''Clathrina lacunosa'' 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 ...

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 hav ...

from the

British Isles The British Isles are a group of islands in the North Atlantic Ocean off the north-western coast of continental Europe, consisting of the islands of Great Britain, Ireland, the Isle of Man, the Inner and Outer Hebrides, the Northern Isles, ...

. The species name means "having holes" and refers to the perforations found in the sides of the sponge. It is usually found on vertical solid surfaces at depths down to 220 m. It is distributed in the north-eastern Atlantic from the

Arctic The Arctic ( or ) is a polar regions of Earth, polar region located at the northernmost part of Earth. The Arctic consists of the Arctic Ocean, adjacent seas, and parts of Canada (Yukon, Northwest Territories, Nunavut), Danish Realm (Greenla ...

to the

Mediterranean The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the e ...

. It is a fairly common sponge but is often overlooked due to its small size.

Description

This is a distinctive sponge, globular on a long thin stem, resembling a tiny balloon on a string. It reaches a maximum length of 3 cm and is often much smaller than this. There is an osculum at the apex of the sponge. Sponge composed of an ovoid body of thin, tightly and regularly anastomosing tubes, and a solid peduncle without any choanoderm. Water-collecting tubes converge into one apical osculum. Colour white in ethanol and light beige when dried. Triactines from the clathroid body range from almost regular to parasagittal with straight actines. Close to the peduncle there are parasagittal spicules with the longest unpaired actine pointing towards the peduncle. The skeleton of the peduncle is composed of large diactines with a break on the middle, and parasagittal triactines with a very long unpaired actine and short paired actines. Irregular diactines of variable sizes are present at low numbers in the peduncle. All actines are cylindrical with slightly blunt to sharp points.

References

World Register of Marine Species entry
Clathrina Fauna of the Atlantic Ocean Animals described in 1842 {{calcarea-stub