The Isthmosacanthidae acanthocephalan species of the genus Serrasentis are parasites of marine teleosts and an elasmobranch. In this study, Serrasentis gibsoni n. sp. is described from the intestines of four flatfish species (Paralichthyidae), namely Ancyclopsetta quadrocellata, Cyclopsetta chittendeni, Syacium gunteri, and S. papillosum from 10 oceanic sites in the Gulf of Mexico (GoM). Twenty sequences of the ‘barcoding’ region of cytochrome C oxidase subunit I gene were obtained from 20 adults of Serrasentis gibsoni n. sp. Additionally, five sequences of the barcoding region were obtained from five adults of rhadinorhynchid Gorgorhynchus lepidus from C. chittendeni, S. papillosum and one species of Haemulidae, Haemulom aurolineatum, from five oceanic sites from the GoM. Two phylogenetic approaches were followed: Bayesian inference and maximum likelihood. In both phylogenetic reconstructions, the sequences of Serrasentis gibsoni n. sp. were recovered as a monophyletic group within the genus Serrasentis and placed as a sister group to G. lepidus. However, due to the lack of molecular data for species of the Isthmosacanthidae and Rhadinorhynchidea, these phylogenetic inferences must be taken with caution. Serrasentis gibsoni n. sp. is the first species of Serrasentis described from Paralichthyidae flatfish species from marine waters of the Americas and from the GoM. Based on the barcoding data set analyzed, Serrasentis gibsoni n. sp. appears to have high intraspecific genetic variation; thus, it is necessary to continue exploring the genetic diversity of this species to infer its intraspecific evolutionary patterns.

Characteristics of Lactic Acid Bacteria (LAB) isolated from rotifers, Brachionus plicutilis, resembled those of Lactobacillus plantarum or Carnobacterium sp. It was investigated whether the artificial maintenance of a high concentration of LAB in rotifers might increase their dietary value for turbot larvae, particularly when the fish were infected with pathogenic Vibrio sp. One LAB strain was cultivated, then introduced daily into the enrichment medium of rotifers. In this way, LAB were retrieved in large amounts in turbot, and a significant limitation of larval mortality rate was observed when turbot were challenged with pathogenic vibrio at day 9. The inoculum concentration of LAB had a decisive effect on survival rate, and the optimum was between 107 and 2 × 107 Colony Forming Units (CFU) daily added per ml of the enrichment medium (53% survival rate after 72 h of challenge, versus 8% for the infected control group without LAB).