Early ontogeny of the commercially valuable fish red-bellied pacu Piaractus brachypomus (Characiformes,Serrasalmidae) from the Amazon,Brazil

The initial development of the red-bellied pacu Piaractus brachypomus is described using morphological, meristic and morphometric characteristics. A total of 127 individuals were analysed (47 in the yolk-sac, 35 in pre-flexion, five in flexion, 20 in post-flexion and 20 in juvenile) with standard length varying between 2.92 and 48.61 mm. The larvae are born poorly developed and have a discoidal yolk at ~6.33 mm standard length. During early ontogeny, the mouth passes from terminal to subterminal and the anal opening reaches the vertical line over the midline region of the body. There are changes in body shape from long and moderate to deep, head length from small to large, and eye diameter from moderate to large. Dendritic chromatophores were present in the ventral, dorsal and upper part of the swim bladder in the early larval stages. Rounded spots are evident all over the body in juveniles. The total number of myomeres ranges from 39 to 41 (20–23 pre-anal, 17–20 post-anal). Through the morphometric relationships, it was evidenced that the greatest changes during the initial ontogeny of P. brachypomus occur in the transition from the post-flexion stage to the juvenile period, indicating changes in behaviour, foraging and physiology.     

Chromosome mapping of repetitive sequences in four Serrasalmidae species (Characiformes)

The Serrasalmidae family is composed of a number of commercially interesting species, mainly in the Amazon region where most of these fishes occur. In the present study, we investigated the genomic organization of the 18S and 5S rDNA and telomeric sequences in mitotic chromosomes of four species from the basal clade of the Serrasalmidae family: Colossoma macropomum, Mylossoma aureum, M. duriventre, and Piaractus mesopotamicus, in order to understand the chromosomal evolution in the family. All the species studied had diploid numbers 2n = 54 and exclusively biarmed chromosomes, but variations of the karyotypic formulas were observed. C-banding resulted in similar patterns among the analyzed species, with heterochromatic blocks mainly present in centromeric regions. The 18S rDNA mapping of C. macropomum and P. mesopotamicus revealed multiple sites of this gene; 5S rDNA sites were detected in two chromosome pairs in all species, although not all of them were homeologs. Hybridization with a telomeric probe revealed signals in the terminal portions of chromosomes in all the species and an interstitial signal was observed in one pair of C. macropomum.     

First record of Seriola vivoliana Cuvier, 1833 in the Mediterranean

One specimen of Almaco jack Seriola rivoliana is recorded for the first time in the Mediterranean Sea. It was caught in a purse seine off Lampedusa Island in June 2000 and is listed as a new alien fish from the Atlantic Ocean.     

Trophic relationship between the Patinga hybrid (Piaractus mesopotamicus x Piaractus brachypomus) and Echinorhynchus gomesi Machado Filho, 1948 in fish farms

A total of 122 Patinga specimens were collected from fish farms (P1, P2 and P3), and only those from fish farm P1 were shown to be infected with Echinorhynchus gomesi. In addition, fish in this study were shown to have diets that consisted of 21 different food items, and Notodiaptomus sp. (Copepoda: Calanoida) was identified as a potential intermediate host for E. gomesi.     

A new Myleus species (Characiformes: Serrasalmidae) from the Rio Tapajós basin,Brazil

Myleus pachyodus, a new serrasalmid species, is described from the Rio Teles Pires and Rio Jamanxim, both tributaries of the Rio Tapajós in Mato Grosso and Pará states, Brazil. The new species differs from all congeners by having a remarkable ontogenetic thickening of the teeth shifting from slender incisiform in juveniles to thick bulky teeth at standard length ≥ 100 mm, whereas congeners present slender, antero‐posteriorly flat teeth throughout all life stages. The new species further differs from congeners by having 18–20 branched dorsal‐fin rays, by the lack of a diastema between contralateral outer series of premaxillary teeth and by the presence of 16–25 prepelvic spines, with the anteriormost spine never reaching the vertical through the pectoral‐fin origin.     

