The calcareous sponges of

class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an analytical concept used differentl ...

Calcarea are members of the animal phylum Porifera, the cellular sponges. They are characterized by

spicule Spicules are any of various small needle-like anatomical structures occurring in organisms Spicule may also refer to: *Spicule (sponge), small skeletal elements of sea sponges *Spicule (nematode), reproductive structures found in male nematodes ( ...

s made of calcium carbonate in the form of calcite or

aragonite Aragonite is a carbonate mineral, one of the three most common naturally occurring crystal forms of calcium carbonate, (the other forms being the minerals calcite and vaterite). It is formed by biological and physical processes, including pre ...

. While the spicules in most species have three points, in some species they have either two or four points.

Biology

All sponges in this class are strictly marine, and, while they are distributed worldwide, most are found in shallow tropical waters. Like nearly all other sponges, they are sedentary filter feeders. All three sponge body plans are represented within class Calcarea : asconoid, syconoid, and leuconoid. Typically, calcareous sponges are small, measuring less than in height, and drab in colour. However, a few brightly coloured species are also known. Calcareous sponges vary from radially symmetrical vase-shaped body types to colonies made up of a meshwork of thin tubes, or irregular massive forms. The skeleton has either a mesh or honeycomb structure.

Classification

Of the 15,000 or so species of Porifera that exist, only 400 of those are calcareans. Calcarean sponges first appeared during the Cambrian, and their diversity was greatest during the

Cretaceous period The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of t ...

. Recent molecular analysis suggests the class Calcarea should be designated as a phylum, in particular the first to have diverged in the

Animal Animals are multicellular, eukaryotic organisms in the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic material, Cellular respiration#Aerobic respiration, breathe oxygen, are Motilit ...

ia. The calcareous sponges are divided into two subclasses and six orders: Class Calcarea * Subclass

Calcinea The Calcinea are a subclass of the calcareous sponges. Its phylum is Porifera and class is Calcarea. Branching is usually dichotomous or umbellate with anastomoses An anastomosis (, plural anastomoses) is a connection or opening between tw ...

** Order

Clathrinida The Clathrinida are an order of calcareous sponges found in marine environments. These sponges have an asconoid structure and lack a true dermal membrane or cortex. The spongocoel is lined with choanocytes Choanocytes (also known as "collar ce ...

** Order

Murrayonida The Murrayonida are an order of sea sponges in the subclass Calcinea. Taxonomy The order consists of four known species, in three families: Family Murrayonidae Dendy & Row, 1913 * '' Murrayona phanolepis'' Kirkpatrick, 1910 - discovered by ...

* Subclass

Calcaronea Calcaronea is a Class (biology), subclass of sea sponges in the class Calcarea. They are Calcarea with the triactines and the basal system of tetractines sagittal (i.e. the rays of the spicule make unequal angles with each other), exceptionally r ...

** Order

Baerida Baerida is an order of sea sponges in the subclass of Calcaronea, first described in 2000 by Radovan Borojevic, Nicole Boury-Esnault and Jean Vacelet Jean Vacelet is a French marine biologist who specialises in the underwater fauna of the Medit ...

** Order

Leucosolenida Leucosolenida is an order of 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 cha ...

** Order

Lithonida Minchinellidae is a family of calcareous sponges in the order Calcarea. It is the only family in the monotypic class Lithonida. Description Calcaronea with reinforced skeleton consisting either of linked or cemented basal actines of tetract ...

** Order Pharetronida† Clathrina clathrus Scarpone 055

References

External links

UCMP: Calcarea
{{Taxonbar, from=Q209924 Taxa named by James Scott Bowerbank