No abstract

Last but not least, I wish to express my deepest gratitude for my family: my mom, my dad, who took care my little daughter during three years of my research and study. They sacrificed their happiness for my happiness, their days for my days. I would like to thank for my sisters and my brother for your effort to look after my daughter during my absence. Above all, I would express my special thanks to my husband Cao D.V and my daughters, Lan Chi and Bao An, for your endless love, understanding and support. You are the most important persons in my life and have been my greatest motivation.

Three Haliotrema spp. are reported from the Vietnamese grouper. Morphological and morphometric characters show minor deviations from original descriptions of H. cromileptis Young, 1968 and H. epinepheli Young, 1968 . The third encountered species ( Haliotrema sp.) appears to be new to science. Genetically, H. cromileptis clusters with Bravohollisia , Pseudohaliotrema , and Haliotrema . The group is well supported by partial large subunit rDNA (LSU), complete small subunit rDNA (SSU), and partial SSU + ITS1 rDNA analyses. Ingroup phylogenetic relationships are not well resolved. Haliotrema cromileptis , H. fleti Young, 1968 , and Pseudohaliotrema sphincteroporus Yamaguti, 1953 are closely related to a monophyletic group of 5 Haliotrema spp. characterized by bell- or horn-shaped bases of the male copulatory organ (MCO), which contains an accessory piece. Based on SSU rDNA, H. cromileptis is a sister species to P. sphincteroporus and, together, they form a clade to 3 other Haliotrema spp. characterized by a bell-shape based MCO with an accessory piece. Data analysis conducted on partial SSU + ITS1 rDNA confirms the close phylogenetic relationship of H. cromileptis , H. fleti , H. chenhsintaoi Zhang, 2001 (possessing a horn-shaped base of the MCO), and Bravohollisia rosetta Lin, 1995. However, because major differences in diagnostic characters exist, this genetic relationship needs further elucidation.

Elopicola bristowi sp. n. infects the blood vascular system of Hawaiian ladyfish, Elops hawaiensis, in the Eastern Sea. It differs from the only nominal congener Elopicola nolancribbi by the combination of having rows of ventrolateral tegumental spines, a proportionally long oesophagus, anterior caeca, vasa efferentia coalescing ventral to the posterodextral margin of the testis, a post-testicular metraterm, a dextral common genital pore lateral to the oötype, and genitalia that are enantiomorphic relative to those of E. nolancribbi. Elopicola franksi sp. n. infects the heart and blood vascular system of Atlantic tarpon, Megalops atlanticus, in the Gulf of Mexico. It differs from its congeners by the combination of lacking ventrolateral tegumental spines and having an elongate body (6× longer than wide), a proportionally long oesophagus, a compact testis at level of the distal ends of the posterior caeca, and a post-testicular common genital pore at level of the oötype. Phylogenetic analyses based on the small subunit ribosomal DNA (18S), large subunit ribosomal DNA (28S), and internal transcribed spacer 2 (ITS2) genes revealed considerable genetic differences between these taxa. The 18S+28S tree showed a monophyletic Elopicola sister to all aporocotylids infecting fishes of Euteleosteomorpha. The ITS2 tree showed Paracardicoloides yamagutii as the sister taxon to Elopicola spp.

We herein diagnose blood fluke (Digenea: Aporocotylidae) infections in sea cagereared cobia (Rachycentron canadum) from Nha Trang Bay, Vietnam, using morphology, nucleotide sequences, scanning electron microscopy, and histopathology. This is the first report of this blood fluke beyond the Gulf of Mexico and contributes to our understanding of the disease implications of aporocotylid infections among marine aquacultured fishes. Blood flukes were morphologically identified as Psettarium cf. anthicum by having the combination of an extremely elongate body with rows of straight, ventrolateral tegumental spines and a sinistral posterolateral protuberance, an H-shaped intestine with asymmetrical posterior ceca, a lobed ovary, an ootype posterior to the male genital pore, and an extensively convoluted uterus located between the ovary and ootype. A comparison of the large subunit ribosomal DNA (28S), small subunit ribosomal DNA (18S), and internal transcribed spacer 2 (ITS2) derived from blood flukes infecting cobias in Nha Trang Bay and Gulf of Mexico revealed 5 (99.5% similarity in 28S), 3 (99.8%, 18S), and 12 (98.9%, ITS2) nucleotide differences between the geographic isolates. Adult blood flukes pierced the endocardium and penetrated the spongy myocardium or lesioned endocardium of the cobias from Nha Trang Bay. The associated heart lesion comprised fibro-granulomatous endocarditis with accompanying endocardial thrombi, including focal effacement of the endocardium adjacent to thrombi, hyperplasia of endocardial cells yielding a thickened endocardium within which adult flukes resided or fluke remnants were located, clusters of large epitheliod granulomas within thrombi and within the basal endocardium, and minute granulomas in spongy myocardium enclosing probable blood fluke eggs. These pathological alterations suggested that heavily-infected cobia may suffer reduced cardiac output via thrombi blocking normal blood flow and emboli causing infarcts. Acute mortality may be likely for heavily-infected cobias during periods of high cardiac output, e.g., during feeding in a sea cage, if concomitant with, or resulting in, circulation of emboli. The lesioned endocardium may reduce efficiency of respiratory gas exchange to cardiac myocytes as well as impair endocardial cell immune function.

