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At least 901 records · Page 50Linked to original sources
PubMed1981

Modification of motor neuron size and position in the central nervous system of adult snapping shrimps.

Cell bodies of claw closer motor neurons in snapping shrimp are dimorphic. Snapper claw motor neurons are larger than corresponding pincer claw motor neurons, but the relative sizes of these cells are reversed during claw transformation. An additional neuronal modification occurs early within this period, in that the pincer claw dorsal inhibitor cell body migrates within the nervous system, from a dorsal to a ventral position. These findings are evidence of rapid, reversible changes in the nervous system following the trigger for the transformation process.

Animals↗
PubMed1988

Cryopreservation of sperm from the marine shrimp Sicyonia ingentis.

Sperm from a marine shrimp, Sicyonia ingentis, were frozen to -196 degrees C using a variety of cooling rates and cryoprotectants. A cooling rate of 1 degree C/min resulted in minimal cell breakage. Sperm samples were frozen in solutions of known membrane stabilizers--trehalose, sucrose, proline, and glycerol. These compounds were somewhat effective but a dramatic increase in sperm viability was seen when DMSO was present in the freezing medium. Sperm viability was assessed using the in vitro acrosome reaction technique of Griffin et al. (1987). The highest sperm survival (56%) was obtained with samples frozen at 1 degrees C/min in a 5% (v/v) DMSO solution. No decrease in viability was seen in sperm samples stored in liquid nitrogen (-196 degrees C) for 1 month.

Animals↗
PubMed1984

Changes in myofibrillar gene expression during fiber-type transformation in the claw closer muscles of the snapping shrimp, Alpheus heterochelis.

Isotopes of a number of crustacean myofibrillar proteins have been identified with sodium dodecyl sulfate-polyacrylamide electrophoresis, and their distribution in muscles of the snapping shrimp has been examined. Fast-slow differences in distribution have been observed for myosin light chains and tropomyosin. In contrast, three troponin T subunits have been resolved, each specific to one of the three muscles examined. This result suggests that expression of crustacean contractile proteins is not accomplished by a simple coexpression of a battery of slow or fast isotopes. In addition, the expression of these proteins was examined during the quasi-developmental fiber-type transition of the main claw closer muscle during the reversal of claw asymmetry in response to the loss of the large snapper appendage. The changes observed appear similar to the cross-innervation induced changes in gene expression of vertebrate muscle.

Animals↗
PubMed1984

Absence of detectable 5-methylcytosine in DNA of embryos of the brine shrimp, Artemia.

DNA from three developmental stages of the brine shrimp, Artemia was found to be undermethylated compared to DNA from calf thymus and salmon sperm. Using high-performance liquid chromatography we found that DNA hydrolysates from both dormant cysts and prefeeding nauplii contain less than 1 residue of 5-methylcytosine per 59 kilobases, placing Artemia DNA in the "insect type" category. The absence of detectable 5-methylcytosine in DNA of developing Artemia supports the view that methylation status alone cannot account for regulation of transcription in protostomes, and that DNA methylation may be more common among deuterostomes.

5-Methylcytosine↗
PubMed1989

Molecular cloning of the Na,K-ATPase alpha-subunit in developing brine shrimp and sequence comparison with higher organisms.

We report here the molecular cloning, nucleotide sequence, and predicted amino acid sequence of an alpha-subunit of the developmentally useful model, Artemia. The amino acid sequence shows divergence from that of mammals, birds, Torpedo, and Drosophila. However, regions in the putative ATP binding and transmembrane domains show absolute or high levels of conservation. Major differences occur in the amino-terminal domain and several other hypervariable regions. These differences are consistent with the suggestion that the brine shrimp is a 'fast clock' organism which diverged from the precursors of vertebrates 0.5-1 billion years ago.

Amino Acid Sequence↗
PubMed1984

Ecdysteroids in the shrimp Palaemon serratus: relations with molt cycle.

Ecdysteroids were studied during the molt cycle of the shrimp Palaemon serratus using radioimmunoassay and HPLC. Continuous presence of ecdysteroids was observed in whole extracts, with two hormonal peaks: a minor peak during stage B and a major one during stage D2. The ecdysteroid titers were generally higher in females than in males. The ecdysteroid peak at stage B was more pronounced in the integument (cuticle and epidermis) than in other tissues and, at this time, 20-hydroxyecdysone was the predominant form. The observed 20-hydroxyecdysone peaks in stages B and D2 are correlatable to the previously reported rise in integumental carbonic anhydrase activity.

Animals↗
PubMed1991

Binding proteins for a peptide hormone in the shrimp, Sicyonia ingentis: evidence from photoaffinity labeling with red pigment concentrating hormone analogs.

