Dendritic properties of uropod motoneurons and premotor nonspiking interneurons in the crayfish Procambarus clarkii Girard

Dendritic properties of uropod motoneurons and premotor nonspiking interneurons of crayfish have been studied using intradendritic recording and current injection. The input resistance of phasic motoneurons (5.20 ± 0.5 M; mean ± standard error) measured by injecting constant hyperpolarizing current was significantly lower than that of tonic motoneurons (10.3 ± 2.6 M; 0.02 < P < 0.05). The membrane time constant of phasic motoneurons (7.3 ± 0.9 ms) was also significantly shorter than that of tonic motoneurons (24.3 ± 2.5 ms; P < 0.001). Both types of motoneurons behaved linearly during hyperpolarization and sub-threshold depolarization. Nonspiking interneurons showed outward rectification upon depolarization. During hyperpolarization, their membrane behaved linearly and showed significantly higher input resistance (19.5 ± 2.5 M) than phasic and tonic motoneurons (P < 0.001). Their membrane time constant (38.0 ± 5.7 ms) was significantly longer than that of phasic motoneurons (P < 0.001) but not than that of tonic motoneurons (P > 0.05). In response to intracellular injection of sinusoidally oscillating current, phasic motoneurons showed one or two spikes per depolarization period irrespective of oscillating frequency ranging from 1 to 16 Hz. Tonic motoneurons showed larger numbers of spikes per stimulus period at lower frequencies. Nonspiking interneurons also showed phase-locked effects on the motoneuron spike activity. The effective frequency range over which injected oscillating current could modulate motoneuron spike activity was similar for tonic motoneurons and nonspiking interneurons.     

The slow muscles in the uropod of crayfish,Procambarus clarkII

• 1.1. The fiber types of uropod muscles of the crayfish, Procambarus clarkii, were determined by the myofibrillar ATP-ase histochemistry and electrophysiology.
• 2.2. The ATP-ase histochemistry was carried out on the sections of the whole tailfan and the slow muscles were identified as being of the slow type on the basis of their low staining intensities.
• 3.3. The location of slow bundles in the mixed type muscles i.e. the dorsal rotator (DRT), the ventral rotator (VRT), and the telson-uropodalis posterior (TUP) was confirmed.
• 4.4. TUP was newly revealed in this study to be a mixed muscle.

     

The effects of some putative transmitters and biogenic amines on uropod abductor muscle in the crayfish Procambarus clarkii and Cambaroides japonicus

The effects of some putative transmitters and biogenic amines were examined on the uropod ventral abductor exopodite (AbdExV) muscle in two crayfish species Procambarus clarkii and Cambaroides japonicus. Bath application of L-glutamate to the AbdExV muscle caused sustained contract while gamma-aminobutyric acid (GABA) depressed the nerve-evoked contraction of the muscle. Acetylcholine (ACh) had no effect on both the resting tension and the nerve-evoked contraction. Iontophoresis of L-glutamate and GABA onto the surface of the muscle fiber further confirmed that glutamate and GABA are the possible excitatory and inhibitory transmitters respectively at the neuromuscular junction of AbdExV muscle. Bath application of 5-hydroxytryptamine (5-HT) and octopamine (Oct) caused enhancement of the nerve-evoked contraction but dopamine (DA) had no effect on both the resting tension and the nerve-evoked contraction.     

The effects of acetylcholine, carbamylcholine and gamma-aminobutyric acid on uropod motoneurons in the crayfish Procambarus clarkii and Cambaroides japonicus

The effects of acetylcholine (ACh), carbamylcholine and gamma-aminobutyric acid (GABA) on the spike activity of uropod motoneurons were investigated electrophysiologically in the crayfish Procambarus clarkii Girard and Cambaroides japonicus de Haan. High concentrations of ACh were required to bring about an increase in the spike discharge of uropod motoneurons while carbamylcholine, which is not destroyed by cholinesterase, caused a marked increase in the motoneuron spike discharge even in low concentrations. Application of GABA in concentrations of 10(-5)-10(-2) M caused the decrease in the spike discharge of uropod motoneurons. Under the condition that the synaptic transmission onto uropod motoneurons was blocked by perfusing EGTA containing Ca2+-free saline with high-Mg2+, ACh increased the spike discharge of uropod motoneurons whereas GABA decreased it. The results suggested that ACh and GABA function as excitatory and inhibitory transmitters, respectively, in the crayfish central nervous system.     