Coeuritrema Mehra, 1933, previously regarded as a junior subjective synonym of Hapalorhynchus Stunkard, 1922, herein is revised to include Coeuritrema lyssimus Mehra, 1933 (type species), Coeuritrema rugatus (Brooks et Sullivan, 1981) comb. n., and Coeuritrema platti Roberts et Bullard sp. n. These genera are morphologically similar by having a ventral sucker, non-fused caeca, two testes, a pre-testicular cirrus sac, an intertesticular ovary, and a common genital pore that opens dorsally and in the sinistral half of the body. Phylogenetic analysis of the D1-D3 domains of the nuclear large subunit ribosomal DNA (28S) suggested that Coeuritrema and Hapalorhynchus share a recent common ancestor. Coeuritrema is morphologically most easily differentiated from Hapalorhynchus by having ventrolateral tegumental papillae and a definitive metraterm that is approximately 3−7× longer than the uterus. Coeuritrema comprises species that reportedly infect Asiatic softshell turtles (Testudines: Trionychidae) only, whereas Hapalorhynchus (as currently defined) comprises blood flukes that reportedly infect those hosts plus North American musk turtles (Sternotherus Bell in Gray) and mud turtles (Kinosternon Spix), both Kinosternidae, North American snapping turtles (Chelydridae), Asiatic hard-shelled turtles (Geoemydidae) and African pleurodirans (Pelomedusidae). Coeuritrema platti sp. n. infects the blood of Chinese softshell turtles, Pelodiscus sinensis (Wiegmann), cultured in the Da Rang River Basin (Phu Yen Province, Vietnam). It differs from C. lyssimus by having a narrow hindbody (< 1.6× forebody width), ventrolateral tegumental papillae restricted to the hindbody, a short cirrus sac (< 10% of corresponding body length), a transverse ovary buttressing the caeca, a short, wholly pre-ovarian metraterm (~ 10% of corresponding body length), and a submarginal genital pore. It differs from C. rugatus by having small ventrolateral tegumental papillae, testes without deep lobes, and a Laurer's canal pore that opens posterior to the vitelline reservoir and dorsal to the oviducal seminal receptacle. The new species is only the second turtle blood fluke reported from Vietnam.

The blue swimming crab (Portunus pelagicus Linnaeus, 1758) is one of the commercially exploited crab fishery resources in Vietnam. This is the first study to provide a broad survey of genetic diversity, population structure and migration patterns of P. pelagicus along the Vietnamese coastline. The crab samples were collected from northern, central and southern Vietnam. Here, we used a panel of single nucleotide polymorphisms (SNPs) generated from restriction site-associated DNA sequencing (RADseq). After removing 32 outlier loci, 306 putatively neutral SNPs from 96 individuals were used to assess fine-scale population structure of blue swimming crab. The mean observed heterozygosity (Ho) and expected heterozygosity (He) per locus was 0.196 and 0.223, respectively. Pairwise Fst and hierarchical AMOVA supported significant differentiation of central and northern from southern populations (P<0.01). Population structure analyses revealed that P. pelagicus in the south is a separate fisheries unit from the north and center. Contemporary migration patterns supported high migration between northern and central populations and restricted genetic exchange within the southern population. In contrast, historic gene flow provides strong evidence for single panmictic population. The results are useful for understanding current status of P. pelagicus in the wild under an environment changing due to natural and anthropogenic stresses, with implications for fisheries management.

Platt sinuosus Roberts & Bullard n. g., n. sp. (type-species) infects the kidney and mesenteric blood vessels of Mekong snail-eating turtles, Malayemys subtrijuga (Schlegel & Müller), in the Mekong River Basin. Species of Platt Roberts & Bullard n. g. are unique by the combination of having a papillate ventral sucker, vasa efferentia that are dorsal to the gonads, a massive cirrus-sac that is directed anteriad or laterad, and a vitellarium that surrounds the intestinal caeca. The new species resembles Platt ocadiae (Takeuti, 1942) Roberts & Bullard n. comb. but differs from it by having an external seminal vesicle that overlaps with or is immediately posterior to the level of the ventral sucker. Seven species previously of Hapalorhynchus Stunkard, 1922 are reassigned herein to Platt: P. odhnerensis (Mehra, 1933) Roberts & Bullard n. comb.; P. yoshidai (Ozaki, 1939) Roberts & Bullard n. comb.; P. ocadiae; P. oschmarini (Belous, 1963) Roberts & Bullard n. comb.; P. sutlejensis (Mehrotra, 1973) Roberts & Bullard n. comb.; P. synderi (Platt & Sharma, 2012) Roberts & Bullard n. comb.; and P. tkachi (Platt & Sharma, 2012) Roberts & Bullard n. comb. A dichotomous key to Platt spp. is provided. Hapalorhynchus sheilae (Mehrotra, 1973) Bourgat, 1990 and Hapalorhynchus mica (Oshmarin, 1971) Bourgat, 1990 are considered as species inquirendae, and Hapalorhynchus indicus (Thapar, 1933) Price, 1934 and Hapalorhynchus macrotesticularis (Rohde, Lee, & Lim, 1968) Brooks & Sullivan, 1981 are considered as species incertae sedis. Phylogenetic analysis of the large subunit rDNA (28S) showed P. sinuosus and P. snyderi to be sister taxa distinct from a monophyletic Hapalorhynchus and Coeuritrema platti Roberts & Bullard, 2016.