Feeding kinematics and morphology of the alligator gar (Atractosteus spatula,Lacépède, 1803)

Living gars are a small clade of seven species that occupy an important position on the actinopterygian phylogenetic tree as members of Holostei, sister-group to teleosts, and exhibit many plesiomorphic traits used to interpret and reconstruct early osteichthyan feeding mechanisms. Previous studies of gar feeding kinematics have focused on the ram-based, lateral-snapping mode of prey capture found in the narrow-snouted Lepisosteus genus, whereas this study focuses on a member of the broad-snouted Atractosteus sister-genus, the alligator gar (Atractosteus spatula, Lacépède, 1803). High-speed videography reveals that the feeding system of alligator gars is capable of rapid expansion from anterior to posterior, timed in a way to generate suction, counteract the effects of a bow-wave during ram-feeding, and direct a unidirectional flow of water through the feeding system. Reconstructed contrast-enhanced μCT-based cranial anatomy and three-dimensional modeling of linkage mechanics show that a lateral-sliding palatoquadrate, flexible intrasuspensorial joint, pivoting interhyal, and retractable pectoral girdle increase the range of motion and expansive capabilities of the alligator gar feeding mechanism. Reconstructions of muscular anatomy, inferences from in vivo kinematics, and in situ manipulations show that input from the hyoid constrictors and hypaxials play an important role in decoupling and modulating the dual roles of the sternohyoideus during feeding: hyoid retraction (jaw opening) and hyoid rotation (pharyngeal expansion). The alligator gar possesses an intricate feeding mechanism, capable of precise control with plesiomorphic muscles that represent one of the many ways the ancestral osteichthyan feeding mechanism has been modified for prey capture.     

Molecular inferences about the genus Hypostomus Lacépède, 1803 (Siluriformes: Loricariidae): a review

This review compiles and discusses the use of genetic markers applied in the study of the fish genus Hypostomus Lacépède, 1803 (Siluriformes: Loricariidae). The database comprises 51 peer-review articles that were published in the last 52 years (1968–2020) and that approach analysis based on different classes of genetic markers. The use of cytogenetic and enzymatic markers was predominantly especially in population studies with the genus Hypostomus, while mitochondrial markers were the majority in phylogenetic studies. Although significant methodological advances have occurred for molecular evaluation, they are still modestly applied to the study of neotropical fish genera, in which Hypostomus is included. New perspectives, especially on integrative approaches, are needed to improve our knowledge of the genetic functionality of fishes.

     

Larval development of the freshwater croaker Pachypops fourcroi (La Cépède 1802) (Perciformes: Sciaenidae)

The larval development of Pachypops fourcroi from the lower Amazon River was described through morphological, meristic and morphometric features. Sixty-five larvae were examined and present a moderate body, slightly elliptical eyes and head ranging from moderate to large. The mouth is initially terminal and becomes subterminal throughout development with three barbels in the mentonian region. The larvae of P. fourcroi can be differentiated from other Sciaenidae in the Amazon basin by the pigmentation pattern, the presence of barbels, head depth, body depth and diameter, and shape of the eye.     

Comparative studies of bile salts. 5α-Chimaerol, a new bile alcohol from the white sucker Catostomus commersoni Lacépède

1. G.l.c. examination of bile alcohols prepared from the sucker Catostomus commersoni Lacépède (family Catostomidae) showed that although 5α-cyprinol (5α-cholestane-3α,7α,12α,26,27-pentol) was a minor constituent, the principal bile alcohol was an undescribed substance, probably present in the bile as the C-26 sulphate ester, whose i.r., n.m.r. and mass spectra agreed with the structure 5α-cholestane-3α,7α,12α,24,26-pentol. 2. M_D studies suggest that this 5α-chimaerol is the 24(+), 25S enantiomer and that 5β-chimaerol (chimaerol) from Chimaera monstrosa bile also has the 24(+), 25S configuration. These findings imply that bile alcohol biosynthesis in suckers and chimaeras includes stereospecific oxidation of cholesterol at C-26. 3. C. commersoni bile acids (present in minor amounts) probably consist largely of 3α,7α,12α-trihydroxy-5α-cholan-24-oic acid (allocholic acid). 4. 5α-Chimaerol sulphate and 5α-cyprinol sulphate are probably biochemically equivalent as bile salts, and can be considered as arising by parallel evolution.     

