Ultrastructure of the microsporidian Inodosporus octospora (Thelohaniidae), a parasite of the shrimp Palaemon serratus (Crustacea, Decapoda). (1/94)

A parasite of the muscle of the shrimp Palaemon serratus has been examined by light and electron microscopy. Development occurs among myofibrils and induces ultrastructural alterations of the muscle fibers causing white discoloration. This microsporidian is characterized by uninucleate, later diplokaryotic and di-diplokaryotic meronts. The mother cell develops by rosette-like budding into 8 uninucleate sporoblasts, each containing 3 tape-like filaments attached to the wall that is enclosed in a persistent sporophorous vacuole. Each sporoblast gives rise to a uninucleate spore that possesses 3 elongated tape-like filaments attached to the spore wall, like spore tails. The morphological characters of the spores, redescribed in the present study, suggested that the spores belonged to Inodosporous octospora. The possibility that in the future members of Inodosporus sp. may be considered a new parasite group is discussed.  (+info)

The susceptibility of the giant freshwater prawn Macrobrachium rosenbergii to Lactococcus garvieae and its resistance under copper sulfate stress. (2/94)

Addition of copper sulfate (0.1 to 0.4 mg l(-1)) to tryptic soy broth (TSB) had no effect on growth rate of the bacterial pathogen Lactococcus garvieae. Giant freshwater prawns Macrobrachium rosenbergii were injected with L. garvieae (4 x 10(6) colony-forming units [cfu] prawn(-1)) grown in TSB or TSB containing copper sulfate at 0.1, 0.2, 0.3 or 0.4 mg l(-1). After 48 h, the cumulative mortality was significantly (p < 0.05) higher for prawns exposed to L. garvieae grown in 0.4 mg l(-1) copper sulfate than at the lower concentrations examined. In other experiments, prawns were injected with TSB-grown L. garvieae (4 x 10(6) and 2 x 10(5) cfu prawn(-1)), then held in water containing copper sulfate. After 8 h the mortality of L. garvieae-exposed prawns held in water containing 0.4 mg l(-1) copper sulfate was significantly higher than prawns held in water containing 0.2 and 0.3 mg l(-1) copper sulfate. At the lower L. garvieae density, cumulative mortality of prawns increased directly with ambient copper sulfate concentrations in the range of 0.2 to 0.4 mg l(-1). All prawns survived a 168 h exposure to 0.1 mg l(-1) copper sulfate. Prawns exposed to different concentrations of copper sulfate were examined for hemocyte density, phenoloxidase activity and respiratory burst. No significant differences in hemocyte density were observed among treatments. In prawns following a 48 h exposure to 0.1 mg l(-1) copper sulfate, phenoloxidase activity was decreased, but respiratory burst was increased. In conclusion, copper sulfate increased the virulence of L. garvieae to M. rosenbergii and modulated its immune system. Copper sulfate at 0.1 mg l(-1) decreased susceptibility of M. rosenbergii to L garvieae infection, whereas at 0.2 mg l(-1) the susceptibility was increased. The generation of superoxide anion by M. rosenbergii exposed to copper sulfate at a concentration higher than 0.2 mg l(-1) was considered to be cytoxic.  (+info)

Effect of nitrite on interaction between the giant freshwater prawn Macrobrachium rosenbergii and its pathogen Lactococcus garvieae. (3/94)

Addition of nitrite-N at 1.5 mg l(-1) in tryptic soy broth (TSB) significantly (p < 0.05) decreased the growth rate of the bacterial pathogen Lactococcus garvieae and significantly (p < 0.05) reduced mortality compared to zero nitrite controls when injected into giant freshwater prawns Macrobrachium rosenbergii at 5 x 10(5) colony-forming units (CFU) per prawn. In other experiments, whereby prawns were injected with TSB-grown L. garvieae (5 x 10(5) CFU prawn(-1)) and then held in water containing nitrite-N, mortality at 72 h post-injection was significantly (p < 0.05) higher for prawns held in water containing 1.68 mg l(-1) nitrite than at lower concentrations. Prawns exposed to different concentrations of nitrite-N were examined for THC (total hemocyte count), phenoloxidase activity, respiratory burst, phagocytic activity and bacterial clearance efficiency. No significant differences in THC and phenoloxidase activity were observed among treatments. With prawns exposed to nitrite-N for 168 h (7 d) at 1.59 mg l(-1), phagocytic activity and clearance efficiency decreased, while at 1.15 mg l(-1) or more, respiratory burst increased, generating the superoxide anion at levels considered cytoxic to the host. We conclude that nitrite-N at 1.68 mg l(-1) causes depression in the immune response and increased mortality in M. rosenbergii infected with L. garvieae.  (+info)

A new polypeptide toxin from the nematocyst venom of an Okinawan sea anemone Phyllodiscus semoni (Japanese name "unbachi-isoginchaku"). (4/94)