Physiology and excitation-contraction coupling in the intestinal muscle of the crayfish Procambarus clarkii

The intestinal muscles of Procambarus clarkii are striated and yet they are specialized to produce slow peristaltic waves of contraction, not unlike those seen in vertebrate visceral smooth muscle. These muscles cannot be tetanized either by repetitive stimulation or by elevated potassium saline. The excitation-contraction (E-C) coupling mechanism was explored and compared with that known in crustacean skeletal muscle. Contraction is dependent on external Ca2+ which triggers the release of intracellular calcium from the sarcoplasmic reticulum (SR) via calcium-induced calcium release (CICR). Whereas contraction force is proportional to [Ca2+]o up to that in normal saline (13.4 mM), higher levels of Ca2+ reduce force. Ryanodine, which blocks calcium release from the SR, abolishes electrically stimulated contractions and CICR. Relaxation is achieved by removal of calcium from the cytosol in at least two ways, first by the re-loading of calcium into the SR by Ca2+-ATPases and second by the movement of calcium out of the cell by extruding it across the sarcolemma via Na+/Ca2+-exchangers. It is hypothesized that the inability of this muscle to show tetanus arises from inactivation of the voltage-gated calcium channels by high calcium. This is supported by the result that caffeine application causes an increase in tonus and size of phasic contractions by circumventing the sarcolemma and dumping SR calcium stores.     

Morphological asymmetry and behavioral laterality in the crayfish, Procambarus clarkii

Lateral asymmetry is found widely among vertebrates, but is scarcely observed in invertebrates. Here, morphological asymmetry and behavioral laterality of a wild crayfish, Procambarus clarkii, was investigated. The carapace morphology of crayfish showed left–right differences; in some, the right side of the carapace was larger than the left side, while in others, the left side was larger. A bimodal distribution in the direction of escape behaviors induced by a tactile stimulus was also observed. Experimental crayfish were definitively divided into two groups: individuals that frequently jumped leftward (right type) and those that jumped rightward (left type). Moreover, carapace asymmetry and lateralized escape responses were significantly correlated. These results suggest that crayfish exhibit left–right dimorphism in natural populations. The ecological advantages and maintenance mechanisms underlying these behaviors are also discussed.     

Histological organization of the intestine in the crayfish Procambarus clarkii

Six longitudinal ridges span the length of the intestine in the crayfish Procambarus clarkii. A simple columnar epithelium with tetralaminar cuticle lines the lumen. Folds of the epithelium overlie a dense irregular connective tissue packed with mixed acinar (alveolar) glands. Mucous secretions are probably involved with formation and lubrication of faecal strings; neither the nature nor the role of the serous secretions is immediately apparent. Aggregations of cells with large cytoplasmic vacuoles, called bladder cells, appear in the subepithelial connective tissue near the tops of the intestinal ridges. The bladder cells are suitably positioned to bolster the integrity of the ridges. Striated muscle of the intestine occurs in inner longitudinal and outer circular layers. The inner longitudinal layer consists of six strips, with one strip associated with the base of each intestinal ridge. The outer circular layer is essentially complete, but there are periodic apertures in this layer on the left and right sides of the intestine, providing nerves and haemolymph vessels with access to the interior of the gut. Based on histological features, and consistent with reports on other crayfish, we conclude that the intestine of P. clarkii has a proctodeal (ectodermal) origin.     

Unexpected divergence among identified interneurons in different abdominal segments of the crayfish Procambarus clarkii

The command elements that initiate and coordinate the abdominal movements in crayfish show little similarity between the various abdominal segments. Our criteria for similarity among interneurons were based on both cell morphology and electrophysiology. By contrast, previously published evidence shows much greater intersegmental similarity in the skeletal, muscular, motoneuronal, and sensory components of the abdominal system in crayfish, structures that are controlled by or send information to the command elements. Therefore, unlike the command elements, these structures have retained nearly identical form and function in the various segments. We also found in different ganglia examples of interneurons involved with abdominal positioning behavior that have similar morphology but different function and vice versa. Such interneurons could represent divergent pairs of serial homologues. It is unknown why so many of the abdominal positioning interneurons have become different. The various ganglia may perform subtly different functions, requiring differences in the positioning interneurons but not in the motor neurons or muscles. Alternatively, some of the abdominal positioning interneurons underlie more than one behavior; consequently, selection acting on these multiple functions may have changed these interneurons through evolution.     

