New polymorphic microsatellite loci for population studies in the European anchovy, Engraulis encrasicolus (L.)

Eleven microsatellite loci were developed in the European anchovy, Engraulis encrasicolus, and tested in samples from two geographically distant populations (Atlantic and Mediterranean Sea). Number of alleles ranged from eight to 28 and observed heterozygosity from 0.440 to 0.920. There was no evidence of linkage disequilibrium, although two loci are indeed linked. All loci were in Hardy-Weinberg equilibrium, except for one locus in the Atlantic and two loci in the Mediterranean sample. These three loci plus two more showed evidence for null alleles.     

Systemic infection of Kudoa lutjanus n. sp. (Myxozoa: Myxosporea) in red snapper Lutjanus erythropterus from Taiwan

A new species of Kudoa lutjanus n. sp. (Myxosporea) is described from the brain and internal organs of cultured red snapper Lutjanus erythropterus from Taiwan. The fish, 260 to 390 g in weight, exhibited anorexia and poor appetite and swam in the surface water during outbreaks. Cumulative mortality was about 1% during a period of 3 wk. The red snapper exhibited numerous creamy-white pseudocysts, 0.003 to 0.65 cm (n = 100) in diameter, in the eye, swim bladder, muscle and other internal organs, but especially in the brain. The number of pseudocysts per infected fish was not correlated with fish size or condition. Mature spores were quadrate in apical view and suboval in side view, measuring 8.2 +/- 0.59 microm in width and 7.3 +/- 0.53 microm in length. The 4 valves were equal in size, each with 1 polar capsule. Polar capsules were pyriform in shape, measuring 3.62 +/- 0.49 microm in length and 2.2 +/- 0.49 microm in width. Mild inflammatory responses or liquefaction of host tissue were associated with K. lutjanus n. sp. infection. The junction of shell valves appeared as overlapping, straight lines. The polar filament formed 2 to 3 coils. A general PCR (polymerase chain reaction) primer for Kudoa amplified the small subunit (SSU) rDNA sequences, and the amplified gene was sequenced. It was evident from the phylogenetic tree that the 3 strains tested, AOD93020M, AOD93028M and AOD93028B, were identical and belonged to the Kudoa SS rRNA subgroup. The evolutionary tree showed that these strains form a unique clade, at a distance from other Kudoa species and myxosporeans. The spore's morphological and ultrastructural characteristics, as well as the SS rDNA properties of the isolates, were also essentially identical and served to distinguish them from representative Kudoa. It is, therefore, proposed that the strains isolated from the diseased red snapper be assigned to a new species.     

Isolation of polymorphic microsatellite loci from the European anchovy,Engraulis encrasicolus

The European anchovy (Engraulis encrasicolus L., Engraulidae) is a widely spread fish resource which is overexploited along its area of distribution. A proper knowledge of the population genetic structure of this fish species is crucial to allow a sustainable management of fishery stocks. We developed five polymorphic microsatellite loci (expected heterozygosity per locus ranging from 0.46 to 0.97) for E. encrasicolus. These genetic markers can be applied to define the population genetic structure of European anchovy.     

Life history, pathology, and description of Kudoa ovivora n. sp. (Myxozoa, Myxosporea): an ovarian parasite of Caribbean labroid fishes

We describe Kudoa ovivora n. sp. from ovaries of bluehead wrasse, Thalassoma bifasciatum, and record its presence in 6 species (Labroidei) collected in the San Blas Islands. Panama. Kudoa ovivora spores are quadrate with rounded edges in apical view, oval-shaped with apical valve extensions in side view (mean spore dimensions: length 6.5 microns, width 7.7 microns, thickness 6.9 microns; mean polar capsule dimensions: length 2.1 microns, width 1.5 microns). This is the first Kudoa species from gonads of fishes. Prevalence of infection varied among labrids (Thalassoma bifasciatum, Halichoeres bivittatus, Halichoeres garnoti, Halichoeres poevi), with T. bifasciatum exhibiting the greatest prevalence. Density of infection, measured as percent infected eggs, also varied among species with highest densities occurring in H. garnoti. Kudoa ovivora may not require an intermediate host because fishes fed infected tissue developed more infections than unfed fish. Infected eggs are inviable and larger and heavier than uninfected eggs. Infected eggs contain more organic and inorganic material, indicating that K. ovivora increases resource allocation to eggs. Therefore, infected females may have reduced growth, fecundity, and/or spawning activity. Because males were uninfected and all identified hosts are protogynous sequential hermaphrodites, further studies of K. ovivora may provide new insights on the costs/benefits of sex change.     

