Respiration in relation to ion uptake in the crayfish Austropotamobius pallipes (Lereboullet).

1. O2 uptake was determined for periods of 23-46 h in salt-depleted crayfish held in deionized water (DW) or Na-free media at 10 degrees C. These media were replaced by artificial lakewater media (ALW) containing 0-2-0-6 mM Na and O2 uptake was again determined for periods of 24-66 h. 2. During net ion uptake in ALW the metabolic rate was either elevated or depressed. Standard metabolism in ALW altered by amounts equivalent to 0-1 - 15-5% (mean 6-4 (15) +/- 4-4% S. D.) of the metabolic rate measured during salt-depletion. On three occasions the metabolic rate was elevated by 22-0 - 66-7%, but some of this increase may have been due to locomotor activity. 3. The calculated values for thermodynamic work involved in ion transport were 0-056 - 0-268 J/10 g. h at 10 degrees C, or 1-5 - 7-2% of the mean standard metabolic rate. Most of the observed changes in metabolic rate lie within the limits of experimental error (ca. +/- 7%). Hence the energetic cost of ion transport is too small for direct measurement in intact crayfish.     

Ultrastructure and ion transport in gill epithelium of the crayfish,Astacus leptodactylus Esch

Summary Active ion transport against a high electrochemical potential gradient occurs across the epithelium of the gill processes of crayfish. The transport occurs in a thin sheet of cytoplasm underlying cuticula. This cytoplasm is supplied with irregular microvilli on the apical side. The basal plasma membrane invaginates into the cytoplasm forming a dense membrane system which is in close contact with numerous elongated mitochondria. The cytoplasm of the adhering cells is divided by a septated desmosome. It is suggested that the infolded membranes are the main place of ion transport and the close contact of mitochondria with them supplies the optimal energetic conditions for transport.Abbreviations ATP Adenosine-5-triphosphate - ADP adenosine-5-diphosphate     

Mitochondrial DNA variation and population genetic structure of the white-clawed crayfish, Austropotamobius pallipes pallipes

Here we report a high level of mtDNA variationfrom RFLP analysis within A. p. pallipes from 21 French and 4British populations. Seventeen haplotypes were recorded among 269individuals. Nucleotide sequence divergence (p) among mtDNAhaplotypes ranged from 0.0019 to 0.0425. Nucleotide diversity ()ranged from 0.01 to 0.006 (mean = 0.0031) and from 0 to 0.001(mean = 0.00037) for populations located in southern and northernFrance, respectively. Graphical representation from principalcoordinate analysis based on Nei's genetic distance values amongpopulations showed two groups, cluster A, including the 16populations sampled in the north-western and north-easternFrance, England and Wales and cluster B containing 9 populationssampled in the central and southern of France. No geneticdifferences were noted among the most northern French and Englishpopulations whereas marked interpopulation genetic diversity wasobserved in southern populations. Such genetic heterogeneityamong populations of A. p. pallipes appears to be related tohabitat fragmentation and subsequent recolonizations fromrefugial areas during the Pleistocene. Implications for theconservation of A. p. pallipes are discussed.     

The distribution of the crayfish, Austropotamobius pallipes, in British waters

SUMMARY. The distribution of Austropotamobius pallipes , the only freshwater crayfish indigenous to the British Isles, is examined using over 300 records collected since 1970. The majority of records are for England where crayfish are found in areas associated with base-rich easily weathered substrata. Waters containing crayfish tend to be in the pH range 7–9, with calcium levels above 5 mg l⁻¹. Crayfish are found in a wide variety of habitats ranging from deep water-filled quarries with a soft substratum to shallow fast-flowing streams.     

