Phylogeography of noble crayfish (Astacus astacus) reveals multiple refugia

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Microanatomy of the abdominal stretch receptors of the crayfish (Astacus fluviatilis L.)

Microanatomical studies on the abdominal stretch receptor organs of the crayfish Astacus fluviatilis L. have been carried out in order to establish a basis for the physiological work that has been, and is being carried out on stretch receptors of various species of crayfish. Important differences have been found between these organs and those previously described by Alexandrowicz for the lobsters Homarus vulgaris and Palinurus vulgaris. With the aid of silver-impregnated preparations the relationship of sensory endings and muscle fibers has been shown as well as the pattern of the efferent innervation. The physiological significance of the histological findings has been discussed.     

Size and structure of crayfish (Astacus astacus) populations on different habitats in Finland

The many inland waters in Finland make crayfish production an important potential resource. The rational utilization and management of this resource requires knowledge of the size and structure of the crayfish populations. The difficulties often encountered in catching crayfish complicate population studies. Mark-recapture and electric fishing have been used in the studies. The number of adult crayfish measuring more than 70 mm in a 4-ha lake was estimated at 620, and the number in a 13-ha lake at 3 480. In the lakes, the density of adult crayfish was around 0.6–1.4 m^–2 and in one stream studied about 2.5 m^–2 rising to several individuals per m² in the best biotopes.     

The cytotoxic reaction of hemocytes from the freshwater crayfish, Astacus astacus

Crayfish hemocytes displayed cytotoxic capacity towards all tested mammalian tumor and nontumor cell lines. The ratio required for the cytotoxic action of effector cells to target cells was at least 1:1. The lysis of the target cells required a minimum of 1 hr to become detected. After separation and isolation of the hemocyte populations of crayfish, the semigranular and granular cells retained their cytotoxic capacity. These cells contain the prophenoloxidase activating (proPO) system, a complement-like pathway, which in an activated form lyses semigranular cells in vitro, but failed to kill the tested target cells.     

alpha2-Macroglobulin from hemolymph of the freshwater crayfish Astacus astacus.

1. A high mol. wt proteinase inhibitor has been purified from the haemolymph of the freshwater crayfish Astacus astacus. 2. The protein is a disulphide-bonded dimer (Mr 390,000) of two identical polypeptide chains (Mr 185,000). 3. The inhibitor displays a broad specificity and protects trypsin from inhibition by soybean trypsin inhibitor and thus is similar to vertebrate alpha 2-macroglobulin. 4. The alpha 2-macroglobulin-like inhibitor from Astacus interacts with bovine trypsin in an equimolar stoichiometry thereby decreasing tryptic hydrolysis of N-benzoyl-L-arginine-ethylester to 50% residual activity. In contrast, the activity of Astacus protease, a digestive zinc proteinase from crayfish toward succinyl-alanyl-alanyl-alanyl-4-nitroanilide is inhibited almost completely. 5. Sensitivity of the inhibitor to methylamine and autolytic cleavage suggests the presence of an internal thioester bond. 6. The N-terminal amino acid sequence of Astacus alpha 2-macroglobulin is strongly related to the alpha 2-macroglobulins from Pacifastacus leniusculus (91% identity) and from the lobster Homarus americanus (72% identity). In contrast, only 25% of the residues are identical with the alpha 2-macroglobulin from the horseshoe crab Limulus polyphemus. There is also a faint similarity to human complement protein C3 and human alpha 2-macroglobulin.     

Millimeter-wave effects on electric activity of crayfish stretch receptors

The effects of super high frequency (SHF) microwaves (34-78 GHz) on rates of spontaneous firing of the slowly adapting, stretch-receptor neurons of crayfish were studied. Initially, irradiation of continuously perfused, fluid-cooled preparations at power densities to 250 mW/cm2 caused a transient decrease in the rate of spontaneous firing (the dynamic response). Subsequently, with extinction of the SHF field, the rate of firing increased, finally stabilizing at pre-exposure levels (stationary phase). Rates of firing also increased when the receptor muscle was stretched, and they were inversely correlated with small, field-induced increases of temperature (approximately 1.5 degrees C). The response to SHF radiation did not depend on frequency if temperature of the medium was constant. No resonant peaks were found when the millimeter range of frequencies was scanned.     

