Reproduction of Mothocya epimerica (Crustacea: Isopoda: Cymothoidae), parasitic on the sand smelt Atherina boyeri (Osteichthyes: Atherinidae) in Greek lagoons.
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The reproduction and growth pattern of Mothocya epimerica (Crustacea: Isopoda: Cymothoidae), a protandrous hermaphroditic gill parasite of Atherina boyeri (Osteichthyes: Atherinidae), were investigated in the Mesolongi and Etolikon lagoons. The parasite shows an extensive reproductive period. Gravid females were found between April and November, and juveniles between May and December. M. epimerica grew allometrically (slopes of the total weight-total length regressions were >3). Females were significantly heavier than males. The relationship between number of eggs or mancas larvae (F) and total length (TL) was investigated in gravid female parasites in which the marsupium was still closed; the relationship was clearly curvilinear: F = 0.128TL3.18. The number of eggs or mancas larvae held in the marsupia of females increased proportionally with female length, varying from 39 in an isopod of 6.3 mm length to 158 in one of 8.5 mm length. The average number of eggs or mancas larvae was 76.70 +/- 27.8. (+info)
Episymbiotic microbes as food and defence for marine isopods: unique symbioses in a hostile environment.
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Symbioses profoundly affect the diversity of life, often through novel biochemical services that symbionts provide to their hosts. These biochemical services are typically nutritional enhancements and less commonly defensive, but rarely both simultaneously. On the coral reefs of Papua New Guinea, we discovered unique associations between marine isopod crustaceans (Santia spp.) and episymbiotic microbes. Transmission electron microscopy and pigment analyses show that episymbiont biomass is dominated by large (20-30 microm) cyanobacterial cells. The isopods consume these photosymbionts and "cultivate" them by inhabiting exposed sunlit substrates, a behaviour made possible by symbionts' production of a chemical defence that is repulsive to fishes. Molecular phylogenetic analyses demonstrated that the symbiotic microbial communities are diverse and probably dominated in terms of population size by bacteria and small unicellular Synechococcus-type cyanobacteria. Although largely unknown in the oceans, defensive symbioses probably promote marine biodiversity by allowing niche expansions into otherwise hostile environments. (+info)
First record of Cymothoa indica (Crustacea, Isopoda, Cymothoidae) infecting the cultured catfish Mystus gulio in India.
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Cymothoa indica (Isopoda, Cymothoidae) is reported parasitizing the long-whiskered catfish Mystus gulio, cultured in an experimental cage in India. The specimens observed were adult males and females, which had mainly settled in the buccal cavity of juvenile catfish. The species was previously known from wild populations of Siganidae and Belonidae, but this is the first record of C. indica parasitizing the cultured long-whiskered catfish. Serious lesions, typical of a crustacean infection, were macroscopically visible inside the buccal cavity. The cumulative mortality, over a period of 10 d, was 100%. The parasitic problem was not successfully dealt with, due to an unexpected prevalence and very swift mortality. (+info)
Cymothoa indica (Crustacea, Isopoda, Cymothoidae) parasitizes the cultured larvae of the Asian seabass Lates calcarifer under laboratory conditions.
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Parasitic disease in fishes is one of the most important factors limiting aquaculture production and its economic viability. Cymothoa indica, a cymothoid isopod, is reported here for the first time parasitizing cultured larvae of the Asian seabass Lates calcarifer in India. Fourteen-day-old L. calcarifer larvae of mean weight 8.73 +/- 0.03 mg were fed with wild zooplankton in the laboratory. On Day 14 of rearing, larvae were found parasitized by cymothoids. Infected larvae reached a mean (+/- SE) weight of 98.86 +/- 0.30 mg, while uninfected specimens weighed 117 +/- 0.43 mg at the end of the experiment (Day 21). C. indica occurred in the branchial and anterodorsal regions of infected fish, where resultant skin lesions were red, hemorrhagic, without scales and with abundant secreted mucus. The cumulative mortality over the 3 wk period was 16.54 %. These parasites are transferred to the host via the zooplankton used as food; this could easily be overcome, either by filtering wild zooplankton to remove the infectious swimming larvae of C. indica or by using cultured copepods. (+info)
The neuropeptide proctolin potentiates contractions and reduces cGMP concentration via a PKC-dependent pathway.
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As in many other arthropods, the neuropeptide proctolin enhances contractures of muscles in the crustacean isopod Idotea emarginata. The enhancement of high K+-induced contractures by proctolin (1 micromol l-1) was mimicked upon application of the protein kinase C (PKC) activator phorbol-12-myristate 1-acetate (PMA) and was inhibited by the PKC inhibitor bisindolylmaleimide (BIM-1). The potentiation was not inhibited by H89, a protein kinase A (PKA) inhibitor. Proctolin did not change the intracellular concentration of 3',5'-cyclic adenosine monophosphate (cAMP) whereas it significantly reduced the intracellular concentration of 3',5'-cyclic guanosine monophosphate (cGMP). The reduction of cGMP was not observed in the presence of the PKC inhibitor BIM-1. 8-Bromo-cGMP, a membrane-permeable cGMP analogue, reduced the potentiating effect of proctolin on muscle contracture. We thus conclude that proctolin in the studied crustacean muscle fibres induces an activation of PKC, which leads to a reduction of the cGMP concentration and, consequently, to the potentiation of muscle contracture. (+info)
Photosensitive neurogenic heart of the isopod crustacean Ligia exotica.