Ontogeny of osmoregulation in the crayfish Astacus leptodactylus

Osmoregulation was studied during the postembryonic development of Astacus leptodactylus Eschscholtz 1823 in juvenile stages 1-8 and in adults. Juveniles hatch and later stages develop in freshwater or in moderately saline waters. The time of acclimation from freshwater to a saline medium increased from early juveniles to adults. At all stages, it was longer than in comparable stages of marine crustaceans, reflecting the high impermeability of the teguments to water and ions. All stages were able to hyperisoosmoregulate. In freshwater, the ability to hyperosmoregulate was established at hatching and increased during development. The hemolymph osmolality increased from 286 mosm kg-1 in stage 1 juveniles to 419 mosm kg-1 in adults. All stages also hyperregulated at low salinities (7 per thousand and 13 per thousand salinity) and were osmoconformers at higher salinities up to 21 per thousand salinity. The lowest isosmotic salinity tended to increase with the developmental stages. The ability to osmoregulate at hatch and throughout postembryonic development is probably a key physiological adaptation in this and other freshwater crayfish.     

An automatic respirometer for determining oxygen uptake in crayfish (Austropotamobius pallipes (Lereboullet)) over periods of 3-4 days.

1. An automatic respirometer has been developed for continuous measurements over 3-4 days on 1-15 g crayfish. The sensor is a modified Mackereth oxygen electrode. Respiration is recorded on a millivolt potentiometric pen recorder during closed periods when the O2 concentration in the medium falls to a predetermined level. A solenoid-operated valve is then opened via a relay circuit energized by a reed switch mounted on the recorder. Medium flows through the respirometer until the O2 concentration is raised back to another predetermined level. Artificial media containing little or no nutrient salts are used to restrict the growth of microbes. 2. Respiration was determined chiefly on crayfish (Austropotamobius pallipes) with body wet weights of 7-0-12-5 g at 10-0 degrees C. In unrestrained but relatively quiescent animals, standard metabolism is described by the regression equation, ln O2 uptake = 3-3037 + 1-002 ln body wt. In restless crayfish active metabolism is described by the equation, ln O2 uptake = 4-4412 + 0-861 ln body wt.     

Biosynthesis of Astacus protease, a digestive enzyme from crayfish

For the first time, the site of biosynthesis of a well characterized invertebrate digestive enzyme is localized. The enzyme chosen, Astacus protease, is a zinc-metalloenzyme occuring in high concentration in the gastric fluid of the freshwater crayfish Astacus astacus. Enzyme production was stimulated in adult crayfish either by feeding or by removal of the gastric fluid. Immunohistochemistry, cytology and investigation with radioactive tracers demonstrate that in the hours following stimulation, new enzyme was produced in the F-cells of the midgut gland and subsequently discharged into the midgut gland lumen. The enzyme was then accumulated and stored extracellularly in the cardiac stomach in active form. The mechanism of enzyme production observed in Astacus differs considerably from vertebrates suggesting an alternative model for synthesis and storage of digestive enzymes.     

Origin and colonization history of the white-clawed crayfish,Austropotamobius pallipes,in Ireland

The presence of the white-clawed crayfish Austropotamobius pallipes complex in Ireland is suspected to be a result of human translocations. Two hypotheses have been formulated about the origin of the crayfish: from British populations or from western French populations. In order to resolve this question, nine Irish crayfish populations (a total of 124 individuals) were sampled along a south-north cline and investigated by combining two molecular markers: mtDNA and RAPDs. The mtDNA marker, analysed by RFLP on the entire molecule, showed an absence of polymorphism within and among Irish populations. The RFLP haplotype found in Irish populations was only recorded in western French populations and was different from those found in English populations. This result may be explained by a human introduction of crayfish to Ireland from western French populations. RAPD analysis showed a clinal reduction of genetic variability within Irish populations from south to north, associated with an increase in their genetic differentiation. A stepwise model of translocation from the south to the north of Ireland is proposed and discussed.     