Light- and electron-microscope description of Kudoa paralichthys n. sp. (Myxozoa,Myxosporea) from the brain of cultured olive flounder Paralichthys olivaceus in Korea

A new Myxosporea, Kudoa paralichthys n. sp., is described from the brain of cultured olive flounder Paralichthys olivaceus in South Korea. Mature spores were quadrate in apical view, measuring 5.19 +/- 0.54 microm in length, 8.23 +/- 0.50 microm in width, and 6.87 +/- 0.45 microm in thickness. Four valves were equal in size, each with 1 polar capsule. Polar capsules were pyriform in shape, measuring 2.2 +/- 0.22 microm in length and 1.2 +/- 0.14 microm in breadth. The sporoplasm consisted of a larger outer cell completely surrounding a smaller inner one, and had cytoplasmic projections. The junctions of shell valves were L-shaped. The sutural planes converged at the anterior ends of the spores and were associated with 4 small apex prominences in the central meeting point of the spores.     

Interannual variability and intraannual stability of the otolith shape in European anchovy Engraulis encrasicolus (L.) in the Bay of Biscay

In this study 1047 samples of European anchovy Engraulis encrasicolus caught in 2001, 2002 and 2003 in different areas of the Bay of Biscay were examined using otolith shape analysis. For the years 2001 and 2003, 1 year-old individuals were dominant, whereas for the year 2002 they were less common; in contrast 2 year-old individuals represented 74% of the total individuals, suggesting that the fisheries in 2002 were mainly supported by the strong recruitment of 2000. The classification success of the discriminant analysis indicated a strong separation between year groups ( P < 0·001), overall, 98% of individuals were correctly classified. Results from both jackknife and Cohen's kappa procedures confirmed the high rates of classification success obtained by the discriminant analysis (99 and 97%, respectively). Stability in the intraannual shape analysis leads to the idea that individuals were affected by the same intraannual environmental conditions in the Bay of Biscay. Variability in the interannual shape analysis could indicate that the spawning population is composed of European anchovy from different origins every year. In general differences observed suggested that the European anchovy in the Bay of Biscay were members of three or more different communities or entities.     

Energy density of anchovy Engraulis encrasicolus L. in the Adriatic Sea

European anchovy Engraulis encrasicolus , with total lengths ranging from 40·0 to 132·5 mm, were sampled during October 2002 and May 2003 in the northern Adriatic Sea in order to estimate their energy densities ( E _D). A highly significant ( P  < 0·001) relationship between E _D(y)(J g⁻¹wet mass) and per cent dry mass ( x ) was found: y  = 321 x  − 3316·9 ( n  = 161, r ² = 0·82).     

Phylogeography of the cosmopolitan marine parasite Kudoa thyrsites (Myxozoa: Myxosporea)

Kudoa thyrsites (Myxozoa: Multivalvulida) is a cosmopolitan marine parasite of fishes associated with post-mortem tissue degradation. Financial losses incurred as a result of these infections are of concern to commercial fisheries. There is conflicting evidence whether K. thyrsites represents a cryptic species complex. Myxospore morphology is very similar for K. thyrsites across its range, but preliminary genetic analyses show some differences. Kudoa thyrsites and the morphologically similar Kudoa histolytica were examined from hosts in British Columbia, Canada, Oregon, USA, Chile, England, South Africa, Australia, and Japan. We compared myxospore morphology and DNA sequences of heat shock protein 70 and the small subunit, large subunit, and internal transcribed spacer 1 of the ribosomal DNA. There was some morphological variation between regional representatives, inconsistent with genetic analyses. Phylogenetically, major separations correlated to four broad geographic regions: Japan, Australia, eastern Pacific, and eastern Atlantic. Within these regions there was little additional genetic structure. These data are evidence for regional subdivision of K. thyrsites suggesting global transplantation of fishes has yet to homogenize these distinctions. Within regions, parasite gene flow appears to be high between host species, suggesting little host specificity and minimal cryptic speciation. Our data also indicate that K. histolytica is not a valid species, as it was morphologically and genetically indistinguishable from K. thyrsites.     

