Alexandre Wagner Silva Hilsdorf

Genetics of neotropical fish: from chromosomes to populations

The Neotropical freshwater fish fauna is very rich—according to the most recent catalogue 71 families and 4,475 species have been described. However, only a small amount of general information is available on the composition of Neotropical marine fishes. In Brazil, 1,298 marine species have been recorded. General analysis of available cytogenetic and population genetic data clearly indicates research has been mainly concentrated on freshwater fishes. Thus, today, cytogenetic information is available for 475 species of Characiformes, 318 species of Siluriformes, 48 species of Gymnotiformes, 199 freshwater species that do not belong to the superorder Ostariophysi, and only 109 species of marine fishes. For the species studied, only about 6% have sex chromosomes and about 5% have supernumerary or B chromosomes. A review of the cytogenetic studies shows that these data have provided valuable information about the relationships between fish groups, the occurrence of cryptic species and species complexes, the mechanism of sex determination and sex chromosome evolution, the distribution of nucleolus organizer regions, the existence supernumerary chromosomes, and the relationship between polyploidy and evolution. In relation to populations in Neotropical marine waters, the studies have shown the presence of cryptic species, which has important implications for fishery management. Different levels of genetic structuring can be found among Neotropical freshwater migratory fish species. This raises important implications for fish population genetic diversity and consequently its sustainable utilization in inland fisheries and aquaculture, specifically for conservation of ichthyo-diversity and survival.

Variabilidade genética de duas variedades de tilápia nilótica por meio de marcadores microssatélites

The objective of this work was to evaluate the genetic variability of two Nile tilapia strains (Oreochromis niloticus), Chitralada and Red Stirling, as well as its offsprings submitted to genetic enhancement programs, in intensive systems farming by microsatellites markers. Thirty individuals of each parental strain, 30xa0crossbred (CH) individuals from Chitralada and Red Stirling strains, and 30xa0individuals from Red Stirling progeny (RR) were used. Five microsatellites loci were utilized: UNH104, UNH108, UNH118, UNH222 e UNH231. Low values of inbreeding were observed with a negative FIS in both strains and their crossings. Genetic differences between the two strains were detected through FSTxa0=xa00.131 and RSTxa0=xa00.130. The parental strains Chitralada and Red Stirling presented 24.4% of genetic distance, which produced 23.5% of hybrid vigor in the CH stock.

Induced spawning of the endangered Neotropical species Steindachneridion parahybae (Siluriformes: Pimelodidae)

The surubim do Paraiba (Steindachneridion parahybae) is a freshwater catfish endemic to the Paraiba do Sul River basin, Brazil. This species has been seriously threatened by environmental disturbances in the last several decades. Wild Steindachneridion parahybae males and females were collected in 2003 and taken to the hatchery of a power plant of the Companhia Energetica de Sao Paulo (CESP). Steindachneridion parahybae broodstocks were artificially induced to reproduce in December 2003 using a combination of carp pituitary extract (CPE) and human chorionic gonadotropin (hCG). Oocytes and milt were stripped; the fertilized eggs were transferred to 60-liter conical incubators and hatched larvae distributed in nine horizontal trays. Exogenous feed was started just after yolk sac absorption. A high rate of cannibalism and photophobia were observed during the larval period, resulting in a 26% survival rate from larvae to fingerlings.

Microsatellite variation and population genetic structure of a neotropical endangered Bryconinae species Brycon insignis Steindachner, 1877: implications for its conservation and sustainable management

Piabanha (Brycon insignis) is a freshwater fish species from the drainages in Southeastern Brazil. During the 1950s, it was an important economic and food resource for local populations, but dramatic and continuous environmental degradation seriously jeopardized the B. insignis populations in the region. Microsatellite markers were used to assess the genetic structure of wild populations of B. insignis and compare the genetic variability and integrity of the wild populations with a captive population. Samples of DNA from 208 specimens from geographically isolated populations were analyzed. Population genetic structure was investigated using FST, RST estimates as well as AMOVA. All five loci used in this study were polymorphic with observed heterozygosity ranging from 0.77 (± 0.15) to 0.88 (± 0.07) in the wild population and 0.90 (± 0.09) in the captive population and the allelic richness average were 7.56 (± 0.27) and 5.80 (± 1.02), respectively. Overall genetic differences were significantly partitioned among populations (FST = 0.072, p = 0.034). Evidence of a genetic bottleneck was found in some of the wild populations, but especially in the captive population. The results showed that genetic variability still can be found in B. insignis populations which are currently structured possibly due to anthropic actions. The implications of these findings for the management and conservation of B. insignis populations are discussed.