Comparison of ageing methods and growth rates for largemouth bass,Micropterus salmoides Lacépède,from northern latitudes

Synopsis Ages determined by counts of apparent annuli on scales, sagittae, vertebrae, pectoral fin ray and dorsal fin spine cross sections of largemouth bass from northern populations, which are older and slower growing fish than in the southern parts of its native range, were compared to establish the accuracy of each method. Linear regression techniques indicated strong agreement (r> 0.9) among ages assigned from the examination of scales, sagittae, and vertebrae. The pattern of growth zones on pectoral fin ray and dorsal fm spine cross sections proved too variable for accurate age determination. Limited data suggest that ages greater than 7+ assigned from scales were more likely to underestimate true ages than the other body parts used, although none of these methods gave satisfactory results. Examination of scales from recovered tagged fish, and the similarity between back-calculated lengths of fish through age 7+ to annulus I and observed lengths of juvenile largemouth bass near the end of their first growing season, support the validity of ages determined from scales. Despite a very limited amount of habitat suitable for largemouth bass and severe climatic conditions, growth of this species in Tadenac Lake was similar to growth in other waters north of the Great Lakes. Differences in physical characteristics among these waters does not appear to influence growth rates of largemouth bass, but probably affects production and biomass.     

Differential expression for tissue-specific isozymes in three species of Hypostomus Lacépède, 1803 (Teleostei: Loricariidae)

The expression patterns of 14 enzymatic systems in skeletal muscle, liver and heart tissues of three species of Hypostomus from the Iguaçu River basin (Brazil) were investigated. Although the patterns were similar for the three species, different tissues showed differential expressions, and the data showed that differential tissue expressions of isoperoxidases may be due to preferential combination or association of polypeptide subunits. The detected patterns for SOD isozymes showed that the quaternary structures of these enzymes were in disagreement with the subunit number reported for the majority of other vertebrate groups. Tissue-specific restriction on heterotetramer formation also were described in LDH and MDHP isozymes. Thus, these tissue-specific gene expression character in the species of Hypostomus have the greatest potential to be recognized and applied in systematic studies among species of Hypostomus.     

Taurine in the marine hydrozoan Hydractinia echinata: stabilizer of the larval state?

Taurine (beta-aminoethane sulfonic acid) is present in high concentrations in tissue of planula larvae of the marine hydrozoan Hydractinia echinata. It has been proposed to function as a stabilizer of the larval state mainly because of the previous findings that larvae induced to undergo metamorphosis appeared to lose most of their taurine, and taurine added to the medium antagonizes metamorphosis. Release of taurine was assumed to be a necessary prerequisite for the onset of metamorphosis. The primary aim of the present study was to confirm this by determination of taurine release accompanying metamorphosis induction by inducers other than CsCl. However, a decrease of the larval tissue taurine content was not found, irrespective of schedule of treatment and the inducer applied. The cause for this difference from the preceding study could not be clarified. Taurine in the medium, even at low concentration, causes elevated tissue concentrations high enough to cause general adverse effects on cell physiology. In order to ascribe an alternative function to taurine in H. echinata variations of the free amino acid pool under osmotic stress were examined. The tissue concentration of beta-alanine strongly correlates with the salinity of the medium. Large amounts of gamma-aminobutyric acid (GABA) are present in animals adapted to high salinity. Taurine content appears not to depend on osmolarity of the medium. Nevertheless, taurine may constitute the foundation of the cellular organic osmolyte system of the H. echinata larva.     

Paracapillaria (Paracapillaria) gastrica n. sp. (Nematoda: Capillariidae) from the marine fish Synodus variegatus Lacépède (Synodontidae,Aulopiformes) off New Caledonia

Systematic Parasitology - Based on light and scanning electron microscopical studies, a new nematode parasite, Paracapillaria (Paracapillaria) gastrica n. sp. (Capillariidae), is described from the...     

