RÉSUMÉ
Fish populations that bear considerable pressure levels tend to show a decline in the average size of individuals, with the small and unexploited species replacing the large and exploited ones. It is important to carry on with their characterization in areas where they are becoming an important source of food for local human populations. An example of such species are parrotfishes, whose responses to external factors such as fishing need to be understood and predicted. In this study, we used a diver-operated stereo-video to examine individual body size, sex ratios and proportion of species of the parrotfish assemblage and analyze them on a qualitative fishing pressure gradient at four oceanic islands in the Colombian Caribbean. We reported over 10,000 occurrences of eleven parrotfish species, of which we estimated the total length of over 90%, grouping them into three size categories (large, medium, and small). Our data showed a spatial variation of parrotfishes' abundances, biomass, and individual body size. Observed differences are size-category-dependent throughout the qualitative fishing pressure. In general, the medium-bodied species had smaller sizes, lower abundances, and thus lower contribution to the total parrotfish biomass at the most heavily fished island. Unexpectedly, we found evidence of possible indirect effects over the small-bodied species Scarus iseri and Scarus taeniopterus with significantly greater abundances, and larger sizes of males of S. iseri, at the higher fishing pressure sites. Overall, our data highlights the extent of the spatial variation in the parrotfish communities at relatively short distances, and present new insights into the responses of parrotfish species on a spectrum of body sizes along a gradient of human pressure.
Sujet(s)
Chasse , Perciformes , Humains , Animaux , Mâle , Iles , Antilles , Caraïbe , Produits de la merRÉSUMÉ
A fourth species of the genus Rhonciscus (Lutjaniformes: Haemulidae) is described from various specimens collected by small-scale fishers from the insular upper slope of western Puerto Rico. The new species was molecularly recovered as sister to the Eastern Pacific R. branickii, to which it bears many morphological similarities. It is distinguished from other Rhonciscus species by the number of scale rows between the dorsal fin and the lateral line (7), larger and thus fewer scales along the lateral line (48-50), large eyes (9.4-10.4 times in SL), longer caudal peduncle (15.2-20% of SL), larger sized penultimate (14.7-19.1% in SL) and last (7.4-9.5% in SL) dorsal fin spines which translates to a less deeply notched dorsal fin, and its opalescent silver with golden specks live coloration. This grunt, only now recognized by ichthyologists, but well known by local fishers that target snappers and groupers between 200 and 500 m in depth, occurs in far deeper waters than any western Atlantic grunt.
Sujet(s)
Poissons , Perciformes , Animaux , Porto Rico , Perciformes/anatomie et histologieRÉSUMÉ
Recently, different studies have revealed the existence of complexes of marine fish species of several genera from the Western Atlantic (e.g., Bagre, Peprilus, Bairdiella, Pogonias and Menticirrhus), with a correspondence between recognized species and well-established geographic areas such as the Gulf of Mexico, the Caribbean, and Brazil, showing the need to improve the taxonomic knowledge of coastal fishes in the region. In this work, we revalidate and redescribe Pareques lineatus (Cuvier, 1830) described from Brazil, and redescribe and designate a neotype to P. acuminatus (Bloch & Schneider, 1801) to differentiate it properly from its congeners. The recognition of P. acuminatus for the east coast of the USA plus the Gulf of Mexico and of P. lineatus for Brazil, with the West Indies and southern Caribbean as an area of overlap, brings new information about biodiversity in Western Atlantic coastal areas and confirms a previously proposed major biogeographical boundary.
Sujet(s)
Poissons-chats , Perciformes , AnimauxRÉSUMÉ
The genus Acyrtus Schultz, 1944 currently includes four species distributed in the western Atlantic (WA), three occurring from the Bahamas to the southern Caribbean, and one endemic to the Fernando de Noronha Archipelago in north-east Brazil. We describe a new species of Acyrtus based on morphology and genetics from several individuals caught at artificial hard substrates deployed between 10 and 16 m deep at Malpelo Island, Colombian Pacific. The Malpelo clingfish, Acyrtus arturo new species, differs from all its WA congeners by a combination of morphology, meristics and genetics. This species is unique within Acyrtus in having the greatest number of caudal rays (12-13). It can also be distinguished by the greater body height (19.8-27.8% standard length), its longer disc (34.0-39.1% standard length) and the greater distance between anus and disc (13.9-18.1% standard length). A. arturo sp. nov. is the first Acyrtus so far recorded from the eastern Pacific and adds to the already high number of fishes endemic to Colombia's remote oceanic territory of Malpelo.
