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At least 199 records · Page 11Linked to original sources
PubMed2001

Molecular evolution of the small subunit ribosomal DNA in woodlice (Crustacea, Isopoda, Oniscidea) and implications for Oniscidean phylogeny.

The small subunit ribosomal DNA (ssu rDNA) of 13 isopods was sequenced. The entire length of the ribosomal gene is unusually long, resulting from the presence of five expansion elements accounting for more than 40% of the gene. We found that in terrestrial isopods the length of the ssu rDNA ranges from 2414 bp (Ligidium hypnorum) to 3537 bp (Cubaris murina). This is the longest metazoan ssu rDNA reported to date. The conserved regions are highly informative for analysis of the early nodes of the tree, whereas the variable expansion elements are better suited to reconstruction of the branching pattern between closely related taxa. The suggested relationship among Synochaeta, Crinochaeta, and Diplochaeta based on the conserved regions confirms that based on previous morphological analyses. In contrast, the phylogeny within the Crinochaeta based on the entire ssu rDNA including the variable domains is in conflict with that based on most of the morphological analyses. The phylogenetic analyses of the ssu rDNA support a repeated independent evolution of the three different types of pleopodal lungs in the Crinochaeta.

Amino Acid Sequence↗
PubMed1999

Involvement of tryptophan metabolism in the body color of crustacea.

The terrestrial isopod, Armadillidium vulgare is usually grey or black in color, however, red ones are occasionally found in the field. This is caused by the mutation of the ommochrome genesis in the integument. We focused our experiments on the mechanism of pigment genesis in which tryptophan metabolism had been expected to be different from the grey or black wild types. We obtained the result that 3-hydroxyanthranilic acid content was significantly higher in the red phenotype than in the wild type, and kynureninase activity was also higher in the red phenotype.

3-Hydroxyanthranilic Acid↗
PubMed1993

Mitochondrial DNA polymorphism and feminizing sex factors dynamics in a natural population of Armadillidium vulgare (Crustacea, Isopoda).

Sex determination in Armadillidium vulgare may be under the control of two parasitic sex factors that reverse genetic males into functional neo-females. The first feminizing factor (F) is a Wolbachia and the other (f) is probably a sequence of the F bacterial DNA unstably integrated into the host genome. Both of these feminizing factors are mainly maternally transmitted. Here we investigate the mitochondrial DNA polymorphism of wild iso-female lineages harbouring either F or f. Among the four haplotypes present in the population, two were the f-harbouring lineages, while two were common to the F- and f-harbouring lineages. This result suggests that there has been an introgression of the f factor into lineages infected by F Wolbachia. Based on previous data, we propose two different ways to account for such introgression. Given the particular dynamics of feminizing factors (f-harbouring lineages increase in populations at the expense of F-harbouring lineages), such an introgression should prevent the replacement of F-linked mitochondrial types by f-linked mitochondrial types in wild populations.

Animals↗
PubMed1982

Rhabdom breakdown in the eye of Cirolana borealis (Crustacea) caused by exposure to daylight.

The effect of daylight on the compound eye was investigated in the deep-water crustacean isopod Cirolana borealis Lilljeborg. The animals were captured and fixed at night ('dark-exposed', i.e. not exposed to light) and day ('daylight-exposed'), respectively. Changes in light and darkness have an effect on the retinula cells; the ultrastructure of dark-exposed eyes is characterized by well-preserved organelles and cytoplasm. The photoreceptor membranes covering the microvilli are regularly aligned, and the outline of the villi is smooth. Electron-dense pigment granules are evenly distributed in the cytoplasm of the retinula cell outside the rhabdom. Daylight-exposed eyes differ from the dark-exposed eyes in the following aspects: (i) the microvilli are disrupted, (ii) retinula-cell pigment is found in the rhabdom, and (iii) the cytoplasm of retinula cells is vesiculated. These results are interpreted as retinal damage caused by excess exposure to light.

Animals↗
PubMed1978

Scanning electron microscope studies of the egg shell in some anostraca (Crustacea: Branchiopoda).

The tertiary shell of the eggs of anostracan crustaceans consists of two layers, an outer cortex and an inner alveolar layer. Scanning electron microscope studies show that, in most species, these layers are separated by a subcortical space which intercommunicates with spaces in the cortex and with the meshwork of the alveolar layer. No evidence was found for direct communication between pores on the surface of Branchipus stagnalis eggs and the subcortical space. No surface pores were found in the eggs of Branchinecta packardi, Chirocephalus diaphanus, Artemia salina, nor in eggs of the notostracan Triops cancriformis. Similarities in structure and possible functions of the egg shells of anostracan crustaceans and certain insects are discussed in relation to similarities in certain features of their environments.

