| Rossella | |
|---|---|
 | |
| Rossella veluta | |
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Porifera |
| Class: | Hexactinellida |
| Order: | Lyssacinosida |
| Family: | Rossellidae |
| Subfamily: | Rossellinae |
| Genus: | Rossella Carter, 1872 |
| Type species | |
| Rossella antarctica Carter, 1872 | |
| Species | |
See text. | |
| Synonyms [1] | |
| |
Rosella is a genus of glass sponges in the family Rossellidae. It is found in the Antarctic and sub-Antarctic regions. [2]
Species are thick-walled saccular sponges. Calycocomes (six rayed spicules with secondary rays emanating from a solid calyx) are always present. They are often accompanied by spherical discohexactines (six rayed spicules with secondary rays ending as small discs), mesodiscohexasters (microscleres with primary rays that are rearranged by fusion to form eight compound primary rays situated at the corners of a cube. Secondary rays end as small discs) and microdiscohexasters (smaller forms of mesodiscohexasters). [2]
Dermalia (outer spicules of any size class) are usually pentactines, sometimes with stauractines (cross-like spicules with four perpendicular rays) and hexactines. Prostalia lateralia (large protruding spicules), when present, are monaxons (spicules with a single axis) and sometimes pentactines. The hypodermal pentactine spicules (spicules with five rays) may be differentiated into spicules with claw-like ends, serving as a means of attachment to the substrate the sponge is growing on. They commonly have paratropal and orthotropal tangential rays. [2]
The choanosomal skeleton is made of diactines (two rayed spicule with rays aligned on the same axis), and rarely hexactines (spicule with six perpendicular rays). Atralia (spicules associated with the atrial cavity) are mainly hexactines, rarely with pentactines or diactines. [2]
Rossella species are abundant on the Antarctic shelf, where they may cover as much as half of the sea floor. [3] As such, they play an important role in forming the benthic communities of this region. They form biogenic structures, increasing the structural complexity of the sea floor of this region. This more heterogeneous space can be utilised by other species. [3]
A wide variety of invertebrate species also live within the sponge structure, including foraminiferans, polychaetes, amphipods, isopods, tanaids, copepods, ostracods, acari, pycnogonids, gastropods, bivalves, and nematodes. A sponge may host thousands of specimens and tens of species per 100 ml. [4]
The relationships between the species in this genus are not particularly well understood. The species composition has changed dramatically over the years, depending on which criteria are used. [3] The external forms of this genus are highly variable, even within a single species. [2] There is strong genetic evidence for a species flock in this genus, that is an accumulation of a large number of closely related species confined to a small area. [5] [3] These typically represent a rapid evolution of a dominant (and endemic) group in a region, resulting in many similar species. The current evidence suggests that this genus contains two clades corresponding to the well-defined species R. antarctica, and the diverse assemblage of species that has been termed the R. racovitzae flock. [3] More research is needed to understand how many species fall in this genus and how they are related.
The following species are, however, currently (October 2021) recognised: [1]
Minchinellidae is a family of calcareous sponges, members of the class Calcarea. It is the only family in the monotypic order Lithonida. The families Petrobionidae and Lepidoleuconidae have also sometimes been placed within Lithonida, though more recently they have been moved to the order Baerida. Thanks to their hypercalcified structure, minchinellids have a fossil record reaching as far back as the Jurassic Period.
Hexasterophora are a subclass of glass sponges in the class Hexactinellida. Most living hexasterophorans can be divided into three orders: Lyssacinosida, Lychniscosida, and Sceptrulophora. Like other glass sponges, hexasterophorans have skeletons composed of overlapping six-rayed spicules. In addition, they can be characterized by the presence of hexasters, a type of microsclere with six rays unfurling into multi-branched structures.
Chondrocladia is a genus of carnivorous demosponges of the family Cladorhizidae. Neocladia was long considered a junior synonym, but has recently become accepted as a distinct genus.
Lyssacinosida is an order of glass sponges (Hexactinellida) belonging to the subclass Hexasterophora. These sponges can be recognized by their parenchymal spicules usually being unconnected, unlike in other sponges in the subclass where the spicules form a more or less tightly connected skeleton. Lyssacine sponges have existed since the Upper Ordovician, and three families are still alive today. The Venus' flower basket is one of the most well-known and culturally significant of the glass sponges.
Spicules are structural elements found in most sponges. The meshing of many spicules serves as the sponge's skeleton and thus it provides structural support and potentially defense against predators.
Reticulosa is an extinct order of sea sponges in the class Hexactinellida and the subclass Amphidiscophora. Reticulosans were diverse in shape and size, similar to their modern relatives, the amphidiscosidans. Some were smooth and attached to a surface at a flat point, others were polyhedral or ornamented with nodes, many were covered in bristles, and a few were even suspended above the seabed by a rope-like anchor of braided glass spicules.
Clathrina broenstedi is a species of calcareous sponge from the Weddell Sea. The species is named after Holger Brøndsted, a Danish sponge researcher. The only spicules present in this species are triactines.
Euplectellidae is a family of glass sponges (Hexactinellids) belonging to the order Lyssacinosa, first represented in the Ordovician fossil record, substantially older than molecular estimates of the clade's age.
Rossellidae is a family of glass sponges belonging to the order Lyssacinosa. The family has a cosmopolitan distribution and is found at a large range of depths.
Caulophacus is a genus of glass sponges belonging to the subfamily Lanuginellinae.
Sceptrulophora is an order of hexactinellid sponges. They are characterized by sceptrules, a type of microsclere with a single straight rod terminating at a bundle of spines or knobs. An anchor- or nail-shaped sceptrule is called a clavule. A fork-shaped sceptrule, ending at a few large tines, is called a scopule. A broom-shaped sceptrule, ending at many small bristles, is called a sarule.
Aspidoscopulia is a genus of glass sponge in the family Farreidae.
Claviscopulia is a genus of glass sponge in the family Farreidae.
Lonchiphora is a genus of glass sponge in the family Farreidae.
Chonelasma is a genus of sea sponge in the family Euretidae.
Bolosoma is a genus of pedunculated siliceous sponges belonging to the family Euplectellidae. This genus lives in deep-sea environments and provides a habitat for a plethora of other benthic species, giving Bolosoma an incredibly important ecological role in the ecosystems it is a part of.
Infantella is a genus of demosponges in the family Coelospharidae. The species in this genus differ from those in other genera through having a single kind of diactinal megascleres and no mircoscleres. This genus contains 6 species.
Penares is a widely distributed genus of demosponges.
Tetilla is a genus of demosponges in the family Tetillidae. It is widely distributed. They are mainly found in deeper habitats.
Rossella antarctica is a relatively small species of glass sponge. It is widely distributed in the southern hemisphere, particularly in the Antarctic and sub-Antarctic regions.