Threatened fishes of the world: Steindachneridion parahybae (Steindachner, 1877) (Siluriformes: Pimelodidae)

Common name: Surubim do Paraiba. Conservation status: Critically endangered in Brazilian Red List (Rosa and Lima 2005), and regionally extinct in Sao Paulo State (Sao Paulo 2008). Steindachneridion parahybae is a migratory freshwater species and critically endangered in Paraiba do Sul River Basin. Identification: maxillary barbel short, reaching or surpassing origin of pectoral-fin insertion; pectoral and adipose fins short; pelvic fin very short, never reaching anus. Ground color in alcohol light grayish, abdomen whitish, large dark brown blotches irregularly distributed over head and trunk in an irregular, vermiculated or dotted pattern (Garavello 2005). Distribution: Endemic to the Paraiba do Sul River Basin (Garavello 2005). Abundance: In the 1950 s there were some records of capture of this specie of around 1,000 kg/year just in the part of the basin (Machado and Abreu 1952) and nowadays there are no capture records in the Sao Paulo State (Sao Paulo 2008). Habitat and ecology: Freshwater benthopelagic species, prefers bottoms with sand and stones; mainly carnivorous (Moraes and Caramaschi 1993). Reproduction: S. parahybae is a migratory species ascending the rivers to reproduce during summer. Threats: (1) Construction of dams in the Paraiba do Sul River which block the reproductive migration and act as a barrier to dispersal; (2) riparian habitat destruction; (3) water pollution, due to the high industrial development of the region; and (4) fishing. Conservation action: Since 2003, the Hydrobiology and Aquaculture Unit of CESP (Paraibuna/SP), has been supporting a fish restocking program (Caneppele et al. 2004) and fisheries efforts, funded by a governmental program (ANEEL 2006) will be important to estimate the occurrence and genetic evaluation of the specie. Conservation recommendation: Establish habitat protection and monitoring riparian zone; Environ Biol Fish DOI 10.1007/s10641-009-9480-9

Influence of spawning procedure on gametes fertilization success in Salminus hilarii Valenciennes, 1850 (Teleostei: Characidae): Implications for the conservation of this species

Artificial reproduction and gamete fertilization were evaluated in Salminus hilarii wild and domesticated broodstocks. Wild and domesticated broodstocks were artificially induced to reproduction using a carp pituitary treatment. Four groups were considered: Group 1 (G1), fish caught in the wild maintained for three years in the same conditions as the domesticated broodstocks and spawned naturally; Group 2 (G2), broodstock born and raised in captivity and spawned naturally; Group 3 (G3), wild broodstocks, which were manually stripped for gamete collection and dry fertilization; and Group 4 (G4), domesticated males and females, also manually stripped. Oocytes, eggs, and larvae were sampled at different time intervals throughout embryonic development. Yolk sac absorption occurred approximately 24-29 h after hatching. Twenty-six h after hatching, the larvae mouths opened. Cannibalism was identified just 28-30 h after hatching. There was no morphological difference in embryonic development among all groups. The number of released eggs per gram of female was: G1: 83.3 ± 24.5 and G2: 103.8 ± 37.4; however, the fertilization success was lower in G2 (42.0 ± 6.37 %) compared with G1 (54.7 ± 3.02%) (P = 0.011). Hand-stripping of oocytes was not successful and the fertilization rate was zero. The reproduction of this species in captivity is viable, but it is necessary to improve broodstock management to enhance fertilization rates and obtain better fingerling production for restocking programs.

Isolation and characterization of polymorphic microsatellite loci from Salminus hilarii (Characiformes: Characidae)

Salminus hilarii is a carnivorous fish species which inhabits different drainages in the Neotropical region. Despite the absence of this species in the commercial freshwater fishery, it plays an important role in the food chain, keeping the ecological balance in the freshwater ecosystems. We isolated 9 polymorphic microsatellite markers with alleles varying between 6 and 17 per locus in a test population of 20 individuals. Two loci (Sh49 and Sh65) showed significant departure from Hardy–Weinberg equilibrium (Pxa0<xa00.05). No significant linkage disequilibrium between pairs of loci was found. These loci will provide useful molecular markers to assess genetic variability of wild and captive populations used in stocking programs.

