Crayfish

The linguistic-cultural image of the Polish rak ‘crayfish’
The article attempts to reconstruct the Polish linguo-cultural image of rak ‘crayfish’ (Astacus astacus). Following the model of Dictionary of Folk Stereotypes and Symbols, the data taken into account include the word’s etymology, its lexicographic treatment (including phraseology) in dictionaries of contemporary Polish, in dialectal dictionaries and in dictionaries of former stages of Polish, texts of folklore, and ethnographic accounts. The following definition of the crayfish has been proposed accordingly: “The crayfish (rak) is a small, hairless and featherless animal of little value, its body being protected by
a carapace. It has long antennae, two prehensile and sharp chelipeds that are used for
protection, many legs and eyes located in the back of the body. It lives in water (rivers
and ponds), in holes it builds for itself. It isn’t known where it spends the winter. It can pinch, moves backwards in an ungainly and slow manner, makes no sound and kills its victims by biting into their bodies. It is closest to fish. Crayfish are sought for their meat, of which they have very little – they are then roasted or cooked. They are considered
exquisite food. Parts of the crayfish’s body are used as medicine for various ailments. The crayfish is thought to be connected with the underworld”.

This research was conducted to evaluate the nutrient content of Astacus leptodactylus in various populations in the lakes Iznik and Egirdir, as well as in Hirfanlı Dam Lake and Keban Dam Lake, all in Turkey. Crayfish meat yield ranged from a minimum of 11.3% to a maximum of 16.3% of wet weight in specimens from Keban and Iznik, respectively. Meat yield was significantly different, depending on the living environment. The protein content of the meat of A. leptodactylus ranged from 15.4 to 17.5%. The moisture content of crayfish was significantly lower in the high lipid containing Iznik Lake's crayfish. Crayfish lipids were poor in saturated fatty acids, but rich in PUFA's and in particular EPA, DHA and ARA. In all groups, the major saturated fatty acids were palmitic acid, stearic acid and myristic acid. Among the omega-6 fatty acid series, a high level of ARA was observed in crayfish meat. EPA may be considered as the major omega-3 fatty acid in crayfish lipids. There was no single fatty acid indicating regional differences in crayfish specimens. RÉSUMÉ Ce travail a été conduit pour évaluer la teneur en éléments nutritifs de Astacus leptodactylus dans différentes populations des lacs Iznik et Egidir et des lacs de barrage Hirfan1 et Keban, tous en Turquie. Le contenu en chair des écrevisses va d'un minimum de 11,3% à un maximum de 16,3% du poids frais dans les spécimens de, respectivement, Keban et Iznik. Le taux de chair a été significativement différent, en fonction du milieu de vie. Le contenu en protéine de la chair d' A. leptodactylus va de 15,4 à 17,5%. La teneur en eau des écrevisses a été significativement plus basse chez les écrevisses riches en lipides du lac Iznik. Les lipides étaient pauvres en acides gras saturés, mais riches en PUFA et en particulier EPA, DHA et ARA. Dans tous les groupes, les acides

The sale of crayfish in the pet trade has increased in recent decades, and a substantial fraction of the world's entire range of crayfish species is available in the pet trade. The market for pet crayfish creates two major concerns: the potential for over exploitation of natural populations of crayfish to supply the pet trade, and the negative consequences resulting from the release of non-indigenous crayfish into natural habitats. The chain from the source of crayfish to the final owner can be lengthy, and each step in the supply chain needs to be studied by different methods. While there are often regulations intended to limit the trade of crayfish as pets, they differ widely from place to place and seem to have limited success in changing the behaviour of owners of pet crayfish.

The pet trade is a significant source of introductions of non-indigenous aquatic species, such as crayfish. To test whether legislation that regulates the ownership of ornamental animals for aquariums had the desired effect of reducing the availability of those pets, classified advertising websites were monitored for sales of crayfish in jurisdictions with and without legislation regulating the ownership of crayfish. Advertisements from Canadian provinces with legislation against owning crayfish were compared to provinces without such legislation. The population adjusted number of advertisements for crayfish, and number of distinct sellers of crayfish, was significantly lower in one of two provinces that prohibited crayfish compared to provinces that permitted crayfish. This mixed outcome suggests that legislation alone does not consistently reduce online trade in crayfish.