The venomous sea anemone Phyllodiscus semoni causes cases of severe stinging. We isolated Phyllodiscus semoni toxin 20A (PsTX-20A), a hemolytic and lethal polypeptide (20 kDa), from the nematocyst venom of this species for the first time. Furthermore, we sequenced the cDNA encoding PsTX-20A. The deduced amino acid sequence of PsTX-20A showed that this toxin was a new member of the actinoporin family, which consists of several cytolytic polypeptides originating from sea anemones. PsTX-20A showed lethal toxicity to the shrimp Palaemon paucidens when administered via intraperitoneal injection (LD50, 50 microg/kg) and hemolytic activity toward 0.8% sheep red blood cells (ED50, 80 ng/ml).  (+info)

Effect of benzalkonium chloride stress on immune resistance and susceptibility to Lactococcus garvieae in the giant freshwater prawn Macrobrachium rosenbergii. (5/94)

Addition of benzalkonium chloride (BKC) at 0, 0.3, 0.6 and 1.0 mg l(-1) to tryptic soy broth (TSB) had no effect on growth of Lactococcus garvieae, a bacterial pathogen of the giant freshwater prawn Macrobrachium rosenbergii. However, injection of the cultured cells into prawns at a dose of 4 x 10(6) colony-forming units (cfu) prawn(-1) resulted in significantly higher mortality at 120 h (p < 0.05) in prawns injected with cells grown in the absence of BKC than in prawns injected with cells grown in the presence of BKC. In other experiments, prawns were injected with TSB-grown L. garvieae (4 x 10(6) and 3 x 10(5) cfu prawn(-1)) and then held in water containing BKC at 0, 0.3, 0.6 and 1.0 mg l(-1). After 120 h, mortality was significantly higher in all the BKC treatments than in the control without BKC. Prawns showed no significant differences in total hemocyte count (THC) or differential hemocyte count (DHC) amongst treatment and control groups. However, 96 h exposure to 0.3 mg l(-1) BKC or more resulted in a decrease in phenoloxidase activity and an increase in respiratory burst to levels considered to be cytoxic. In summary, exposure of L. garvieae to BKC at 0.3 mg l(-1) or more decreased its virulence to M. rosenbergii, while exposure of M. rosenbergii to BKC at 0.3 mg l(-1) or more increased its susceptibility to L. garvieae infection.  (+info)

Role of maxilla 2 and its setae during feeding in the shrimp Palaemon adspersus (Crustacea: Decapoda). (6/94)

The movements of the basis of maxilla 2 in Palaemon adspersus were examined using macro-video recordings, and the morphology of its setae was examined using both scanning and transmission electron microscopy. The basis of maxilla 2 performs stereotypical movements in the latero-medial plane and gently touches the food with a frequency of 3-5 Hz. The medial rim of the basis of maxilla 2 carries three types of seta. Type 1 is serrate, type 2 and 3 are serrulate, and type 2 has a prominent terminal pore. Type 2 is innervated by 18-25 sensory cells whose cilia protrude through the terminal pore and are in direct contact with the external environment. The structure of type 2 setae indicates that they are mainly gustatory, although still bimodal due to their innervation by presumed chemosensory and mechanosensory neurons. Distally, the three types of setae have a complex arrangement of the cuticle involving water-filled canals, which may serve to improve flexibility. Type 1 and 3 setae have fewer sensory cells (4-9) but probably also have a bimodal sensory function. The function of type 1 setae is probably to protect type 2 setae, while type 3 setae might serve to groom the ventral side of the basis of maxilla 1.  (+info)

Metschnikowia bicuspidata and Enterococcus faecium co-infection in the giant freshwater prawn Macrobrachium rosenbergii. (7/94)

In May 2001, an epizootic yeast and bacterial co-infection in the giant freshwater prawn Macrobrachium rosenbergii occurred in Taiwan causing a cumulative mortality of 25%. The diseased prawns had a yellowish-brown body color, milky hemolymph, opaque, whitish muscles, and were approximately 7 mo old with total lengths ranging from 8 to 10 cm. Histopathological examination showed marked edema, yeast infiltration, and necrotic lesions with inflammation in the muscles, hepatopancreas and other internal organs. We isolated 2 pathogens from the diseased prawns, one was a yeast (AOD081MB) and the other a gram-positive coccus (AOD081EF). The gram-positive coccus was identified as Enterococcus faecium by the API 20 Strepsystem, conventional biochemical tests, and it had 99% 16S rDNA sequence identity (GenBank Accession Number AJ276355) to E. faecium (GenBank Accession Number AF529204). The sequence of a PCR product from the D1/D2 domain of 26S rDNA (GenBank Accession Number AF529297) from the yeast gave 99% sequence identity to Metschnikowia bicuspidata (GenBank Accession Number U44822). Experimental infections with these isolates produced gross signs and histopathological changes similar to those observed in the naturally infected prawns. The lethal doses (LD50) for isolate E. faecium AOD081EF, M. bicuspidata AOD081MB and the co-infection were 4.7 x 10(4), 2.6 x 10(2), and 2.4 x 10(2) colony-forming units prawn(-1), respectively. This is the first report of a confirmed co-infection of M. bicuspidata and E. faecium in prawn aquaculture.  (+info)

Infection of the isopod Tachaea spongillicola on freshwater prawns Macrobrachium spp. in southern India. (8/94)

This paper reports the infection of freshwater prawns belonging to the genus Macrobrachium by the isopod parasite Tachaea spongillicola in a freshwater river system of southeastern India.  (+info)

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