Synopsis of the species of Kudoa Meglitsch, 1947 (Myxozoa: Myxosporea: Multivalvulida)

A synopsis of the species of Kudoa Meglitsch, 1947 (Myxozoa, Myxosporea, Multivalvulida) is presented, including 95 nominal species. For each species the most relevant morphological and morphometric features are indicated in tabulated format. Included are data on the site of infection within the host, the type-host and type-locality, plus a full bibliography of the original records for these species. Molecular data (GenBank accession numbers) are also provided whenever possible.     

Ceratomyxa hungarica n. sp. and Chloromyxum proterorhini n. sp. (Myxozoa: Myxosporea) from the freshwater goby Proterorhinus marmoratus (Pallas)

When studying the parasite fauna of freshwater gobies Proterorhinus marmoratus collected from the reaches of the River Danube around Budapest, two species of Myxosporea were recovered, a renal and a gall-bladder form. Previously no myxosporeans had been reported from this fish species. The spores and pseudoplasmodia of the parasite described as Ceratomyxa hungarica n. sp. were found in the convoluted tubules of the kidney and in the cavity of Bowman's capsule. The pseudoplasmodia were loosely attached to the wall of the tubules, causing their distention. Within each pseudoplasmodium two spores were formed. In the case of Chloromyxum proterorhini n. sp. only spores floating freely in the contents of the gall-bladder were found. Since Ceratomyxa species are typically marine fish parasites, Proterorhinus marmoratus, a fish species which has adapted to freshwater, appears to have retained some of its marine myxosporean fauna.     

Analysis of Kudoa thyrsites (Myxozoa: Myxosporea) spore antigens using monoclonal antibodies.

A method employing Percoll gradient centrifugation was developed to purify Kudoa thyrsites spores from somatic muscle tissue of Atlantic salmon Salmo salar. Highly purified spores were then used to immunize inbred BALB/c mice for derivation of hybridomas secreting Kudoa-specific monoclonal antibodies (mAbs). Analysis of mAbs by immunofluorescence microscopy and flow cytometry showed that several were specific for antigens on the surface of K. thyrsites spores whereas other mAbs reacted with polar capsules or with polar filaments of spores of K. thyrsites, K. paniformis and K. crumena. Immunoblots on spore lysates using the surface-binding mAbs showed a broad band of 46 to > 220 kDa, whereas mAbs specific for antigens of polar capsules and polar filaments detected sharper bands of various molecular masses, depending on the Kudoa species. The dominant epitope of the K. thyrsites spore surface antigen was shown to be carbohydrate as determined by its sensitivity to treatment with anhydrous trifluoromethane sulfonic acid and by its resistance to treatment with Proteinase K. Immunofluorescence microscopy using the K. thyrsites-specific mAbs on isolated, intact, permeabilized plasmodia and on thin sections of somatic muscle tissue containing plasmodia revealed intense labeling of spores both within the spore-producing plasmodia and in the flesh of infected Atlantic salmon. As few as 100 spores were detected by immunoblotting, indicating that these mAbs have potential for use in developing a field-based diagnostic test.     

Ceratomyxa seriolae n. sp. and C. buri n. sp. (Myxozoa: Myxosporea) from the gall-bladder of cultured yellowtail Seriola quinqueradiata

Ceratomyxa seriolae n. sp. and C. buri n. sp. (Myxozoa: Myxosporea) were found in the gall-bladder of cultured yellowtail Seriola quinqueradiata Temminck & Schlegel (Carangidae) in Japan. Mature spores of C. seriolae n. sp. were elongate and 6.5 (6.0-7.5) m long and 33.7 (28.0-41.5) m thick. Disporous plasmodia of C. seriolae n. sp., 40-100 m in size, were amoeboid to spherical. C. buri n. sp. were elliptical with a flattened posterior end, 6.5 (5.5-7.5) m long and 14.3 (11.0-16.5) m thick. Spherical plasmodia of C. buri n. sp., 15-20 m in diameter, were disporous. In periodical sampling of yellowtail bile from August, 1999 to February, 2000, the two new species of Ceratomyxa, as well as Myxobolus spirosulcatus Maeno, Sorimachi, Ogawa & Kearn 1995, first appeared in October, and the prevalences were very variable (20-100%) during the study period.     

