Female Crayfish Research Articles

Concentration of Heavy Metals in Different Tissues of Astacus leptodactylus from Aras Dam of Iran

Due to different human activities in the vicinities of Aras dam, various pollutants such as heavy metals are entered into the reservoir and thus polluting the aquatic ecosystem. As a result, this heavy metal is accumulated in the tissues of Astacus leptodoctylus, which is considered as one the abundant species of crayfish that has got important food values and is of economic importance due to its export to other countries. In this research, the bioaccumulation of heavy metals in different tissues of this animal is taken into consideration. The concentration of Fe, Cu, Zn, Mn, Pb, Ni, Co and Cr among the tissues of female and male Astacus leptodactylus has been determined. The highest concentration of Cu and Fe was found in the gills and the highest level of Zn was found in hepatopancreas. Besides, the highest Mn concentration was recognized in exoskeleton. Furthermore, no significant difference was found between the male and female crayfish in the concentration of the heavy metals in their tissues, except for the concentration of some of the metals such as Fe in some of the tissues such as hepatopancreas.

The effect of the chemical environment on interactions in groups of crayfish

Most of our knowledge of social behaviour in crustaceans stems from observations of pairs of animals engaged in conflict. Less consideration has been given to the dynamics of group behaviour. We investigated whether chemical signals affect the dynamic of groups of Cherax destructor. Animals were exposed to odours collected from male, female, moulted or dominant crayfish, or from fish. We observed agonistic encounters in the group during a 15 min period after the introduction of the odour. There was a decrease in threat behaviours when the male odour was added. We conclude from this that an olfactory stimulus can affect the dynamic of group interactions and the results suggest that the outcome is likely to be different from that obtained with paired or single individuals.

Male–Female Communication in the Crayfish Orconectes rusticus: The Use of Urinary Signals in Reproductive and Non‐Reproductive Pairings

AbstractAnimals use sensory communication to locate conspecifics, food, shelter, and avoid predators. Using urine visualization techniques as well as Digital Particle Illumination Velocimetry, we examined the role of urinary signals and current generations during social interactions of male and female crayfish. Both reproductive and non‐reproductive crayfish were paired to gain a better understanding of how reproductive state influences communication. Analyses of agonistic and mating events were paired in time with recorded urine release and current generation, illustrating a correlation of chemical communication with ritualized social behavior. Four treatment groups were run with specific combinations of different reproductive status: (1) both opponents reproductively active, (2) only the male in reproductive, (3) only the female reproductive, or (4) both opponents non‐reproductive. Results showed differences between treatment groups in urine release, current generation, and social behavior. Within reproductive pairings, both the male and female crayfish generated currents and released urine at higher rates than those in other treatment groups. Urine was released most often when opponents were in chelae contact with each other and these releases were often accompanied by anterior current generation. In addition, communication was different in reproductive trials where mating occurred. Overall, the results indicate that the use of hydrodynamic and chemical signals changes as a function of reproductive state and that this change in communication probably indicates readiness to mate.

Dishonest Signals of Strength in Male Slender Crayfish (Cherax dispar) during Agonistic Encounters

Many animals resolve disputes without combat by displaying signals of potential strength during threatening displays. Presumably, competitors use each other's displays to assess their relative strengths, and current theory predicts that these signals of strength should generally be honest. We tested this prediction by investigating the relationships among morphology, performance, and social dominance in males of the slender crayfish Cherax dispar. Crayfish routinely use their enlarged front claws (chelae) for both intimidation and fighting, making this species ideal for studying the honesty of weapon size. We evaluated five competing models relating morphological and physiological traits to dominance during paired competitive bouts. Based on the best model, larger chelae clearly resulted in greater dominance; however, chela strength had no bearing on dominance. Thus, displays of chela size were dishonest signals of strength, and the enlarged chelae of males seemingly function more for intimidation than for fighting. In addition, an analysis of the performance of isolated chela muscle showed that muscle from male crayfish produced only half the force that muscle from female crayfish produced (236.6+/-26.4 vs. 459.5+/-71.6 kN m(-2)), suggesting that males invest more in developing larger chelae than they do in producing high-quality chela muscle. From our studies of crayfish, we believe dishonest signaling could play a greater role in territorial disputes than previously imagined.

