Not so much a sea bass: Divergent European sea bass (Dicentrarchus labrax L.) freshwater incursions

European sea bass (Dicentrarchus labrax [Linnaeus, 1758]) is a euryhaline marine migrant fish highly valuable for fisheries and aquaculture. Although juveniles are known to use estuaries and occasionally move to freshwater environments, these freshwater incursions had not been reported for adults. Recently, this behavior was observed in the Tagus River (Portugal) for adults occurring up to 150 km from the river mouth, about 80 km upstream from the tidal influence, suggesting the existence of a freshwater contingent. Fisheries management of sea bass should consider the putative existence of a freshwater contingent.

Newly Described Coccidia Goussia bayae from White Perch Morone americana: Morphology and Phylogenetics Support Emerging Taxonomy of Goussia within Piscine Hosts

In March and April 2016, 150 white perch ( Morone americana) were collected from various localities in Chesapeake Bay and examined for coccidia. A previously undescribed species of coccidia was observed in the hepatic bile ducts and gallbladder of all white perch (100%) examined. We describe this species using morphological characteristics, histology, and gene sequences of the small-subunit ribosomal DNA ( rDNA), large-subunit rDNA, and mitochondrial genes cytochrome oxidase 1 ( COI), cytochrome oxidase b ( Cytb), and cytochrome oxidase 3 ( COIII). Oocysts of Goussia bayae n. sp. were subspherical with a single-layered smooth wall and measured (length [L] × width [W]) 26.2 × 21.8 μm, with a L/W ratio of 1.2. A micropyle was present but a micropyle cap, polar granules, and oocyst residuum were absent. Each oocyst contained 4 sporocysts that were ellipsoidal and measured (L × W) 12.6 × 7.8 μm, with a L/W ratio of 1.6. A pair of sporozoites was present, but sporocysts lacked a Stieda body and residuua. Meronts and gamonts were epicellular in biliary epithelial cells and oocysts were coelozoic in hepatic and common bile ducts and gallbladder. This is the first report of Goussia spp. from white perch and the first mitochondrial DNA sequence reported from a Goussia species. Phylogenetic analysis indicates basal placement of G. bayae to Eimeriidae, Choleoeimeria, and Sarcocystidae.

Multiple vitellogenins and product yolk proteins in European sea bass (Dicentrarchus labrax): Molecular characterization, quantification in plasma, liver and ovary, and maturational proteolysis

Three complete vitellogenin (Vtg) polypeptides of European sea bass (Dicentrarchus labrax), an acanthomorph teleost spawning pelagic eggs in seawater, were deduced from cDNA and identified as VtgAa, VtgAb and VtgC based on current Vtg nomenclature and phylogeny. Label free quantitative mass spectrometry verified the presence of the three sea bass Vtgs or their product yolk proteins (YPs) in liver, plasma and ovary of postvitellogenic females. As evidenced by normalized spectral counts, VtgAb-derived protein was 2- to 5-fold more abundant, depending on sample type, than for VtgAa, while VtgC-derived protein was less abundant, albeit only 3-fold lower than for VtgAb in the ovary. Western blotting with Vtg type-specific antisera raised against corresponding gray mullet (Mugil cephalus) lipovitellins (Lvs) detected all three types of sea bass Vtg in the blood plasma of gravid females and/or estrogenized males and showed that all three forms of sea bass Lv undergo limited partial degradation during oocyte maturation. The comparatively high levels of VtgC-derived YPs in fully-grown oocytes and the maturational proteolysis of all three types of Lv differ from what has been reported for other teleosts spawning pelagic eggs in seawater but are similar to recent findings for two species of North American Moronidae, the striped bass (Morone saxatilis) and white perch (Morone americana), which spawn pelagic and demersal eggs, respectively in fresh water. Together with the high Vtg sequence homologies and virtually identical structural features of each type of Vtg between species, these findings indicate that the moronid multiple Vtg systems do not substantially vary with reproductive environment.