''Gilvossius tyrrhenus'' (formerly ''Pestarella tyrrhena'') 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 ...

thalassinidea Thalassinidea is a former infraorder of decapod crustaceans that live in burrows in muddy bottoms of the world's oceans. In Australian English, the littoral thalassinidean ''Trypaea australiensis'' is referred to as the ''yabby'' (a term whic ...

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group can ...

(''ghost shrimp'' or ''mud shrimp'') which grows to a length of . It lives in burrows in shallow sandy parts of the sea-bed in the

Mediterranean Sea 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 ...

and northern

Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...

. It is the most common thalassinidean in the Mediterranean, and has been used as bait by

fishermen A fisher or fisherman is someone who captures fish and other animals from a body of water, or gathers shellfish. Worldwide, there are about 38 million commercial and subsistence fishers and fish farmers. Fishers may be professional or recreati ...

for at least 200 years.

Description

''G. tyrrhenus'' is a small crustacean, up to long, with a soft

exoskeleton An exoskeleton (from Greek ''éxō'' "outer" and ''skeletós'' "skeleton") is an external skeleton that supports and protects an animal's body, in contrast to an internal skeleton (endoskeleton) in for example, a human. In usage, some of the ...

apart from two large, unequal

claw A claw is a curved, pointed appendage found at the end of a toe or finger in most amniotes (mammals, reptiles, birds). Some invertebrates such as beetles and spiders have somewhat similar fine, hooked structures at the end of the leg or tarsus ...

s. It is whitish or greenish-grey, with pink or blue spots. Because of its burrowing lifestyle, ''G. tyrrhenus'' has small eyes on short stalks, and its

maxilliped An appendage (or outgrowth) is an external body part, or natural prolongation, that protrudes from an organism's body. In arthropods, an appendage refers to any of the homologous body parts that may extend from a body segment, including anten ...

s can form an operculum; the

telson The telson () is the posterior-most division of the body of an arthropod. Depending on the definition, the telson is either considered to be the final segment of the arthropod body, or an additional division that is not a true segment on accou ...

is very short, and the

rostrum Rostrum may refer to: * Any kind of a platform for a speaker: **dais **pulpit * Rostrum (anatomy), a beak, or anatomical structure resembling a beak, as in the mouthparts of many sucking insects * Rostrum (ship), a form of bow on naval ships * Ros ...

is almost entirely absent. Larval development is rapid and involves few stages.

Eggs Humans and human ancestors have scavenged and eaten animal eggs for millions of years. Humans in Southeast Asia had domesticated chickens and harvested their eggs for food by 1,500 BCE. The most widely consumed eggs are those of fowl, especial ...

hatch into a

zoea Crustaceans may pass through a number of larval and immature stages between hatching from their eggs and reaching their adult form. Each of the stages is separated by a moult, in which the hard exoskeleton is shed to allow the animal to grow. The ...

l stage, which is followed by a second zoea and then a

megalopa Crustaceans may pass through a number of larval and immature stages between hatching from their eggs and reaching their adult form. Each of the stages is separated by a moult, in which the hard exoskeleton is shed to allow the animal to grow. The ...

stage before adulthood. This rapid development allows the larvae to settle down into their adult habitat of relatively undisturbed muddy substrates, before they have travelled too far as

plankton Plankton are the diverse collection of organisms found in water (or air) that are unable to propel themselves against a current (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a crucia ...

ic larvae. Larval development is retarded by low salinities and aided by warmer temperatures, giving ''G. tyrrhenus'' a shorter reproductive season in the north of its range than in the south.

Distribution and ecology

''G. tyrrhenus'' was first described from the

Tyrrhenian Sea The Tyrrhenian Sea (; it, Mar Tirreno , french: Mer Tyrrhénienne , sc, Mare Tirrenu, co, Mari Tirrenu, scn, Mari Tirrenu, nap, Mare Tirreno) is part of the Mediterranean Sea off the western coast of Italy. It is named for the Tyrrhenian pe ...

, and is found throughout 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 Europe, Western and Southern Europe and Anatolia, on the south by North Africa ...

as well as in the

from Mauritania and the Canary Islands north to

Ireland Ireland ( ; ga, Éire ; Ulster Scots dialect, Ulster-Scots: ) is an island in the Atlantic Ocean, North Atlantic Ocean, in Northwestern Europe, north-western Europe. It is separated from Great Britain to its east by the North Channel (Grea ...

, in the

Kattegat The Kattegat (; sv, Kattegatt ) is a sea area bounded by the Jutlandic peninsula in the west, the Danish Straits islands of Denmark and the Baltic Sea to the south and the provinces of Bohuslän, Västergötland, Halland and Skåne in Sweden ...

, and in the

North Sea The North Sea lies between Great Britain, Norway, Denmark, Germany, the Netherlands and Belgium. An epeiric sea, epeiric sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the ...

as far as southern

Norway Norway, officially the Kingdom of Norway, is a Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of Jan Mayen and the ...

. Related species occur in the

Black Sea The Black Sea is a marginal mediterranean sea of the Atlantic Ocean lying between Europe and Asia, east of the Balkans, south of the East European Plain, west of the Caucasus, and north of Anatolia. It is bounded by Bulgaria, Georgia, Rom ...

, and ''G. tyrrhenus'' avoids water of low salinity, such as

estuaries An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environmen ...

and the

Baltic Sea The Baltic Sea is an arm of the Atlantic Ocean that is enclosed by Denmark, Estonia, Finland, Germany, Latvia, Lithuania, Poland, Russia, Sweden and the North and Central European Plain. The sea stretches from 53°N to 66°N latitude and ...

. The burrows of ''G. tyrrhenus'' may be up to deep. They comprise a spiral central shaft up to 20 mm wide, with one or more shallow U–shaped shafts (up to wide) which lead to the surface of the sediment where they emerge as holes or funnel–shaped depressions. These shafts may be linked by further sections, and a number of side–chambers are found filled with

seagrass Seagrasses are the only flowering plants which grow in marine environments. There are about 60 species of fully marine seagrasses which belong to four families (Posidoniaceae, Zosteraceae, Hydrocharitaceae and Cymodoceaceae), all in the or ...

. The overall volume of the burrow may reach . New tunnels are continually opened and old ones filled in. ''G. tyrrhenus'' feeds directly on the sediment, and receives nutrition from the debris collected in the debris chambers, as well as from the

foraminifera Foraminifera (; Latin for "hole bearers"; informally called "forams") are single-celled organisms, members of a phylum or class of amoeboid protists characterized by streaming granular ectoplasm for catching food and other uses; and commonly ...

ns and algae which live on the walls of the burrow. The activity of ''G. tyrrhenus'' leads the walls of the burrow to be enriched with three times the ambient number of nematodes and more than 100 times the number of foraminiferans in the surrounding sediments. ''G. tyrrhenus'' is parasitised by the isopod '' Ione thoracica'' and the barnacle '' Parthenopea subterranea''.

References

{{Taxonbar, from=Q2934123 Thalassinidea Crustaceans of the Atlantic Ocean Crustaceans described in 1792