Vaccination of European sea bass Dicentrarchus labrax with avirulent Mycobacterium marinum (iipA::kan mutant).

Mycobacteriosis is a chronic progressive disease affecting teleost fishes all over the world. No vaccine is commercially available against its main etiological agent, Mycobacterium marinum. The mycobacterial gene responsible for invasion and intracellular persistence, iipA, is known to modulate M. marinum pathology. The innate and adaptive immune responses in sea bass (Dicentrarchus labrax) vaccinated with M. marinum iipA::kan mutant with (and without) the use of adjuvant, with (and without) a booster vaccination were monitored. The adjuvanted vaccine induced enhanced immune responses. TNF-α transcription levels were extremely high in spleen of the fish vaccinated with the addition of adjuvant in both fish vaccinated once and twice, followed by an IgM response highly specific for M. marinum. Also, histologically, granulomas started appearing in spleen and head-kidney tissues (but with no visible bacteria) within a month after vaccination, mainly with the adjuvanted vaccine. This was followed by reduction in pathology, as demonstrated by the lower number of granulomas (with visible bacteria), indicating that even heat-killed bacteria were able to elicit granulomatous formations. Adhesion of the internal organs and moderate pigmentation were observed in the perivisceral adipose tissue of nearly all vaccinated fish. Although the adjuvanted heat-killed avirulent iipA::kan mutant clearly induced a strong humoral and adaptive immune response, the booster treatment did not seem to have produced a significantly higher degree of protection from the disease compared to fish that received a single vaccination.

Co-existence of Myxobolus spp. (Myxozoa) in gray mullet (Mugil cephalus) juveniles from the Mediterranean Sea.

Gray mullet (Mugilidae) occur in all seas and are farmed widely around the world, and thus, the risk of their parasites spreading through transport of aquaculture seed is a serious concern. Among others, gray mullets typically host a diversity of myxosporeans, a group in which spore morphometrics of genera has been consistently shown to be inadequate for determination of species. In this study, we investigated Myxobolus Bütschli 1882 (Myxosporea) species found in two fingerling stocks of Mugil cephalus caught in the wild off the coasts of the eastern (Israel) and western (Spain) Mediterranean. Although we observed similar morphological features, significant dissimilarities in spore size and differences in Myxobolus species SSU rDNA sequences were noted. Genetic analyses demonstrated that multiple Myxobolus species, some with SSU rDNA sequences new to GenBank, infected the stock from Spain. In addition, Myxobolus DNA was found associated with several types of host tissue (gill, tail, and internal organs), and sequence analyses indicated that multiple species of Myxobolus were also present, sometimes in different tissues from the same fish. The results suggest that the gray mullets supported a collection of several different Myxobolus species with similar morphology.

Edwardsiella piscicida-like pathogen in cultured grouper.

An Edwardsiella sp. was isolated from the kidney of diseased groupers (Epinephelus aeneus and E. marginatus) cultured in Eilat (Israel, Red Sea). Affected fish presented a severe suppurative nephritis with large abscesses occasionally spreading into the surrounding musculature. Biochemical profiles and phenotypic comparisons failed to provide a clear identification to the species level, and genetic analysis of the 16S subunit failed to discriminate between Edwardsiella piscicida, E. tarda and E. ictaluri. Analysis of the gyrB gene, however, placed the grouper isolates into the E. piscicida-like group, a newly recognized taxon which also encompasses the non-motile strains previously classified as atypical E. tarda. Initial genomic analysis revealed the presence of the Edwardsiella type 3 secretion system (T3SS) but also revealed a pathogenicity island encoding a second T3SS with homology to the locus of enterocyte effacement of Escherichia coli. Further analysis revealed 3 different type 6 secretion systems that were also present in all sequenced isolates of Edwardsiella piscicida-like strains. Based on estimated DNA-DNA hybridization values and the average nucleotide index, the grouper strain fits into the E. piscicida-like phylogroup described as E. anguillarum sp. nov. The peculiarities associated with this isolate and the association of other conspecific piscine isolates from multiple marine and brackish water species suggest a link of the entire E. piscicida-like phylogroup to the marine environment.

Complete Genome Sequence of an Edwardsiella piscicida-Like Species Isolated from Diseased Grouper in Israel.

The Edwardsiella piscicida-like sp. is a Gram-negative facultative anaerobe that causes disease in some fish species. We report here the complete genome sequence of a virulent isolate from a diseased white grouper (Epinephelus aeneus) raised on the Red Sea in Israel, which contains a chromosome of 3,934,167 bp and no plasmids.

