SEARCH · PubMed Health
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
The collagen embedding Sacculina roots is synthesized by hemocytes of Carcinus maenas and is described. Hemocytes engaged in the secretion of collagen as a reaction against a parasite constitute a defensive mechanism still largely unknown within Crustacea.
The distribution of cholecystokinin-like immunoreactivity was studied in the stomatogastric nervous systems, pericardial organs, and haemolymph of four species of decapod crustacea, by using immunocytochemical and radioimmunoassay techniques. Whereas cholecystokinin-like immunoreactivity was found within the stomatogastric nervous systems of all four species, its distribution in each is unique. Two species (Panulirus interruptus and Homarus americanus) have cholecystokinin-like immunoreactivity within fibers and neuropil of the stomatogastric ganglion (STG); two other species (Cancer antenarius and Procambarus clarkii) do not. Further, the cholecystokinin-like immunoreactivity within the STGs of Panulirus and Homarus arise from distinct structures; from a projection of anterior ganglia in Panulirus, and from somata within the posterior motor nerves in Homarus. The staining in the other ganglia of the stomatogastric nervous system also shows some interspecies variability, although it appears to be more highly conserved than staining within the STG. These differences in staining were confirmed by measuring the amount of CCK-like peptide present in tissue extracts of ganglia by radioimmunoassay. In contrast to the variable staining within the STG, all four species have cholecystokinin-like immunoreactivity within the neurosecretory pericardial organs and thoracic segmental nerves. This cholecystokinin-like immunoreactivity is contained within fibers and within varicosities that coat the surface of these structures. The location of this staining and the presence of detectible levels of CCK-like peptide in the haemolymph suggests that CCK-like peptides in decapod crustacea may be utilized as neurohormones.
Analysis of data obtained from molecular hybridization of 3H-labeled repetitious DNA has been utilized to reconstruct the broad outlines of phylogenetic relationships among decapod Crustacea. This molecular reconstruction agrees reasonably well with the paleontological record, and with other schemes obtained by comparative morphological and serological approaches. Preliminary evidence is in line with the hypothesis that continuous addition of new repeated sequence families to the genome over long periods of time may in part account for the correlation observed between percent repetitious DNA hybridized and divergence time. It is tentatively concluded that a core of DNA base sequence homology has been highly conserved throughout the evolution of the Crustacea. Demonstration of inter-species sequence homology has important implications to models which relegate a genetic regulatory function to repeated DNAs.
In the populations of aquatic troglobitic Crustacea, breeding females are found all year round, with an annual peak. Data about their biological cycle suggest four phases of reproduction per year. Synchronisation of egg-laying (for the fraction of females actually reproducing) seems to happen for several species of Crustacea both in nature and at the laboratory. The onset of reproduction is sharpest either late winter or mid-spring, and its amplitude decreases along the annual cycle. The existence of a seasonal trigger is probable.
The sequence and timing of morphological changes during envelope formation was followed in diapause eggs of Pontella mediterranea (Crustacea, Copepoda). The multilayer coat enveloping these eggs resulted from the exocytosis of 4 types of cortical vesicles that sequentially released their contents in the perivitelline space. These included small high-density vesicles (hDV) with electron-dense material, vesicles (V) with dense ring granules and a uniform matrix contained within the same compartment, large high-density (HDV) vesicles, and large moderately dense (MDV) vesicles. All of these cortical vesicles were present in newly spawned, fertilized eggs. Their exocytosis resulted from egg activation. One of these cortical vesicles (V) was similar in morphology to the intracisternal granules precursors of endogenous yolk. Intracisternal granules, characteristic of previtellogenic oocytes of many crustaceans, were present in previtellogenic oocytes of P. mediterranea but disappeared in later stages of oocyte development once yolk formation was completed. We discuss the role of cortical vesicles in the formation of the complex extracellular coat enveloping copepod diapause eggs.
The ultrastructure of the compound eyes of five species of mysids (Crustacea: Mysidacea), Praunus flexuosus, Siriella norvegica, Mysidopsis gibbosa, Neomysis integer and Erythrops serrata, is described. The ommatidia are constructed on a common plan, but there are considerable differences in detail. Common features include the arrangement of the cornea, crystalline cone and the basement membrane. The number of retinular cells differ: in Neomysis and Erythrops there are seven, whereas in the other species there are eight, the eighth cell forming a distal rhabdom, which consequently is lacking in the ommatidia of Neomysis and Erythrops. Another difference is the epirhabdom, which is lacking in Erythrops, but present in the other species. The epirhabdom is an extracellular structure, probably serving as a dioptric element. The pigment arrangement is similar in the first four species. The pigment shield consists of the distal pigment, distal reflecting pigment, proximal pigment (in the retinular cells) and the proximal reflecting pigment. The distal and proximal pigments are dark screening pigments. In addition to these, there are basal red pigment cells, which are mainly located below the basement membrane. In Erythrops there are three kinds of pigment cells: distal pigment cells, distal reflecting pigment cells and basal red pigment cells. Besides the basal red pigment cells, the distal pigment cells contain red pigment granules.