Ranging behaviour of a large freshwater invertebrate, the white-clawed crayfish Austropotamobius pallipes

• 1 Radio‐telemetry and mark‐recapture methods were used to study the summer movements of adult and juvenile white‐clawed crayfish, Austropotamobius pallipes from a wild population in a small braided stream, Dalton Beck, North Yorkshire, U.K. Radio‐transmitters were attached to the chelae of 18 large (> 35 mm carapace length) crayfish and individuals were subsequently located to within 0.15 m. Additionally a total of 888 crayfish were marked with carapace brands, and 83 were recaptured.
• 2 Radio‐tracked crayfish exhibited significantly greater local activity at dusk (21.00–00.00) than at dawn (03.00–06.00), or during morning (09.00–12.00) and afternoon (15.00–18.00) monitoring periods.
• 3 The greatest movements of radio‐tracked crayfish occurred within 2 days of release. After this time, periods of residence were interspersed by movements to new locations, interpreted as establishment of ephemeral home areas. It is suggested that the initial large movements were the result of a ‘fright response’ following capture.
• 4 Movements varied widely between individuals, some moving more than 300 m in 10 days, while others showed little movement over an equivalent time period. Mean (±SE) daily movements were 4.6 ± 3.0 m for males and 1.5 ± 1.0 m for females. Although crayfish often used specific home sites for in excess of 7 days, displaced animals did not return to home sites.
• 5 The total distances travelled and the mean distance travelled per day by individual radio‐tagged crayfish did not differ significantly between upstream or downstream directions or between males and females. This was also the case for marked crayfish used in mark‐recapture studies.
• 6 Positive correlations between distance moved per day and size (carapace length) were found for downstream movements by male and female crayfish, but not for upstream movements.
• 7 Some preliminary observations of the response of crayfish to flood events suggested that these could be catastrophic with two out of five tracked crayfish found dead after a high stream‐discharge event.

     

A study of reproductive females of the freshwater crayfish Austropotamobius pallipes

Details of the female annual reproductive cycle in the population from Northumberland are given. Mating occurs in October and is followed by egg laying in early November. Eggs are carried by females until the following July–August when hatching occurs. The smallest berried female caught was 25 mm carapace length (C.L.) and this was chosen as the minimum size for adult females. Only 40–50% of adult females, hand-caught, were berried in the Spring following egg laying; but this percentage was low largely because few females in the size classes below 28 mm C.L. were berried. The reasons for adult females being non-reproductive in a year are discussed.     

The growth of the freshwater crayfish A ustropotamobius pallipes in Northumbria

SUMMARY. Growth increments, moult frequency and growth rates of individuals in a population of the freshwater crayfish Austropotamobius pallipes were followed for a period of 3 years during a mark-recapture study. There was an inverse relationship between body size and the growth increment relative to body size. The absolute increment increased from the juvenile to the young adult stage and thereafter declined with increasing body size.
Differences between the adult male, reproductive female, non-reproductive female and juvenile subpopulations in the size of growth increments are reported and growth increments during the two major moult periods of each year are compared. The effect of the endoparasite Thelohania contejeani and of chela regeneration was to reduce slightly the growth increments.
Instantaneous growth rates declined throughout life in both sexes, but adult males maintained higher growth rates than adult females, particularly in the largest size class studied. The effect of reproduction on growth appeared to be most severe in the smallest breeding females. Males maintained the tendency to moult twice annually to a larger size than females. A simplified construction of the relationship between size and age in the population is presented for each sex. The oldest animals were estimated to be at least 11 years old.     

Branchiobdellidan infestation on endangered white-clawed crayfish (Austropotamobius pallipes) in the UK

Branchiobdellidans or crayfish worms are clitellate annelids and ectosymbionts of freshwater crayfish. An investigation of branchiobdellidan infestation was undertaken in a population of endangered white-clawed crayfish (Austropotamobius pallipes) in the river Aire, UK. Thirty two percent of animals were infested either by the adult parasite or their cocoons (n=107). Parasite burden increased with host size, but did not differ with sex. Observations of crayfish gill tissue revealed a strong positive relationship between melanization of filaments and parasite prevalence and burden. Taxonomic identification revealed that 1 species of branchiobdellidan was present, Branchiobdella astaci. The first sequences were generated for this species and phylogenetically analysed alongside published sequences for 5 other branchiobdellidan species in Europe. The position of B. astaci within the genus Branchiobdella was confirmed, and it was found to cluster as a sister group to B. parasita.