Size scaling of whole‐body metabolic activity in the noble crayfish (Astacus astacus) estimated from measurements on a single leg

1. Use of electron transport system (ETS) activity in a single leg for estimating whole‐body ETS activity was explored in the noble crayfish Astacus astacus. Oxygen consumption and ETS activity of the whole body and of a walking leg were measured in different‐sized animals at 10 °C to compare the size scaling of oxygen consumption, whole‐body ETS activity and the ratio of whole‐body ETS activity to oxygen consumption (ETS/R). 2. Electron transport system activity of a leg and the ratio of ETS activity of a whole crayfish to that of a leg were correlated with wet mass of animals. Therefore, metabolic potential in whole noble crayfish can be estimated on the basis of the measured ETS activity in a single leg and crayfish mass. This approach provides a valuable tool for determining metabolic characteristics of crayfish without killing them. 3. Mass‐specific oxygen consumption decreased with increasing wet mass, while ETS activity of whole crayfish showed no significant correlation with wet mass. Both oxygen consumption and ETS activity correlated significantly with protein mass. 4. The increase in ETS/R with increasing wet mass of the noble crayfish indicates that small organisms exploit a greater proportion of their metabolic potential for standard metabolism than larger ones. This is the first report on ETS/R in crayfish.     

Innervation pattern of the deep extensor abdominal muscle in the crayfish species Astacus astacus

The deep extensor abdominal muscle consisting of one medial and two lateral muscle bundles together with the nerve innervating the muscles of crayfish species Astacus astacus, was prepared. Light microscopic investigations of methylene blue stained preparations showed that the nerve innervating the deep extensor abdominal muscle consists of five distinct axons. The five axons were stained separately with lucifer yellow and the innervation pattern of the axons was determined. To confirm the histological results the axons were also stimulated with a suction electrode to elicit excitatory postsynaptic currents on the muscle membrane which were detected using a macro patch electrode. The muscle is innervated by a common excitatory and a common inhibitory axon branching over all three muscle bundles and sending additionally a branch to the L1-bundle of the next posterior segment, and by two axons specific for the two lateral muscle bundles. The axon specific for the innervation of the L1-bundle sends also a branch to the L1-bundle of the next posterior segment. In addition there is one excitatory axon which directly innervates the medial muscle bundle of the next posterior segment branching in most of the cases also to the medial bundle of the segment where it originates.Abbreviations DEAM deep extensor abdominal muscle - EPSC excitatory postsynaptic current - IPSC inhibitory postsynaptic current - L lateral - M medial - GABA -aminobutyric acid     

Diurnal variations in physiology and behaviour of the noble crayfish Astacus astacus and the signal crayfish Pacifastacus leniusculus

Heart rate, locomotor activity, and oxygen consumption were recorded simultaneously and continuously in seven individuals of the noble crayfish Astacus astacus (Linneus 1758) and seven individuals of the signal crayfish Pacifastacus leniusculus (Dana 1852). The recordings were made in the laboratory over 7 days at 15°C under a 12?:?12?h dark?:?light regime. Circadian rhythms in heart rate, locomotor activity and oxygen consumption were found both in A. astacus and P. leniusculus. Increased heart rate, locomotor activity, and oxygen consumption levels during night time in both A. astacus and P. leniusculus illustrated expression of nocturnal behaviour. No differences in oxygen consumption levels were observed between A. astacus and P. leniusculus. Also, no significant difference between heart rate levels or heart rate variances was found in A. astacus and P. leniusculus at night. During day, however, heart rate levels, heart rate variances and locomotor activity were higher in P. leniusculus than in A. astacus. The higher activity level in P. leniusculus than in A. astacus during daytime indicates that P. leniusculus is less strictly nocturnal than is A. astacus.     

Diurnal variations in physiology and behaviour of the noble crayfish Astacus astacus and the signal crayfish Pacifastacus leniusculus

Heart rate, locomotor activity, and oxygen consumption were recorded simultaneously and continuously in seven individuals of the noble crayfish Astacus astacus (Linneus 1758) and seven individuals of the signal crayfish Pacifastacus leniusculus (Dana 1852). The recordings were made in the laboratory over 7 days at 15°C under a 12 : 12 h dark : light regime. Circadian rhythms in heart rate, locomotor activity and oxygen consumption were found both in A. astacus and P. leniusculus. Increased heart rate, locomotor activity, and oxygen consumption levels during night time in both A. astacus and P. leniusculus illustrated expression of nocturnal behaviour. No differences in oxygen consumption levels were observed between A. astacus and P. leniusculus. Also, no significant difference between heart rate levels or heart rate variances was found in A. astacus and P. leniusculus at night. During day, however, heart rate levels, heart rate variances and locomotor activity were higher in P. leniusculus than in A. astacus. The higher activity level in P. leniusculus than in A. astacus during daytime indicates that P. leniusculus is less strictly nocturnal than is A. astacus.