Thyca
| Thyca | ||||||||||||
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Thyca ectoconcha sucks on Linckia multifora |
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| Scientific name | ||||||||||||
| Thyca | ||||||||||||
| Adams & Adams , 1854 |
Thyca is the name of a genus of marine snails from the Eulimidae family, whose 10 species live as ectoparasites on the outside of starfish .
features
The parasitic snails of the genus Thyca have a cap or bowl-shaped snail shell with a large housing mouth and without an operculum to close the mouth of the housing. This means that the shape of the housing differs greatly from that of other Eulimidae such as the genus Eulima . The needle-shaped embryonic thread ( protoconch ) is similar to that of other Eulimidae. The snails have a fully developed mantle cavity with a gill for breathing. The antennae are fused into a fold on which the two eyes sit. The snout of these creatures is greatly enlarged and is used to attach themselves to the host animal. Because of this function, it is also known as a pseudopus, while the actual foot is only a rudimentary tip next to the snout. In the middle of the dummy base is an opening through which the long trunks ( Proboscis ) is driven outwardly to penetrate the skin of the host and passed to the nutrient-rich Hämalkanäle (between the calcareous plates blood vessels ) to penetrate the starfish.
The sexes of parasites differ greatly in their appearance (pronounced sexual dimorphism ): The dwarf males are only about 0.1 to 0.6 times the size of the females, with the male living in the female's shell and mating with the female if necessary. The fertilized eggs develop into free-swimming Veliger larvae, which later settle on other starfish and metamorphose into parasitic snails .
The Thyca snails attach themselves to the starfish with such force that they can no longer be detached without injuring the host. Most species live as adults on the underside of the host. Due to its flat shape, its housing is hardly damaged when the starfish moves; only the needle-shaped protoconch is eroded.
Systematics
The genus Thyca was first described in 1854 by Henry and Arthur Adams in their work The genera of recent mollusca as the subgenus Thyca , naming the two species Thyca astericola (Adams and Reeve) and Thyca crystallina (Gould) and placed in the family Capulidae . Anders Warén put them in 1983 in his revision of the family Eulimidae because of their characteristic protoconch and their way of life as parasites on echinoderms to the Eulimidae.
species
The following species of snail belong to the genus Thyca :
Subgenus Thyca (Bessomia) (Berry, 1959)
- Thyca callista (Berry, 1959) (on Phataria unifascialis (Gray, 1840) and Pharia pyramida (Gray, 1840) , Eastern Pacific: Gulf of California, Mexico, Panama)
- Thyca crystallina (Gould, 1846) (on Linckia laevigata , more rarely also on Linckia multifora , Indo-Pacific)
- Thyca ectoconcha (P. Sarasin & F. Sarasin, 1887) (on Linckia multifora , Indo-Pacific)
- Thyca hawaiiensis (Warén, 1980) (Indo-Pacific, species of starfish not determined by the descriptor)
Subgenus Thyca (Kiramodulus) (Kuroda, 1949)
- Thyca lactea (Kuroda, 1949) (on Pseudarchaster sp. And others, deep sea of the Pacific)
- Thyca nardoafrianti (Habe, 1976) (to Nardoa frianti Koehler, 1910 , Pacific: Japan, Philippines)
Subgenus Thyca (Thyca) (H. Adams & A. Adams, 1854)
- Thyca astericola (A. Adams & Reeve, 1850) (to Protoreaster nodosus (Linnaeus, 1758) , sibogae pentaceraster Doederlein, 1916 , pentaceraster tuberculatus (Müller & Troschel, 1842) , Iconaster longimanus (Möbius, 1859) , Western Pacific, first record Sulu Sea north from Borneo )
- Thyca stellasteris (Koehler & Vaney, 1912) (on Stellaster childreni (Gray, 1840) , Nardoa tuberculata (Gray, 1840) , Nardoa frianti (Koehler, 1910) , probably also on Echinaster luzonicus , Pacific, Indonesia)
Without assignment of the subgenus
- Thyca sagamiensis (Kuroda & Habe, 1971) (Japan, Korea, starfish species not determined by the descriptor)
The snails described as Thyca pellucida (Kükenthal, 1897) are dwarf males of Thyca crystallina (Gould, 1846) and thus a synonym .
literature
- Thomas WM Cameron: Parasites and Parasitism. Wiley, New York 1956. pp. 199-201.
- Anders Warén: Revision of the Genera Thyca, Stilifer, Scalenostoma, Mucronalia and Echineulima (Mollusca, Prosobranchia, Eulimidae). Zoologica Scripta 9, 1980, pp. 187-210.
- Anders Warén: A Generic Revision of the Family Eulimidae (Gastropoda, Prosobranchia). Journal of Molluscan Studies 49 (Supplement 13), pp. 1-96, 1983, here pp. 76-80. doi: 10.1093 / mollus / 49.Supplement_13.1
- 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.
- Henry Adams, Arthur Adams: The genera of recent Mollusca: arranged according to their organization. J. Van Voorst, London 1858. Gen. Capulus , sub-gen. Thyca Adams & Adams, Th. Astericola , Adams and Reeve. Th. Crystallinus , Gould. P. 372.
- Paulus Schiemenz: Parasitic snails. Biologisches Centralblatt 9, 1889, pp. 567-574, 585-594.
Web links
- 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.
- Fischhaus Zepkow: Family Eulimidae
Individual evidence
- ↑ Thyca H. Adams & A. Adams, 1854. WoRMS , 2018. Retrieved February 12, 2019.
- ↑ Mondomarino: Thyca stellasteris