Sujet(s)
Poissons , Animaux , Bahamas , Brésil , Caraïbe , Océans et mersRÉSUMÉ
The genus Chaenopsis presently includes 10 species, four in the eastern Pacific and six in the western Atlantic. Five individuals of an undescribed species of this genus were obtained at Gorgona Island in the eastern Pacific of Colombia, in depths between 3 and 5 m. This new species differs from all the Eastern Pacific species in an array of traits including meristic, coloration and morphometric characters. Chaenopsis celeste new species differs from its only sympatric species, C. deltarrhis, in having fewer pectoral rays, fewer dorsal spines and more dorsal-fin soft rays and anal-fin elements. This new species is found over shallow sandy, rubble and small rocks bottoms from Costa Rica to Colombia.
Sujet(s)
Poissons , Animaux , Colombie , Costa Rica , Océan PacifiqueRÉSUMÉ
Two new species of Characidium, C. tatama and C. dule, are described from the biogeographic Chocó region in western Colombia. Both new species are supported by both morphological and molecular data. C. tatama from the San Juan River in the Pacific and C. dule from the Atrato River in the Caribbean portion of Colombia are both distributed in the upper and lower portions of these basins. An extensive comparison with other trans- and cis-Andean species of Characidium was made, in addition to species delimitation, using COI sequences by distinct methods (GMYC, ABGD, bPTP).
Sujet(s)
Biodiversité , Characiformes/classification , Répartition des animaux , Animaux , Characiformes/anatomie et histologie , Characiformes/génétique , Colombie , Complexe IV de la chaîne respiratoire/génétique , Rivières , Spécificité d'espèceRÉSUMÉ
Speciation and the interactions between recently diverged species are thought to be major causes of ecological and morphological divergence in evolutionary radiations. Here, we explore the extent to which geographical overlap and time since speciation may promote divergence in marine species, which represent a small fraction of currently published studies about the patterns and processes of speciation. A time-calibrated molecular phylogeny of New World haemulid fishes, a major radiation of reef and shore fishes in the tropical West Atlantic and East Pacific, reveals 21 sister species pairs, of which eight are fully sympatric and 13 are allopatric. Sister species comparisons show a non-significant relation between most of the phenotypic traits and time since divergence in allopatric taxa. Additionally, we find no difference between sympatric and allopatric pairs in the rate of divergence in colour pattern, overall body shape, or functional morphological traits associated with locomotion or feeding. However, sympatric pairs show a significant decrease in the rate of divergence in all of these traits with increasing time since their divergence, suggesting an elevated rate of divergence at the time of speciation, the effect of which attenuates as divergence time increases. Our results are consistent with an important role for geographical overlap driving phenotypic divergence early in the speciation process, but the lack of difference in rates between sympatric and allopatric pairs indicates that the interactions between closely related species are not dominant drivers of this divergence.
