Parasites of the aquaculture candidate Siganus canaliculatus Park, 1797 (Siganidae: Perciformes) from Omani waters, including their potential to indicate environmental health

This study aims to investigate the parasite fauna of a marine herbivorous fish inhabiting the coasts of the Sultanate of Oman. The parasite fauna of S. canaliculatus is highly diverse and species rich marine parasite community. The results of this study provide insight into the richness and diversity of the marine ecosystem in the waters of Oman. Several species were reported for the first time as new host and locality records. Some are described and identified as new species to science. in addition, the study provided an opportunity to assess the status of the marine ecosystem of Oman

Omanicotyle heterospina n. gen. et n. comb. (Monogenea: Microcotylidae) from the gills of Argyrops spinifer (Forsskal) (Teleostei: Sparidae) from the Sea of Oman

Background: The Sultanate of Oman's aquaculture industry is expanding with an on-going assessment of potential new fish species for culture. The king soldier bream, Argyrops spinifer (Forsskål) (Sparidae), is one such species that is under consideration. During a routine health assessment of specimens caught in the Sea of Oman throughout the period November 2009 to March 2011, a number of gill polyopisthocotylean monogeneans were recovered. Methods: A subsequent study of the monogeneans using a range of morphology-based approaches indicated that these were Bivagina heterospina Mamaev et Parukhin, 1974. In the absence of pre-existing molecular data, an expanded description of this species is provided, including a differential diagnosis with other species and genera belonging to the subfamily Microcotylinae Monticelli, 1892 with the subsequent movement of this species to a new genus to accommodate it. Results: The polyopisthocotyleans collected from the gills of A. spinifer appear to be unique within the family Microcotylidae Taschenberg, 1879 in that, morphologically, they possess a pair of large, muscular vaginae each armed with a full crown of 16-18 robust spines and a unique dorsal region of folded tegument, which permits their discrimination from species of Bivagina Yamaguti, 1963. Sequencing of the SSU rDNA (complete 1968 bp) and LSU rDNA (partial 949 bp) places the specimens collected during this study within the subfamily Microcotylinae, but the LSU rDNA sequence differs from Bivagina and also from other microcotylid genera. Morphological features of B. heterospina sensu Mamaev et Parukhin, 1974 and the specimens collected from the current study are consistent with one another and represent a single species. The vaginal armature of these worms is unique and differs from all other genera within the Microcotylinae, including Bivagina, and its movement to Omanicotyle n. gen. to accommodate this species is proposed. Conclusions: A new genus, Omanicotyle n. gen., is erected to accommodate Omanicotyle [Bivagina] heterospina n. comb. which represents the first monogenean to be described from Omani marine waters. Given the pathogenic potential of microcotylids on captive held fish stocks, a full assessment of Omanicotyle heterospina n. gen. et n. comb. is now required before large-scale production commences

The In Vitro Activity of a Range of Natural Bioflavonoids Against Five Species of Pathogenic Fish Bacteria

The in vitro antibacterial activity of thirty two plant-derived compounds (26 crude herbal extraction and 6 pure citrus-based bioflavonoids) were tested on five different species of aquatic bacterial pathogens (Aeromonas hydrophila, A. salmonicida, A. sobria, Edwardsiella ictaluri, and E. tarda) over a period of 72 hours at 22 oC. From the agar diffusion test, six pure citrus-based bioflavonoids (apigenin, catechin, hesperidin, morin, naringin and quercetin) appeared to impact on growth when used at concentrations ranging from 10 ppm - 1000 ppm. To confirm their effect on the growth dynamics of each bacteria, a 1000 ppm dose of the appropriate bioflavonoid was added to a bacterial culture and daily changes in culture growth were measured. Quercetin was found to be bacteriocidal against all the bacterial strains. Morin was found to be bacteriocidal against only 4 out of 6 strains while hesperidin was found to affect the growth of all the tested bacterial strains, working both as a bacteriocidal and as a bacteriostatic agent. Apigenin performed poorly and had no effect on the growth of any bacterial strain while catechin and naringin were found to be generally bacteriostatic in action but had little impact on the growth of the Aeromonad strains. From the current in vitro work, it was concluded that certain plant extracts do have an impact on the growth dynamics of select bacteria and show potential as alternatives to the use of antimicrobials, but further research is required to assess their performance in vivo

The In Vitro Activity of a Range of Natural Bioflavonoids Against Five Species of Pathogenic Fish Bacteria

The in vitro antibacterial activity of thirty two plant-derived compounds (26 crude herbal extraction and 6 pure citrus-based bioflavonoids) were tested on five different species of aquatic bacterial pathogens (Aeromonas hydrophila, A. salmonicida, A. sobria, Edwardsiella ictaluri, and E. tarda) over a period of 72 hours at 22 oC. From the agar diffusion test, six pure citrus-based bioflavonoids (apigenin, catechin, hesperidin, morin, naringin and quercetin) appeared to impact on growth when used at concentrations ranging from 10 ppm - 1000 ppm. To confirm their effect on the growth dynamics of each bacteria, a 1000 ppm dose of the appropriate bioflavonoid was added to a bacterial culture and daily changes in culture growth were measured. Quercetin was found to be bacteriocidal against all the bacterial strains. Morin was found to be bacteriocidal against only 4 out of 6 strains while hesperidin was found to affect the growth of all the tested bacterial strains, working both as a bacteriocidal and as a bacteriostatic agent. Apigenin performed poorly and had no effect on the growth of any bacterial strain while catechin and naringin were found to be generally bacteriostatic in action but had little impact on the growth of the Aeromonad strains. From the current in vitro work, it was concluded that certain plant extracts do have an impact on the growth dynamics of select bacteria and show potential as alternatives to the use of antimicrobials, but further research is required to assess their performance in vivo.

