|Shell of T. crystallina|
Thyca crystallina is a species of sea snail, a marine gastropod mollusc in the family Eulimidae. It is one of nine species within the genus Thyca , all of which are parasitic on starfish in the Indo-Pacific Ocean. This species was first described in 1846 by the American conchologist Augustus Addison Gould as Pileopsis crystallina but was later transferred to Thyca .
The shell of T. crystallina is conical, transparent and slightly curved, and is sculptured with longitudinal grooves.The colour is variable and may be tan or bluish; the colouring does not necessarily resemble that of the host starfish.
The species is located in the Indian Ocean and western Pacific Ocean, ranging from Madagascar to Hawaii.
Thyca crystallina is an ectoparasite of a starfish, often the blue starfish Linckia laevigata or the multicolour Linckia multifora .The mollusc larvae tend to settle on the upper side of one of the arms of the starfish, usually near its attachment to the disc. As they grow, they migrate to the underside of the arm, settling on the right side of the starfish's ambulacral groove, and orientating themselves towards its mouth, and here they become firmly attached. All the larger molluscs are female, and the larger of these have dwarf males attached to the starfish living under the front end of their mantles.
This mollusc is at an early stage of becoming parasitic and has relatively few modifications to adopt this lifestyle.The ventral surface has a central mouth and adheres to the starfish by suction created by the muscular pharynx. Nourishment is derived from grazing the host's tissues and the suction eventually forms a lesion. On larger individuals, a proboscis is inserted deeper into the host's tissues.
Echinoderm is the common name given to any member of the phylum Echinodermata of marine animals. The adults are recognizable by their radial symmetry, and include such well-known animals as starfish, sea urchins, sand dollars, and sea cucumbers, as well as the sea lilies or "stone lilies". Echinoderms are found at every ocean depth, from the intertidal zone to the abyssal zone. The phylum contains about 7000 living species, making it the second-largest grouping of deuterostomes, after the chordates. Echinoderms are also the largest phylum that has no freshwater or terrestrial (land-based) representatives.
Starfish or sea stars are star-shaped echinoderms belonging to the class Asteroidea. Common usage frequently finds these names being also applied to ophiuroids, which are correctly referred to as brittle stars or basket stars. About 1,500 species of starfish occur on the seabed in all the world's oceans, from the tropics to frigid polar waters. They are found from the intertidal zone down to abyssal depths, 6,000 m (20,000 ft) below the surface.
Trematoda is a class within the phylum Platyhelminthes. It includes two groups of parasitic flatworms, known as flukes.
The crown-of-thorns seastar, Acanthaster planci, is a large starfish that preys upon hard, or stony, coral polyps (Scleractinia). The crown-of-thorns starfish receives its name from venomous thorn-like spines that cover its upper surface, resembling the biblical crown of thorns. It is one of the largest starfish in the world.
Linckia laevigata is a species of sea star in the shallow waters of tropical Indo-Pacific.
The Ophidiasteridae are a family of sea stars with about 30 genera. Occurring both in the Indo-Pacific and Atlantic Oceans, ophidiasterids are greatest in diversity in the Indo-Pacific. Many of the genera in this family exhibit brilliant colors and patterns, which sometimes can be attributed to aposematism and crypsis to protect themselves from predators. Some ophidiasterids possess remarkable powers of regeneration, enabling them to either reproduce asexually or to survive serious damage made by predators or forces of nature. Some species belonging to Linckia, Ophidiaster and Phataria shed single arms that regenerate the disc and the remaining rays to form a complete individual. Some of these also reproduce asexually by parthenogenesis.
The common starfish, common sea star or sugar starfish is the most common and familiar starfish in the north-east Atlantic. Belonging to the family Asteriidae, it has five arms and usually grows to between 10–30 cm across, although larger specimens are known. The common starfish is usually orange or brown, and sometimes violet; deep-water specimens are pale. The common starfish is to be found on rocky and gravelly substrates where it feeds on molluscs and other benthic invertebrates.
Linckia is a genus of sea stars found mainly in the Indo-Pacific region. They are known to be creatures with remarkable regenerative abilities, and capable of defensive autotomy against predators. They reproduce asexually.
Linckia guildingi, also called the common comet star, Guilding's sea star or the green Linckia, is a species of sea star found in the shallow waters of the tropical Pacific Ocean, Indian Ocean, Atlantic Ocean and the Caribbean Sea.
Linckia multifora is a variously colored starfish in the family Ophidiasteridae that is found in the Indian Ocean and Red Sea. Its common names include the Dalmatian Linckia, mottled Linckia, spotted Linckia, multicolor sea star and multi-pore sea star.
Asexual reproduction in starfish takes place by fission or through autotomy of arms. In fission, the central disc breaks into two pieces and each portion then regenerates the missing parts. In autotomy, an arm is shed with part of the central disc attached, which continues to live independently as a "comet", eventually growing a new set of arms. Although almost all sea stars can regenerate their limbs, only a select few sea star species are able to reproduce in these ways.
Linckia columbiae is a species of starfish in the family Ophidiasteridae. It is found in the East Pacific where it ranges from California (USA) to northwest Peru, including offshore islands such as the Galápagos. Common names include fragile star, Pacific comet sea star and variable sea star.
Thyca is a genus of small sea snails, marine gastropod mollusks in the family Eulimidae. These snails are ectoparasites of starfish; they are relatively unmodified, the underside having become a suction disc with a central mouth that draws nourishment from the host's tissues.
Asterias forbesi, commonly known as Forbes sea star, is a species of starfish in the family Asteriidae. It is found in shallow waters in the northwest Atlantic Ocean and the Caribbean Sea.
Orchitophrya stellarum is a species of single-celled marine ciliates, a member of the class Oligohymenophorea. It is found living freely in the north Atlantic and Pacific Oceans but is also parasitic, being found inside the gonads of starfish.
Thyonicola americana is a species of parasitic sea snail, a marine gastropod mollusc in the family Eulimidae. It infests the sea cucumbers Eupentacta quinquesemita and Eupentacta pseudoquinquesemita in Puget Sound and other parts of the northeastern Pacific Ocean.
Eupentacta quinquesemita is a species of sea cucumber, a marine invertebrate with an elongated body, a leathery skin and tentacles surrounding the mouth. It is commonly known as the stiff-footed sea cucumber or white sea cucumber, and occurs on rocky coasts in the northeastern Pacific Ocean.
Coscinasterias muricata is a species of starfish in the family Asteriidae. It is a large 11-armed starfish and occurs in shallow waters in the temperate western Indo-Pacific region.
Clistosaccus is a genus of barnacles which are parasitic on hermit crabs. It is a monotypic genus, and the single species is Clistosaccus paguri, which is found in the northern Atlantic Ocean and the northern Pacific Ocean.