Amino acid sequence of crayfish (Astacus fluviatilis) trypsin If

The complete amino acid sequence of trypsin from the crayfish Astacus fluviatilis has been determined. The protein was fragmented with cyanogen bromide after S-carboxymethylation of the reduced disulfide bonds and by trypsin after S-carboxymethylation as well as after succinylation of lysine residues and aminoethylation of the reduced disulfide bonds. Peptides were purified by gel filtration and by reversed-phase high-performance liquid chromatography. Stepwise degradation was performed in a spinning cup sequencer. The enzyme contains 237 amino acid residues and has a molecular weight of 25 030. In contrast to bovine trypsin, it contains three rather than six disulfide bonds which are paired in the same fashion as those in trypsin from Streptomyces griseus. The constituents of the active site of bovine trypsin are present in corresponding positions in the crayfish enzyme. Crayfish trypsin shows 43.6% sequence identity with the bovine enzyme as compared to 40.0% identity with the S. griseus enzyme. The present analysis affords the first detailed view into the evolution of trypsins at the invertebrate level.     

The chemistry of a chitin-protein from crayfish (Astacus fluviatilis) (author's transl)]

A chitin-protein complex is obtained from crayfish (Astacus fluviatilis) by gentle decalcification with acetic acid and EDTA. The complex is treated with lithium rhodanide, urea, anhydrous formic acid, pronase, papain, anhydrous formamide or 1N NaOH. The first three of these substances have little or no effect on the stability of the chitin-protein complex. The enzymes remove most of the protein, and the last two reagents remove all of it. The protein remaining bound to the polysaccharide after treatment of the chitin-protein complex with pronase or papain is relatively rich in glycine. Quantitative analysis yielded values for the acetyl, glucosaminyl and amino acid residues which reproduce the composition of the corresponding chitin-protein complex. In these calculations however, allowance must be made for the fact that glucosamine is partly destroyed by the acid by hydrolysis and interferes with the determination of basic amino acids. The results of the present work suggest that the chitin in crayfish is present in the form of a stable complex with protein, possibly held together by covalent binding of the protein to the chitin, with glycine as the connecting amino acid.     

Molecular phylogeny and zoogeography of the freshwater crayfish genus Cherax Erichson (Decapoda: Parastacidae) in Australia

The evolutionary history and biogeography of freshwater-dependent taxa in Australia is of intrinsic interest given the present-day aridity of this continent. Cherax is the most widespread and one of the most species-rich of Australia's nine freshwater crayfish genera. The phylogenetic relationships amongst 19 of the 23 Australian Cherax were established from mitochondrial DNA sequences representing the 12S rRNA and 16S rRNA gene regions. The relationships among species support an initial east–west separation, followed by a north–south divergence in eastern Australia. Molecular clock estimations suggest that these divergences date back to the Miocene. The phylogenetic relationships support endemic speciation within geographical regions and indicate that long-distance dispersal has not led to recent speciation as previously hypothesized. This new evolutionary scenario is consistent with the climatic history of Australia and the evolutionary history of other similarly distributed freshwater-dependent organisms in Australia.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 81 , 553–563.     

Histology and histochemistry of the intermoult integument in the ghost crab Ocypoda platytarsis (Milne-Edwards) (Crustacea: Brachyura).

The histological and histochemical aspects of the integument have been described and discussed during the intermoult period of Ocypoda platytarsis. Histological observations revealed that the cuticle comprises of four layers namely epicuticle, exocuticle, endocuticle and membranous layers. Various types of cells in the subepidermal tissue have also been elucidated.     

First record of Lagenophrys dennisi (Ciliophora: Peritrichia) on the exoskeleton of crayfish Cambarellus patzcuarensis

Lagenophrys dennisi, a peritrich ciliate, was observed attached to the exoskeleton of the crayfish Cambarellus patzcuarensis in Lake Pátzcuaro, Michoacán, Mexico. Lagenophrys dennisi presents a hemispheroidal, suboval or oval lorica in dorsal view, the distinctive lorica aperture consists of a pair of lips highly arched, unthickened, and smooth. Comparison of morphometric characters of the ciliate with previous records is made. Structures such as a "V"-shaped lorica suture, collar ridges, and myoneme are proposed for species identification. An anterior crescentic thickening on the dorsal surface of the lorica was observed under the scanning electron microscope. Lagenophryids were associated with 11 of 13 body parts with antennules and rostrum showing the highest prevalence. Lagenophrys dennisi was also found attached to submerged glass slides. This study represents the first record of L. dennisi on C. patzcuarensis and the first record of its presence in Mexico.     

