Pestarella tyrrhena
Encyclopedia
Pestarella tyrrhena is a species
of thalassinidea
n crustacean
(ghost shrimp or mud shrimp) which grows to a length of 70 mm (2.8 in). It lives in burrow
s in shallow sandy parts of the sea-bed in the Mediterranean Sea
and northern Atlantic Ocean
. It is the most common thalassinidean in the Mediterranean, and has been used as bait
by fishermen
for at least 200 years.
apart from two large, unequal claw
s. It is whitish or greenish-grey, with pink or blue spots. Because of its burrowing lifestyle, P. tyrrhena has small eyes on short stalks, and its maxillipeds can form an operculum
; the telson
is very short, and the rostrum
is almost entirely absent.
Larval
development is rapid and involves few stages. Eggs
hatch into a zoeal stage, which is followed by a second zoea and then a megalopa 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
ic larvae. Larval development is retarded by low salinities and aided by warmer temperatures, giving P. tyrrhena a shorter reproductive season in the north of its range than in the south.
, and is found throughout the Mediterranean
as well as in the Atlantic Ocean
from Mauritania
and the Canary Islands
north to Ireland
, in the Kattegat
, and in the North Sea
as far as southern Norway
. Related species occur in the Black Sea
, and P. tyrrhena avoids water of low salinity, such as estuaries
and the Baltic Sea
.
The burrows of P. tyrrhena may be up to 62 centimetres (24.4 in) deep. They comprise a spiral central shaft up to 20 mm wide, with one or more shallow U–shaped shafts (up to 11 mm or 0.433070866141732 in 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
. The overall volume of the burrow may reach 300 millilitre (2.70002700027E-08 imp fl oz). New tunnels are continually opened and old ones filled in. P. tyrrhena feeds directly on the sediment, and receives nutrition from the debris collected in the debris chambers, as well as from the foraminifera
ns and algae
which live on the walls of the burrow. The activity of P. tyrrhena leads the walls of the burrow to be enriched with three times the ambient number of nematode
s and more than 100 times the number of foraminiferans in the surrounding sediments.
P. tyrrhena is parasitised
by the isopod Ione thoracica and the barnacle
Parthenopea subterranea.
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 thalassinidea
Thalassinidea
Thalassinidea is an 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 , frequently used as bait for estuarine fishing; elsewhere, however, they are...
n crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
(ghost shrimp or mud shrimp) which grows to a length of 70 mm (2.8 in). It lives in burrow
Burrow
A burrow is a hole or tunnel dug into the ground by an animal to create a space suitable for habitation, temporary refuge, or as a byproduct of locomotion. Burrows provide a form of shelter against predation and exposure to the elements, so the burrowing way of life is quite popular among the...
s in shallow sandy parts of the sea-bed in the Mediterranean Sea
Mediterranean Sea
The Mediterranean Sea is a sea connected to the Atlantic Ocean surrounded by the Mediterranean region and almost completely enclosed by land: on the north by Anatolia and Europe, on the south by North Africa, and on the east by the Levant...
and northern Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
. It is the most common thalassinidean in the Mediterranean, and has been used as bait
Bait (luring substance)
Bait is any substance used to attract prey, e.g. in a mousetrap.-In Australia:Baiting in Australia refers to specific campaigns to control foxes, wild dogs and dingos by poisoning in areas where they are a problem...
by fishermen
Fisherman
A fisherman or fisher 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 fishermen and fish farmers. The term can also be applied to recreational fishermen and may be used to describe both men...
for at least 200 years.
Description
P. tyrrhena is a small crustacean, up to 70 millimetres (2.8 in) long, with a soft exoskeletonExoskeleton
An exoskeleton is the external skeleton that supports and protects an animal's body, in contrast to the internal skeleton of, for example, a human. In popular usage, some of the larger kinds of exoskeletons are known as "shells". Examples of exoskeleton animals include insects such as grasshoppers...
apart from two large, unequal claw
Claw
A claw is a curved, pointed appendage, found at the end of a toe or finger in most mammals, birds, and some reptiles. However, the word "claw" is also often used in reference to an invertebrate. Somewhat similar fine hooked structures are found in arthropods such as beetles and spiders, at the end...
s. It is whitish or greenish-grey, with pink or blue spots. Because of its burrowing lifestyle, P. tyrrhena has small eyes on short stalks, and its maxillipeds can form an operculum
Operculum
Operculum may refer to:*Operculum , a stiff structure resembling a lid or a small door that opens and closes**Operculum , a lid on the shell of some gastropods**Operculum , a lid on the orifice of some bryozoans...
