Homosclerophorida is an order of marine
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 throu ...
s. It is the only order in the
monotypic class Homoscleromorpha. The order is composed of two families:
Plakinidae and
Oscarellidae.
Taxonomy
Homoscleromorpha is phylogenetically well separated from
Demospongiae. Therefore, it has been recognized as the fourth class of sponges.
It has been suggested that Homoscleromorpha are more closely related to eumetazoans than to the other sponge groups, rendering sponges paraphyletic.
[Sperling, Pisani and Peterson 2007, cited in: The Cambrian Explosion p. 80, Erwin and Valentine 2013] This view has not been supported by later work using larger datasets and new techniques for phylogenetic inference, which tend to support sponges as monophyletic, with Homoscleromorpha grouping together with
Calcarea.
On the basis of molecular and morphological evidence, the two families
Plakinidae and
Oscarellidae have been reinstated.
There are 117 species in this group divided into 9 genera.
The spiculate genera in this group are ''
Aspiculophora'', ''
Corticium'', ''
Placinolopha'', ''
Plakina'', ''
Plakinasterella'', ''
Plakortis'' and ''
Tetralophophora''.
The aspiculate species are the genera ''
Oscarella'' and ''
Pseudocorticium''.
Description
These sponges are massive or encrusting in form and have a very simple structure with very little variation in
spicule form (all spicules tend to be very small).
Reproduction
Reproduction (or procreation or breeding) is the biological process by which new individual organisms – "offspring" – are produced from their "parent" or parents. Reproduction is a fundamental feature of all known life; each individual or ...
is
viviparous
Among animals, viviparity is development of the embryo inside the body of the parent. This is opposed to oviparity which is a reproductive mode in which females lay developing eggs that complete their development and hatch externally from the ...
and the
larva
A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle.
...
is an oval form known as an
amphiblastula. This form is usual in
calcareous sponge
The calcareous sponges of class Calcarea are members of the animal phylum Porifera, the cellular sponges. They are characterized by spicules made of calcium carbonate in the form of calcite or aragonite. While the spicules in most species ha ...
s but is less common in other sponges.
Habitat
Homoscleromorpha are exclusively marine sponges that tend to encrust on other surfaces at shallow depths. These sponges typically inhabit shady locations, under overhangs and inside caves. In the Mediterranean Sea, 82% of the species in this taxon can be found in caves, and 41% of them are found nowhere else.
References
External links
What are sponges? Queensland MuseumSponge guide
Taxa named by Arthur Dendy
{{demosponge-stub