Herbivory is a fundamental process that controls primary producer abundance and regulates energy and nutrient flows to higher trophic levels. Despite the recent proliferation of small-scale studies on herbivore effects on aquatic plants, there remains limited understanding of the factors that control consumer regulation of vascular plants in aquatic ecosystems. Our current knowledge of the regulation of primary producers has hindered efforts to understand the structure and functioning of aquatic ecosystems, and to manage such ecosystems effectively. We conducted a global meta-analysis of the outcomes of plant–herbivore interactions using a data set comprised of 326 values from 163 studies, in order to test two mechanistic hypotheses: first, that greater negative changes in plant abundance would be associated with higher herbivore biomass densities; second, that the magnitude of changes in plant abundance would vary with herbivore taxonomic identity. We found evidence that plant abundance declined with increased herbivore density, with plants eliminated at high densities. Significant between-taxa differences in impact were detected, with insects associated with smaller reductions in plant abundance than all other taxa. Similarly, birds caused smaller reductions in plant abundance than echinoderms, fish, or molluscs. Furthermore, larger reductions in plant abundance were detected for fish relative to crustaceans. We found a positive relationship between herbivore species richness and change in plant abundance, with the strongest reductions in plant abundance reported for low herbivore species richness, suggesting that greater herbivore diversity may protect against large reductions in plant abundance. Finally, we found that herbivore–plant nativeness was a key factor affecting the magnitude of herbivore impacts on plant abundance across a wide range of species assemblages. Assemblages comprised of invasive herbivores and native plant assemblages were associated with greater reductions in plant abundance compared with invasive herbivores and invasive plants, native herbivores and invasive plants, native herbivores and mixed-nativeness plants, and native herbivores and native plants. By contrast, assemblages comprised of native herbivores and invasive plants were associated with lower reductions in plant abundance compared with both mixed-nativeness herbivores and native plants, and native herbivores and native plants. However, the effects of herbivore–plant nativeness on changes in plant abundance were reduced at high herbivore densities. Our mean reductions in aquatic plant abundance are greater than those reported in the literature for terrestrial plants, but lower than aquatic algae. Our findings highlight the need for a substantial shift in how biologists incorporate plant–herbivore interactions into theories of aquatic ecosystem structure and functioning. Currently, the failure to incorporate top-down effects continues to hinder our capacity to understand and manage the ecological dynamics of habitats that contain aquatic plants.

The import of aquarium animals has been increasing worldwide in recent years. Despite its contribution to world trade and the economy, this trade also comprises one of the main pathways for the introduction of non-indigenous animals. In the past decade, crayfish has become a popular
pet as well as a potential threat to the environment upon its escape or release. Since the Czech Republic is one of the world’s leading importer, exporter, and producer of aquatic ornamental animals, we prepared a detailed analysis of crayfish imports. The present paper provides a complete
list of countries supplying ornamental crayfish and examines trends of their prices and imported quantities during the past decade (2003–2012). Indonesia has been identified as the leading supplier in recent years. The annual average price of imported crayfish has varied over the evaluated
period within the range of c0.76–4.72 per individual and it is rising annually by c0.15. The quantity of live crayfish imported for aquarium purposes has not been affected significantly by the price per individual and it has
grown rapidly. Therefore a constant monitoring of this pet trade sector is strongly recommended for the future.

The effects of dietary calcium chloride (CaCl 2) concentration on the growth, survival, moulting and body composition of Astacus leptodactylus were studied. Diets were prepared using supplementation of 0 (control), 30, 60 and 120 g kg À1 calcium chloride commercial trout larvae diet containing 50% protein and 12% lipid. Astacus leptodacty-lus larvae with an average total length of 22.0 AE 0.05 mm (TL) and weight of 0.53 AE 0.01 g obtained from eighteen ovigerous females collected from Seydisehir Sugla Dam lake in Konya, Turkey, were stocked in 0.2-m 2 aquariums at a rate of 50 crayfish m À2 and reared for 90 days. The experiments included four treatments (diets) with three replicates each. Calcium chloride exerted positive effects on growth, moulting frequency, feed efficiency and survival of narrow-clawed crayfish. Crayfish fed with 60 g calcium kg À1 calcium chloride-supplemented diet exhibited the highest weight gain and specific growth rate (SGR) but the lowest survival rate (63.3%) (P < 0.05). There were no significant differences (P > 0.05) in mean moisture (803.5 g kg À1) and protein content (177.0 g kg À1) in crayfish tail meat. However, lipid values were between 3.8 and 11.6 g kg À1 and significantly different among the diets (P < 0.05). Diet with 60 g kg À1 calcium chloride is recommended for the best growth of freshwater crayfish.