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The heart of animals is regulated through the central nervous system in response to external sensory stimuli. We found, however, that the adult neurogenic heart of the isopod crustacean Ligia exotica has photosensitivity. The beat frequency of the isolated heart decreased in response to a light stimulus. Magnitude of the response was stimulus intensity dependent and the heartbeat frequency decreased to less than 80% of the dark value during illumination of the white light with an intensity of 6.0 mW cm-2. The spectral sensitivity curve of the heart photoresponse peaked at a wavelength around 520 nm. In response to 530 nm monochromatic light, the relationship between light intensity and response magnitude was linear and the threshold intensity was 7.26 x 1012 quanta cm-2 s-1. Bursting activity of the cardiac ganglion, which is located in the heart and acts as the cardiac pacemaker deceased in frequency in response to illumination by white light. This fact suggests that the heart photoresponse of L. exotica results from the photosensitivity of the cardiac ganglion neurons. The photoresponse of the heart therefore contributes to regulation of cardiac output in addition to other regulatory systems. (+info)
The complete mitochondrial genome of the common sea slater, Ligia oceanica (Crustacea, Isopoda) bears a novel gene order and unusual control region features.
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BACKGROUND: Sequence data and other characters from mitochondrial genomes (gene translocations, secondary structure of RNA molecules) are useful in phylogenetic studies among metazoan animals from population to phylum level. Moreover, the comparison of complete mitochondrial sequences gives valuable information about the evolution of small genomes, e.g. about different mechanisms of gene translocation, gene duplication and gene loss, or concerning nucleotide frequency biases. The Peracarida (gammarids, isopods, etc.) comprise about 21,000 species of crustaceans, living in many environments from deep sea floor to arid terrestrial habitats. Ligia oceanica is a terrestrial isopod living at rocky seashores of the european North Sea and Atlantic coastlines. RESULTS: The study reveals the first complete mitochondrial DNA sequence from a peracarid crustacean. The mitochondrial genome of Ligia oceanica is a circular double-stranded DNA molecule, with a size of 15,289 bp. It shows several changes in mitochondrial gene order compared to other crustacean species. An overview about mitochondrial gene order of all crustacean taxa yet sequenced is also presented. The largest non-coding part (the putative mitochondrial control region) of the mitochondrial genome of Ligia oceanica is unexpectedly not AT-rich compared to the remainder of the genome. It bears two repeat regions (4x 10 bp and 3x 64 bp), and a GC-rich hairpin-like secondary structure. Some of the transfer RNAs show secondary structures which derive from the usual cloverleaf pattern. While some tRNA genes are putative targets for RNA editing, trnR could not be localized at all. CONCLUSION: Gene order is not conserved among Peracarida, not even among isopods. The two isopod species Ligia oceanica and Idotea baltica show a similarly derived gene order, compared to the arthropod ground pattern and to the amphipod Parhyale hawaiiensis, suggesting that most of the translocation events were already present the last common ancestor of these isopods. Beyond that, the positions of three tRNA genes differ in the two isopod species. Strand bias in nucleotide frequency is reversed in both isopod species compared to other Malacostraca. This is probably due to a reversal of the replication origin, which is further supported by the fact that the hairpin structure typically found in the control region shows a reversed orientation in the isopod species, compared to other crustaceans. (+info)
Mutualism or parasitism? The variable outcome of cleaning symbioses.
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The exact nature of many interspecific interactions remains unclear, with some evidence suggesting mutualism and other evidence pointing to parasitism for the same pair of interacting species. Here, we show spatial variation in the outcome of the cleaning relationship between Caribbean cleaning gobies (Elacatinus evelynae) and longfin damselfish (Stegastes diencaeus) over the distribution range of these species, and link this variation to the availability of ectoparasites. Cleaning interactions at sites with more ectoparasites were characterized by greater reductions in ectoparasite loads on damselfish clients and lower rates of removal of scales and mucus (i.e. cheating) by cleaning gobies, whereas the opposite was observed at sites where ectoparasite abundance was lower. For damselfish clients, cleaning was therefore clearly mutualistic in some locations, but sometimes neutral or even parasitic in others. Seasonal variability in ectoparasite abundance may ensure that locally low parasite availability, which promotes cleanerfish cheating, may be a transient condition at any given site. Conflicting conclusions about the nature of cleaning symbioses may, therefore, be explained by variation in ectoparasite abundance. (+info)