Quantitative morphometric and histopathological study in rabbit oviducts after microsurgical treatment

The histopathological lesions remaining after microsurgical tubal reanastomosis were investigated quantitatively by light microscopy and qualitatively by transmission and scanning electron microscopy. In 23 rabbit oviducts, the influence of the suture material poly-p-dioxanon and polyglactin-910 and post-operative time interval (6 and 12-15 weeks) was evaluated and compared with non-anastomosed contralateral oviducts as well as with those of unoperated controls. Except in the controls, partial deciliation, pathological kinocilia structure, microvilli and cytoplasmic blebs were found in all tissues, demonstrating an almost complete endosalpingeal restoration. A statistically significant increase of the muscular thickness was observed on the operated and unoperated sides and was due to fibrosis and expressed by cell/stroma ratio. Subepithelial microgland-like structures also appeared on both sides. As neither the kind of suture material nor time intervals led to differences in tissue reaction and, moreover, as similar alterations were found in the non-anastomosed oviducts, the lesions are presumed to be mainly the response to laparotomy.     

Tracking the history of an invasion: the freshwater croakers (Teleostei: Sciaenidae) in South America

In this study, the competing hypotheses of single vs. double colonisation events for freshwater Pachyurinae (Sciaenidae) in South America is tested and the historical biogeography of the expansion of this clade within the continent is reconstructed based on phylogenetic analysis. Parsimony and Bayesian inference (BI) for 19 marine and freshwater species assigned to Sciaenidae, Haemulidae and Polypteridae were determined based on partial sequences of the mitochondrial 16S and cytochrome b genes and fragments of the nuclear Tmo‐4C4 and rhodopsin genes. A parsimonious ancestral character reconstruction of euryhalinity was performed on a clade of families of closely related fishes to evaluate the role of ecological fitting in the colonisation of freshwater by a marine sciaenid. The parsimony and BI phylogenetic hypotheses for the concatenated sequences supported the monophyly of the freshwater Sciaenidae. Divergence of the two freshwater clades of Sciaenidae, Pachyurinae and Plagioscion, occurred within the Amazon Basin. Within Pachyurinae, two clades were recovered: one composed of species from the Amazon and the Paraná Basin and a second with representatives from the São Francisco and south‐eastern Atlantic basins. The results were compatible with the hypothesis of a single colonisation event of South American freshwater habitats by a marine lineage. The hypothesis of gradual adaptation to freshwater was rejected in favour of the hypothesis of ecological fitting. Sciaenidae, or a subordinate lineage within the family, is ancestrally capable of withstanding exposure to low‐salinity habitats, which putatively facilitated the colonisation of freshwater habitats. The subsequent diversification and expansion of Pachyurinae across South America followed this colonisation and replicated the general pattern of the area relationships of South American river basins for several other fish groups.     

The phylogenetic status of the Ancyrocephalidae Bychowsky, 1937 (Monogenea: Dactylogyroidea)

Phylogenetic analysis of selected subfamily and family taxa within the Dactylogyroidea indicates that the Ancyrocephalidae Bychowsky, 1937, is unnatural. The family contains both poly- and paraphyletic features. The analysis supports the previous elevation of the Pseudomurraytrematinae to family status and suggests that revision of the Ancyrocephalidae is necessary. Two options for revision are provided; that of returning the taxon to subfamily status within the Dactylogyridae is preferred, requiring a change in status of the Heterotesiidae to a subfamily within the Dactylogyridae.     

Parasites, fossils and geologic history: Historical biogeography of the South American freshwater croakers, Plagioscion spp. (Teleostei, Sciaenidae)

A hypothesis on the historical biogeography of the freshwater croakers, Plagioscion spp. (Teleostei: Sciaenidae), is developed based on data from the phylogeny of their monogenoidean parasites (Platyhelminthes), the geology of South America and the fossil record. Analyses suggest that the common ancestor of Plagioscion spp. colonized freshwater concomitantly with the common ancestor of their parasites, Euryhaliotrema spp. Colonization probably occurred via a marine transgression through western Venezuela that developed about 20 million years ago (Mya). This transgression with its postulated highly variable temporal and spatial salinity conditions most likely represented the facilitating event associated with freshwater colonization. A less likely alternative, that colonization occurred via the Mar del Plata in southern South America, is not supported by the geographical distributions and putative phylogeny of extant species of Plagioscion .     

Nucleosomes,transcription, and probability

Speaking of current measurements on single ion channel molecules, David Colquhoun wrote in 2006, “Individual molecules behave randomly, so suddenly we had to learn how to deal with stochastic processes.” Here I describe theoretical efforts to understand recent experimental observations on the chromatin structure of single gene molecules, a molecular biologist''s path toward probabilistic theories.     

Context of diversification of the viviparous Gyrodactylidae (Platyhelminthes, Monogenoidea)

Using four criteria proposed a decade ago by Brooks & McLennan to identify a case of adaptive radiation indicates that the evolutionary history of the viviparous clade of the Gyrodactylidae is dominated by nonvicariant processes. The viviparous clade, with 446 species, has significantly more species than its sister clade (one species), and high species richness was shown to be an apomorphic trait of only the viviparous gyrodactylids within the Gyrodactylidae. Reconciliation of the phylogenetic tree of the viviparous Gyrodactylidae with that of its hosts showed a low probability for cospeciation suggesting that adaptive modes of speciation and not vicariance were predominant during the historical diversification of the clade. The proposed hypothesis suggests that the Gyrodactylidae originated on the South American continent about 60 Mya after geographical dispersal and host switching of its common ancestor to demersal freshwater catfishes by a marine ancestor. Development of hyperviviparity and the consequent loss of 'sticky' eggs in conjunction with other symplesiomorphic and apomorphic features allowed rapid diversification coupled with high dispersal to new host groups and geographical areas by viviparous members of the Gyrodactylidae.