Jay V. Huner

Variation in body composition and exoskeleton mineralization as functions of the molt and reproductive cycles of the noble crayfish, Astacus astacus L. (Decapoda, astacidae), from a pond in central finland

Abstract 1. 1. Male and those female crayfish (Astacus astacus) not reproductively active during the previous autumn molt in early summer while egg bearing females do not molt until mid-summer after the young are released, in central Finland. 2. 2. Organic reserves in hepatopanceas (digestive gland) are much higher in premolt and intermolt males and previously non-reproductive females preparing to produce ova than premolt and intermolt females that were reproductively active during the preceding year. The percentages of moisture in the hepatopancreas and abdominal muscle range from 53–83% and 75–84%, respectively, in males and females depending on molt stage and reproductive status. 3. 3. Lipid, ash, crude protein, crude fat, crude carbohydrate, and total energy of hepatopancreas samples were approximately 15–20, 0.5, 0.5, 4–5, 1.0, and 1.0–1.5 times, respectively, the levels recorded in abdominal muscle samples. Ranges for hepatopancreas values were: 289–457 mg/g dry weight; 4. 3.7–4.8 g/100g; 24–36 g/100g; 44–63 g/100g; 6–19g/100g; and 2670–3150 kJ/100 g, respectively. 5. 4. The amount of mineral matter is similar in the intermolt (stage C) carapaces, dorsal abdominal terga, and chelae of males and females (73–79%) although chelae have 1–3% more mineral matter. Carapace mineral matter declines 5–10% during early phases of the premolt period (stage D).

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. 1. 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. 2. 2. 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. 3. 3. Cast exoskeletons were more heavily mineralized (4–7%) but less dense than intact exoskeletons in A. astacus. 4. 4. 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. 5. 5. 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.

Interactions of Freshwater Prawns, Channel Catfish Fingerlings, and Crayfish in Earthen Ponds

Abstract Prawns (Macrobrachium rosenbergii) were cultured in 0.04-ha ponds alone at densities of 25,000 and 50,000/ha, and at 25,000/ha with channel catfish fry (Ictalurus punctatus) at 150,000/ha. Catfish were also cultured alone at the same density. Mean survival was poor (prawns, 14-22%; catfish, 14-18%) and production was low (prawns, 90-270 kg/ha; catfish, 640 - 770kg/ha) after 140 days for prawns and 110 days for catfish. Survival and production values were lowest for prawns in the polyculture ponds (P < 0.05). Resident crayfish (Procambarus clarkii and P. acutus acutus) were harvested from all ponds (490 - 550 kg/ha).

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.

Sequential Pond Flooding: A Prospective Management Technique for Extended Production of Bait-Size Crawfish

Abstract Twelve 0.005-hectare earthen ponds with established crawfish populations [Procambarus clarkii (Girard)] were drained in June 1973 and four each were flooded on 1 September, 1 October, and 1 November 1973. Substantial numbers of bait-size (5.0–7.0 cm total length) crawfish were available from early October through May 1974 when ponds were drained. Population dynamics differed considerably from previously reported studies and are discussed. Trapping was selective for nonmolting crawfish and is the recommended harvesting technique if crawfish are to be held for over 1–2 days.

Effects of temperature upon ablation-to-molt interval and mortality of red swamp crawfish (Procambarus clarkii) subjected to bilateral eyestalk ablation

Abstract The shortening in molt interval and induced mortality due to crawfish eyestalk ablation are the main factors that need to be evaluated for the application of ablation technology in commercial softshell crawfish production. Effects of temperature on the ablation-to-molt interval and mortality of ablated red swamp crawfish ( Procambarus clarkii ) were investigated in laboratory scale recirculating culture systems in two studies conducted in separate years. Higher temperatures resulted in a shorter molt interval but higher mortality. With temperatures that ranged from 15 °C to 30 °C, the mean ablation-to-molt interval was reduced from 18.4 days to 6.4 days for immature crawfish and from 26.3 to 8.3 days for mature crawfish, respectively. Mortality, on the other hand, increased from 24.8 to 38.6% for immature crawfish and from 36 to 47% for mature crawfish, respectively. For immature crawfish, the majority of the mortality occurred within several days following ablation; but for mature crawfish, additional mortality occurred in molting. In both studies, the mortality varied among experiments, suggesting that other factors also played important roles in determining mortality.