Haematological characteristics of Brazilian Teleosts: III. Parameters of the hybrid tambacu (Piaractus mesopotamicus Holmberg x Colossoma macropomum Cuvier) (Osteichthyes, Characidae)

Fifty six specimens of the hybrid tambacu (Piaractus mesopotamicus Holmberg, 1887 male x Colossoma macropomum Cuvier, 1818 female) were collected from fishfarm of Guariba, São Paulo, to evaluate their haematology. Fishes presented 400.0 to 3,100.0 g total weight and 20.0 to 52.0 cm total length. Haemoglobin, haematocrit, mean corpuscular haemoglobin content (MCHC) and percentage of defense blood cells including leucocytes and thrombocytes, were studied. Statistical analysis showed positive correlation (P<0.01) between haematocrit, MCHC and haemoglobin rate. Nevertheless, thrombocytes and lymphocytes showed negative correlation (P<0.01).

Myoarchitecture and vasculature of the heart ventricle in some freshwater teleosts

The morphological characteristics of the ventricular myocardium and of coronary vascularization were studied in three freshwater teleost species, Piaractus mesopotamicus, Colossoma macropomum and Clarias gariepinus (African catfish), by correlating their ventricular shapes and swimming habits. In Piaractus mesopotamicus and Colossoma macropomum, species with highly active swimming habits, the cardiac ventricle showed a pyramidal shape and a richly vascularized myocardium consisting of an outer compact layer and inner spongy layer. In Clarias gariepinus, a less active species, we observed a saccular ventricle with a mixed myocardium and coronary arteries, in contrast to the ventricular structure of other species described in the literature.

Diencephalic asymmetries: morphological, immunohistochemical and ultrastructural analysis of habenular nuclei in elasmobranchs and teleosts

The habenular nuclei are diencephalic structures present in Vertebrates and they form, with the associated fiber systems, a part of the system that connects the telencephalon to the ventral mesencephalon (Concha M. L. and Wilson S. W., 2001). In representative species of almost all classes of Vertebrates the habenular nuclei are asymmetric, both in terms of size and of neuronal and neurochemical organization, although different types of asymmetry follow different evolutionary courses. Previous studies have analyzed the spread and diversity of the asymmetry in species for which data are not clear (Kemali M. et al., 1980). Notwithstanding that, it’s still not totally understood the evolution of the phenomenon, and the ontogenetic mechanisms that have led to the habenular asymmetry development are not clear (Smeets W.J. et al., 1983). For the present study 14 species of Elasmobranchs and 15 species of Teleostean have been used. Brains removed from the animals have been fixed using 4% paraformaldehyde in phosphate buffer; brains have been analyzed with different tecniques, and I used histological, immunohistochemical and ultrastructural analysis to describe this asymmetry. My results confirm data previously obtained studying other Elasmobranchs species, in which the left habenula is larger than the right one; the Teleostean show some slightly differences regarding the size of the habenular ganglia, in some species, in which the left habenular nucleus is larger than the right. In the course of studies, a correlation between the habits of life and the diencephalic asymmetry seems to emerge: among the Teleostean analyzed, the species with benthic life (like Lepidorhombus boscii, Platichthys flesus, Solea vulgaris) seem to possess a slight asymmetry, analogous to the one of the Elasmobranchs, while in the other species (like Liza aurata, Anguilla anguilla, Trisopterus minutus) the habenulae are symmetrical. However, various aspects of the neuroanatomical asymmetries of the epithalamus have not been deepened in order to obtain a complete picture of the evolution of this phenomenon, and new searches are needed to examine the species without clear asymmetry, in order to understand the spread and the diversity of the asymmetry among the habenulae between the Vertebrates.

Identification of a third distinct estrogen receptor and reclassification of estrogen receptors in teleosts

This paper describes three distinct estrogen receptor (ER) subtypes: ERα, ERβ, and a unique type, ERγ, cloned from a teleost fish, the Atlantic croaker Micropogonias undulatus; the first identification of a third type of classical ER in vertebrate species. Phylogenetic analysis shows that ERγ arose through gene duplication from ERβ early in the teleost lineage and indicates that ERγ is present in other teleosts, although it has not been recognized as such. The Atlantic croaker ERγ shows amino acid differences in regions important for ligand binding and receptor activation that are conserved in all other ERγs. The three ER subtypes are genetically distinct and have different distribution patterns in Atlantic croaker tissues. In addition, ERβ and ERγ fusion proteins can each bind estradiol-17β with high affinity. The presence of three functional ERs in one species expands the role of ER multiplicity in estrogen signaling systems and provides a unique opportunity to investigate the dynamics and mechanisms of ER evolution.

Brain morphology in large pelagic fishes: A comparison between sharks and teleosts

A quantitative comparison was made of both relative brain size (encephalization) and the relative development of five brain area of pelagic sharks and teleosts. Two integration areas (the telencephalon and the corpus cerebellum) and three sensory brain areas (the olfactory bulbs, optic tectum and octavolateralis area, which receive primary projections from the olfactory epithelium, eye and octavolateralis senses, respectively), in four species of pelagic shark and six species of pelagic teleost were investigated. The relative proportions of the three sensory brain areas were assessed as a proportion of the total 'sensory brain', while the two integration areas were assessed relative to the sensory brain. The allometric analysis of relative brain size revealed that pelagic sharks had larger brains than pelagic teleosts. The volume of the telencephalon was significantly larger in the sharks, while the corpus cerebellum was also larger and more heavily foliated in these animals. There were also significant differences in the relative development of the sensory brain areas between the two groups, with the sharks having larger olfactory bulbs and octavolateralis areas, whilst the teleosts had larger optic tecta. Cluster analysis performed on the sensory brain areas data confirmed the differences in the composition of the sensory brain in sharks and teleosts and indicated that these two groups of pelagic fishes had evolved different sensory strategies to cope with the demands of life in the open ocean.