Two photoaffinity analogs of the crustacean erythrophore (red pigment) concentrating hormone (RPCH) have been synthesized and shown to cause pigment concentration in the shrimp Sicyonia ingentis. These two modified oligopeptides have azidosalicylamide groups which allow introduction of an 125I label and enable photochemically induced covalent attachment to a specific binding site. Incubation of [125I]-ASA-Glu1-CC-2 with the 100,000g membrane pellet and cytosol fraction from epidermis, eyestalks, muscle, and central nervous system (CNS), followed by irradiation, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and autoradiography results in covalent modification of certain protein bands in the membranes of selected tissues. Two such proteins were observed in neural tissues and showed competitive displacement by excess RPCH, indicative of specific high-affinity binding. This is the first report of peptide hormone-binding proteins in an invertebrate and provides further evidence of a role for RPCH as a neurotransmitter in the CNS.

Amino Acid Sequence↗
PubMed1975

X-ray induced behavioral reactions and detection mechanisms in the shrimp.

Red Ghost Shrimp, Callianassa californiensis, were shown from behavioral and electrophysiological studies to respond to ionizing radiation. When exposed to X-rays at 52 R/sec, the majority of intact animals could detect and avoid further irradiation by escaping into a shielded section of the test chamber. Animals continued to display escape responses after removal of eyestalks and antennae. Significant avoidance activity also occurred with partial-body exposure and indicated the existence of a radiation-sensitive receptor on the abdomen. Electroretinograms elecited by beta- and X-radiation sources corresponded closely with the waveforms produced by visible light stimulation. Electroantennograms were recorded from isolated antennules following stimulation with glutamic acid, beta-, and X-radiation. Biphasic on-off phases were recorded with an intermediate phase present during the longer duration exposures. Similarly, bioelectrical potentials were recorded from swimmeret preparations with exposure to beta- and X-radiation. The electrophysiological evidence indicates that the eye, antennules, and possibly chemoreceptors on the abdominal segments serve as routes for detection of ionizing radiations.

Abdomen↗
PubMed1976

The fine structure of a parasitic ciliate Terebrospira during ingestion of the exoskeleton of a shrimp Palaemonetes.

The ciliated protozoan, Terebrospira chattoni, invades the exoskeleton of the shrimp, Palaemonetes pugio, eating out long galleries parallel to the surface of the exoskeleton. Solubilization of the exoskeleton occurs around an area of the elaborately infolded surface membrane at the anterior of the organism. Dissolved products of the digestion of the exoskeleton are taken into the body by the formation of coated vesicles at pores in the membrane. The surface membrane that is taken in by pinocytosis is apparently recycled by the introduction into the membrane of organelles implicated in membrane recycling in other ciliates. Acid phosphatase can be demonstrated on the surface membrane as well as in the endocuticle around the organism.

Acid Phosphatase↗
PubMed1976

Light and dark adaptational changes in the accessory eye of the shrimp, Palaemonetes.

The fine structure of the accessory eye of the shrimp, Palaemonetes, was studied after light and dark adaptation. Adjacent to the principal compound eye, the accessory eye is a small compound eye composed of about 20 ommatidia which are smaller in structure to the ommatidia of the principal compound eye. During dark adaptation, rhabdomal microvilli increase in length; however, little pigment migration occurs. The implications of these changes in relation to the function of the accessory eye are discussed.

Animals↗
PubMed1978

A morphological study on gills of the brown shrimp, Penaeus aztecus.

The gills of Penaeus aztecus were examined by light and electron microscopy. They are dendrobranchiate, consisting of a central axis with biserially arranged branches that subdivide into bifurcating filaments. A septum divides the lumina of these structures into afferent and efferent channels. Hemolymph from the sternal sinus flows through the afferent channels into the filaments where it is directed into the efferent channels and finally to the pericardial cavity. In addition to these channels, numerous blood vessels permeate the gill. The cuticle covering the gill overlies a thin epithelium which is separated from hemolymph by a basal lamina. The epithelium, which is active in cuticle secretion, has a series of pillar processes that form subcuticular lacunae. The apical membranes of epithelial cells become folded in shrimp exposed to hypo- and hyperosmotic salinities. Granular cells that contain elaborate Golgi apparati and several types of granules are present throughout the gill. Nephrocytes resembling glomerular podocytes line the efferent channels. A large nerve traverses the septum in the axis.

Animals↗
PubMed1981

The syncytial nature and phagocytic activity of the branchial podocytes in the grass shrimp, Palaemonetes pugio.

The morphology of the branchial podocytes in the grass shrimp, Palaemonetes pugio, was investigated in relation to the molt cycle. The podocytes are located in the efferent hemolymph channels in the gill axis, and possess a specialized plasmalemma consisting of interdigitating pedicel processes which are bridged by thin diaphragms. The topography of the plasmalemmal surface suggests that these cells, like similar cells in other arthropods, function in the ultrafiltration of micro- and macromolecular substances from the hemolymph. Additionally, the branchial podocytes exhibit phagocytic activity. This activity, though evident during the pre-molt period, is most prominent during the early post-molt period. Among the cell types subjected to phagocytosis by podocytes are the secretory cells of the tricellular and rosette-type dermal glands and the epithelial cells of the gill axis. During the late pre-molt and early post-molt periods, the podocytes often appear as syncytia, containing as many as four nuclei. The exact interrelationships between phagocytosis and syncytial formation remain to be ascertained. These aspects and the possible ambulatory abilities of the branchial podocytes are discussed.

