Eugerres

Abstract: Fish of the family Gerreidae, mainly species of the genera Diapterus and Eugerres, have high potential for cultivation, because of their saline tolerance. A detailed cytogenetic analysis of Diapterus auratus, Diapterus rhombeus and Eugerres brasilianus was conducted using conventional staining, C-banding, Ag-NOR, AT/GC-specific fluorochrome staining and mapping of ribosomal sequences with 5S and 18S rDNA probes. All the species exhibited symmetrical karyotype, 2n = 48 acrocentric chromosomes. Ag-NORs and 18S rDNA are present in the interstitial position on pair 1 (genus Diapterus) and pair 6 in Eugerres brasilianus. The 5S rDNA sites, located in the interstitial position (pair 11), are conserved in the three species. Heterochromatic regions are similar in the Diapterus species, showing a pattern of reduced and centromeric bands, differing from E. brasilianus, where, in addition to these, more prominent interstitial bands were observed. GC-rich regions are located at ribosomal sites. Karyotypic comparison between Diapterus and Eugerres reveals similarity in chromosomal macrostructure, differing in C-positive heterochromatin distribution and position of 18S sites, indicating the occurrence of structural microrearrangements. Although complementary analyses are needed, the similarities observed for these and other species suggest the possibility of breaking postzygotic barriers and their potential use, through induced interspecific or intergeneric hybridizations.

Abstract: Fish family Gerreidae, commonly known as mojarras or silver-biddies is one of the most representative groups in aquatic systems of tropical and subtropical areas of the world (Yanez-Arancibia 1980, Matheson and McEachran 1984). Gerreidae comprises some 100 nominal species grouped in eight genera (Eschmeyer 2012), two of which are monotypic: Pentaprion and Ulaema. Currently, two species are considered valid in Parequula, eight in Eugerres, six in Diapterus, 10 inEucinostomus, and 28 inGerres (Froese and Pauly 2012). Although, since the 19th century, the mojarras have been subject of many studies, mostly focused on ecological issues, their taxonomy at specificand sometimes generic levels is still confusing (De La Cruz-Aguero and Galvan-Magana 1993, Chen et al. 2007). At present, the taxonomic status of more than 50 nominal species, mainly included in the last three mentioned genera, has not recently been revised and some gerreid taxa still have recognition problems and their taxonomic validity is questionable, e.g.: Ulaema lefroyi (Goode, 1874); Eucinostomus havana (Nichols, 1912);Diapterus aureolus (Jordan et Gilbert, 1882); Eugerres periche (Evermann et Radcliffe, 1917). ACTA ICHTHYOLOGICA ET PISCATORIA (2012) 42 (4): 297–306 DOI: 10.3750/AIP2012.42.4.03

Abstract: Two little-known species of Spinitectus (Nematoda: Cystidicolidae) were, for the first time, recorded from fishes of the Lacantun River (Usumacinta River basin) in the Lacandon rain forest, Chiapas, southern Mexico: S. tabascoensis Moravec, Garcia-Magana et Salgado-Maldonado, 2002 in intestines of Ictalurus furcatus (Valenciennes) (Ictaluridae) (adults and juveniles), Cathorops aguadulce (Meek) and Potamarius nelsoni (Evermann et Goldsborough) (both Ariidae) (in both only juveniles), and S. osorioi Choudhury et Perez-Ponce de Leon, 2001 in Atherinella alvarezi (Diaz-Pardo) (Atherinopsidae) (adults in intestine) and Eugerres mexicanus (Steindachner) (Gerreidae) (adults and juveniles in stomach). Eugerres mexicanus, C. aguadulce and P. nelsoni represent new host records. Detailed light and electron microscopical studies of S. tabascoensis revealed some taxonomically important, previously not observed features, such as cuticular spines arranged in four sectors, the cephalic structure, the number (2) of ventral precloacal ridges or the structure of the male caudal end. Therefore, Spinitectus tabascoensis is redescribed. Spinitectus macrospinosus Choudhury et Perryman, 2003, described from ictalurids in Canada and the USA, is considered its junior synonym. Spinitectus tabascoensis seems to be a specific parasite of Ictalurus spp., whereas C. aguadulce and P. nelsoni, as well as some other fishes, serve only as its paratenic hosts. The definitive hosts of S. osorioi are atherinopsid fish (A. alvarezi, Chirostoma spp.), whereas the gerreid E. mexicanus probably serves only as its postcyclic host.

Abstract: Four nominal species of eastern Pacific Eugerres were reviewed for taxonomy and systematics based on type specimens and their respective diagnoses, as well as other material from their distributional range. Meristic characteristics, such as the number of gill rakers in the lower limb of the first branchial arch, were useful to separate three species: Eugerres lineatus (Humboldt, 1821) (15–19, mode 17), Eugerres axillaris (Gunther, 1864) (11–14, mode 13), and Eugerres brevimanus (Gunther, 1864) (12–13, mode 12), while Eugerres periche (Evermann and Radcliffe, 1917) was recognized as a synonym of E. brevimanus. Confusion in nomenclature due to erroneous gill raker numbers assigned to E. axillaris and E. lineatus by Meek and Hildebrand (1925) is clarified: E. lineatus has more than 15 gill rakers (not 11), and E. axillaris has 12 gill rakers (not 15). Eugerres brevimanus differs from others in its numerous pored scales, enlarged lips, and short pectoral fins. Canonical variate analysis with 21 box truss characters was performed, which classified the specimens into three distinct groups (P < 0.0000), with 96.4% correct classification. The most use ful character for group classification was the distance between the last dorsal and first anal spine bases (P < 0.000007). The amphi-American gerreid genus Eugerres Jordan and Evermann, 1927 consists of seven nominal species (sensu Eschmeyer, 1998) that are known from estuarine and freshwater habitats. Three species: Eugerres brasilianus (Cuvier, 1830), Eugerres plumieri (Cuvier, 1830), and Eugerres mexicanus (Steindachner, 1863) occur in the western Atlantic (Deckert and Greenfield, 1987); and four species: Eugerres axillaris (Gunther, 1864), Eugerres lineatus (Humboldt, 1821), Eugerres brevimanus (Gunther, 1864), and Eugerres periche (Evermann and Radcliffe, 1917) occur in the eastern Pacific (Deckert, 1973; Bussing, 1995). The validity of E. periche is questionable because it is represented by only five specimens in natural history collections (holotype in the USNM: 77743, and four specimens in the NRM: 29352). Also, based on a critical examination of the holotype, Deckert (1973) regarded this species as a synonym of E. axillaris. The species now included in the genus Eugerres were first treated by Evermann and Meek (1883, 1886) as members of the American Gerres, in a section of gerreids having serrated preorbital and preopercular bones. They regarded G. axillaris as a junior synonym of Gerres lineatus (Humboldt, 1821) due to great morphological similarity between the species. Jordan and Evermann (1927) proposed Eugerres as a new genus, for species with serrated preopercle and preorbital bones. The Pacific representatives of Eugerres were reviewed for the first the time by Regan (1903), who examined the type specimens of Gerres (including Eugerres species sensu stricto) deposited in the British Museum of Natural History (BMNH). Ac cording to Regan (1903), the paratype of G. lineatus had 15 gill rakers on the lower limb, in contrast to the lower number observed in the holotypes of G. axillaris and