Gonadal development and biochemical composition of female crayfish Cherax quadricarinatus (Decapoda: Parastacidae) in relation to the Gonadosomatic Index at first maturation

Gonadal development of female crayfish Cherax quadricarinatus at first maturation (25.5 ± 3.8 g) was investigated using morphological criteria (Gonadosomatic and Hepatosomatic Indices or GSI and HSI), biochemical composition (proteins, lipids, and carbohydrates) of the gonad and hepatopancreas, histological indicators (oocyte diameter, frequency of pre-vitellogenic, vitellogenic, and post-vitellogenic oocytes), and histochemical analyses (percentage coverage of lipid and carbohydrate reserves or LI and CI). There was a negative relation between GSI and HSI ( P < 0.01). Protein ( P < 0.01), lipid ( P < 0.01), and carbohydrate ( P < 0.01) contents in the gonad were dependent on GSI. At mature stages, higher concentrations of protein and lipid reserves were observed, while carbohydrates diminished. In hepatopancreas, the lipid content decreased in relation to GSI ( P < 0.05). There was no evidence that protein and carbohydrate components in the hepatopancreas varied in relation to GSI ( P > 0.05). High statistical power (> 0.99 for both contents) indicates that protein and carbohydrate concentration remains relatively constant throughout gonadal development. A significant decrease in the frequency of oogonia ( P < 0.01), pre-vitellogenic oocytes ( P < 0.01), and primary vitellogenic oocytes ( P < 0.01) was observed as maturation was reached. A mathematical inflexion point showed that there was a maximum frequency of secondary vitellogenic oocytes at 4.06 GSI. There were increases in diameter and nuclei of oocytes at all developmental stages ( P < 0.05). LI increased as oocytes developed ( P < 0.01). CI varied between stages ( P < 0.01) and peaked at the primary vitellogenic stage. The dynamics of biochemical composition of gonad and hepatopancreas of female C. quadricarinatus was in agreement with similar studies in decapods. The usefulness of the GSI as an indicator of reproduction stage and female broodstock management is addressed.

Novelty stress and reproductive state alters responsiveness to sensory stimuli and 5-HT neuromodulation in crayfish

Sensory stimuli can produce varied responses depending on the physiological state of an animal. Stressors and reproductive stage can result in altered biochemical status that changes the responsiveness of an animal to hormones and neuromodulators, which affects whole animal behavior in relation to sensory stimuli. Crayfish serve as a model for examining the effects of neuromodulators at the neuromuscular junctions (NMJs) and for alterations in stereotypic behaviors for particular stimuli. Thus, we used crayfish to examine the effect of novelty stressors in males and the effect of being gravid in female crayfish to exogenous application of serotonin (5-HT). The responsiveness of neuromuscular junctions to 5-HT revealed that stressed as well as gravid crayfish have a reduced response to 5-HT at NMJs. The stressed crayfish were not fatigued since the basal synaptic responses are large and still showed a pronounced response to 5-HT. Using intact animals to examine a tail flip behavior, we showed that the rate of habituation in tail flipping to a strong repetitive stimulus on the telson is reduced in stressed males. Gravid females show no tail flipping behavior upon telson stimulation.

Success and failure in a lotic crayfish invasion: the roles of hydrologic variability and habitat alteration

Summary1. This paper examines the distribution, habitat relationships, and potential for spread of non‐native signal crayfish (Pacifastacus leniusculus) in streams of the Truckee River catchment, California, U.S.A. Crayfish associations with natural features and with impoundments and flow alteration were examined in a survey of 33 streams. Abundance changes were followed over 5 years, which included some of the highest and lowest flows on record, in three streams, two unregulated and one regulated. Movement of marked crayfish was studied in one 0.5 km stream reach just upstream from a reservoir.2. Signal crayfish were most abundant in low‐gradient streams and were positively associated with proximity to reservoirs (both upstream and downstream). Crayfish were more likely to be found in regulated than unregulated sites, and did not occur in sites upstream of barriers, such as culverts, that separated them from reservoirs or lakes.3. Crayfish declined in abundance in years following particularly intense and prolonged wet‐season spates, leading to a negative association between crayfish abundance and both peak discharge and duration of bankfull flows.4. Crayfish moved distances of up to 277 m, and at rates of up to 120 m day−1, suggesting significant dispersal ability. Larger crayfish moved greater distances and were more likely to move downstream. Female crayfish showed a pattern of upstream movement in early summer and downstream movement late in the summer, opposite the pattern found in two other studies.5. These results suggest that natural or artificial gradient barriers and, in regulated systems, management of flow regimes to include bankfull or greater flows may help to control invasive crayfish in streams.