In the recent volume of collected essays ‘Ancient Fishing and Fish Processing in the Black Sea region’, edited by Prof. Tønnes Bekker-Nielsen (2005) the crayfish, or the common, European lobster are neglected despite their significance in the ancient diets. Since Carl Linnaeus (1758) the specie is classified as homarus gammarus/ europeus / vulgaris.
However, this saltwater crustacean has a wide distribution area in the Eastern Atlantic, the entire Mediterranean, and the Black Sea, and has an important nutrition and economic role. It is still a highly esteemed food source and is fished throughout its range, fetching high prices.
In real life it may grow to a length of 60 cm and an average mass of 1 kg, can live more than 100 years and bears a conspicuous pair of claws. Crayfish is found within the continental shelf to depths of 150 m, though is more common at depths above 50 m within rocky substrates, but may also burrow into cohesive mud or form depressions in sand, using rocky reefs for shelter. From a dietary point of view the crayfish provides the highest level in proteins and minerals (by weight), more than any other type of fish or marine animals, surpassing the nutritional value of milk, and particularly calcium.
The Mediterranean crayfish is well described by the ancient authors (Aristotle, Historiae Animalium, 530a 30-33; Aelian, De Natura Animalium, 4.10; Varro, 3.11.3; Columella, 8.15.6; Mart. 2.43.12; Iuven. 5.84; Pliny, HN 27.9, 32.148).
A city in Bithynia was named after the crayfish – Ἀστακός / Astacus (Strabo 12.4.2).
As this paper will demonstrate, the crayfish occurred to be significant for the Western Euxine and Propontic coasts, in particular for Apollonia Pontika in Thrace and Astakos in Bithynia, since it is constantly shown on their coins for nearly 200 years as a city-emblem. It also frequently appears on the coinages of a number of cities in Magna Graecia, such as Akragas, Himera, Selinus, Panormos, Solus and Tarent in the 5th and 4th century BC.

Background: The noble crayfish (Astacus astacus) displays a complex historical and contemporary genetic status in Europe. The species divergence has been shaped by geological events (i.e. Pleistocene glaciations) and humanly induced impacts (i.e. translocations, pollution, etc.) on its populations due to species commercial value and its niche degradation. Until now, limited genetic information has been procured for the Balkan area and especially for the southernmost distribution of this species (i.e. Greece). It is well known that the rich habitat diversity of the Balkan Peninsula offers suitable conditions for genetically diversified populations. Thus, the present manuscript revisits the phylogenetic relationships of the noble crayfish in Europe and identifies the genetic make-up and the biogeographical patterns of the species in its southern range limit. Results: Mitochondrial markers (i.e. COI and 16S) were used in order to elucidate the genetic structure and diversity of the noble crayfish in Europe. Two of the six European haplotypic lineages, were found exclusively in Greece. These two lineages exhibited greater haplotypic richness when compared with the rest four (of "Central European" origin) while they showed high genetic diversity. Divergence time analysis identified that the majority of this divergence was captured through Pleistocene, suggesting a southern glacial refugium (Greece, southern Balkans). Furthermore, six microsatellite markers were used in order to define the factors affecting the genetic structure and demographic history of the species in Greece. The population structure analysis revealed six to nine genetic clusters and eight putative genetic barriers. Evidence of bottleneck effects in the last ~5000 years (due to climatic and geological events and human activities) is also afforded. Findings from several other research fields (e.g. life sciences, geology or even archaeology) have been utilized to perceive the genetic make-up of the noble crayfish.