Animals↗
PubMed1984

Junctional relationships between germinal cells and sustentacular cells in the testes of a palaemonid shrimp.

Testes of the palaemonid shrimp Macrobrachium rosenbergii were prepared for study in the light, scanning and transmission electron microscopes and shown to be composed of solid, convoluted cords of tissue composed of two major sets of cells, spermatogenic and sustentacular cells. Among the spermatogenic cells, preleptotene spermatocytes and encysted spermatozoa were of most frequent occurrence. The sustentacular cells sent long, cytoplasmic extensions ramifying between and around tightly packed spermatocytes of the seminiferous cords and separated the spermatocytes from the basal lamina which surrounded the cords. Spermatocytes formed desmosome-like and short gap junctions with one another, while sustentacular cells formed intermediate-like junctions and gap junctions with spermatocytes. No special junctions between one sustentacular cell and another were encountered in the present study.

Animals↗
PubMed1994

The intrarhabdomal filters in the retinas of mantis shrimps.

The intrarhabdomal filters in the photoreceptors of compounds eyes of 32 species of mantis shrimps (Crustacea: Stomatopoda), representing seven families within the superfamilies Lysiosquilloidea and Gonodactyloidea, were surveyed by microspectrophotometry of filters in fresh cryosections of the retina. A total of up to four classes of filters exist in stomatopods: two each in Rows 2 and 3 of the midband. All lysiosquilloid species lacked the proximal filter in Row 3; a few also lacked the proximal Row 2 class. While most gonodactyloid species had all four possible classes, in some species the proximal filters of Row 3 and (in one case) Row 2 were missing. In all, at least 11 distinct spectral classes of pigments were found. Absorption spectra suggested that the filter pigments were probably carotenoids or carotenoproteins, although the distal filter of Row 3 was often exceptional, appearing to contain a mixture of pigments. While the types of pigments found in the filters of the various species generally followed taxonomic lines, numerous exceptions were found that were apparently related to the ecological requirements of the various species.

Animals↗
PubMed1994

Ultraviolet photoreception in mantis shrimp.

An UV-sensitive class of photoreceptors exists in all regions of the retinas of mantis shrimps. UV photosensitivity apparently resides in rhabdomeres of the eighth retinular cell (R8) that lies atop each rhabdom; and in ommatidia where the R8 rhabdomere consists of microvilli parallel in a single direction, sensitivity is maximal when the e-vector of plane-polarized light is parallel to the microvilli. Spectral sensitivity of the UV photoreceptor peaks at 345 nm and is best explained by the presence of a photopigment with lambda max near 325 nm overlain by material that absorbs UV light at wavelengths below approximately 350 nm. Rhabdomeres of R8 cells in several different retinal regions of a variety of species examined contain a photopigment absorbing maximally below 340 nm. Under appropriate conditions, a metapigment with lambda max near 460 nm can be formed. UV vision may be useful for enhancing the visual contrast of midwater predators or prey.

Animals↗
PubMed1982

Molecular cloning and characterization of ribosomal RNA genes from the brine shrimp.

A library of genomic DNA from the brine shrimp, Artemia, has been constructed with the Charon 4A phage vector, utilizing EcoRI passenger fragments. Screening this library with purified Xenopus laevis cloned rDNA genes has resulted in the identification and plaque purification of a recombinant containing a complete Artemia (18 S + 26 S) rDNA repeat unit. A physical map derived from the analysis of restriction endonuclease digests of the repeat unit, which measures 13.9 kilobase pairs, is similar to the map derived from genomic DNA. In common with several other species, the 26 S rRNA gene terminates with a HindIII recognition site.

Animals↗
PubMed1987

An in vivo 31P-NMR study of the possible regulation of glycogen phosphorylase a by phosphagen via phosphate in the abdominal muscle of the shrimp Crangon crangon.

31P-NMR spectroscopy has been used to determine the concentrations of Pi and phosphagen in the abdominal muscle of the shrimp Crangon crangon at rest and to follow the changes during their recovery after exhaustive work in vivo. Additionally, the effect of physiological Pi concentrations to the phosphorylase a activity has been examined. At rest, the cytoplasmic Pi and phosphagen concentrations were 1 mM and 38 mM, respectively. After exhaustive work the concentrations of both metabolites were in the same range (20 mM). During recovery, the time course of phosphagen regeneration correlates with the decrease of Pi, as the sum of the concentrations of these metabolites is constant. The ATP level was stable throughout the experiment. The phosphorylase a, which was already present in the resting muscle, was virtually inactive at the resting Pi level (1 mM). During work, however, Pi, which is probably generated by phosphagen-ATP splitting, might ensure a sufficient activation of phosphorylase a.

Adenine Nucleotides↗