Sexual difference in modes of selection on the pleopods of crayfish (Decapoda: Astacoidea) revealed by the allometry of developmentally homologous traits

Crayfish have five pairs of abdominal limbs called pleopods. In males, the first and second pairs of pleopods are used for transferring spermatophores to the female during copulation. The remaining pleopods in males have no obvious function. Female crayfish use their pleopods to carry eggs. Accordingly, it is expected that the selection pressures that act on the pleopods differ between males and females. To test this hypothesis, we estimated modes of selection on pleopods in two species of crayfish (Procambarus clarkii and Pacifastacus trowbridgii) by comparing allometric relationships in functional and nonfunctional pleopods. Since pleopods are serially homologous traits, developmental constraints on these traits appear to be minimal. The lengths of the first male pleopods, used in copulation, showed lower allometric values and less dispersion around the regression line, suggesting that they have been under stabilizing selection. This likely occurs because the major selective force is the ability of males to copulate with females of various sizes. The pleopods of females showed higher allometric values than pleopods of males without an assigned function. This suggests that the pleopods of females have been under directional selection, most likely because they are longer and can therefore carry more eggs.

Sex determination in crayfish: are intersex Cherax quadricarinatus (Decapoda, Parastacidae) genetically females?

In the Australian red-claw crayfish Cherax quadricarinatus (von Martens) (Decapoda, Parastacidae), a gonochoristic species, seven different combinations of intersex individuals (with both male and female genital openings) have been described. However, to date, the genetic basis for this phenomenon has not been investigated. This study was designed to test a simple chromosome-based sex-determination model for C. quadricarinatus that assumes the male to be the homogametic (ZZ) sex. According to our model, intersex individuals that are functionally males are genetically females (WZ). Individual crosses were performed between intersex and female crayfish, with control crosses being performed between normal males and females. The control crosses yielded, in most cases, the expected 1:1 sex ratio in the F1 progeny. Crosses between intersex individuals and females yielded a 1:3 (male:female) sex ratio in most crosses. According to our hypothesis, one-third of the females produced in a cross of a female with an intersex animal should be WW females. The hypothesis was tested by crossing normal males with F1 females, which were progeny of intersex fathers. These crosses yielded almost 100% females, a finding that conforms to the above-suggested sex determination model for C. quadricarinatus and the female WZ genotype of intersex individuals.

The Influence of Androgenic Gland Implantation on the Agonistic Behavior of Female Crayfish (Cherax Quadricarinatus) in Interactions with Males

The effect of the androgenic gland (AG) on female agonistic behavior was studied in the Australian freshwater crayfish Cherax quadricarinatus . Interactions between large males and smaller individuals of three types - sham-operated females, females implanted with the AG and intact males - were compared. Half-hour-long pair encounters were staged in large aquaria and monitored with a video camera. Interactions between crayfish of the same or opposite gender(s) were of a clearly agonistic character, without any courtship or reproductive elements. The large males were the winners of all fights. Small males fought more often and for longer periods of time, and grasped their male opponents for longer periods of time, than sham operated females. AG-implanted females occupied an intermediate position between the two genders in their fighting behavior. In addition, AG-implanted females performed 'crawling over' (a tolerance-indicative act which is more pronounced towards the other sex) over the large males less frequently than the sham operated females did, and were also treated by these males more like males than females, with regard to this behavior. The behavioral changes in AG-implanted females followed the general trend of masculinization also evident in the morphological and physiological changes in their gonads and the appearance of male secondary sexual characters.

Functional significance of crayfish in stream food webs: roles of omnivory, substrate heterogeneity and sex

Heterogeneity of species interactions in food webs can result from characteristics of substrates as well as attributes of top consumers. We performed a streamside channel experiment to evaluate the impact of crayfish on lower trophic levels in detritus‐based (leaf packs) and algal‐based food webs (hard‐bottoms). After 43 days, both male and female crayfish had dramatically promoted leaf decomposition, with males processing material at a faster rate. However, the difference in leaf processing rates was not related to a greater level of male activity. Despite the sex‐related difference in residual leaf dry mass, densities of invertebrates in leaf packs were similarly low in the presence of crayfish of either sex, due to resource consumption, physical dislodgment (bioturbation) and/or predation. No trophic cascade was evident in the leaf pack assemblage. In the hard‐bottom assemblage, the results confirmed circumstantial field evidence that crayfish reduce predatory Tanypodinae and indirectly increase collector‐gatherer Chironominae following the prediction of a trophic cascade. However, no other taxa were indirectly facilitated, because of strong direct effects of crayfish on algal abundance (through direct consumption and bioturbation). Overall, impacts of crayfish on lower trophic levels were more pronounced in the structurally complex, detritus‐based assemblages than in its hard‐bottom, algal‐based counterpart. This conflicts with the expectation that net predation effects should be weaker where structural complexity is greater but is mainly a consequence of the profound engineering effects of crayfish in reducing colonisable substrate when they shred and disturb detrital material. Effects of crayfish may therefore propagate differently and with varying strength depending on substrate. Moreover, engineering activities and predation by crayfish appear to have been of overwhelming significance with subtle sex differences in leaf processing rates failing to lead to differences in invertebrate densities.