Karyotypic diversification in Hypostomus Lacépède, 1803 (Siluriformes, Loricariidae): biogeographical and phylogenetic perspectives

Hypostomus is a species-rich genus of fish with unclear systematics and phylogenetic relationships. Ten species of Hypostomus (H. albopunctatus, H. ancistroides, H. cochliodon, H. commersoni, H. faveolus, H. hermanni, H. aff. paulinus, H. regani, H. strigaticeps and H. topavae) were cytogenetically analyzed through Giemsa staining and silver nitrate impregnation, and the obtained data were correlated to the available biogeographical and phylogenetic analyses for the genus. Although the silver stained nucleolar organizer regions (AgNORs) were found to vary significantly among the species, the diploid numbers could be correlated to the distribution of the species on northern and southern South America river basins. Species with the lower diploid numbers (2n = 64) were associated to northern hydrographic basins and showed a single AgNORs bearing pair. Diploid numbers of 66–68 chromosomes and of 70–84 chromosomes were correlated to two major clades within Hypostomus and southern hydrographic basins, and showed AgNORs varying on number and position. Our results show that cytogenetic data can be correlated to the phylogeny and biogeography of the genus, helping to clarify its complex evolutionary history.     

Previtellogenic oocytes of South African largemouth bass Micropterus salmoides Lacépède 1802 (Actinopterygii,Perciformes) - the Balbiani body,cortical alveoli and developing eggshell

The ovaries of the largemouth bass Micropterus salmoides, an alien and invasive species in South Africa, contain a germinal epithelium which consists of germline and somatic cells, as well as previtellogenic and late vitellogenic ovarian follicles. The ovarian follicle consists of an oocyte surrounded by follicular cells and a basal lamina; thecal cells adjacent to this lamina are covered by an extracellular matrix. In this article, we describe the Balbiani body and the polarization and ultrastructure of the cytoplasm (ooplasm) in previtellogenic oocytes. The nucleoplasm in all examined oocytes contains lampbrush chromosomes, nuclear bodies and several nucleoli near the nuclear envelope. The ultrastructure of the nucleoli is described. Numerous nuage aggregations are present in the perinuclear cytoplasm in germline cells as well as in the ooplasm. Possible roles of these aggregations are discussed. The ooplasm contains the Balbiani body, which defines the future vegetal region in early previtellogenic oocytes. It is comprised of nuage aggregations, rough endoplasmic reticulum, Golgi apparatus, mitochondria, complexes of mitochondria with nuage-like material, and lysosome-like organelles. In mid-previtellogenic oocytes, the Balbiani body surrounds the nucleus and later disperses in the ooplasm. The lysosome-like organelles fuse and transform into vesicles containing material which is highly electron dense. As a result of the fusion of the vesicles of Golgi and rough endoplasmic reticulum, the cortical alveoli arise and distribute uniformly throughout the ooplasm of late previtellogenic oocytes. During this stage, the deposition of the eggshell (zona radiata) begins. The eggshell is penetrated by canals containing microvilli and consists of the following: the internal and the external egg envelope. In the external envelope three sublayers can be distinguished.     

A New Species of Trimeresurus Lacépède, 1804(Squamata: Viperidae) from Southwestern China,Vietnam, Thailand and Myanmar

The pit vipers of the genus Trimeresurus Lacépède, 1804 is one of the largest groups of Asian snakes, distributed from India to China and Indonesia. Recent surveys in Jiangcheng and Simao, Yunnan Province, China resulted in a new species previously allocated to T. albolabris. Combining morphological and molecular data, we describe it as Trimeresurus guoi sp. nov. The new species morphologically differs from T. albolabris in the yellow green ventral color; an indistinct ventrolateral line; the a bsence of a postocular stripe; the firebrickred iris; a dark red stripe on dorsal tail; hemipenes with relatively weak sparse papillae, reaching 23 rd subcaudal when unextruded. Molecularly, the new species forms a clearly divergent lineage(BPP 1.00/UFB 100). Uncorrected pairwise distances of mitochondrial gene Cyt b between the new species and other known species of the subgenus Trimeresurus range from 0.052(T. albolabris) to 0.071(T. insularis).     