Asynchronous swimmeret beating during defense turns in the crayfish, Procambarus clarkii

Swimmeret beating was monitored in freely moving specimens of the crayfish Procambarus clarkii as they exhibited defense turn responses to tactile stimuli. Analysis of videotape records revealed alterations in swimmeret beating during turning responses compared to straight, forward walking. During turns, swimmerets beat with shorter periods and smaller amplitude power strokes than during straight walking. Coordination between swimmerets also changed. Swimmerets on the side toward which the animal turned tended to lag behind their contralateral partners, rather than beat in synchrony as in straight walking, and ipsilateral coordination was loosened relative to straight walking. Asynchronous swimmeret beating accompanied asymmetric motions of the uropods in a manner similar to that observed during statocyst-dependent equilibrium reactions in P. clarkii, but removal of the statoliths did not eliminate turn-associated responses of the swimmerets. The coordinated action of the swimmerets and uropods may contribute to the torque that rotates the animal in the yaw plane. Implications of the observed changes in swimmeret coordination for understanding the underlying neuronal control system are discussed.     

Methyl farnesoate controls adult male morphogenesis in the crayfish, Procambarus clarkii

Adult male crayfish Procambarus clarkii exist in two morphotypes. They continue to molt as adults, switching between Form Is and Form IIs. Form Is are primary reproductive types, with large chelae and spines on the ischiopodites of the third and fourth pair of walking legs. Form IIs are non-reproductive types with smaller chelae and no spines on the ischiopodites. We investigated the hormonal control of these transitions in two ways, by eyestalk ablation and by methyl farnesoate (MF) treatments. Eyestalk ablation accelerates molting and increases MF levels in the blood. MF is a hormone that regulates both reproduction and morphogenesis. MF concentrations were determined in two ways. The hemolymph samples were extracted first, then purified, using normal phase HPLC. The fractions containing MF were collected and analyzed for MF concentration, utilizing both internal and external standards by GC/MS. The other hemolymph samples were analyzed from individual animals by HPLC. The concentrations of ecdysteroids were determined by radioimmunoassay. In the control animals, 4 out of 4 untreated Form I males molted into Form II, while 6 out of 7 Form IIs molted into Form Is. Eight of 8 ablated Form Is molted into Form IIs as expected, while 5 of 5 ablated Form IIs molted into Form IIs, instead of Form Is. MF treatment of intact animals resulted in 6 of 7 Form Is becoming Form IIs and 5 of 6 Form IIs becoming Form IIs. These results were highly significant in comparison of Form I and IIs in each treatment (eyestalk intact, eyestalk ablated and eyestalk intact with MF) by a chi square analysis, P = 0.006, P < 0.0005, and P = 0.013, respectively. MF premolt blood levels suggested that Form IIs were produced in the presence of 1.3 ng/ml MF, while Form Is result from MF levels less than 0.5 ng/ml. Since both eyestalk ablation and MF treatment resulted in the failure of Form IIs becoming Form Is, it was concluded that the control of morphogenesis of primary reproductives (Form Is) depends on a low level of MF prior to the molt, while Form IIs are formed in the presence of increased levels of MF.     

Discovery of four natural clones in a crayfish species Procambarus clarkii

Self-cloning is quite rare in shrimp, lobsters, crayfish and crabs. Here we report the discovery of four natural clones of red swamp crayfish (Procambarus clarkii), each containing 2-6 genetically identical individuals, during the genotyping of 120 individuals with five microsatellites. The four clones were heterozygote at most of the five microsatellite loci. Phylogenetic analysis using microsatellite genotypes suggests recent origin of the four clones. Sequencing a part of the mitochondrial gene Cox I confirmed that the four clones were from the species Procambarus clarkii.     