Reproductive Biology of the Crayfish Orconectes luteus (Creaser) in a Missouri Stream

The reproductive biology of the crayfish Orconectes luteus (Creaser) from the Jacks Fork River, Missouri, was studied. Data on reproduction, fecundity and growth were obtained from monthly or semimonthly collections over 27 mo. Females oviposited in March or April, depending on water temperature, and the young became independent by May or June. Seasonal growth and molting began when water temperatures exceeded about 9 C in spring and ceased when water temperatures dropped below 8 C in fall. About one-third of the male and female crayfish became sexually mature their first year of life. Adult males began molting to the reproductive state (Form I) in September and October and returned to the nonreproductive state (Form II) in April and May when the females were carrying eggs and young. Newly hatched young went through two molts before becoming independent from the female in the third instar. A significant positive relation was found between crayfish size and number of ovarian eggs, pleopodal eggs and size of pleopodal eggs. Significantly greater numbers of ovarian vs. pleopodal eggs were found at both sites.

INFESTATION RATE OF BRANCHIOBDELLIDS IN AUSTROPOTAMOBIUS PALLIPES ITALICUS FROM A STREAM OF CENTRAL ITALY: PRELIMINARY RESULTS

Species identity, infestation rate and distribution over the host body of branchiobdellids (Annelida, Clitellata) have been analysed in an Austropotamobius pallipes italicus population from the National Park of the Foreste Casentinesi, Monte Falterona and Campigna (central Italy). Branchiobdella italica - the nearly unique species present in our samples - did not differ in its occurrence among the size classes of its host, while female crayfish showed a significantly higher infestation rate than the other sex. Branchiobdellids were mostly found on gill chambers and cephalothorax base, and only in the case of larger crayfish and males did they occupy other body areas.

Growth, morphometrics, size at maturity, sexual dimorphism and condition index of Austropotamobius torrentium Schrank

Growth, morphometric relationships and the size at maturity of the Stone crayfish Austropotamobius torrentium, a highly endangered European crayfish species, were investigated, in order to provide information for future protection management. Analyses of the weight–length relationship of A. torrentium revealed that males gained weight faster than females. This difference is due to an increased growth of chelae of males larger than 50 mm, which is assumed to be the size of sexual maturity of males. Female crayfish reached sexual maturity at 59 – 65 mm total length. The sex ratio in the studied sections of the brook Biberbach in Lower Austria was balanced. The estimated annual instantaneous growth rates ranged from 0 to 1.84. The growth rate declined rapidly in both sexes with increasing crayfish size. The crayfish condition showed the tendency to decline from May to August. The average crayfish condition was significantly higher in the section with superior current heterogeneity and percentage of potential shelter stones.

Rusty crayfish (Orconectes rusticus) movement within and between habitats in Trout Lake, Vilas County, Wisconsin

The exotic rusty crayfish, Orconectes rusticus, has invaded northern Wisconsin watersheds and is causing severe ecological alterations. We investigated the processes of rusty crayfish dispersal and movement within Trout Lake, Vilas County, Wisconsin, using a mark and recapture technique. We examined the effects of crayfish size, gender, and original location on distance traveled. Some O. rusticus moved up to 221 m in 2 d, but most crayfish remained in their original habitat (distances ranged from 0–58 m). Distances traveled were similar for both male and female crayfish. Crayfish size did not affect the patterns of movement. Crayfish did not travel greater distances over time, which may be an artifact of 2 groups of crayfish: those that stayed in their local habitat and those that moved far distances. Comparisons with published dispersal and movement data suggest that large movements are observed occasionally in both lotic and lentic habitats. For rusty crayfish, these movements have important implications for invasion rates.

Physiological effects of methyl farnesoate and pyriproxyfen on wintering female crayfish Cherax quadricarinatus

Methyl farnesoate (MF), the predominant juvenile hormone-like compound of crustaceans, was found in the hemolymph of female Cherax quadricarinatus crayfish. Administration of MF to C. quadricarinatus females during their winter reproductive arrest period had no effect on reproduction; however, it did have a tendency to accelerate molting. However, since MF caused increased mortality (∼47% survival in the high MF treatment), we were not able to draw definitive conclusions regarding its physiological affect. In contrast, administration of pyriproxyfen, a juvenile hormone analog, did not cause significant mortality (95% survival in the high pyriproxyfen treatment), although it accumulated in high quantities in the hepatopancreas and, to a lesser extent, muscle tissue, ovaries and gills. The highest dose of pyriproxyfen used in this study, 20 μg/gram animal body weight/week, caused a delay in spawning, which became statistically significant from the seventeenth week. This dose of pyriproxyfen caused a tendency of acceleration of molting without any effect on molt increment. The results of this study show that pyriproxyfen does not seem to be toxic to the crayfish, even in relatively high doses, and might affect the energetic balance between molt and reproduction.