Typology and distribution of ganglion cells in the retina of lamprey (Lampetra fluviatilis)

Retinal ganglion cells (GC) of the Lamprey were studied after in vitro labeling of these cells by iontophoretic deposition of horseradish peroxidase into the optic nerve. The majority of GC are located at the boundary between the inner nuclear layer and the inner plexiform layer; a small proportion (20%) lies in the vitreous portion of the inner plexiform layer. Four types of GC were identified.     

The occurrence and distribution of Dermocystidium percae (Mesomycetozoea) in perch (Perca fluviatilis) in the lower Thames Valley,UK

The occurrence and microhabitat distribution of Dermocystidium percae on perch (Perca fluviatilis) was investigated in four sites in the lower Thames Valley, south‐east England. Fish were infected at all sites, with the highest prevalence occurring in a commercial fishery and the lowest in a large impounded water storage reservoir. The microhabitat distribution of D. percae cysts on the perch favoured the dorsal and anal fins, in contrast to previous studies, although a single occurrence on the gills was reported. The role of host stress on the prevalence of D. percae is discussed.     

Distribution of calcium phosphate in the exoskeleton of larval Exeretonevra angustifrons Hardy (Diptera: Xylophagidae)

Distribution and organisation of the mineral, amorphous calcium phosphate (ACP), has been investigated in the exoskeleton of the xylophagid fly larva Exeretonevra angustifrons Hardy. While head capsule and anal plate are smooth with a thin epicuticle, the epicuticle of the body is thicker and shows unusual micro-architecture comprised of minute hemispherical (dome-shaped) protrusions. Electron microprobe analysis and energy dispersive spectroscopy revealed heterogeneity of mineral elements across body cuticle and a concentration of ACP in the epicuticle, especially associated with the hemispherical structures. Further imaging and analysis showed the bulk of the ACP to be present in nano-sized granules. It is hypothesised that the specific distribution of ACP may enhance cuticular hardness or durability without reducing flexibility.     

The spermatogenesis of Ephydatia fluviatilis (Porifera)

Summary Spermatogensis of the freshwater sponge Ephydatia fluviatilis begins with differential mitosis of choanocytes in the flagellated chambers. The spermatogonia thus produced aggregate in the mesenchyme by amoeboid movement. They are surrounded by dendritic cells which eventually form the walls of spermatocysts, within which spermatogenesis takes place. Notable features are the early formation of flagella in first order spermatocytes and the appearance of two flagella in the metaphase of the second maturation division.Spermatids and spermatozoa are arranged in characteristic ways. The spermatids have their heads near the spermatocyst wall, with the flagella pointing toward the center. Later the spermatozoan heads form a median band in the spermatocyst, and the flagella extend toward the periphery.Normally all stages of spermatogenesis can be found simultaneously in a given sponge, but development within a single spermatocyst proceeds in relative synchrony. Young spermatocysts can take up additional free spermatogonia; moreover, spermatocysts at about the same stage of development, up to a maximal diatmeter of 200 m, can fuse with one another.The E. fluviatilis studied here seem to be gonochorists.     

The distribution of polarization sensitivity in the crayfish retinula

In many arthropod eyes the ommatidia contain two classes of retinular cells with orthogonally oriented microvilli. These receptors provide the basis for two-channel polarization vision. In several contexts such as navigation or the detection of polarization contrast, two channels may be insufficient. While solutions to this problem are known (e.g. in insects and stomatopod crustaceans) none have been found in the majority of decapods. To examine this issue further, the polarization sensitivity and the E-vector angle eliciting a maximum response (theta (max)) were measured at over 300 loci on the crayfish retinula. The polarization response ratio (which is proportional to polarization sensitivity) was similar at all locations on the retinula. Around the central pole of the eye, theta (max) was distributed about the vertical and horizontal axes. Along the dorsal rim, the distribution of theta (max) exhibits modes at 0 degrees , 45 degrees and 90 degrees and a small mode at 135 degrees relative to the dorso-ventral axis of the eyestalk (0 degrees ). Smaller numbers of cells (20 to 25%) with theta (max )near the diagonal were also found in anterior and posterior retinula areas. Thus crayfish visual interneurons, which integrate signals from multiple ommatidia may have access to a multi-channel polarization analyzer.     

Effects of calcium and salinity on the growth rate of Ephydatia fluviatilis (Porifera: Spongillidae)

The freshwater sponge, Ephydatia fluviatilis (Porifera: Spongillidae), was maintained in a continuous-flow laboratory culture system under several conditions of calcium ion (Ca⁺⁺) concentration and salinity. Experimental results suggest that sponge growth rate increases with increasing Ca⁺⁺ concentration, that sponge growth rate decreases with increasing salinity, and that the negative effect of higher salinity can be overcome by increasing Ca⁺⁺ concentration. The experimental results correlate well with field observations on the effects of salinity and Ca⁺⁺ on the distribution of E. fluviatilis.