''Cryptasterina hystera'' is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

starfish Starfish or sea stars are Star polygon, star-shaped echinoderms belonging to the class (biology), class Asteroidea (). Common usage frequently finds these names being also applied to brittle star, ophiuroids, which are correctly referred to ...

. It is found in a limited region of the coast of Australia and is very similar in appearance to '' Cryptasterina pentagona''. The two appear to have diverged from a common ancestral line a few thousand years ago.

Distribution

''Cryptasterina hystera'' is native to a small number of locations on the coasts of Australia at the southern end of the range of ''Cryptasterina pentagona''. It occurs around the shores and islands of Statue Bay (23°15′S; 150°45′E), in south east Queensland, and is typically found under rocks and among

mangrove A mangrove is a shrub or tree that grows mainly in coastal saline water, saline or brackish water. Mangroves grow in an equatorial climate, typically along coastlines and tidal rivers. They have particular adaptations to take in extra oxygen a ...

s in the upper

intertidal zone The intertidal zone or foreshore is the area above water level at low tide and underwater at high tide; in other words, it is the part of the littoral zone within the tidal range. This area can include several types of habitats with various ...

Biology

''Cryptasterina hystera'' is a

hermaphrodite A hermaphrodite () is a sexually reproducing organism that produces both male and female gametes. Animal species in which individuals are either male or female are gonochoric, which is the opposite of hermaphroditic. The individuals of many ...

; the

gonad A gonad, sex gland, or reproductive gland is a Heterocrine gland, mixed gland and sex organ that produces the gametes and sex hormones of an organism. Female reproductive cells are egg cells, and male reproductive cells are sperm. The male gon ...

s can produce both

sperm Sperm (: sperm or sperms) is the male reproductive Cell (biology), cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile sperm ...

and eggs and are known as ovotestes. Fertilization of the eggs take place when sperm liberated by another starfish is drawn into the gonad through the gonoduct. The eggs are few in number and have large yolks and are retained inside the starfish which is viviparous. The brachiolaria larvae that develop inside the gonads "swim" in the fluid there and are eventually released into the sea through the gonopore as juvenile starfish. Members of the family Asterinidae appear prone to rapid change in their reproductive life cycle and ''Cryptasterina hystera'' is one of several species that has recently diverged from its ancestral line. It has recently been recognised as a separate species from ''Cryptasterina pentagona'', a morphologically similar species but with a different native range and a different method of reproduction. In a research study, embryos were removed from the gonads of ''Cryptasterina hystera'' and reared in the laboratory. It was found that the larvae developed normally and exhibited similar behaviour to that of the larvae of free-spawning starfish. After about sixteen days they sank to the bottom and underwent metamorphosis into juveniles in a normal manner.

References

{{Taxonbar, from=Q2622408 Asterinidae Echinoderms of the Pacific Ocean Marine fauna of Australia Endemic fauna of Australia Animals described in 2003