The species complex Astyanax fasciatus Cuvier (Teleostei, Characiformes) – a multidisciplinary approach

Cytogenetic data have provided important clues that the Astyanax fasciatus populations from the Upper Paraná River basin could be a part of a more diverse fish group, usually included on the same taxa. Samples collected in Cachoeira de Emas, SP, in Mogi-Guaçu River basin, show two major cytotypes presenting 2 n = 46 and 2 n = 48 chromosomes, with distinct karyotypic formula, despite the fact that the molecular data suggested some degree of gene flow between these cytotypes. Cytogenetic and morphometric analyses were performed in this species, aiming to contribute to the understanding of the natural history from such fish group. Two allopatric populations with distinct standard cytotypes were analysed, and the data obtained suggest the separation into two groups.     

Growth of the tambaqui Colossoma macropomum (Cuvier) (Characiformes: Characidae): which is the best model?

In order to decide which is the best growth model for the tambaqui Colossoma macropomum Cuvier, 1818, we utilized 249 and 256 length-at-age ring readings in otholiths and scales respectively, for the same sample of individuals. The Schnute model was utilized and it is concluded that the Von Bertalanffy model is the most adequate for these data, because it proved highly stable for the data set, and only slightly sensitive to the initial values of the estimated parameters. The phi values estimated from five different data sources presented a CV = 4.78%. The numerical discrepancies between these values are of not much concern due to the high negative correlation between k and Linfinity viz, so that when one of them increases, the other decreases and the final result in phi remains nearly unchanged.     

First record of the Late Cretaceous starfish Metopaster parkinsoni (Forbes, 1848) in Iran

A body fossil of the starfish Metopaster parkinsoni was collected from chalky rocks of the Coniacian – Santonian transition in the Abderaz Formation at the Padeha section, east of Mashhad (Kopet-Dagh, Iran). The species is common in the English Chalk and is well known from the Cenomanian to the Maastrichtian of Europe. The new Iranian occurrence of M. parkinsoni extends its geographical range of 700 km to the South and 2500 km to the East. The species proliferated in upper offshore environments of the North Tethyan continental shelves. The outstanding occurrence of many well-preserved specimens during the Coniacian – Santonian transition in Europe and Iran may be related to favorable taphonomic conditions driven by the Ocean Anoxic Event (OAE III).     

Collapse of Lake Whitefish Coregonus clupeaformis (Mitchill, 1818) species pair in Como Lake,Ontario

Lake Whitefish (Coregonus clupeaformis) species pairs exist in a small number of northern temperate lakes in North America. Sympatric populations of dwarf and normal‐sized whitefish represent a continuum of morphological and genetic divergence among these lakes. In this study, we used morphological and age data to assess the status of the Lake Whitefish species pair in Como Lake, Ontario (Canada). Whitefish were collected with gill‐nets from spawning shoals during the fall of 2012 and 2014 and compared with archived (circa 1989) dwarf and normal‐sized specimens. Our study indicates that the two previously collected forms have been replaced by a single form with a different morphology and age structure. In comparison to archived specimens, contemporary Lake Whitefish were larger, deeper‐bodied and older; with more gill rakers, lateral line scales, smaller eyes and a wider interorbital width. We hypothesize that the recent invasion of Como Lake by Spiny Waterflea (Bythotrephes longimanus) has affected whitefish growth rates and changed the ecosystem conditions that previously maintained the species pair.     

First record of Girardinichthys viviparus in Lake Tecocomulco, Mexico

A significant population of Chapultepec splitfin Girardinichthys viviparus was discovered in Lake Tecocomulco. Measurements of males and females and comments on the need for conservation of this locality are given.     

First record of Miocene crustaceans from Hormozgan Province,Southern Iran

Four decapod crustacean species from the Middle Miocene Mishan Formation of Hormozgan Province, Southern Iran are described. Three species of leucosiid crabs represent the first fossil record for their respective genera outside the Indo-Pacific region. The oldest records for Leucosia sensu lato, Phylira sensu lato, and Arcania are from Middle Miocene deposits of the Indo-Pacific, and thus their paleobiogeographic distribution is extended for this lapse of time. Harpactocarcinus miocenicus n. sp. represents the youngest and most oriental occurrence for a typically Eocene genus, whose species are known mainly from Central Europe. This contribution represents the first formal report for Tertiary crustaceans from Iran.