Female Crayfish Research Articles

Evaluation of a Nondestructive Method for Determining Body Composition of White River CrayfishProcambarus acutus

Abstract A nondestructive method for determining body composition by measuring total body electrical conductivity (TOBEC) was evaluated with 36 male and 36 female white river crayfish Procambarus acutus, ranging from 82 to 122 mm total length (TL) and from 16.62 to 67.11 g wet weight (WW). Significant relationship with an R 2 of 0.999 was observed using TOBEC and WW for lean body mass (LBM), whereas WW, TL, or a combination of these variables were significantly correlated with protein (R 2 = 0.914), ash (R 2 = 0.902), and water content (R 2 = 0.978). The correlation coefficient was the lowest for lipid content (R 2 = 0.652) using TOBEC and WW. The predictive models for LBM, lipid, and ash were significantly different for male and female crayfish. Relative body composition for a standard-size female crayfish was 3.48% lipid and 9.71% ash compared with 1.91% lipid and 11.85% ash for a male. Analysis of an independent group of eight male and female crayfish demonstrated that TOBEC and WW jointly were reliabl...

The structure and function of the androgenic gland in Cherax destructor (Decapoda: Parastacidae)

This paper is the first published description of the androgenic gland in Cherax destructor. The androgenic gland has been shown to control sexual differentiation in the decapods. An androgenic gland hormone may allow hormonal sex reversal for the production of monosex populations in aquaculture, leading to increases in production. Standard histological techniques revealed androgenic glands consisting of cords of epithelial cells attached to the posterior vas deferens, either appearing as multiple cords of cells, a single cord of cells, or a cord associated with masses of cells. Each androgenic gland was sheathed in connective tissue, which attached the androgenic gland to the vas deferens. The androgenic activity of the androgenic glands was demonstrated by injecting female crayfish with a crude homogenate of terminal vas deferens and attached glandular tissue. A significantly higher number of females, relative to controls, receiving this homogenate developed male gonopores as well as displaying inhibition of vitellogenesis and oosetae development. These results indicate that Cherax destructor display similar androgenic glands to other crustaceans, and that these glands have a possible role in secondary sexual differentiation.

Effect of Acclimation Temperature and TemperatureChanges on Molting and Survival of Ablated and Non‐ablated Crayfish Orconectes virihs

Abstract.The effect of acclimation temperatures for producing soft‐shell crayfish, and changes upward from acclimation temperature, were evaluated in crayfish Orconectes virilis subjected to either hemilateral or bilateral eyestalk ablation. In each experiment, 60 juvenile O. virilis were reared for 21 d at temperatures ranging from 20 C to 30 C. Equal numbers of male and female crayfish ranging in weight from 5.0 g to 16.0 g were used in each study. In the first three experiments, crayfish were acclimated and maintained at a constant temperature. In the remaining experiments, crayfish were subjected to a step‐wise increase in temperature of either 5 or 10 C. Molting was highest in crayfish acclimated to 25 C prior to experimentation at 25 C (experiment 2) and in crayfish acclimated to 14 C prior to experimentation at 20 C (experiment 4). Total molts during these two experiments were 51 (85.0%) and 56 (93.3%), respectively. Bilateral eyestalk ablation resulted in significant reductions in the intermolt period in experiments 1 (acclimation temperature 20 C, experimental temperature 20 C), 3 (acclimation temperature 30 C, experimental temperature 30 C) and 6 (acclimation temperature 15 C, experimental temperature 25 C), while hemilateral eyestalk ablation had no effect on molting when compared to control (non‐ablated) crayfish. Bilateral eyestalk ablation resulted in a significant reduction in survival in experiments 5 (acclimation temperature 20 C, experimental temperature 25 C) and 6 (acclimation temperature 15 C, experimental temperature 25 C). Significantly more females molted in one experiment (acclimation temperature 20 C, experimental temperature 25 C), but not in any others. The results of these studies demonstrate that bilateral eyestalk ablation and water temperatures are effective methods of inducing molting in crayfish.

Schooling preferences for familiar fish vary with group size in a wild guppy population

The ability of fish to recognize and preferentially associate with familiar conspecifics has been well documented in a series of laboratory experiments. In this paper we investigate the schooling preferences of wild female guppies, Poecilia reticulata, in the Upper Tunapuna River in Trinidad and confirm that they do indeed prefer to associate with familiar individuals. The guppies in this river occur in a series of pools that become isolated during the dry season. These fish interact solely with other individuals in their pool for periods of several months at a time and thus have ample opportunity to become accustomed to one another. Our study also reveals that the tendency of female guppies to school with familiar fish declines as the group size in which they naturally live increases. Preferences are strong when there are small numbers of females in a pool, but diminish thereafter. This indicates that the expression of familiarity is constrained by group size. The basis of recognition and the consequences of schooling preferences for familiar individuals are discussed.