Sujet(s)
Évolution biologique , Caractéristiques du cycle biologique , Perciformes/anatomie et histologie , Perciformes/physiologie , Phénotype , Animaux , Océan Atlantique , Spéciation génétique , Géographie , Océan Pacifique , PhylogenèseRÉSUMÉ
BACKGROUND: The anthropogenic modification of trophic pathways is seemingly prompting the increase of jellyfish populations at the expense of planktivorous fishes. However, gross generalizations are often made because the most basic aspects of trophic ecology and the diverse interactions of jellyfish with fishes remain poorly described. Here we inquire on the dynamics of food consumption of the medusoid stage of the scyphozoan jellyfish Stomolophus meleagris and characterize the traits and diversity of its symbiotic community. METHODS: S. meleagris and their associated fauna were sampled in surface waters between November 2015 and April 2017 in Málaga Bay, an estuarine system at the Colombian Pacific. Stomach contents of medusae were examined and changes in prey composition and abundance over time analysed using a multivariate approach. The associated fauna was identified and the relationship between the size of medusae and the size those organisms tested using least-square fitting procedures. RESULTS: The presence of S. meleagris medusa in surface waters was seasonal. The gut contents analysis revealed that algae, copepods and fish early life stages were the more abundant items, and PERMANOVA analysis showed that the diet differed within the seasons (P(perm) = 0.001) but not between seasons (P(perm) = 0.134). The majority of the collected medusae (50.4%) were associated with individuals of 11 symbiotic species, 95.3% of them fishes, 3.1% crustaceans and 1.6% molluscs. Therefore, this study reports 10 previously unknown associations. The bell diameter of S. meleagris was positively related to the body sizes of their symbionts. However, a stronger fit was observed when the size relationship between S. meleagris and the fish Hemicaranx zelotes was modelled. DISCUSSION: The occurrence of S. meleagris was highly seasonal, and the observed patterns of mean body size through the seasons suggested the arrival of adult medusae to the estuary from adjacent waters. The diet of S. meleagris in the study area showed differences with previous reports, chiefly because of the abundance of algae that are seemingly ingested but not digested. The low number of zooplanktonic items in gut contents suggest the contribution of alternative food sources not easily identifiable. The observed changes in the composition of food in the guts probably reflect seasonal changes in the availability of prey items. The regular pattern in the distribution of symbionts among medusae (a single symbiont per host) and the positive host-symbiont size relationship reflects antagonistic intraspecific and interspecific behaviour of the symbiont. This strongly suggest that medusa represent an "economically defendable resource" that potentially increases the survival and recruitment of the symbionts to the adult population. We argue that, if this outcome of the symbiotic association can be proven, scyphozoan jellyfish can be regarded as floating nurseries.
RÉSUMÉ
Whereas most of the studies that discuss the evolutionary divergence of Anolis lizards have dated the clade's crown group in between 31 and 64â¯Ma, a single study has recovered a significantly older age for the same node (87â¯Ma). These differences also entail notable consequences on the preferred biogeographical hypothesis for the whole clade. Here we analyze a total of seven dating strategies by combining three calibration sources in independent BEAST runs to infer the most probable divergence timing for anole lizards (a mitochondrial rate for ND2 gene, the Anolis dominicanus fossil, and a group of fossils assigned to the Priscagamines, Iguanines, and Idontosaurus clades). Based on the estimated timing, we also addressed whether chronograms differ the most in deeper or shallower nodes by exploring the trend in the standard deviation of mean ages between chronograms across time. Next, we focus on the pattern for a single shallow node by hypothesizing the biogeography of the island-endemic Malpelo anole (Anolis agassizi), and evaluating the temporal congruence between the species' divergence and the island geology. The estimated set of ages suggests that anoles most likely diverged 72â¯Ma (71-73â¯Ma), with the crown group established around 58â¯Ma (51-65â¯Ma). Dispersal is therefore supported as the major driver in the biogeography of the group (and in Caribbean lineages in particular). Our analyses also indicated that (1) rate-based analyses pulled dates toward younger ages, (2) the differences in node ages between chronograms decrease towards the tips regardless of the position of the constrained node, and that (3) the estimated age for deep nodes (e.g. Anolis stem) is highly influenced when deep nodes are also constrained. The latter two results imply that the estimated age for shallower nodes is largely unaffected by the used temporal constraint. The congruence of all chronograms for the Malpelo anole also supports this finding. Anolis agassizi was found to have diverged before the emergence of Malpelo island in each analysis (anole: 19-31â¯Ma vs. Malpelo island: 16-17â¯Ma). Finally, we recommend when performing absolute dating analyses to first test for sequence saturation in the analyzed dataset (especially when calibrations are based on molecular rates). Our study also points out the importance of using multiple node constraints, especially when placed deeply in the tree, for fossil-based divergence dating analyses.