Hematozoa of teleosts from Lizard Island, Australia with some comments on their possible mode of transmission and the description of a new hemogregarine species

Little is known of the blood parasites of coral reef fishes and nothing of how they are transmitted. We examined 497 fishes from 22 families, 47 genera, and 78 species captured at Lizard Island, Australia, between May 1997 and April 2003 for hematozoa and ectoparasites. We also investigated whether gnathiid isopods might serve as potential vectors of fish hemogregarines. Fifty-eight of 124 fishes caught in March 2002 had larval gnathiid isopods, up to 80 per host fish, and these were identified experimentally to be of 2 types, Gnathia sp. A and Gnathia sp. B. Caligid copepods were also recorded but no leeches. Hematozoa, found in 68 teleosts, were broadly hemogregarines of 4 types and an infection resembling Haemohormidium. Mixed infections (hemogregarine with Haemohormidium) were also observed, but no trypanosomes were detected in blood films. The hemogregarines were identified as Haemogregarina balistapi n. sp., Haemogregarina tetraodontis, possibly Haemogregarina bigemina, and an intraleukocytic hemogregarine of uncertain status. Laboratory-reared Gnathia sp. A larvae, fed experimentally on bruslitail tangs, the latter heavily infected with the H. bigemina-like hemogregarine, contained hemogregarine gamonts and possibly young oocysts up to 3 days postfeeding, but no firm evidence that gnathiids transmit hemogregarines at Lizard Island was obtained.

Trophic niche overlap of sprat and commercial small pelagic teleosts in the Gulf of Lions (NW Mediterranean Sea)

Increasing abundance of non-commercial sprats and decreasing biomass and landings of commercial anchovies and sardines justify the need to study the feeding ecology and trophic niche overlap of these planktivorous species in the Gulf of Lions. Their diet has been investigated on the basis of stomach content and stable isotope analyses in 2011 and 2012 according to different depths and regions in the study area. The main prey were Corycaeidae copepods, Clauso/Paracalanus, Euterpina acutifrons and Microsetella, for sprats and small copepods, such as Microsetella, Oncaea and Corycaeidae, for anchovies and sardines. This is the first time that the diet of sprats is described in the Gulf of Lions. Sprats fed on a larger size spectrum of prey and seem to be more generalist feeders compared to anchovies and sardines. Ontogenetic changes as well as spatial and temporal variations of the diet occurred in the three species. Stable isotope analysis revealed mobility of sardines and sprats among feeding areas while anchovies exhibited preferred feeding areas. Sprats showed a higher relative condition assessed by C/N ratios than sardines and anchovies. Our results showed an overlap of the trophic niches for the three species, indicating a potential trophic competition in the Gulf of Lions.

Survey on the digenean and monogenean helminthes of clupeidae (teleosts) from southern part of Caspian Sea

The helminthes parasites fauna of 313 specimens of Caspian herrings (Clupeonella cultriventris, Clupeonella engrauliformis, Clupeonella grimmi) caught from catching localities situated in southeast of Caspian Sea Were investigated during winter 2008 until autumn 2009. A total of 3 helminthes species were found. They were including Pseudopentagramma symmetrica from intestine (mid gut, hind gut and cecae) Bunocotyle cingulata in intestine, Mazocreas alosae the only monogenean with Marine origin in the gills of infected specimens. In addition to two zoonotic species including Contracecum sp. and Anisakis sp. in digestive system, muscle and ovary and an Acanthocephal, Corynosoma strumosum in intestine which were previously reported. We can conclude that the main characteristic of the helminthes parasites community of Clupeidae species studied is the dominance of the endoparasites species due mainly to the digenean Pseudopentagramma symmetrica and Bunocotyle cingulata and the relative scarcity of ectohelminthes fauna. In this paper the latest data of helminthes fauna and community ecology of digenean of Clupeidae species are presented and the community structure of Pseudopentagramma symmetrica is discussed.

Ionic composition of endolymph in teleosts: Origin and importance of endolymph alkalinity

Ionic (Na+, K+, Cl-, PO43-, pH), total CO2, total calcium and protein concentrations in the plasma and endolymph of the inner ear were compared in trout Oncorhynchus mykiss and turbot Scophthalmus maximus. In both species, saccular endolymph was characterized by high levels of K+ and total CO2 and in trout by an alkaline pH, The kinetic characteristics of proton secretion across the saccular epithelium of trout were investigated using a titration technique in which isolated saccules were mounted as closed sacs. The rate of proton secretion depends strongly on the pH of the Ringer's solution and secretion stops at a pH below 7.2, Proton secretion is driven by an energy-dependent mechanism involving basolateral ouabain-sensitive Na+/K+ exchangers. Proton secretion was partially inhibited by acetazolamide and completely inhibited in Na+-free Ringer or in the presence of 1 mmol l(-1) amiloride. A cellular model stressing the importance of proton exchange through the saccular epithelium is proposed to explain the regulation of endolymph pH, a crucial factor for the deposition of otolith calcium.