Multiple freshwater invasions of the tapertail anchovy (Clupeiformes: Engraulidae) of the Yangtze River

Freshwater fish evolved from anadromous ancestors can be found in almost all continents. The roles of paleogeographic events and nature selection in speciation process often are under focus of research. We studied genetic diversity of anadromous and resident tapertail anchovies (Coilia nasus species complex) in the Yangtze River Basin using 4,434 nuclear loci, and tested the history of freshwater invasion of C. nasus. We found that both C. brachygnathus and C. nasus were valid species, but the resident C. nasus taihuensis and the anadromous C. nasus were not different genetically based on Bayes factor species delimitation (BFD*). Maximum likelihood tree, Network, PCA and STRUCTURE analyses all corroborated the results of BFD*. Two independent freshwater invasion events of C. nasus were supported, with the first event occurring around 4.07 Ma and the second happened around 3.2 Ka. The time of the two freshwater invasions is consistent with different paleogeographic events. Estimation showed that gene flow was higher within ecotypes than between different ecotypes. F‐DIST analyses identified 120 disruptive outliers by comparing C. brachygnathus to anadromous C. nasus, and 21 disruptive outliers by comparing resident C. nasus to anadromous C. nasus. Nine outliers were found to be common between the two comparisons, indicating that independent freshwater invasion of C. nasus might involve similar molecular pathways. The results of this study suggest that adaptation to landlocked freshwater environment of migratory fish can evolve multiple times independently, and morphology of landlocked ecotypes may cause confusion in their taxonomy.     

A new species of anchovy,Encrasicholina auster (Clupeiformes: Engraulidae) from Fiji,southwestern Pacific Ocean

ABSTRACT

Encrasicholina auster sp. nov. (Clupeiformes: Engraulidae) is described on the basis of six specimens collected from Fiji, southwestern Pacific Ocean. The new species is distinguished from congeners by the following combination of characters: long upper jaw (posterior tip extending beyond posterior margin of preopercle) 20.8%–22.5% standard length (SL); long lower jaw 19.0%–20.7% SL; long head 29.1%–29.2% SL; three unbranched rays in the dorsal and anal fins; transverse scales 11; branched pectoral-fin rays 12–13; pseudobranchial filaments 19–21; gill rakers 45–49, 40–43, 26–31 and 22–25 on the first, second, third and fourth gill arches, respectively.     

Intraretinal variability and specialization of cones in Japanese anchovy (Engraulis japonicus,Engraulidae)

The retina of anchovies is characterized by an unusual arrangement and ultrastructure of cones. In the retina of Japanese anchovies, Engraulis japonicus, three types of cones are distributed into rows. The nasal, central, temporal, and ventro‐temporal regions of the retina were occupied exclusively by the long and short cones. Triple cones, made up of two lateral components and one smaller central component, were found only in the dorsal and ventro‐nasal retinal regions. In the outer segments of all short and long cones from the ventro‐temporal region, the lamellae were oriented along the cell axis and were perpendicular to the lamellae in the long cones, providing a morphological basis for the detection of polarization. This lamellar orientation is unique to all vertebrates. The cones were examined with respect to regional differentiation in their size and spectral properties via light microscopy, transmission electron microscopy, and microspectrophotometry. Various dimensions of cones were measured in preparations of isolated cells. The cones from the ventro‐temporal region had different dimensions than cones of the same type located in other retinal regions. Triple cones from the dorsal region were significantly larger than triple cones from the ventro‐nasal region. The spectral absorbance of the lateral components of triple cones in the ventro‐nasal retina was identical to the absorbance of all long and short cones from the ventro‐temporal region. These are shifted to shorter wavelengths relative to the absorbance of the lateral components of the triple cones located in the dorsal retina. Thus, the retina of the Japanese anchovy shows some features of regional specialization common in other fishes that improves spatial resolution for the upwards and forwards visual axis and provides spectral tuning in downwelling light environment. That results from the differentiation of cone types by size and by different spectral sensitivity of various retinal areas. J. Morphol. 277:472–481, 2016. © 2016 Wiley Periodicals, Inc.     