Roles of neurotransmitters in regulating reproductive hormone release and gonadal maturation in decapod crustaceans

Summary Experiments done in this laboratory showed 5-hydroxytryptamine (5-HT) stimulates gonadal maturation in male and female sand fiddler crabs, Uca pugilator, and red swamp crayfish, Procambarus clarkii. This action of 5-HT is indirect, 5-HT apparently stimulating release of the gonad-stimulating hormone (GSH) that is present in the brain and thoracic ganglia. For example, studies with ovarian explants showed 5-HT has no direct effect on the ovary. But, when ovarian explants were incubated with 5-HT and brain or thoracic ganglia, the incubation medium produced greater ovarian maturation than did the medium when ovarian explants were incubated with brain or thoracic ganglia alone, 5-HT presumably enhancing GSH release. In males 5-HT not only induces testicular maturation but also development of the androgenic glands. 5-HT in males, as in females, apparently triggers GSH release; but in males GSH in turn stimulates the androgenic glands which release the androgenic gland hormone, resulting in testicular maturation. In contrast, dopamine (DA) inhibits gonadal maturation in both sexes. Methionine enkephalin, like DA, slows ovarian maturation. Red pigment-concentrating hormone (RPCH), like 5-HT, stimulates ovarian maturation both in vivo and in vitro, apparently by stimulating GSH release. RPCH does not affect the ovary directly. Calcium appears to act here as a second messenger for RPCH. The implications of these findings for enhancing the culture of crustaceans is discussed.

Mechanical use of crayfish chelae

Chela mechanical function was investigated by comparing individuals of the crayfish Orconectes propinquus (Girard) with and without the mechanical use of their chelae (dactyls held closed with rubberbands or glue) to determine if crayfish need the mechanical function of chelae to feed, to deter predators, to survive in the field, and to copulate with mates. Laboratory studies showed that crayfish did not require the use of their chelae to consume algae or snails, but fewer crayfish consumed juvenile insects when their pincers were non‐functional. Male and female crayfish with functional pincers were just as susceptible to snapping turtle predators in the laboratory and just as likely to be recaptured in the field as those with non‐functional pincers. Laboratory mating experiments with two males and a single female showed that only males with the mechanical use of their chelae copulated. These results indicate that O. propinquus require their chelae for mating but do not require functioning chelae to feed ...

Implantation of Androgenic Glands into Immature Female Crayfish, Procambarus clarkii, with Masculinization of Sexual Characteristics

Implantation of Androgenic Glands into Immature Female Crayfish, Procambarus clarkii, with Masculinization of Sexual Characteristics

Carotenoids and their derivatives in organs of the maturing female crayfish Cherax quadricarinatus

Carotenoids were separated by high-performance liquid chromatography from organ homogenates of pre-vitellogenic (oocyte diameter ∼300μm) and late-vitellogenic (oocyte diameter >1mm) Cherax quadricarinatus females. Carotenoids were present predominantly in the cuticle and in the late-vitellogenic ovary. Smaller amounts were present in the hepatopancreas, and almost no carotenoids were found in the muscular tissue. The cuticle contained mostly esterified astaxanthins. The ovaries contained mostly non-esterified astaxanthin. Pre-vitellogenic ovaries were also relatively rich in lutein, whereas late-vitellogenic ovaries were relatively rich in β-carotene. The hepatopancreas contained mostly β-carotene. Possible roles for the different carotenoids in the cuticle and ovary of the crayfish are discussed.

Naphthalene-Induced Atresia in the Ovary of the Crayfish, Procambarus clarkii

Female crayfish, Procambarus clarkii, were exposed to 10 ppm naphthalene to determine its effect on ovarian development. Ovaries were removed for examination after 1, 2, 4, 6, 8, 10, 12, and 15 days of exposure to the naphthalene. Crayfish that had been exposed to naphthalene for 15 days were then returned to clean freshwater for 1, 2, 4, 5, 7, 10, and 15 days to determine whether the ovaries would recover from the naphthalene exposure. The ovarian index, which reflects the weight of the ovary, decreased gradually over the 15-day naphthalene exposure period. The previtellogenic and vitellogenic oocytes degenerated. Intense atresia along with yolk resorption led to this decrease in the ovarian index. In contrast, the ovaries of the control crayfish developed into ripe gonads. However, immature oocytes reappeared in the ovaries of the crayfish subjected to depuration, which suggests that the ovary of P. clarkii can recover from naphthalene-induced atresia.