Ireland is one of the few locations in Europe where non-indigenous North American crayfish species have not been introduced, and is a refuge for endangered white-clawed crayfish, Austropotamobius pallipes (Lereboullet, 1858). The parthenogenetic crayfish species Marmorkrebs, Procambarus fallax f. virginalis (Hagen, 1870), is sold in the pet trade in Ireland within the recorded range of A. pallipes. Marmorkrebs risk being introduced into Irish waters, where they could threaten A. pallipes populations, particularly as a vector for crayfish plague.

The article attempts to reconstruct the linguacultural image of the Polish rak 'crayfish' (Astacus astacus). Following the model adopted in the Dictionary of Folk Stereotypes and Symbols, the relevant data include the word's etymology, its lexicographic treatment (including phraseology) in dictionaries of contemporary Polish, in dialectal dictionaries and in dictionaries of former stages of Polish, texts of folklore, and ethnographic accounts. The following definition of the crayfish has been proposed accordingly: " The crayfish (rak) is a small, hairless and featherless animal of little value, its body being protected by a carapace. It has long antennae, two prehensile and sharp pincers that are used for protection, many legs, and eyes located in the back of the body. It lives in water (rivers and ponds), where it digs holes. It is unknown where it spends the winter. It can pinch, moves backwards in an ungainly and slow manner, makes no sound and kills its victims by biting into their bodies. It is closest to fish. Crayfish are sought for their meat, of which they have very little – they are roasted or boiled. Crayfish are considered exquisite food. Parts of the crayfish's body are used as medicine for various ailments. The crayfish is thought to be connected with the underworld " .

The pathogenic chytrid fungus Batrachochytrium dendrobatidis (Bd) has been linked to global declines and extinctions of amphibians, making it one of the most devastating wildlife pathogens known.  Understanding the factors that affect disease dynamics in this system is critical for mitigating infection and protecting threatened species.  Crayfish are hosts of this pathogen and can transmit Bd to amphibians.  Because they co-occur with susceptible amphibian communities, crayfish may be important alternative hosts for Bd.  Understanding the prevalence and seasonal dynamics of crayfish infections is of agricultural and ecological interest in areas where crayfish are farmed and traded for human consumption.  We conducted a survey of Bd in farmed and natural crayfish (Procambarus spp.) populations in Louisiana, United States.  We found that Bd prevalence and infection intensity was low in both farmed and native populations, and that prevalence varied seasonally in wild Louisiana crayfish.  This seasonal pattern mirrors that seen in local amphibians.  As crayfish are an important globally traded freshwater taxon, even with low prevalence, they could be an important vector in the spread of Bd.

The parthenogenetic marbled crayfish, or Marmorkrebs (Procambarus virginalis Lyko 2017), is an emerging model organism. We describe a method to isolate cells from early-stage embryos and culture them in vitro. The identity of the cells was confirmed by sequencing the cyto-chrome c oxidase subunit I (COI) gene. This technique can be applied for use in the manipulation of embryonic parthenogenetic crayfish cells.

Introductions of non-native crayfish around the world are increasingly tied to the distribution, sale, and eventual release of pet crayfish. As part of risk assessment for the introduction of non-native crayfish in North America, I monitored the sale of crayfish on an auction website that specializes in aquatic pets and aquarium supplies for a year. Three species accounted for the majority of sales: the parthenogenetic crayfish, Marmorkrebs (Procambarus fallax f. virginalis), the Cajun dwarf crayfish (Cambarellus shufeldtii), and the orange morph of the endangered Mexican
dwarf crayfish (Cambarellus patzcuarensis). Almost half of individual crayfish sold (48.5%) were Marmorkrebs, which is more than twice as many as C. shufeldtii, the second most commonly sold species. The Louisiana red swamp crayfish (Procambarus clarkii) was often offered for auction, but was bought much less often than the other three species. About 11% of P. clarkii auctions were successful, while more than 45% of auctions were successful for the other three. Four Cherax species were the only crayfish sold online whose native range was outside North America. Neither Marmorkrebs nor the orange morph of C. patzcuarensis can be collected regularly from natural habitats in North America, suggesting that most crayfish sold online in North America are obtained from existing stocks in the pet trade, rather than being collected from natural habitats.