Animals↗
PubMed1978

Ultrastructural observations on the oogenesis of Triops cancriformis (Crustacea, Notostraca).

Each ovarian follicle of Triops cancriformis is four-celled; these cells (one oocyte and three nurse cells) are interconnected by cytoplasmic bridges. In the course of differentiation, the nurse cells are clearly recognizable; they increase in size more than the oocyte and their nuclei contain many nucleoli. For the first time in Arthropoda, yolk globules are reported to be present in nurse cell cytoplasm; these globules arise from the smooth endoplasmic reticulum. The functional significance of the intercellular bridges and the trophic role of the nurse cells are discussed.

Animals↗
PubMed1984

Fine structure and molting of aesthetasc sense organs on the antennules of the isopod, Asellus aquaticus (Crustacea).

In Asellus aquaticus certain distal antennular segments bear single sensilla referred to as aesthetascs. These show a proximal stem and a distal bulbous region. Depending on its position, each aesthetasc is innervated by either 50-60 or 70-80 bipolar sensory cells, the perikarya of which are situated within the pedunculus. Within the antennular segment the dendrites develop unbranched cilia (9 X 2 + 0 structure). The sensory cells are unusual in that mono- as well as biciliary dendrites are present within a single aesthetasc, the ratio of both types being correlated with the number of sensory cells. Cilia and receptor lymph cavity are enveloped by a set of 3-4 inner and 13-14 outer sheath cells, which terminate at the base of the sensillum, so that the delicate and poreless cuticle of the bulbous region encloses only outer segments within the receptor lymph fluid. A new molting type in arthropods is described in which the outer sheath cells alone build the new cuticle, whereas the inner sheath cells most probably have a protective function. A definition of aesthetascs is proposed based on fine-structural criteria. Functionally the sensilla are considered to be chemoreceptors. This assumption is confirmed by experiments with diluted vital dye as well as lanthanum showing that dissolved substances penetrate the poreless cuticle instantaneously.

Animals↗
PubMed1983

Ultrastructural evidence of the ion-transporting role of the adult and larval neck organ of the marine gymnomeran Cladocera (Crustacea, Branchiopoda).

The neck organ of adult and immature forms of four marine gymnomeran Cladocera species (Podonidae) has been characterized morphologically by light-scanning- and electron microscopy. Although displaying some special features, a comparison with organs assuming a comparable regulating function in other organisms indicates that the neck organ of the adult Podonidae exhibits ultrastructural evidence of involvement in ion-transporting mechanisms. The extensive ventral plasma membrane infoldings closely connected with the chondriom and the peculiar organization of the cuticular site associated with the subjacent apical cell limits of the organ are among the chief structural specializations. The fact that similar structures are already present in the embryonic neck organ confirms previous indirect evidence that podonid embryos can hypo-osmoregulate as soon as the ion concentration of the brood chamber rises to that of the outside medium.

Animals↗
PubMed1977

The ultrastructure of the sinus gland of Gammarus oceanicus (crustacea: amphipoda).

The sinus gland of Gammarus oceanicus, like that of other crustaceans, is composed of three elements: neurosecretory axons, glial cells and stromal sheath. Five neurosecretory axon types are identified on the basis of granule diameter, shape, and electron density, and axon matrix density. Exocytosis appears to be the major release mechanism of neurosecretory material. The preterminal regions of neurosecretory axons contain axoplasmic reticulum and neurotubules. Their arrangement in the axon and relationship with one another suggest a transport function. Multilamellar bodies are found in the terminal regions of neurosecretory axons. They arise from mitochondria and may be involved in granulolysis.

Animals↗
PubMed1976

Histological and electron microscopical observations on the effects of different salinities and heavy metal ions, on the gills of Jaera nordmanni (Rathke) (Crustacea, Isopoda).

The effects of different salinities and concentrations of copper, mercury and cadmium ions on the gills of Jaera nordmanni are investigated by means of light and electron microscopy. After exposure to 10% and 50% sea water the gill epithelium cells show a marked uniformity in appearance, possessing characteristically large, sub-cuticular spaces which are prominent between microvilli. With exposure to the heavy metal ions a similar sequence of histological and ultrastructural changes occur in all the gill epithelial cells, culminating in cell breakdown. The ultrastructural changes include distended microvilli, dilated endoplasmic reticulum, dissociated ribosomes, diffuse (swollen) cytoplasm, swollen mitochondria and a basal membrane withdrawn from the basal lamina. An increase in the number of haemocytes is also commonly observed in the haemolymph spaces during heavy metal ion exposure. The significance of the morphological changes undergone by the gill epithelial cells after exposure to different salinities and heavy metal ion concentration, are discussed in relation to the physiological functioning of the gill.