; the telson
Telson
The telson is the last division of the body of a crustacean. It is not considered a true segment because it does not arise in the embryo from teloblast areas as do real segments. It never carries any appendages, but a forked "tail" called the caudal furca is often present. Together with the...
is very short, and the rostrum
Rostrum (anatomy)
The term rostrum is used for a number of unrelated structures in different groups of animals:*In crustaceans, the rostrum is the forward extension of the carapace in front of the eyes....
is almost entirely absent.
Larval
Crustacean larvae
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...
development is rapid and involves few stages. Eggs
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
hatch into a zoeal stage, which is followed by a second zoea and then a megalopa 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
Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...
ic larvae. Larval development is retarded by low salinities and aided by warmer temperatures, giving P. tyrrhena a shorter reproductive season in the north of its range than in the south.
Distribution and ecology
P. tyrrhena was first described from the Tyrrhenian SeaTyrrhenian Sea
The Tyrrhenian Sea is part of the Mediterranean Sea off the western coast of Italy.-Geography:The sea is bounded by Corsica and Sardinia , Tuscany, Lazio, Campania, Basilicata and Calabria and Sicily ....
, and is found throughout the Mediterranean
Mediterranean Sea
The Mediterranean Sea is a sea connected to the Atlantic Ocean surrounded by the Mediterranean region and almost completely enclosed by land: on the north by Anatolia and Europe, on the south by North Africa, and on the east by the Levant...
as well as in the Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
from Mauritania
Mauritania
Mauritania is a country in the Maghreb and West Africa. It is bordered by the Atlantic Ocean in the west, by Western Sahara in the north, by Algeria in the northeast, by Mali in the east and southeast, and by Senegal in the southwest...
and the Canary Islands
Canary Islands
The Canary Islands , also known as the Canaries , is a Spanish archipelago located just off the northwest coast of mainland Africa, 100 km west of the border between Morocco and the Western Sahara. The Canaries are a Spanish autonomous community and an outermost region of the European Union...
north to Ireland
Ireland
Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...
, in the Kattegat
Kattegat
The Kattegat , or Kattegatt is a sea area bounded by the Jutland peninsula and the Straits islands of Denmark on the west and south, and the provinces of Västergötland, Scania, Halland and Bohuslän in Sweden on the east. The Baltic Sea drains into the Kattegat through the Øresund and the Danish...
, and in the North Sea
North Sea
In the southwest, beyond the Straits of Dover, the North Sea becomes the English Channel connecting to the Atlantic Ocean. In the east, it connects to the Baltic Sea via the Skagerrak and Kattegat, narrow straits that separate Denmark from Norway and Sweden respectively...
as far as southern Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
. Related species occur in the Black Sea
Black Sea
The Black Sea is bounded by Europe, Anatolia and the Caucasus and is ultimately connected to the Atlantic Ocean via the Mediterranean and the Aegean seas and various straits. The Bosphorus strait connects it to the Sea of Marmara, and the strait of the Dardanelles connects that sea to the Aegean...
, and P. tyrrhena avoids water of low salinity, such as estuaries
Estuary
An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea....
and the Baltic Sea
Baltic Sea
The Baltic Sea is a brackish mediterranean sea located in Northern Europe, from 53°N to 66°N latitude and from 20°E to 26°E longitude. It is bounded by the Scandinavian Peninsula, the mainland of Europe, and the Danish islands. It drains into the Kattegat by way of the Øresund, the Great Belt and...
.
The burrows of P. tyrrhena may be up to 62 centimetres (24.4 in) deep. They comprise a spiral central shaft up to 20 mm wide, with one or more shallow U–shaped shafts (up to 11 mm or 0.433070866141732 in 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
Seagrass
Seagrasses are flowering plants from one of four plant families , all in the order Alismatales , which grow in marine, fully saline environments.-Ecology:...
. The overall volume of the burrow may reach 300 millilitre (2.70002700027E-08 imp fl oz). New tunnels are continually opened and old ones filled in. P. tyrrhena feeds directly on the sediment, and receives nutrition from the debris collected in the debris chambers, as well as from the foraminifera
Foraminifera
The Foraminifera , or forams for short, are a large group of amoeboid protists which are among the commonest plankton species. They have reticulating pseudopods, fine strands of cytoplasm that branch and merge to form a dynamic net...
ns and algae
Algae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...
which live on the walls of the burrow. The activity of P. tyrrhena leads the walls of the burrow to be enriched with three times the ambient number of nematode
Nematode
The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...
s and more than 100 times the number of foraminiferans in the surrounding sediments.
P. tyrrhena is parasitised
Parasitism
Parasitism is a type of symbiotic relationship between organisms of different species where one organism, the parasite, benefits at the expense of the other, the host. Traditionally parasite referred to organisms with lifestages that needed more than one host . These are now called macroparasites...
by the isopod Ione thoracica and the barnacle
Barnacle
A barnacle is a type of arthropod belonging to infraclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in erosive settings. They are sessile suspension feeders, and have...
Parthenopea subterranea.