Janua pagenstecheri
Encyclopedia
Janua pagenstecheri is a species
of marine polychaete
. It is widely distributed around the British Isles
and across north-western Europe, and has been described as "probably the commonest spirorbid in the world".
Janua pagenstecheri lives attached to substrates
such as seaweed
s including Corallina officinalis
, rocks, stones, shells, and the carapace
s of crab
s. J. pagenstecheri inhabits a shell made of calcium carbonate
in the form of a dextral spiral, with the tube up to 2 mm in diameter. The animal exists in two colour morphs: one bright yellow, which occurs in shallow water, and one much paler, which occurs in deeper water. It differs from Spirorbis spirorbis
in that S. spirorbis retains its eggs in the tube, while J. pagenstecheri incubates them a few at a time in its operculum, and grows a new cap for the operculum after releasing the embryos.
The species was described by Armand de Quatrefages
in 1865, and named after Heinrich Alexander Pagenstecher, professor of zoology
at the University of Heidelberg and the first director of the Hamburg natural history museum.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of marine polychaete
Polychaete
The Polychaeta or polychaetes are a class of annelid worms, generally marine. Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are made of chitin. Indeed, polychaetes are sometimes referred to as bristle worms. More than 10,000...
. It is widely distributed around the British Isles
British Isles
The British Isles are a group of islands off the northwest coast of continental Europe that include the islands of Great Britain and Ireland and over six thousand smaller isles. There are two sovereign states located on the islands: the United Kingdom of Great Britain and Northern Ireland and...
and across north-western Europe, and has been described as "probably the commonest spirorbid in the world".
Janua pagenstecheri lives attached to substrates
Substrate (biology)
In biology a substrate is the surface a plant or animal lives upon and grows on. A substrate can include biotic or abiotic materials and animals. For example, encrusting algae that lives on a rock can be substrate for another animal that lives on top of the algae. See also substrate .-External...
such as seaweed
Seaweed
Seaweed is a loose, colloquial term encompassing macroscopic, multicellular, benthic marine algae. The term includes some members of the red, brown and green algae...
s including Corallina officinalis
Corallina officinalis
Corallina officinalis is a calcareous red seaweed which grows in the lower and mid-littoral zones on rocky shores.It is primarily found growing around the rims of tide pools, but can be found in shallow crevices anywhere on the rocky shore that are regularly refreshed with sea water...
, rocks, stones, shells, and the carapace
Carapace
A carapace is a dorsal section of the exoskeleton or shell in a number of animal groups, including arthropods such as crustaceans and arachnids, as well as vertebrates such as turtles and tortoises. In turtles and tortoises, the underside is called the plastron.-Crustaceans:In crustaceans, the...
s of crab
Crab
True crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" , or where the reduced abdomen is entirely hidden under the thorax...
s. J. pagenstecheri inhabits a shell made of calcium carbonate
Calcium carbonate
Calcium carbonate is a chemical compound with the formula CaCO3. It is a common substance found in rocks in all parts of the world, and is the main component of shells of marine organisms, snails, coal balls, pearls, and eggshells. Calcium carbonate is the active ingredient in agricultural lime,...
in the form of a dextral spiral, with the tube up to 2 mm in diameter. The animal exists in two colour morphs: one bright yellow, which occurs in shallow water, and one much paler, which occurs in deeper water. It differs from Spirorbis spirorbis
Spirorbis spirorbis
Spirorbis spirorbis is a small coiled polychaete that lives attached to seaweeds and eel grass in shallow saltwater.They have a smooth, white, sinistral coiled shell encasing an orange body about 3 mm in length...
in that S. spirorbis retains its eggs in the tube, while J. pagenstecheri incubates them a few at a time in its operculum, and grows a new cap for the operculum after releasing the embryos.
The species was described by Armand de Quatrefages
Jean Louis Armand de Quatrefages de Bréau
Jean Louis Armand de Quatrefages de Bréau was a French naturalist.- Life :He was born at Berthézène, in the commune of Valleraugue , the son of a Protestant farmer. He studied medicine at Strasbourg, where he took the double degree of M.D...
in 1865, and named after Heinrich Alexander Pagenstecher, professor of zoology
Zoology
Zoology |zoölogy]]), is the branch of biology that relates to the animal kingdom, including the structure, embryology, evolution, classification, habits, and distribution of all animals, both living and extinct...
at the University of Heidelberg and the first director of the Hamburg natural history museum.