The upper reached ichthyofauna of the Tietê River, São Paulo, Brazil: aspects of their diversity and conservation

Tiete River is one of the main rivers in the State of Sao Paulo, Brazil. It runs across this state from east to west for 1136 km. The upper reach of the Tiete River is located in the metropolitan region of the city of Sao Paulo where approximately 60% of the original Atlantic Forest remnants has been converted into rural and urban areas. Ichthyofauna of the upper reaches of the rivers is usually characterized by a high level of endemism, small fish with restricted geographic distribution. A qualitative survey of two main tributaries, Paraitinga and Biritiba Mirim Rivers, and a stretch of the Tiete River was carried out in order to ascertain their fish community composition, compare the former fish data collected in the same area and establish biodiversity conservation research programs. The fish fauna in the three riverine systems comprises 5 orders, 9 families, 20 genus and 28 species. One species, Glandulocauda melanogenys, out of sixteen regarded as strictly endemic to the upper reaches of the Tiete River according to previous data was found among the sampled collections. No established alien species were found despite their presence in the upstream reservoir of the Tiete Rivers. Human disturbances and their impacts on fish diversity are discussed, including their relation to the ecotone habitats.

A ictiofauna de cabeceiras do rio Tietê, São Paulo, Brasil

A synthesis of the ichthyofauna of the headwaters of the rio Tiete, based on material from zoological collections and new samplings, is presented. Fifty six species belonging to seven orders and 16 families are recorded to the drainage, increasing previous numbers significantly. The current results show that the headwaters of the rio Tiete possess a singular ichthyofauna composition, diverse from that found in the remaining of the upper Parana basin, with high level of endemic species and great similarity to the species from coastal drainages. This finding corroborates the hypothesis of past river capture between streams and rivers in both drainages. Among the species occurring in the area surveyed, eight are endemic (14.3%), 13 are found in the headwaters of rio Tiete and in the coastal drainages of southeastern Brazil (23.2%), 10 are present throughout the upper Parana basin (17.9%), five are found in the upper Parana basin and in the coastal drainages of southeastern Brazil (8.9%), while 13 show a broader distribution in the South America drainages (23.2%), part of which still remains to be identified. Species diversity increased with the discovery of at least five new species belonging to the genera Cyphocharax, Characidium, Astyanax, Pareiorhina and Australoheros, and four new records for Characidium cf. zebra, Scleromystax barbatus, Crenicicla britskii and Synbranchus cf. marmoratus. At least, seven non-native species are recognized to be established in the region, while 10 other are included in red books.

Phylogeographical Features of Octopus vulgaris and Octopus insularis in the Southeastern Atlantic Based on the Analysis of Mitochondrial Markers

ABSTRACT n The genus Octopus occurs in tropical and temperate oceanic waters throughout the world, and currently includes 112 species, although the phylogenetic relationships among the different taxa are still poorly understood. The cosmopolitan Octopus vulgaris is one of the most widely analyzed cephalopods in genetic studies, primarily because of its ample range and the problems associated with the morphological identification of specimens, which indicate the possible existence of a species complex with a worldwide distribution. Two large-bodied octopus species—O. vulgaris and Octopus insularis—are found in the western South Atlantic. The limits of the geographical range of the O. insularis are still unclear. The current study is based on a phylogeographic analysis of the 2 species in the South Atlantic, with the objective of confirming their monophyletic status and the limits of their geographical distribution in this region. The analyses were based on the mitochondrial genes 16S rDNA and Cytochrome Oxidase subunit I (COI). The topologies generated for both genes confirmed the monophyletíc status of the 2 species. In the case of O. vulgaris, it was possible to confirm the monophyletic status of the specimens from this region relative to those of other areas around the world, although 3 distinct haplogroups were clearly differentiated, corresponding to the Americas, Europe and Africa, and Asia. The differentiation among these 3 groups may be determined by the limitations of the dispersal of paralarvae among continents. Further studies are needed to confirm the possible occurrence of distinct groups in the western South Atlantic, as well as the influence of oceanic currents on the phylogeographical distribution of O. vulgaris on the Brazilian coast.