A transgenic zebrafish model for monitoring xbp1 splicing and endoplasmic reticulum stress in vivo.

Accumulation of misfolded or unfolded proteins in the endoplasmic reticulum (ER) triggers ER stress that initiates unfolded protein response (UPR). XBP1 is a transcription factor that mediates one of the key signaling pathways of UPR to cope with ER stress through regulating gene expression. Activation of XBP1 involves an unconventional mRNA splicing catalyzed by IRE1 endonuclease that removes an internal 26 nucleotides from xbp1 mRNA transcripts in the cytoplasm. Researchers have taken advantage of this unique activation mechanism to monitor XBP1 activation, thereby UPR, in cell culture and transgenic models. Here we report a Tg(ef1α:xbp1δ-gfp) transgenic zebrafish line to monitor XBP1 activation using GFP as a reporter especially in zebrafish oocytes and developing embryos. The Tg(ef1α:xbp1δ-gfp) transgene was constructed using part of the zebrafish xbp1 cDNA containing the splicing element. ER stress induced splicing results in the cDNA encoding a GFP-tagged partial XBP1 without the transactivation activation domain (XBP1Δ-GFP). The results showed that xbp1 transcripts mainly exist as the spliced active isoform in unfertilized oocytes and zebrafish embryos prior to zygotic gene activation at 3 hours post fertilization. A strong GFP expression was observed in unfertilized oocytes, eyes, brain and skeletal muscle in addition to a weak expression in the hatching gland. Incubation of transgenic zebrafish embryos with (dithiothreitol) DTT significantly induced XBP1Δ-GFP expression. Collectively, these studies unveil the presence of maternal xbp1 splicing in zebrafish oocytes, fertilized eggs and early stage embryos. The Tg(ef1α:xbp1δ-gfp) transgenic zebrafish provides a useful model for in vivo monitoring xbp1 splicing during development and under ER stress conditions.

Phylogeny of Coccomyxa (Myxosporea: Myxidiidae) spp. with the description of a new species from Bathygobius cyclopterus (Gobiidae) in the northern Red Sea.

Two species of Coccomyxa Léger et Hesse, 1907, one of the least studied myxosporean genera, are reported from shallow coastal waters in the Gulf of Eilat, Red Sea, Israel. A new species, Coccomyxajirilomi sp. n. is described from the spotted frillgoby Bathygobius cyclopterus (Valenciennes) (Gobiidae). It forms polysporous plasmodia that invade the liver and form packed clusters inside the bile ductules. Plasmodia also occur in the bile ducts and gall bladder of the host, attached to the epithelial lining or free floating in the bile. Infected hepatic bile ductules packed with plasmodia were partially occluded, with evidence of cholestasis, periductular fibrosis and pericholangitis. The mature spore is ellipsoid, has smooth valves and contains a single polar capsule with the polar filament arranged in 4-5 oblique coils. Spore dimensions are 9.0-11.3 x 5.0-7.0 microm. A second species, Coccomyxa sp., with smaller 7.6-9.6 x 4.2-5.2 microm and more delicate spores, was found in the gall bladder of the rippled rockskipper, Istiblennius edentulus (Forster et Schneider) (Blenniidae). The small subunit (SSU) rDNA sequence analysis of both Coccomyxa species suggests that they are closely related to members of the genera Myxidium, Zschokkella and Auerbachia, whose members infect the gall bladder of marine fish.

Habitat selection and home range in the Blanford's fox, Vulpes cana: compatibility with the resource dispersion hypothesis.

This paper presents analyses of habitat-use and home range size in the Blanford's fox. We predicted, from the resource dispersion hypothesis (RDH), that home ranges would encompass similar areas of combined fruitful habitats, but widely different areas of useless habitats, and thus that home ranges would be larger where such fruitful patches are fragmented and widely dispersed. Home range estimates of 0.5-2.0 km2 were calculated for 16 adult Blanford's foxes, using three different methods. There were no significant differences in home range size between sexes or study sites. One habitat, dry creekbed, was the most frequently visited in all home ranges. Dry creekbed provided abundant prey for the foxes and only sparse cover for their predators. Both the available area of creekbed in each range, and the area of creekbed patches that was used by the foxes, were independent of home range size. However, the variance in home range size was explained by the mean distance between the main denning area and the most frequently used patches of creekbed. These results are in accord with some predictions of the resource dispersion hypothesis.