Animals↗
PubMed1979

Fine structure of sensory tubes on the antennule of Conchoecia spinirostris (Ostracoda, Crustacea). A new type of sensillum in crustaceans.

In addition to setae, the first antennae of Conchoecia spinirostris also bear soft sensory tubes (female: 4 tubes + 1 seta; male: 2 tubes + 3 setae). These tubes were examined electron microscopically. Each tube is divided into 4 regions: the stem, the bulbous region, the main region, and the tip. A tube contains 40--60 multiciliated dendrites, some hypodermal cells, and nonneuronal cells, and it has a specialized cuticle. Each dendrite develops within the tube, on the terminal 5--8 micron of its inner dendritic segment, approx. 25 cilia in a 9 X 2 + 0 pattern, whose rootlets are absent or only poorly developed. Each cilium splits up into 9 ramifications which extend into the tip. These ramifications partly take a spirallike course and form a ring in the distal main part beneath the cuticle. Their membranes often dilate into spindleshaped swellings. In the center of the middle and distal parts of the main region approx. 7 dendrites without cilia are located, one of them reaches into the tip. The poreless cuticle is extremely delicate and electron lucid. In contrast to the cuticle of the setae it is elastic and soft. Special substructures are described. The tubes are completely covered by a filamentous surface coat. Because of the structure and the thin walled nature of the cuticle, permeability for dissolved substances is assumed. The ciliary ramifications are likely to represent the receptive apparatus. The sensory tubes are interpreted as chemoreceptors. They can best be compared with the chemoreceptors of certain crustaceans, but differ strongly from the types of sensilla found in insects.

Animals↗
PubMed1975

The membrane systems of the cardiac muscle cell of Cirolana borealis Lilljeborg (Crustacea, Isopoda).

The membrane systems of the cardiac muscle cell of the isopod Cirolana borealis Lilljeborg are described. The sarcolemma invaginates at the level of the Z band, forming transverse tubules. Narrow tubules branch off in a longitudinal direction from these transverse and radially arranged Tz-tubules forming a transverse collar at each A-I level, where dyadic and triadic junctions are formed with the sarcoplasmic reticulum. Two different orientations of the coupling discs have been detected in the supercontracted sarcomere, and this observation has been discussed. Adjacent myofibrils are separated by a double layer of sarcoplasmic reticulum.

Animals↗
PubMed1988

Localization of pigment-dispersing hormone (PDH) immunoreactivity in the central nervous system of Carcinus maenas and Orconectes limosus (Crustacea), with reference to FMRFamide immunoreactivity in O. limosus.

By use of antisera raised against synthetic pigment-dispersing hormone (PDH) of Uca pugilator and FMRFamide, the distribution of immunoreactive structures in the central nervous system (CNS) of Carcinus maenas and Orconectes limosus was studied by light microscopy. In both species, a total of 10-12 PDH-positive perikarya occur amongst the anterior medial, dorsal lateral and angular somata of the cerebral ganglion (CG). In C. maenas, one PDH-perikaryon was found in each commissural ganglion (COG) and several more in the thoracic ganglion. In O. limosus, only four immunopositive perikarya could be demonstrated in the ventral nerve cord, i.e., two somata in the anterior and two in the posterior region of the suboesophageal ganglion (SOG). PDH-immunoreactive tracts and fiber plexuses were present in all central ganglia of both species, and individual axons were observed in the connectives. FMRFamide-immunoreactivity was studied in O. limosus only. Neurons of different morphological types were found throughout the entire CNS, including numerous perikarya in the anterior medial, anterior olfactory, dorsal lateral and posterior cell groups of the CG. Four perikarya were found in the COG, six large and numerous smaller ones in the SOG, and up to eight cells in each of the thoracic and abdominal ganglia. In each ganglion, the perikarya form fiber plexuses. Axons from neurons belonging to the CG could be traced into the ventral nerve cord; nerve fibers arising from perikarya in the SOG appeared to project to the posterior ganglia. In none of the structures examined colocalization of PDH- and FMRF-amide-immunoreactivity was observed.

Animals↗