''Goniocidaris umbraculum'' is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of cidaroid

sea urchin Sea urchins () are spiny, globular echinoderms in the class Echinoidea. About 950 species of sea urchin live on the seabed of every ocean and inhabit every depth zone from the intertidal seashore down to . The spherical, hard shells (tests) of ...

that inhabits the

continental shelf A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an island ...

off the southern coasts of

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...

. It is plentiful on a seabed composed of

seashell A seashell or sea shell, also known simply as a shell, is a hard, protective outer layer usually created by an animal or organism that lives in the sea. The shell is part of the body of the animal. Empty seashells are often found washe ...

and

bryozoa Bryozoa (also known as the Polyzoa, Ectoprocta or commonly as moss animals) are a phylum of simple, aquatic invertebrate animals, nearly all living in sedentary colonies. Typically about long, they have a special feeding structure called a l ...

n rubble at a depth of off

Otago Otago (, ; mi, Ōtākou ) is a region of New Zealand located in the southern half of the South Island administered by the Otago Regional Council. It has an area of approximately , making it the country's second largest local government reg ...

Description

''Goniocidaris umbraculum'' grows to a

test Test(s), testing, or TEST may refer to: * Test (assessment), an educational assessment intended to measure the respondents' knowledge or other abilities Arts and entertainment * ''Test'' (2013 film), an American film * ''Test'' (2014 film), ...

diameter of . The main spines are thick, blunt, and usually shorter that the test diameter. The ones on the

aboral Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...

(upper) surface have small flat discs at the tip, and thorn-like projections near the base. The test is greenish-brown and the spines are pale brown, often tinged green near the base. They are often overgrown by

epiphyte An epiphyte is an organism that grows on the surface of a plant and derives its moisture and nutrients from the air, rain, water (in marine environments) or from debris accumulating around it. The plants on which epiphytes grow are called phoroph ...

s such as

hydroids Hydroids are a life stage for most animals of the class Hydrozoa, small predators related to jellyfish. Some hydroids such as the freshwater '' Hydra'' are solitary, with the polyp attached directly to the substrate. When these produce buds ...

sponge Sponges, the members of the phylum Porifera (; meaning 'pore bearer'), are a basal animal clade as a sister of the diploblasts. They are multicellular organisms that have bodies full of pores and channels allowing water to circulate through t ...

s and

Distribution and habitat

''Goniocidaris umbraculum'' is native to the sea around southern New Zealand; it is common in the

Foveaux Strait The Foveaux Strait, (, or , ) separates Stewart Island, New Zealand's third largest island, from the South Island. The strait is about 130 km long (from Ruapuke Island to Little Solander Island), and it widens (from 14 km at Ruapuk ...

, on the eastern coast of South Island as far north as

Cook Strait Cook Strait ( mi, Te Moana-o-Raukawa) separates the North and South Islands of New Zealand. The strait connects the Tasman Sea on the northwest with the South Pacific Ocean on the southeast. It is wide at its narrowest point,McLintock, A H, ...

and on the

Chatham Rise The Chatham Rise is an area of ocean floor to the east of New Zealand, forming part of the Zealandia continent. It stretches for some from near the South Island in the west, to the Chatham Islands in the east. It is New Zealand's most productive ...

, at depths between about , on coarse sand or rubble.

Ecology

This sea urchin broods its eggs, carrying them on the flared

peristome Peristome (from the Greek ''peri'', meaning 'around' or 'about', and ''stoma'', 'mouth') is an anatomical feature that surrounds an opening to an organ or structure. Some plants, fungi, and shelled gastropods have peristomes. In mosses In mosses, ...

that surrounds its mouth. Prior to research into its breeding biology, only two other sea urchins that brood their young had been studied, '' Cassidulus caribaearum'' and ''

Abatus cordatus ''Abatus cordatus'' is a species of sea urchin in the family Schizasteridae. It is native to shallow seas surrounding certain island groups in the southern Indian Ocean. The body is protected by a hard test or shell which is covered with spines ...

'', though several arctic and subarctic species were known to do so. ''Goniocidaris umbraculum'' is a

gonochoric In biology, gonochorism is a sexual system where there are only two sexes and each individual organism is either male or female. The term gonochorism is usually applied in animal species, the vast majority of which are gonochoric. Gonochorism c ...

species, individuals being either male or female. Spawning takes place around July. The eggs have large yolks and are buoyant, and if detached from the female, float to the surface. As they emerge from the

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 the ...

on the aboral surface of the female, the eggs are retained. They are then moved to the peristome, a process that takes several minutes and is achieved by the action of the

tube feet Tube feet (technically podia) are small active tubular projections on the oral face of an echinoderm, whether the arms of a starfish, or the undersides of sea urchins, sand dollars and sea cucumbers; they are more discreet though present on britt ...

and

cilia The cilium, plural cilia (), is a membrane-bound organelle found on most types of eukaryotic cell, and certain microorganisms known as ciliates. Cilia are absent in bacteria and archaea. The cilium has the shape of a slender threadlike projecti ...

, the eggs being guided along channels between the spines; the peristome becomes slightly depressed in order to accommodate the eggs, which are retained by the spines surrounding the mouth for about two months. Sixty eggs can be held in place, and when the juveniles have developed tube feet, they move to other parts of the test, but continue to be brooded for another two months. This unusual reproductive strategy may have developed when this species evolved to live in the colder waters further south than other members of its genus. ''Goniocidaris umbraculum'' feeds on the bryozoan '' Filicea elegans''.

References

{{Taxonbar, from=Q2011829 Cidaridae Fauna of the Pacific Ocean Echinoderms of New Zealand Marine fauna of New Zealand Endemic fauna of New Zealand Animals described in 1878 Taxa named by Frederick Hutton (scientist) Endemic echinoderms of New Zealand