Reproductive biology of Hyphessobrycon eques (Characiformes: Characidae) in Southern Pantanal, Brazil

A New Species of Creptotrematina (Trematoda: Allocreadiidae) from the Red Minor Tetra, Hyphessobrycon eques (Steindachner, 1882) (Characidae) from Brazil, with Comments on the Genetic Divergence of C. Aguirrepequenoi Jiménez-Guzmán, 1973 across a Wide Geographical Range in Middle America

BACKGROUND

Allocreadiids are relatively small digeneans that appear to be restricted to freshwater systems distributed across the world. Allocreadiids are highly diverse in the Americas, particularly in the Neotropical biogeographical region. Their taxonomic history has been rather controversial, with several taxonomic reassessments and the description of new genera and species.

METHODS

We sampled Creptotrematina specimens from a characid collected in the Pardo River, Paranapanema River basin in Brazil, and specimens of C. aguirrepequenoi, from Astyanax spp. in several localities between northern Mexico and Costa Rica. The specimens were studied through integrative approaches using morphological and molecular analyses of the 28S rDNA gene and two different regions of the COI mtDNA gene.

RESULTS

We describe a new species of Creptotrematina which is differentiated from other congeners by the overall body size, but in particular by the size and position of the cirrus-sac, distribution of the vitelline follicles, and extension of uterine loops in the posterior end of body. Phylogenetic analyses of the 28S rDNA and COI mtDNA genes placed the new species in a monophyletic clade together with all other sequenced species of Creptotrematina, and as a sister species of C. batalhensis. Genetic divergences between the new species and other Creptotrematina spp. varied from 1.1 to 1.2% for the 28S rDNA and 12.4-14.3% for the COI mtDNA. Phylogenetic analysis based on COI mtDNA showed the isolates of C. aguirrepequenoi grouped in four monophyletic clades representing populations geographically separated along a wide geographical range spanning between northern Mexico and Costa Rica, with an estimated genetic divergence between 3.9% and 8.9%.

CONCLUSIONS

Our findings based on integrative analyses recognize Creptotrematina saltograndensis n. sp. from a characid collected in the Pardo River, Paranapanema River basin in Brazil and provide validation of the wide geographical distribution of C. aguirrepequenoi across Middle-America parasitizing Astyanax spp.; the genetic divergence of the species through the analysis of two regions of COI mtDNA points towards considering it represent a species complex, although we refrain at the moment on describing a new species, awaiting for further verification using other molecular markers, and obtaining fresh material for a more detailed taxonomic analyses. This study increases the known diversity of allocreadiids and contributes to the understanding of evolutionary relationships, host-parasite relationships, and biogeographic history of the group.

Are fish assemblages recovering after the huge disaster of mining tailing dam collapse in Mariana (Brazil-MG)?

The Doce River basin is located in the Brazilian states of Minas Gerais (MG) and Espírito Santo (ES). Anthropogenic expansion throughout the twentieth century heavily modified the bioecological configuration of the region, which was worsened in November 2015 by the collapse of the Fundão tailing dam in Mariana municipality (MG). Local ichthyofauna suffered a loss of environmental quality, which served as an alert to the possible decline of native species and transformation of fish assemblages. Through a systematic literature review, the present study aimed to investigate the recovery stage of fish assemblage after the disaster. To accomplish this, we selected 14 documents reporting species lists and fish distributions in the area principally affected by the disaster. Data collected about fish assemblage (presence/absence) were spatially (upper, middle, and lower sections) and temporally (pre- and post-disaster) arranged, followed by non-metric multidimensional scaling (NMDS) analysis to assess similarity. We applied the Analysis of Similarities (ANOSIM) non-parametric test to confirm statistically significant differences between groups. We complemented the study by searching for the main bioecological characteristics of the most frequent species raised among the selected documents. NMDS showed differences in the similarity of fish assemblages among the three spatial sections, as confirmed by ANOSIM (p < 0.05), but no differences for the temporal component were observed. Nevertheless, we detected a trend based on continental fish assemblage transformation, as determined by the presence of many non-native species in the post-disaster period, suggesting the better resilience of these species over that of native species. The missing of many native species previously easily collected, mainly from the families Characidae, Loricariidae, and Trichomycteridae, suggested the system moving toward a new condition, probably worsened than the previous one. The ichthyofauna of the estuarine environment, on the contrary, seems to have recovered faster than ichthyofauna from the continental environment.

Reproduction of Hypoptopoma inexspectatum (Holmberg, 1893) (Siluriformes, Loricariidae) in the Southern Pantanal Floodplain, Upper Paraguay River Basin, Brazil

This work aimed to describe the reproductive biology of Hypoptopoma inexspectatum in southern Pantanal. A total of 538 individuals were sampled and analyzed from February 2009 through January 2011 in southern Pantanal. We did not observe differences in sex-ratio, and both sexes presented positive allometric length/weight relationship (LWR). Reproduction occurs mainly from January to February. Females reached first maturation (L50) with 37.80 mm and males with 45.80 mm. Absolute fecundity is estimated in mean=177.43 (sd±127.06) oocytes and relative fecundity in 3.12 (sd±2.23) oocytes/mg. Fecundity is positively correlated with standard length (Spearman r= 0.43; p=0.013), and total spawning is a used spawning strategy for H. inexspectatum.