High concentrations of viruses in the sediments of Lac Gilbert, Québec

Viruses were found to be very abundant in the top layer of the sediments of Lac Gilbert, Québec. Viruses were extracted from the sediments using pyrophosphate buffer, and viruses from the diluted extracts were pelleted onto grids and enumerated using transmission electron microscopy. Viral abundance in the sediments ranged from 6.5 × 10⁸ to 1.83 × 10¹⁰ ml^–1, which is 10- to 1,000-fold greater than the number observed in the water column. This increase corresponds well with the 100- to 1,000-fold increase in bacterial abundance in the sediments. Viral abundance differed significantly among the surface sediment samples taken at different bottom depths and among samples taken at different depths of the water column. Viral abundance also varied significantly between the oxic and anoxic zones of the water column and the sediments. The virus-to-bacteria ratio varied greatly among the different sediment sites but not among depths in the water column. Viral abundance in the water column was related to bacterial abundance and chlorophyll concentration, whereas viruses in the sediments were most abundant in sediments with high organic matter content. Elevated viral abundance and their erratic distribution in the sediments suggest that viruses might play an important role in sediment microbial dynamics. Correspondence to: Roxane Maranger     

Paléoenvironnements des îles japonaises lors de la dernière période glaciaire

The paper summarizes the paleoenvironments of the last glacial time from a viewpoint of glaciation, permafrost and vegetation. Sea level changes played a critical role on glaciation and human migration to Japanese Islands. Glaciation was limited to the high mountains, and its expansion was much larger in the former stage (MIS 3/4) than in the global glacial maximum (MIS 2). A land bridge between Sakhalin and Hokkaido was important for the migration of paleolithic people from Northern Asia to Japan. Discontinuous permafrost environment with forest tundra and Taiga type conifer forest vegetation in Hokkaido supported the paleolithic hunter-gatherers of big games, developing a microblade culture. Termination of last glacial time caused a drastic environmental change such as a decay of glaciers, permafrost and land bridge. Rapid vegetation change decreased big games and the humans changed their food strategy from a big game hunting to a fishing and a gathering plant resources such as acorns and walnuts. This change created a pottery (Jômon) culture which seems to be brought in Hokkaido from the south between 15,000 ∼ 14,000 cal BP. The encounter of paleolithic and southern Jômon peoples in Hokkaido generated a new human group, the northern Jômon people, which might be a origin of the Aïnu, the indigenous people in Japan, especially in Hokkaido.     

Trends in chromosome evolution in the genus Hypostomus Lacépède, 1803 (Osteichthyes, Loricariidae): a new perspective about the correlation between diploid number and chromosomes types

Phylogenetic relationships and identification of species of the genus Hypostomus is still unclear. Considering this, cytogenetics may prove itself as an important tool in understanding the systematic of this genus. Reviews in Hypostomus indicate that the diploid number ranges from 54 to 84 chromosomes, and the increase in diploid number has been associated to higher percentages of subtelocentric and acrocentric chromosomes. Although there is a high number of species in the genus, there are relatively few papers concerning Hypostomus cytogenetics, and most of the data is published as grey literature. With the aim to understand the chromosomal evolution in the genus (correlation between diploid number x chromosomes types), H. ancistroides and H. topavae from the Piquiri River, Upper Paraná River basin, were cytogenetically analyzed, and the diploid number observed was 68 and 80 chromosomes, respectively. Additional data on the diploid number and chromosome formulae was compiled from papers (27 analyses) and abstracts from grey literature (77 analyses). Our analysis shows no correlation between chromosome numbers and percentages of subtelocentric and acrocentric chromosomes for most of the species, since there is considerable variation between these percentages even between species with the same diploid number, indicating that the proportion of chromosome types is not always associated to diploid numbers.     

Henri-Léonard Bertin and the development of agriculture in the Age of Enlightenment

This meeting of the Committee on the History of Science and Epistemology takes place as we celebrate the 250th anniversary of the creation of the world's first veterinary schools, a major event among all those that, in the wake of the Physiocrat movement initiated by Quesnay and DuPont de Nemours, shaped the modernisation of agriculture in France during the 18th century. Henri-Léonard Bertin (1720-1792) was the impetus to the restructuring process. He was well aware that farming should not remain an activity that solely provides a livelihood for the population, but that it needed to be modernised, i.e. it should produce more, and better. His view was that agriculture could become a great source of riches for France and therefore, a true economic and even political force. He used the various official positions he occupied during that period (Intendant of Lyon (1754-1757), Controller General of Finances (1759-1763), Minister-Secretary of State for Agriculture (1763-1780) to initiate a number of reforms that brought about the modernisation of the kingdom's agricultural world.