Predation of zebra mussels by crayfish

The introduction of zebra mussels, Dreissena polymorpha (Pallas), to the Great Lakes has redirected a large amount of energy from the planktonic community to the benthic community. The direct transfer of energy from zebra mussels to other large organisms depends on the resistance of the mussels to predation. This study investigated the ability of the crayfish Orconectes propinquus (Girard) to use zebra mussels as a food source. Laboratory experiments were designed in which predator and prey sizes, as well as densities, were manipulated. When presented with zebra mussels of a range of sizes (5–20 mm), crayfish of all sizes (carapace length 1.5–2.9 cm) ate mussels ≤ 8 mm in length almost exclusively, but mussels up to 17 mm were also consumed. No significant difference in utilization of zebra mussels was found between male and female crayfish. Our findings suggest that crayfish have the potential to alter the size structure of zebra mussel populations, but that per capita mussel consumption decreased at densities > 4 crayfish/m2. Mutual interference among predators or a lack of habitat complexity may explain the reduction of mussel consumption at high densities of crayfish.

Osmotic Responses of Red Swamp Crawfish to Trapping, Sorting, and Storage in a Cooler

Hemolymph osmotic pressures and chloride concentrations were measured in red swamp crawfish Procambarus clarkii at harvest and after storage in a cooler in March and May. Male and female crayfish had similar hemolymph concentrations regardless of treatment, and osmotic pressure and chloride levels were generally stable for a storage period of up to 5 d after harvest. These data suggest that trapping or storage in a cooler causes no dramatic physiological change in red swamp crawfish.

Chemical sex discrimination in the crayfishProcambarus clarkii: Role of antennules

Chemical sex discrimination of conspecifics by male and female crayfish (Procambarus clarkii) was tested. Intact female subjects were more attentive in the presence of stimulus water from males than from females and showed more aggressive postures in the presence of stimulus water from females than from males. Intact males showed more aggressive postures in the presence of stimulus water from males than from females. Females and males with only one inner antennule ramus and one outer ramus performed discrimination and localization almost as well as intact subjects. Subjects with only the two inner rami or only the two outer rami were disadvantaged in either responding to the stimuli or localizing them. The relevance of this outcome to previous conflicting reports on the use of antennules in sex discrimination in crayfish is discussed.

Temperature and photoperiod effects on ovarian maturation and egg laying of the crayfish, Orconectes limosus

Native female crayfish were exposed to a number of different temperature and photoperiod treatment combinations over an 18-week period from November 1988 to March 1989. Four ovarian maturity indices were used to measure ovarian maturation of a control group exposed to a constant temperature of 7 °C and darkness: oocyte diameter, ovary weight, ovarian index and percentage of dark ovaries. The ovarian maturation rate peaked from mid-November to mid-December. The combined conditions of warm temperature (10–12 °C) and darkness successfully accelerated ovarian maturation from mid-December to mid-January and induced egg laying 5 weeks earlier than in the control group. Long-photoperiod exposure (16 h of light per day) did not accelerate ovarian maturation to the same degree; it did not promote earlier egg laying. Warm temperature successfully accelerated egg laying by 3 months in comparison with natural populations.

Chronic toxicity of thiodanr (endosulfan) insecticide to louisiana crayfish, procambarus clarkii

The major objective of this work was to assess the possible long-term effects of Thiodan insecticide on the growth-rate, fecundity and hatching potential of Louisiana crayfish, Procambarus clarkii. Adult males and females were collected from an Experiment Station, and were exposed to 600 ppb Thiodan. Since the aqueous solubility of endosulfan (active ingredient of Thiodan) is very low, the actual concentration of 2, 10, 15 and 600 ppb Thiodan in tap water was determined by electron-capture gas chromatography. The amount of endosulfan I and II in 2 ppb Thiodan was 0.8 and 0.32 ppb, respectively; 10 ppb = 3.8 and 1.52; 15 ppb = 6.3 and 2.52; and 600 ppb = 284 and 113.6 endosulfan I and II, respectively. Male and female crayfish were exposed to 600 ppb Thiodan for 20 weeks during which mating occurred. The mean number of eggs produced by control crayfish (N = 10) was 288 and by treated crayfish (N = 10) was 225, which did not differ significantly. Hatchlings from unexposed crayfish were used to determine the effects of Thiodan on weight, length and molting frequency. Sixty hatchlings were exposed to 2, 10 and 15 ppb Thiodan for a period of 9, 23 and 27 weeks during which they achieved a mean weight (gain) of 0.64, 0.19 and 0.17 g, respectively. Control hatchling gained 0.82, 0.30 and 0.19 g during the same period. These differences were also insignificant statistically. The length (gain) by these hatchlings (control and treated) over the same time period did not differ significantly. There was a slight increase (insignificant) in the molting frequencies of treated hatchlings. Comparative data on the chronic effects of Thiodan for crayfish are not available. Based on the reported LC50 values for grass shrimp, mysid shrimp and Korean shrimp, we conclude that Louisiana crayfish, P. clarkii is more tolerant to this insecticide than the other decapod crustaceans.