Respiratory exchange in decapod crustacea requires the coordinated activity of the heart and the scaphognathites, appendages which ventilate the gills. There is common central nervous system neuronal modulation of both autogenically active systems as well as direct neuronal communication between both systems. The heart and scaphognathites also respond directly to oxygen tension. The neuronal control of the scaphognathites also respond directly to oxygen tension. The neuronal control of the scaphognathites is analyzed at several levels. Particular attention is directed toward the means by which the innately organized and stereotyped motor pattern for forward beating can be altered to produce reversed beating. The importance of sensory feedback in maintaining normal rates of scaphognathite beating is noted. And the phenomenon of bilateral coordination between the morphologically independent scaphognathites is described. Several different models of parts of the over-all scaphognathite neuronal circuitry are presented for heuristic purposes.
Muscle growth in Crustacea may occur during specific stages of the moult cycle, focused around ecdysis when the old cuticle is shed and the new cuticle expands. In order to determine the moult stages in which sarcomeric proteins are synthesized and the regulatory factors involved, actin mRNA levels have been measured in the muscles of two crustaceans. These levels have been followed throughout the moult cycle and in response to passive stretch of walking leg muscle in vivo and to exogenous ecydsteroids applied to muscle preparations in vitro. Actin mRNA levels in both claw and leg muscles were elevated during the pre and postmoult stages of the moult cycle. However, varying patterns of expression are found in claw and leg muscle at specific stages of pre and postmoult. There was no increase in actin mRNA expression in extensor leg muscles in vitro after 6 hours exposure to elevated premoult levels of ecdysteroids. Immobilization of intemoult walking legs to maintain the extensor muscle in continuous passive stretch did not result in increased levels of actin mRNA after 5 days. These results are discussed in relation to the regulation of muscle growth over the moult cycle and to the molecular processes which may be responsible for controlling muscle protein synthesis.
Soluble proteins of hepatopancreatic, extracts of Palaemon serratus (Crustacea, Deapoda) are separated by polyacrylamide gradient gel electoresis. The characterisation of the enzymatic activities is carried out directly on the polyacrylamide gel. The zymogram includes the following activities: acid and alcalin phosphatses, phosphamidase, alpha-glucosidase, beta-glucosaminidase, beta-glucuronidase and twenty bands with esterasic activities. The molecular weights are indicated.
Free fatty acids extracted from the abdominal muscle of Palaemon serratus (Crustacea, Decapoda) maintained on a L-D: 19-5 photoperiod show important circadian variations, characterised by two diurnal maximums and one nocturnal by the end of dark period. Principal maximum is diurnal and occurs 7 hours after the beginning of the light phase.
Hemocyanin has been used as a protein marker for Crustacea speciation. The specificity of the hemocyanin fractions of two Idotea species has been confirmed by mono and bidirection electrophoresis. Four protein fractions have been found in the two Idotea species. However, the molecular weight of each Idotea chelipes fraction is slightly higher. The two fractions of high molecular weight are strongly associated. We assumed a molecular weight of 240,000 for I. chelipes and 230,000 for I. balthica basteri. The two other protein fractions are well separated and have a weight of 130,000 and 77,000 in I. chelipes; 120,000 and 75,000 for I. b. basteri. In contrast, the subspeciation of I. chelipes has not been clearly demonstrated by electrophoresis of the hemocyanin.
