The White-clawed Crayfish

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The importance of white-clawed crayfish

It has a key role in maintaining the balance of aquatic ecosystems, being able to influence the density and distribution of other organisms, through its omnivorous and bioturbatory behavior (reworking soils and sediments), as well as representing an important food source for fish, birds and mammals. These shellfish have also always been an important food resource for the local economies of many countries around the world.

Who is it?

Sistematica

Phylum: Arthropoda

Subphylum: Crustacea

Classe: Malacostraca

Ordine: Decapoda

Famiglia: Astacidae

Genere: Austropotamobius

Specie: Austropotamobius pallipes

Austropotamobius pallipes, has a rather robust appearance, can reach and exceed 12-13 cm in length from the tip of the rostrum to the telson (although in most cases it does not exceed 10 cm) and a weight of 90 grams. The colouring of the body can be brown, yellowish-brown or greenish-brown on the back and sides, while the belly and limbs are whitish. The claws have an irregular internal margin and the ventral part is white.

It has ten appendices, organized into five pairs; the first pair consists of two large claws suitable for offense and defense, the following two pairs end with small claws designed to bring food to the mouth, while the last two pairs end with a pointed structure, called dactylopodite, acting mainly as displacement appendages.

The body of the white –clawded cryfish, Austropotamobius pallipes, has the external skeleton or exoskeleton made up of chitin, a protein substance that gives the membranous coating a horny consistency. The presence of a sclerified exoskeleton provides protection to the internal organs, support as well as facilitating the locomotion of the animal, but does not allow its growth. Therefore, in order to grow, the shrimp must get rid of the old carapace and form a new coating; this phenomenon is called molting or ecdysis and is hormonally regulated. Body growth is limited to the short periods in which it is soft enough to expand, i.e. in the period immediately following the moult.

Where does It live

Austropotamobius pallipes  is widespread throughout the Western portion of the European continent, including Great Britain and Ireland. It is absent in Scandinavia and the southern Balkans. In Italy the species is present throughout the peninsula, it is reported in Sardinia while it is absent in Sicily.

The crayfish, A. pallipes, is the most common indigenous species in Italy.

Threats

 The state of indigenous freshwater crayfish in Italy is seriously compromised, due to the multiplication of threats to their survival, largely associated with the growing anthropization of hydrographic systems in its various forms that has occurred in the last 60 years.

At the end of the 19th century, the state of freshwater crayfish in Italy was already seriously compromised. From 1999 to 2009, 74% of decline was documented in Italy The causes of its rarefaction are manifold and mainly related to anthropic activities: drainage and canalization works; transformation of some rivers into navigable canals; barriers of waterways (dams, locks, etc.); excessive withdrawals and waste of water for industrial, agricultural and civil use; hot water discharges linked to the production of electricity; industrial and urban waste; drought, poaching, fish sowing, acidification of water and deliberate or accidental release of alien species with their parasitic load.