Aspects of the Life History of the Calico Crayfish with Special Reference to Egg Hatching Success

Abstract Life history data were collected on adult (≥25 mm carapace length) female calico crayfish (Orconectes immunis) in conjunction with an egg-hatching study during 1986–1988. Eggs stripped from 10 females in October 1986 and 10 females in September 1987 were pooled each year and hatching success was monitored for samples of 100 eggs placed in each of eight diluter aquaria at 12°C. In fall 1987, berried calico crayfish were cultured at 12, 25, and 30°C and hatching was monitored. Data on length, weight, and number of eggs produced were collected for 28 females in September 1987 and 36 females in April 1988. An additional 456 female crayfish were checked for the presence of eggs. Hatching success was 86% in 1986 and 89% in 1987. The eggs on berried females held at 12°C started to hatch within 33 d. At 25°C, hatching started within 10 d. At 30°C, no hatching occurred, the eggs became orange (indicating death), and most of the eggs later developed fungal infections. The average number of eggs carried was...

The effect of aquatic plant chemistry and morphology on feeding selectivity by the crayfish, Orconectes virilis

SUMMARY. 1. Feeding preference trials conducted with male and female crayfish (Orconectes virilis) showed that out of ten submersed aquatic plant species, Chara sp. and Lemna trisulca were the preferred food sources, followed by Myriophyllum exalbescens or Utricularia vulgaris.2. Analysis of plant fibre, alkaloid, total phosphorus, total and available nitrogen, and organic content showed that crayfish feeding preferences were not related (P>0.5) to plant fibre or alkaloid content but were negatively correlated (P<0.05) with plant nutrient content such that species of low nutritional value (Chara and Lemna) were consistently preferred.3. Despite this preference for low nutrient food, daily intake rates by crayfish for phosphorus, nitrogen and organic matter were greatest when feeding on Lemna or Chara due to the large quantity consumed.4. We suggest that feeding preferences of O. virilis are not determined by plant chemistry but, rather, relate to ease of handling small, short, bottom‐dwelling plants such as Chara and Lemna as compared with large erect, roseate or floating‐leaved forms. Because crayfish are selective herbivores, their introduction into waters where they do not naturally occur could have a dramatic effect on both the species composition and biomass of submersed plants.

Chemical detection of conspecifics in the crayfishProcambarus clarkii: Role of antennules

Tests with female crayfish (Procambarus clarkii) confirm that conspecifics can be detected chemically. The subjects were more attentive in the presence of water from a stranger's tank than in the presence of water from their own tank. Animals with intact antennules performed this discrimination best, but animals with one intact inner ramus and one intact outer ramus also clearly responded. Conspecific chemical discrimination after loss of both inner or both outer rami was weak (trial 2) or absent (trial 1). The relevance of this outcome to previous conflicting reports on the use of antennules in sex and species discrimination in crayfish is discussed.

Consumption and apparent dry matter digestibility of aquatic macrophytes by male and female crayfish ( Orconectes virilis)