Redescription of Aspidogaster limacoides Diesing, 1834 (Aspidogastrea: Aspidogastridae) from freshwater fishes of northern Germany

Aspidogaster limacoides Diesing, 1834 (Aspidogastridae) is redescribed based on light and scanning electron microscopy of specimens from the stomach and intestine of Abramis brama, Rutilus rutilus and Scardinius erythrophthalmus (Actinopterygii: Cyprinidae). The fishes were sampled during 2018 and 2019 at Lake Tollense in Mecklenburg-Western Pomerania, Germany. The prevalence of A. limacoides was highest in R. rutilus (61.7%) followed by Scardinius erythrophthalmus (7.7%) and A. brama (2.9%), while it was absent in Perca fluviatilis from the same lake. The following structures of A. limacoides are described for the first time: a depression on the ventral side of the neck, variations in the number and the arrangement of alveoli, numerous pits scattered all over the body surface, the presence of a few papillae-like structures posterior lateral to the mouth, the number of marginal organs represented by openings of exocrine multicellular glands as shown in histology and the subterminal position of the excretory pore. These characters can be used to distinguish three species of Aspidogaster, namely, A. ijimai, A. conchicola and A. limacoides, suggesting that SEM is a useful and promising tool in differentiating Aspidogaster species. Comparison of molecular data of the ITS1-5.8S-ITS2 regions showed a 94% similarity to A. limacoides from the European part of Russia. Phylogenetic analysis showed that the present specimens clustered in the same clade with A. limacoides sensu stricto, forming a distinct group to the exclusion of congeners

Confocal photos of <i>Pseudempleurosoma haywardi</i> sp. nov.

<p>Confocal microscopy illustrations of male copulatory organ (MCO) of <i>Pseudempleurosoma haywardi</i> sp. nov. with accessory pieces (<b>A-K</b>), from different angles (<b>A-C</b>), at different levels (<b>D-G</b>) and from a second worm (<b>H-K</b>), and of the opisthaptor with its hooks, anchors and bars (dorsal bar concave anterior) (<b>L</b>) as well as from different levels of the dorsal anchor apparatus (outer root extension with chitin containing cap, inner root extension with saucer-type excrescence) (<b>M-P</b>); additional confocal photos are shown in the supporting information <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0184376#pone.0184376.s003" target="_blank">S1 Fig</a>, <a href="https://figshare.com/s/75cc37ed9297dc11d983" target="_blank">https://figshare.com/s/75cc37ed9297dc11d983</a>.</p

Maximum likelihood tree inferred from the analysis of LSU rDNA.

<p>The generated sequences were aligned with their closest matches in GenBank (23 ingroup and <i>Actinocleidus recurvatus</i> as an outgroup taxa). Phylogenetic analysis based on General Time Reversible Model with complete deletion used as gaps missing data treatment. The robustness was assessed using a bootstrap procedure with 1,000 replications [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0184376#pone.0184376.ref020" target="_blank">20</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0184376#pone.0184376.ref021" target="_blank">21</a>]. For sequence details, see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0184376#pone.0184376.s006" target="_blank">S1 Calculation</a> (calculation of best scoring model for phylogeny studies) and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0184376#pone.0184376.s004" target="_blank">S2 Fig</a> (alignment of sequences), <a href="https://figshare.com/s/75cc37ed9297dc11d983" target="_blank">https://figshare.com/s/75cc37ed9297dc11d983</a>.</p

<i>Pseudempleurosoma</i> spp. fish host species ecology and economic value.

<p>Note that almost all host species are aggregating or schooling, reef-associated or associated to muddy bottoms, and of commercial importance (fish ecology and economy data from [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0184376#pone.0184376.ref026" target="_blank">26</a>]).</p

<i>Pseudempleurosoma haywardi</i> sp. nov. (Monogenea: Ancyrocephalidae (<i>sensu lato</i>) Bychowsky & Nagibina, 1968): An endoparasite of croakers (Teleostei: Sciaenidae) from Indonesia

<div><p>An endoparasitic monogenean was identified for the first time from Indonesia. The oesophagus and anterior stomach of the croakers <i>Nibea soldado</i> (Lacépède) and <i>Otolithes ruber</i> (Bloch & Schneider) (n = 35 each) sampled from the South Java coast in May 2011 and <i>Johnius amblycephalus</i> (Bleeker) (n = 2) (all Sciaenidae) from Kedonganan fish market, South Bali coast, in November 2016, were infected with <i>Pseudempleurosoma haywardi</i> sp. nov. Prevalences in the first two croakers were 63% and 46%, respectively, and the two <i>J</i>. <i>amblycephalus</i> harboured three and five individuals. All three croakers represent new hosts for this monogenean genus. We provide infection rates, light microscopical observations, 3D confocal microscopical illustrations, and a morphometric comparison with all congeners. The new species differs in body size, the position and shape of the ovary and testes, and especially in the composition of the dorsal anchor complex, with the dorsal bar being anteriorly concave rather than planar or convex as in its congeners. The dorsal and ventral anchors of this new species are the longest in the genus, whereas the male copulatory organ is the smallest. The first DNA sequences for a member of this genus demonstrate the greatest similarity with endoparasitic freshwater monogeneans from African cichlid fishes. This suggests a freshwater origin for these marine endoparasitic monogeneans.</p></div

Comparative linear measures for <i>Pseudempleurosoma</i> spp.

<p>Comparative linear measures for <i>Pseudempleurosoma</i> spp.</p