Maternal territoriality as an offspring defense strategy in red swamp crayfish (Procambarus clarkii, Girard)

AbstractThe offspring‐defense hypothesis of maternal territoriality in solitary and semisocial mammals [Wolff JO and Peterson JA. 1998. Ethol Ecol Evol 10:227–239] was evaluated in another taxon using maternal and nonmaternal female red swamp crayfish (Procambarus clarkii), a freshwater decapod crustacean that shows pronounced shelter‐related maternal aggression. The maternal females were of three different categories: (1) ovigerous, (2) carrying primarily stage 1 offspring, or (3) tending offspring that were primarily stage 2. Each female was in residence in an individual aquarium containing only a gravel substrate for 24 hr prior to serial intrusions by male conspecifics. Virtually all of the residents, maternal and nonmaternal, excavated a depression (shelter) in the substrate prior to the first intrusion. The results showed that residents in each of the maternal categories won a significantly higher proportion of their encounters than did the nonmaternal residents, which showed only negligible defense and lost every encounter. However, there were no significant differences in encounter outcomes between the maternal resident categories. There was clear defense of the shelter by maternal females, with virtually all fighting being in or around it, thus demonstrating stable, heightened territorial defense throughout these maternal phases of reproduction. This support of the offspring‐defense hypothesis of maternal territoriality is the first such evidence for a freshwater crustacean and is very similar to that recently reported in a related marine decapod, the American lobster (H. americanus). Aggr. Behav. 27:391–403, 2001. © 2001 Wiley‐Liss, Inc.

L to d Amino Acid Isomerization in a Peptide Hormone Is a Late Post-translational Event Occurring in Specialized Neurosecretory Cells

Modification of the chirality of a single amino acid residue within a peptide chain appears to be novel additional mechanism leading to structural and functional diversification of eukaryotic bioactive peptides. This phenomenon has been studied at the cellular level in a neuroendocrine organ which elaborates a mixture of diastereoisomers of a 72-residue neuropeptide, crustacean hyperglycemic hormone. For the first time, amino acid isomerization has been shown to occur in the perikarya of fully specialized neurosecretory cells, as a late step of the maturation of the hyperglycemic hormone precursor and after propeptide cleavage. The specificity and efficiency of this phenomenon indicates the existence of a new enzyme family involved in the biogenesis of peptide hormones.

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

SUMMARY 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. Radiotransmitters 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 (aSE) daily movements were 4.6 a 3.0 m for males and 1.5 a 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.

The relationship between egg size and female size infreshwater crayfish, Astacus leptodactylus

In crayfish reproduction, one of the main factors affecting fecundity is egg size (Corey, 1991). An increase in egg size causes a decrease in fecundity in fish, gammaridean amphipods and similarly in crayfish (Abrahamsson, 1971; Ware, 1975; Steele and Steele, 1991). Although the relationship between fecundity and female size of Astacus leptodactylus has been the subject of much investigation (Cherkashina, 1970; Kossakowski, 1971; Papadopol, 1975; Stypinska, 1979; Koksal, 1988; Harlioglu, 1996), the relationship between egg size and female size of A. leptodactylus is little known (Harlioglu, 1996). Only a few studies have been carried out on crayfish species to evaluate the relation between egg size and female size (Abrahamsson, 1971; Mason, 1978; Lahti and Lindqvist, 1983; Kuris, 1991; Harlioglu, 1996). In order to have an accurate fecundity estimate, which is used in the estimation of recruitment, in addition to the relation between egg number and female size, the relation between female size and egg size should also be considered. Therefore, in the present study, the relationship between egg size and female size, and between egg wet weight and female size in A. leptodactylus was investigated. Males and females of A. leptodactylus were transferred from their natural habitat, the Agin Region of Keban Dam Lake, to the Crayfish Reproduction Unit of the Aquaculture Faculty of Firat University in Cip, Elazig in late summer of 1998. Mating and spawning started in mid-January 1999, and took approximately 3 weeks. The crayfish samples (n = 55, size range = 37–58 mm