Crayfish are generally thought to be omnivores; however, the relative nutritional importance of various foods is poorly understood. In this study, we fed adult (mean weight 18.3 g) male and female crayfish ( Orconectes virilis) 14 aquatic macrophytes and quantified consumption and apparent dry matter digestibility (ADMD). Specifically, we fed cattail ( Typha sp.), horsetail ( Equisetum sp.), bulrush ( Scirpus sp.), arrowhead ( Sagittaria sp.), horned pondweed ( Zannechellia palustris), musk-grass ( Chara sp.), curlyleaf pondweed ( Potamogeton crispus), sago pondweed ( P. pectinatus), American pondweed ( P. nodosus), eel grass ( Vallisneria sp.), water buttercup ( Ranunculus longirostris), water stargrass ( Heteranthera dubia), American lotus ( Nelumbo lutea) and dried, pelleted duckweed ( Lemna sp.). Except for consumption of horned pondweed, there were no significant differences in consumption or ADMD between males and females. Based on the low consumption estimates (ranging from 0.01 to 0.87% body weight/day; overall mean of palatable macrophytes 0.19% body weight/day), it appears that macrophytes do not comprise a major source of nutrients for this size and species. Further, ADMD coefficients were significantly different between macrophytes of similar nutritional composition and may indicate the presence of antinutritional factors. Thus, growth of certain macrophytes in aquaculture ponds should be discouraged, while others may be beneficial as a minor food source or as a source of selected nutrients. Methods for future digestion studies were evaluated and discussed.

Selective foraging by the crayfish Orconectes virilis and its impact on macroinvertebrates

SUMMARY. 1. The impact of crayfish predation on the abundance of macroinvertebrates was examined under semi‐natural conditions. Female (Experiment 1) or male (Experiment 2) crayfish (Orconectes virilis) were held for 5 weeks in twelve small pools (4.67 m2 surface area) at biomasses of 0. 5, 10 or 18 g m−2 (live weight). The pools were stocked with known densities of macroinvertebrates.2. Crayfish significantly affected the abundance of macroinvertebrates in the pools. Differences in the effects of crayfish on macroinvertebrates were related to crayfish sex, the presence of age‐0 crayfish, and the species of macroinvertebrate.3. The abundance of snails (Stagnicola elodes and Physa gyrina) was greatly reduced, in comparison with controls, by biomass of female crayfish ≥10 g m−2 and by biomasses of male crayfish ≥5 g m−2. The total density of non‐molluscan invertebrates was inversely correlated with the biomass of female crayfish but the total biomass of non‐molluscan invertebrates did not differ between treatments. This is consistent with our observation that small invertebrates (<2 mg wet weight) were less numerous, and large amphipods (32–64 mg) were more numerous, in pools stocked with female crayfish. In contrast, male crayfish had little apparent effect on the abundance of non‐molluscan invertebrates.4. Age‐0 crayfish hatched at the end of Experiment 1 and were present in each pool at the start of Experiment 2. Surprisingly, male crayfish preyed little on age‐0 crayfish. At the end of Experiment 2, the densities of age‐0 crayfish varied between six and 116 individuals m−2 and there was a strong inverse correlation between the mean biomass and density of age‐0 crayfish recovered from the pools. This suggests age‐0 crayfish were food limited in the pools and may explain the dominance of oligochaetes (which largely escape predation by burrowing) in the invertebrate community at the end of Experiment 2.5. These results indicate that even relatively low densities of crayfish could greatly affect the abundance of macroinvertebrates in lakes. The introduction of crayfish into lakes (most lakes in Alberta currently have no crayfish) could substantially affect abundance and species composition of the macroinvertebrate community and, ultimately, the fish populations.

The impact of the crayfish Orconectes virilis on aquatic macrophytes

SUMMARY. 1. The impact of crayfish on the biomass, density and shoot morphology of four submersed plant species was examined under semi‐natural conditions. Male or female crayfish (Orconectes virilis) were held for 5 weeks at biomasses of 0, 5, 10 or 18 g m−2 (live weight) in twelve plastic pools (4.67 m2, surface area) containing Potamogeton richardsonii, Myriophyllum exalbescens, Nuphar variegatum and Sparganium eurycarpum.2. Crayfish significantly affected biomass, density and/or shoot morphology of all four macrophyte species. Differences in the effect of crayfish on macrophyte growth were related to plant species, crayfish sex and activity, and the abundance of alternative foods.3. The effect of female crayfish on macrophyte growth was generally stimulatory. Myriophyllum and Potamogeton biomass, Potamogeton density and Myriophyllum length increased in the presence of female crayfish, possibly due to the reduction in herbivorous snails as a result of crayfish predation. In contrast, plant growth decreased in the presence of male crayfish: Myriophyllum, Nuphar and Potamogeton biomass, Myriophyllum and Sparganium density, and Sparganium and Poiamogeton length were reduced at male crayfish biomasses between 5 and 18 g m−2.4. These results indicate that even relatively low densities of crayfish can greatly affect the growth of submersed aquatic plants. Because of their ability to modify aquatic macrophyte, macroinvertebrate and, ultimately, fish communities, the introduction of crayfish into lakes where they do not occur could have a major effect on the structure and composition of the littoral zone.