfish into the inner tissue of the host. One radula is missing. The base of the muzzle is surrounded by a muscular disc made up of an anterior and posterior section. With this suction disk, also known as the "false foot", the snail attaches itself to the starfish's skin with such force that it can no longer be torn off without injuring the host. The snail also has a rudimentary foot, but no operculum.
Distribution and way of life
Thyca ectoconcha is distributed throughout the Indo-Pacific , where its host animal, the comet star ( Linckia multifora ) also lives. While as a young animal it often sits on the top of the host, as an adult it attaches itself to the underside of an arm on the ambulacral groove . In the middle of the pseudopod there is a hole through which the proboscis of the snail is pushed further through the skin of the host to the nutrient-rich hemal canal in the arm.
Development cycle
Thyca crystallina is of separate sex. The adult female lives firmly attached to the host and no longer moves. The dwarf male lives under the female's shell on its proboscis and sinks its own proboscis like this one in the host's skin. The male mates with the female with his long, slender penis . The fertilized eggs develop into free-swimming Veliger larvae, which ensure the spread of the species, develop a protoconch typical of the Eulimidae and metamorphose into parasitic snails on other host starfish .
literature
- Paul Sarasin, Fritz Sarasin: About two parasitic snails. In: Results of scientific research on Ceylon 1884–1886. Volume 1, Issue 1. CW Kreidel, Wiesbaden 1887, pp. 21-31.
- Paulus Schiemenz: Parasitic snails. Biologisches Centralblatt 9, 1889, pp. 567-574, 585-594.
- Mattheus Marinus Schepman, HF Nierstrasz: Parasitic prosobranchs of the Siboga expedition. Siboga expeditie 49. EJ Brill, Leiden 1909.
- Thomas WM Cameron: Parasites and Parasitism. Wiley, New York 1956. pp. 199-201.
- Anders Warén (1980): Revision of the Genera Thyca, Stilifer, Scalenostoma, Mucronalia and Echineulima (Mollusca, Prosobranchia, Eulimidae). Zoologica Scripta 9, pp. 187-210.
- Anders Warén (1983): A Generic Revision of the Family Eulimidae (Gastropoda, Prosobranchia). Journal of Molluscan Studies 49 (Supplement 13), pp. 1-96, here pp. 76-80. doi: 10.1093 / mollus / 49.Supplement_13.1
Web links
Individual evidence
- ^ Yves Müller, Frédéric André: Thyca crystallina (Gould, 1846) [et espèces ressemblantes]. Données d'Observations pour la Reconnaissance et l'Identification de la faune et la flore Subaquatiques (DORIS), December 15, 2018.
- ↑ Waren (1983), p. 78.
- ^ F. Welter Schultes: Picture of Thyca ectoconcha by Raymond Huet . February 21, 2013.
- ↑ Waren (1980), p. 192.