''Parvulastra vivipara'', the Tasmanian live-bearing seastar, is a tiny, uniformly orange-yellow

seastar 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. Starfish ...

, up to across. The species usually has five short arms and is a rounded,

pentagon In geometry, a pentagon () is any five-sided polygon or 5-gon. The sum of the internal angles in a simple polygon, simple pentagon is 540°. A pentagon may be simple or list of self-intersecting polygons, self-intersecting. A self-intersecting ...

shape. Morphological variation is common and three, four or six arms are occasionally present. It is endemic to coastal waters in southeast

Tasmania Tasmania (; palawa kani: ''Lutruwita'') is an island States and territories of Australia, state of Australia. It is located to the south of the Mainland Australia, Australian mainland, and is separated from it by the Bass Strait. The sta ...

Description

''P. vivipara'' is a very small, cushiony seastar with a maximum diameter of . It is normally pentagonal in shape, with five stubby arms, but individuals sometimes occur with four or six arms. The aboral (upper) surface is a plain yellowish-orange.

Distribution and habitat

''P. vivipara'' is

endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

to the waters of south-eastern Tasmania. It is known from thirteen separate locations and because there is no

plankton Plankton are the diverse collection of organisms that drift in Hydrosphere, water (or atmosphere, air) but are unable to actively propel themselves against ocean current, currents (or wind). The individual organisms constituting plankton are ca ...

ic larval stage, this species has limited scope for dispersal. Its total area of occupation is estimated to be under . One of these locations was as a result of an accidental introduction in 1995 when an aquarium population was liberated into the sea at

Woodbridge Woodbridge may refer to: Places Australia *Woodbridge, Western Australia formerly called ''West Midland'' *Woodbridge, Tasmania Canada *Woodbridge, Ontario England *Woodbridge, Suffolk, the location of **Woodbridge (UK Parliament constituency ...

due to a concern over their care during a holiday period. It is found on rock, hiding under stones and in crevices, in the intertidal zone and in very shallow water (under deep).

Ecology

This starfish feeds on the microbial and algal film found on the surface of rocks. It does this by everting (pushing out) its stomach through its mouth, and digesting the film in situ. It feeds at night and on overcast days. ''P. vivipara'' 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 ...

, each individual typically having six to eight female gonads and a single male-type gonad. The seastars mostly self-fertilise, but it is likely that some cross fertilisation occurs. The

embryo An embryo ( ) is the initial stage of development for a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sp ...

s and juveniles are brooded within the mother's body cavity. They are present in various sizes, and usually leave the protective environment to live independently by the time they are 30% of the parent's diameter. They emerge through

gonopore A gonopore, sometimes called a gonadopore, is a genital pore in many invertebrates. Hexapods, including insects, have a single common gonopore, except mayflies, which have a pair of gonopores. More specifically, in the unmodified female, it is ...

s on the aboral surface of the parent, the holes enlarging to let them out. While they are inside the body cavity, they are

cannibalistic Cannibalism is the act of consuming another individual of the same species as food. Cannibalism is a common ecological interaction in the animal kingdom and has been recorded in more than 1,500 species. Human cannibalism is also well documente ...

, the larger ones eating the smaller ones; sometimes one becomes too large to emerge, and remains inside its mother.

Conservation Status

The Department of the Environment of the Australian Government is concerned about the conservation of this species. Threats it has identified include competition from introduced seastar species, predation by these seastars, pollution by sewage, industrial and agricultural discharges, and

habitat destruction Habitat destruction (also termed habitat loss or habitat reduction) occurs when a natural habitat is no longer able to support its native species. The organisms once living there have either moved elsewhere, or are dead, leading to a decrease ...

. In April of 2023, ''P. vivipara'' was determined to be

Critically Endangered An IUCN Red List critically endangered (CR or sometimes CE) species is one that has been categorized by the International Union for Conservation of Nature as facing an extremely high risk of extinction in the wild. As of December 2023, of t ...

by the

IUCN The International Union for Conservation of Nature (IUCN) is an international organization working in the field of nature conservation and sustainable use of natural resources. Founded in 1948, IUCN has become the global authority on the status ...

. Only about 41,600 adults are thought to be alive, and the population continues to decrease due to a variety of factors, including wastewater runoff,

climate change Present-day climate change includes both global warming—the ongoing increase in Global surface temperature, global average temperature—and its wider effects on Earth's climate system. Climate variability and change, Climate change in ...

habitat loss Habitat destruction (also termed habitat loss or habitat reduction) occurs when a natural habitat is no longer able to support its native species. The organisms once living there have either moved elsewhere, or are dead, leading to a decrease ...

, and more.

References

{{Taxonbar, from=Q2651922 Asterinidae Echinoderms of the Pacific Ocean Marine fauna of Australia Endemic fauna of Tasmania Animals described in 1969