| Sycon raphanus | |
|---|---|
 | |
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Porifera |
| Class: | Calcarea |
| Order: | Leucosolenida |
| Family: | Sycettidae |
| Genus: | Sycon |
| Species: | S. raphanus |
| Binomial name | |
| Sycon raphanus Schmidt, 1862 | |
| Synonyms | |
List
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Sycon raphanus is a species of marine invertebrate, a calcareous sponge belonging to the family Sycettidae. The name derives from the Greek, "raphanus", meaning radish, and presumably refers to the sponge's shape.
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 sexes or mating types can produce fertile offspring, typically by sexual reproduction. Other ways of defining species include their karyotype, DNA sequence, morphology, behaviour or ecological niche. In addition, paleontologists use the concept of the chronospecies since fossil reproduction cannot be examined. While these definitions may seem adequate, when looked at more closely they represent problematic species concepts. For example, the boundaries between closely related species become unclear with hybridisation, in a species complex of hundreds of similar microspecies, and in a ring species. Also, among organisms that reproduce only asexually, the concept of a reproductive species breaks down, and each clone is potentially a microspecies.
The calcareous sponges of class Calcarea are members of the animal phylum Porifera, the cellular sponges. They are characterized by spicules made out of calcium carbonate in the form of calcite or aragonite. While the spicules in most species have three points, in some species they have either two or four points.
Family is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy; it is classified between order and genus. A family may be divided into subfamilies, which are intermediate ranks between the ranks of family and genus. The official family names are Latin in origin; however, popular names are often used: for example, walnut trees and hickory trees belong to the family Juglandaceae, but that family is commonly referred to as being the "walnut family".
Contents
Sponges are composed of a jellylike mesohyl sandwiched between two layers of cells. They have a fragile skeleton composed of stiff spicules. They are filter feeders, maintaining a flow of water through their structure which passes out through large openings called oscula.
The mesohyl, formerly known as mesenchyme or as mesoglea, is the gelatinous matrix within a sponge. It fills the space between the external pinacoderm and the internal choanoderm. The mesohyl resembles a type of connective tissue and contains several amoeboid cells such as amebocytes, as well as fibrils and skeletal elements. For a long time, it has been largely accepted that sponges lack true tissue, but it is currently debated as to whether mesohyl and pinacoderm layers are tissues.
Spicules are structural elements found in most sponges. They provide structural support and deter predators. Large spicules that are visible to the naked eye are referred to as megascleres, while smaller, microscopic ones are termed microscleres.
The osculum is an excretory structure in the living sponge, a large opening to the outside through which the current of water exits after passing through the spongocoel. Wastes diffuse into the water and the water is pumped through the osculum carrying away with it the sponge's wastes. Sponges pump large volumes of water; in general, a volume of water equal to the sponge's body size is pumped every five seconds. The size of the osculum is regulated by contractile myocytes. Its size, in turn, is one of the factors which determines the amount of water flowing through the sponge. It can be closed completely in response to excess silt in the water.
