Ossi V. Lindqvist

Comparison of morphology and edible tissues of two important commercial crayfishes, the noble crayfish, Astacus astacus Linné, and the red swamp crayfish, Procambarus clarkii (Girard) (Decapoda, Astacidae and Cambaridae)

Abstract Sexually mature Astacus astacus (37–64 mm cephalothorax length) and Procambarus clarkii (35–70 mm cephalothorax length) differed significantly in appearance. Astacus astacus had larger chelae and broader bodies; however, cephalothorax length-body weight regression curves of males and females of the two species did not differ significantly. Yields of edible muscle, chelae and abdomens were greatest, on a percentage basis, for crayfish in the 40–50 mm cephalothorax length range. Male P. clarkii over 50 mm cephalothorax length yielded comparable amounts of edible muscle to like-sized male A. astacus but female P. clarkii did not as chelae were significantly smaller than those of males or both sexes of A. astacus . Muscle composition was comparable in both species, having the following levels of moisture, protein, lipid, and energy: 79–85%, 80–88%, 13–50 mg/g, and 19 000–22 000 joules/g, respectively. Waste products remaining after removal of abdominal muscles and digestive glands were more protein rich (33 vs. 24%) and had higher energy levels (11 725 vs. 10 950 j/g) in A. astacus than in P. clarkii . This could be accounted for by lower ash (44% vs. 47%) and dry matter (28% vs. 37%) levels in A. astacus .

Exoskeleton mineralization in astacid and cambarid crayfishes (Decapoda, Crustacea)

1. n1. Mean values for mineral matter in intermolt (C4) anterior branchiostegites of warmwater cambarids, Procambarus clarkii and P. a. acutus, were significantly greater (P ≤ 0.05) (77%–78%) than those of the coolwater astacids, Astacus astacus and Pacifastacus leniusculus (71–74%). Values for comparable P. clarkii originating from California, Louisiana and Spain did not differ significantly. Significant differences were noted between two Finnish A. astacus populations. n n2. n2. Chelae were more heavily mineralized than branchiostegites in P. clarkii, but not in A. astacus. Chelae and branchiostegites were either equally mineralized in A. astacus or chelae had lower mineral contents than branchiostegites. However, chelae were far denser than branchiostegites in both species. n n3. n3. Cast exoskeletons were more heavily mineralized (4–7%) but less dense than intact exoskeletons in A. astacus. n n4. n4. There were no significant differences between the degree of mineralization of anterior branchiostegites in young-of-the-year juvenile P. leniusculus and mature, sexually active adults and in subadult A. astacus and mature, sexually active adults. n n5. n5. Anterior branchiostegites and chelae of P. clarkii had substantially higher calcium (ca 26% vs ca 23%) and magnesium (ca 0.36% vs 0.20%) concentrations than either astacid species. Phosphorus concentrations (0.4–2.0%) were generally greater for astacids.

Responses of intermolt noble crayfish, Astacus astacus (Decapoda, Astacidae), to short-term and long-term holding conditions at low temperature

Abstract Crayfish were held at 4°C without feed for periods of 5 days and 11 weeks to determine changes in organic constituents. Short-term changes were not apparent in soluble protein, glycogen, total lipid, and percent moisture in the hepatopancreas. Soluble protein in abdominal muscle declined. Long-term changes in organic constituents were a decline in the hepatopancreas total lipid with an increase in percent moisture and a decline in abdominal muscle glycogen. Some variations could be accounted for by time of capture (early vs. mid-September) and sex.

A comparison of the known life forms of Psorospermium spp. in freshwater crayfish (Arthropoda, decapoda) with emphasis on Astacus astacus L. (Astacidae) and Procambarus clarkii (Girard) (Cambaridae)

Abstract Psorospermium spp. are unicellular organisms of uncertain taxonomic status found in the tissues of crayfish from three crayfish families. We describe the various life forms that we have identified in astacid, cambarid, and parastacid crayfish. A small amoeboid form, 10 μm, is described from juvenile North American Procambarus clarkii . A similar form had been described only once before in European Astacus astacus in the 1930s. Psorospermium spp. described to date are apparently otherwise immobile and often surrounded by a thick wall. Infection becomes apparent in 5th or 6th stage crayfish.

Occurrence of Psorospermium sp. in several North American crayfish species, with comparative notes on Psorospermium haeckeli in the European crayfish, Astacus astacus.

Abstract Psorospermium haeckeli is a thick-walled, unicellular organism widely reported in European astacid crayfish. Its taxonomic status and life cycle have not been elucidated. It is often referred to as a “parasite”, but conclusive evidence has yet to be found. Recent examination of two North American crayfish species, Procambarus clarkii and Procambarus zonangulus, confirmed its presence in the south-central USA (Louisiana) with morphologies that differ from that of P. haeckeli. This form had been previously reported from Orconectes virilis in southern Canada. We report here the presence of this North American form of Psorospermium in additional North American crayfish including Orconectes immunis and Orconectes rusticus from the northern USA (Minnesota and Wisconsin), Procambarus alleni and Procambarus fallax from the southern USA (Florida), and Pacifastacus leniusculus from the western USA. We also confirm this Psorospermium in O. rusticus from eastern Canada (Ontario). It was not, however, confirmed in several additional southern crayfish species including Cambarus diogenes, Cambarellus puer, Fallicambarus fodiens, and Orconectes palmeri. We describe the morphological forms of this Psorospermium and conclude that it is present in many crayfish species in North America.

The crayfish pathogen Psorospermium haeckeli activates the prophenoloxidase activating system of freshwater crayfish in vitro

Abstract Preparations of the crayfish pathogen Psorospermium haeckeli were found to activate the prophenoloxidase activating (proPO) system in haemocyte lysates of two crayfish species Pacifastacus leniusculus and Astacus astacus . This is the first report showing that this parasite can elicit the activation of a defence system in crayfish and that the activation appears to be similar to the activation of the proPO system triggered by different microbial polysaccharides.