Factors influencing the degradation of photoreceptor membrane in the crayfish,Procambarus clarkii

Summary Light-induced degradation of photoreceptor membrane in the crayfish was studied by quantitative light and electron microscopy. The production of lysosomal organelles within the photoreceptor cells was enhanced by presenting the light stimulus intermittently (i.e., flicker) or by doubling its intensity. The enhancement was seen primarily as an increase in the number and size of multivesicular bodies. As these stimulus conditions are likely to facilitate intracellular Ca⁺⁺ fluxes, the results are compatibl with recent speculations that Ca⁺⁺ ions may regulate membrane degradation. To test the possibility that Ca⁺⁺ acts as a signal coupling receptor stimulation with membrane loss, retinas were incubated in the dark with the ionophore A23187 in the presence or absence of external Ca⁺⁺. The results demonstrate that A23187 produces a Ca⁺⁺-dependent increase in lysosomal organelles, predominantly multivesicular bodies. These data are consistent with a role for intracellular Ca⁺⁺ in the degradative process; however, the exact locus of the effect is unclear.Supported by a grant (BNS 8004587) from the National Science Foundation to G.S.H. The authors gratefully acknowledge the helpful discussions and expert technical assistance of Thomas R. Tokarski     

Corazonin promotes tegumentary pigment migration in the crayfish Procambarus clarkii

The undecapeptide corazonin (pGlu-Thr-Phe-Gln-Tyr-Ser-His-Gly-Trp-Thr-AsnNH(2)) elicits a retraction of erythrophore pigment granules and dispersion of leucophore pigment granules in the crayfish Procambarus clarkii. The effects are dose-dependent from 10(-10) to 10(-5)M. Influence on erythrophores is lower than that of Red Pigment Concentrating Hormone (RPCH), which is inactive on leucophores. Corazonin effects are partly blocked by an anti-corazonin antibody, and even less by an anti-RPCH antibody. Corazonin effects are completely suppressed by the calcium chelator BAPTA. Immunoreactive somata and fibers were identified in various regions of the eyestalk (medulla terminalis, medulla interna and medulla externa) with the anti-corazonin antibody. These results suggest the possible existence of a corazonin-like peptide in crustaceans.     

Nutritional status and energy metabolism of crayfish (Procambarus clarkii, Girard) muscle and hepatopancreas

1. Food deprivation resulted in significant decreases in muscle carbohydrate, lipid and water content and increased ATP, ADP, AMP and total adenylate levels over the 21-day experimental period. 2. In the hepatopancreas phosphoarginine was significantly higher on day 21 in the starved crayfish. 3. Muscle energy charges remained within optimal (unstressed) ranges, while hepatopancreatic energy charges of food-deprived crayfish fell into suboptimal (stressed) ranges, indicating the necessity of examining organs separately to accurately ascertain metabolic changes in response to stressors.     

High prevalence of multiple paternity in the invasive crayfish species,Procambarus clarkii

Reproductive strategy is a central feature of the ecology of invasive species as it determines the potential for population increase and range expansion. The red swamp crayfish, Procambarus clarkii, has invaded many countries and caused serious problems in freshwater ecosystems. However, little is known about the effects of environmental conditions on crayfish paternity and offspring traits in the wild. We studied these reproductive characteristics of P. clarkii in wild populations from two different habitats (ponds and ditches) in three locations with different environmental conditions in China. Genotyping of 1,436 offspring and 30 mothers of 30 broods was conducted by using four microsatellites. An analysis of genotyping results revealed that gravid females were the exclusive mother of the progeny they tended. Twenty-nine of 30 mothers had mated with multiple (2-4) males, each of which contributed differently to the number of offspring in a brood. The average number of fathers per brood and the number of offspring per brood were similar (P > 0.05) among six sampling sites, indicating that in P. clarkii multiple paternity and offspring number per brood are independent of environmental conditions studied. Indirect benefits from increasing the genetic diversity of broods, male and sperm competition, and cryptic female choice are a possible explanation for the high level multiple paternity and different contribution of fathers to offspring in this species.     

Serotonergic regulation of crustacean hyperglycemic hormone secretion in the crayfish, Procambarus clarkii

These studies investigate if crustacean hyperglycemic hormone (CHH) is involved in 5-hydroxytryptamine (5-HT)-induced hyperglycemia. Eyestalk ganglia with intact X-organ-sinus gland complex were dissected from the crayfish Procambarus clarkii and incubated under various experimental conditions. Incubation media were then analyzed for the presence of released hyperglycemic factor using an in vivo bioassay. The results show that 5-HT enhanced release of hyperglycemic factor in a dose-dependent manner. This stimulatory effect of 5-HT was significantly decreased by adding ketanserin or methysergide (both 5-HT receptor antagonists) into incubation of eyestalk ganglia. Further, activity of the 5-HT-released hyperglycemic factor could be eliminated by adsorption of incubation media with anti-CHH serum but not by preimmune or anti-5-HT serum. These results confirm the hypothesis that 5-HT enhances release of CHH, which in turn elicits hyperglycemic responses. It is probable that 5-HT activates an excitation-secretion coupling mechanism by interacting with receptors located on the X-organ neurosecretory cells.     