Occurrence of Kudoa sp. (Myxozoa) in Trachurus trachurus L. (osteichthyes) in Portugal

Specimens of Trachurus trachurus L., obtained monthly in a fish market of Oporto from October 1998 to August 1999, were examined for the presence of Kudoa in the muscle. Kudoa sp. spores were found in 84.7% of the specimens (n = 209). The prevalence was not significantly different between seasons and was not related to the host's length. The infection does not seem to have negative effects on the fish quality once no macroscopic pseudocysts or myoliquefaction were detected.     

Chloromyxum inexpectatum n. sp. and Sphaerospora colomani n. sp. (Myxozoa: Myxosporea), parasites of the urinary system of the sterlet,Acipenser ruthenus L.

During the parasitological examination of sterlets, Acipenser ruthenus L., caught for breeding, the developmental stages of two new coelozoic species of Myxosporea were demonstrated in the urinary passages. Chloromyxum inexpectatum n. sp. occurs attached to the epithelial cells of the ureters and urinary bladder. Sphaerospora colomani n. sp. forms bisporoblastic pseudoplasmodia in the lumen of the renal tubules. A further myxosporean species, Zschokkella sturionis Tripathi, 1948, was found in the biliary ducts. The occurrence of this parasite in sterlet has not been reported so far. Examination of blood smears revealed Cryptobia acipenseris and Haemogregarina acipenseris infection. Developmental stages of the coccidia Goussia acipenseris Molnár, 1986 and Goussia vargai Molnár, 1986 were frequently seen in the intestine of the dissected fish.     

Allozyme, mitochondrial-DNA, and morphometrie variability indicate cryptic species of anchovy (Engraulis encrasicolus)

Previous surveys of population structure in the Atlantic-Mediterranean anchovy Engraulis encrasicolus L. have reported heterogeneity in morphology, allozyme frequencies, and mitochondrial DNA haplotype frequencies at a regional scale. In particular, two stocks of anchovy have been detected in the Adriatic Sea. In this paper, the available data is reviewed with the aim to relate genetic variation to geography at the widest possible geographical scale, for investigating the evolutionary mechanisms underlying stock structure in anchovy. Correspondence analysis of allozyme frequencies (24 samples, three polymorphic loci) compiled from the literature indicates three distinct entities in the Mediterranean Sea. Open-sea or oceanic anchovy populations are genetically different from inshore-water populations within a region (Nei's ^ G _ST = 0.035–0.067), while broadscale geographical variation is weak for each of these two habitat-specific forms (^ G _ST = 0.005–0.006). Mitochondrial-DNA haplotype frequencies support the distinction between an inshore form and an oceanic form (^ G _ST = 0.067–0.107), with virtually no genetic differences among oceanic populations across the Gulf of Biscay, the western Mediterranean and the Ionian Sea (^ G _ST = −0.001). If natural selection on marker loci is unimportant, these results indicate the occurrence of two parapatric, genetically distinct, habitat-specific forms that are widely distributed throughout the Mediterranean Sea. Persistent allele and haplotype-frequency differences between these forms indicate reproductive isolation and the presence of an E. encrasicolus species complex in the Mediterranean. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society 75 : 261–269.     

Characterization of Kudoa monodactyli n. sp. (Myxosporea: Multivalvulida) from the Muscle of Monodactylus argenteus (Teleostei: Monodactylidae) from Moreton Bay, Queensland, Australia

Kudoa monodactyli n. sp. is described from the somatic musculature of Monodactylus argenteus from several localities in southern Queensland, Australia. This is the first record of a myxozoan parasite from the family Monodactylidae. The spores typically have five polar capsules, making this species similar to the four other five-valved Kudoa species (K. neurophila, K. muscularis, K. shulmani, K. cutanea) that have been described to date. However, morphometric measurements particularly of spore length and width make the species from M. argenteus distinct from the other species. Comparison of the small subunit ribosomal DNA sequence of this species with its congeners for which sequence data are available, provides further evidence of novelty. Kudoa monodactyli n. sp. displays 38 (of 1,554) nucleotide differences compared with rDNA sequence of Kudoa neurophila, which on phylogenetic analysis places these species in clades exclusive of each other. Phylogenetic analyses also provide evidence that the number of valves per spore in this genus is an imperfect indicator of relatedness.