Twenty species of fishes (n = 20,759) were collected from Dauphin Lake, Manitoba, Canada, to determine the types and numbers of ectoparasites they harbored. Counts of ectoparasites on fishes collected with different gear were compared to evaluate different methods of collection and to estimate rates of recruitment of ectoparasites by fishes. Ectoparasites were found on 11 species of fishes and the majority of these were parasitic leeches (Myzobdella moorei, Cystobranchus verilli, and Placobdella montifera) and parasitic Crustacea (Argulus appendiculosus and Lernaea cyprinacea). Some fishes also were infested by neascus-type metacercariae (blackspot) or had tumors (lymphocystis). The prevalence of ectoparasites was correlated with the abundance, feeding habits, and spatial distribution of fish species. Argulus appendiculosus and blackspot were more prevalent on benthic fishes, whereas M. moorei and tumors were more prevalent on limnetic fishes. Mark-recapture records showed that fishes occupying shallow (less than or equal to 1.5 m) water had a higher prevalence of infestation and 28 of 29 infected fishes caught by gill nets were captured in shallow water. Placobdella montifera was the only ectoparasite found on fishes from deep (1.5-3.5 m) water and the only species that was acquired by fishes previously released with no ectoparasite (2 of 239 fishes). The littoral zone (less than or equal to 1.5 m) comprises only 14% of the surface area and 3% of the volume of Dauphin Lake, yet 72% of all gill-netted fishes harboring ectoparasites were collected there. Intensities of ectoparasites estimated from gill net and pound net samples were similar, but prevalence of ectoparasites estimated from samples obtained with gill nets was lower.
The toxicity of benzamido-2-nitro-5-thiazole (BNT) and 3 derivatives was studied on Lymnaea peregra ovata and Gammarus pulex pulex. These results were compared with the toxicity obtained by application of a basic product, niclosamide. The evaluation of LC50 (50% lethality concentration) was studied to evaluate the toxicity of each product after 4 different assay periods: 24, 48, 72 and 96 h. The compounds had a high toxicity against snails. Molluscicidal effect was higher than the lethal activity against Crustacea. The ortho substitution decreased the toxicity of products compared with BNT.
The process of coagulation of the hemolymph in Macropipus puber (L.) Crustacea Decapod depends on one or several plasmatic factors and on a thermo-labile cellular factor which does not seem to be specific. The existence of these factors has been demonstrated.
The effects of low-level lead (20 micrograms/liter) and/or cadmium (2 micrograms/liter) exposure on the structure and function of different organ systems of the freshwater crayfish. Astacus astacus L. (Crustacea: Decapoda) were estimated by several biochemical and histochemical methods. The animals were incubated during 10 weeks (max.) at a temperature of 10 degrees C and a normal diurnal rhythm. Lead accumulated in high amounts especially in the digestive gland, carapax, and gills, whereas the hindgut and musculature exhibited very low lead levels. Cadmium accumulated particularly in the digestive gland and gills. Lead and cadmium levels were definitely lower in the digestive gland, gills, and carapax of animals incubated in water containing a double, i.e., lead and cadmium load, than in animals kept in water containing only one of these heavy metals. Histochemically both metals could be visualized in a typical distribution within the tissues, such as the carapax, digestive gland, or gills. After several weeks of poisoning, all organs, but especially the digestive gland, showed severe structural impairment. The activities of oxidative enzymes in the digestive gland and gills were significantly lowered after 2 weeks of incubation. Enzyme histochemical evaluation demonstrated changes of reaction intensities within the organs as compared to the controls. GSH S-transferase activities and GSH contents were also distinctly decreased following lead and/or cadmium intoxification. The histochemical demonstration of SH and S-S groups exhibited a stronger staining reaction after 10 weeks of exposure, especially in digestive gland and gills. The results obtained are discussed in view of the specific impairment of function of the organ systems studied, as related to the typical biology of the animal species tested.
Low-density lipoprotein (LDL) with large amounts of phospholipid but not triacylglycerol was isolated from the egg yolk of crustacea sand crayfish Ibacus ciliatus as well as lipovitellin. LDL possessed vitellogenin-degrading proteinase activity. Hemolymph vitellogenin was degraded by incubating with LDL at pH 4.5 for 72 hr at 35 degrees C and apolipoprotein profiles of vitellogenin degraded by LDL were very similar to those of lipovitellin in the egg.
Chlorophyll a and phycocyanin synthesis in the cyanobacterium Calothrix crustacea Schousboe (ecophene Rivularia bullata) have been studied in white light after the application of red and green light pulses. The light quality produces a complementary pattern in the pigment synthesis. Chlorophyll synthesis is stimulated by red light pulses whereas phycocyanin synthesis is by green light pulses. Because the effect of red light on chlorophyll synthesis shows some far-red photoreversibility, the action of phytochrome is proposed. The green light effect on phycocyanin synthesis is only partially reversed by far-red light. This reversion is lost after incubation in white light for two hours. The effect of green light on phycocyanin synthesis could not only be due to phytochrome since theoretically in green light the level of the active form of phytochrome is lower than in red light. Thus, the action of a specific green light photoreceptor is proposed.
Virus-like particles have been observed in the Y organ of the shore Crab., Carcinus maenas. These particles are ovoïd in form and enveloped. Their morphogeneses occur by budding from the plasmic membrane. Their relationship to viruses of Crustacea is discussed.