Pigment dispersing hormone generates a circadian response to light in the crayfish, Procambarus clarkii

Photoreceptor cells have been identified as important structures in the organization of the circadian system responsible for the generation and expression of the electroretinogram (ERG) circadian rhythm. They are the structures where the circadian periodicity is expressed (effectors) and which transform information from external light signals to be conducted to the pacemaker in order to induce adjustments of the rhythm (synchronizers). After isolation, eyestalks perfused in a pigment dispersing hormone (PDH) solution, show significant changes in receptor potential (RP) amplitude and duration. Exogenous PDH injected into intact crayfish induces a migration of retinal shielding pigments to a light-adapted state. A single dose of PDH produces advances or delays in the circadian rhythm of response to light of visual photoreceptors. All these effects depend on the circadian phase of PDH application. Consequently, the determination of the action of exogenous PDH on photoreceptor cells proved to be very helpful in understanding some mechanisms underlying the circadian organization of crayfish.     

Morphology of descending statocyst interneurons in the crayfish Procambarus clarkii Girard

Summary The morphological features of descending interneurons that responded to the artificial bending of statolith hairs were assessed with intracellular recording and staining techniques. Seven statocyst interneurons were identified on the basis of their structure and response characteristics and designated as interneurons S1 to S7. All seven identified interneurons project to the optic lobe, where the optic nerve also projects, and to the dorsal part of the tritocerebrum, where the eyestalk motoneurons originate. All except interneuron S6 also extend their major branches to other neuropilar regions. S2 projects to the dorsal part of the deutocerebrum, where the statocyst nerve terminates, and S3 to the dorsal part of deutocerebrum and the antennal lobe. Four other interneurons (S1, S4, S5, S7) also extend their branches to the parolfactory lobe to which the statocyst nerve projects as well as to the deutocerebrum and antennal lobe. The extensive dendritic projections of S1–S7 suggest that they are complex multimodal interneurons rather than simple relay interneurons, receiving at least visual and statocyst sensory information. The function of the antennal lobe branches, however, has yet to be determined since the functional role of antennal input in equilibrium control is unknown.     

养殖条件下克氏原螯虾亲虾的形态性状研究

为了解人工养殖的克氏原螯虾(Procambarus clarkii)亲虾的生长和形态性状,为人工放养亲本的选择提供参考依据,测定了342尾体重大于20 g的克氏原螯虾的体重(W)、全长(TL)、头胸甲长(CL)、头胸甲宽(CW)、螯足长(ChL)和螯足宽(ChW),比较了雌性和雄性生长和形态参数的差异性,模拟了各参数间的回归方程,并探讨了各参数间的相关性。结果显示,雌性个体体重、螯足长和螯足宽的均值显著低于雄性,而头胸甲长和头胸甲宽的均值则显著高于雄性,全长和丰满度在雌雄之间差异不显著。雌性和雄性个体的优势全长范围均为90～119. 99 mm,优势体重范围分别为20. 0～39. 9 g和30. 0～44. 9 g。克氏原螯虾全长-体重的关系为W_♀=0. 000 01×TL~(3. 381 3)、W_♂=0. 000 01×TL~(3. 230 9),雌性和雄性均为正异速生长;头胸甲长-体重的关系为W_♀=0. 000 1×CL~(3. 215 5)、W_♂=0. 000 2×CL~(3. 179 8);头胸甲长-全长的关系为TL_♀=2. 928 6+2. 027×CL、TL_♂=-5. 036 9+2. 370 1×CL;头胸甲宽-头胸甲长的关系为CL_♀=5. 479 2+1. 942 3×CW、CL_♂=9. 646 8+1. 765 6×CW;螯足宽-螯足长的关系为ChL_♀=-13. 721+6. 679×ChW、ChL_♂=-4. 828+6. 148 7×CW。相关性分析表明,总体上6个参数之间均有显著的正相关关系,其中与体重相关性较高的为全长和头胸甲长与宽。