Sujet(s)
Variation génétique , Lézards/génétique , Animaux , Séquence nucléotidique , Théorème de Bayes , Calibrage , Évolution moléculaire , Fossiles , Phylogenèse , Facteurs tempsRÉSUMÉ
We present a phylogenetic analysis with divergence time estimates, and an ecomorphological assessment of the role of the benthic-to-pelagic axis of diversification in the history of haemulid fishes. Phylogenetic analyses were performed on 97 grunt species based on sequence data collected from seven loci. Divergence time estimation indicates that Haemulidae originated during the mid Eocene (54.7-42.3â¯Ma) but that the major lineages were formed during the mid-Oligocene 30-25â¯Ma. We propose a new classification that reflects the phylogenetic history of grunts. Overall the pattern of morphological and functional diversification in grunts appears to be strongly linked with feeding ecology. Feeding traits and the first principal component of body shape strongly separate species that feed in benthic and pelagic habitats. The benthic-to-pelagic axis has been the major axis of ecomorphological diversification in this important group of tropical shoreline fishes, with about 13 transitions between feeding habitats that have had major consequences for head and body morphology.
Sujet(s)
Biodiversité , Poissons/classification , Phylogenèse , Analyse de variance , Animaux , Comportement alimentaire , Poissons/anatomie et histologie , Méthode des moindres carrés , Phénotype , Analyse en composantes principales , Facteurs tempsRÉSUMÉ
Aquatic hypoxia is a seasonal condition in some coastal and continental wetlands where co-exposure with polycyclic aromatic hydrocarbons (PAHs) pollution may be detrimental to the biota. In the present study, adult tilapia, an euryoxic fish of high economic importance, were intraperitoneally injected with benzo[a]pyrene (BaP) (20 mg kg(-1)) and then exposed to graded hypoxia to assess combined effects on some detoxification and fitness parameters. Seventy-two hours after a stepped decrease in dissolved oxygen (<2 mg L(-1)), BaP treatment resulted in a significant diminution on the biliary BaP concentration (70% of normoxic group) and an increase in blood glucose levels (2.17-fold compared with normoxic group). These effects returned to control values in the following 48 h of hypoxia exposure. BaP-induced CYP1A mRNA levels were unaffected by hypoxia, suggesting that reduced bile BaP concentration may be related with effects on protein amount or enzyme activities. LDH mRNA levels, blood lactate and hematocrit remained without change, suggesting no extreme detrimental effects for tilapia in the short-term of the BaP-hypoxia challenge. Our results indicate that BaP treatment and hypoxia targeted glucose metabolism and biliary BaP elimination, probably by favoring the storage of BaP in tilapia tissues.
Sujet(s)
Benzo[a]pyrène/toxicité , Bile/composition chimique , Cytochrome P-450 CYP1A1/métabolisme , Foie/effets des médicaments et des substances chimiques , Tilapia/métabolisme , Polluants chimiques de l'eau/toxicité , Animaux , Benzo[a]pyrène/composition chimique , Glycémie/analyse , Cytochrome P-450 CYP1A1/génétique , Hématocrite , Hypoxie , L-Lactate dehydrogenase/génétique , L-Lactate dehydrogenase/métabolisme , Acide lactique/sang , Foie/métabolisme , ARN messager/métabolisme , Facteurs temps , Polluants chimiques de l'eau/composition chimiqueRÉSUMÉ
The relationship between habitat complexity and species richness is well established but comparatively little is known about the evolution of morphological diversity in complex habitats. Reefs are structurally complex, highly productive shallow-water marine ecosystems found in tropical (coral reefs) and temperate zones (rocky reefs) that harbor exceptional levels of biodiversity. We investigated whether reef habitats promote the evolution of morphological diversity in the feeding and locomotion systems of grunts (Haemulidae), a group of predominantly nocturnal fishes that live on both temperate and tropical reefs. Using phylogenetic comparative methods and statistical analyses that take into account uncertainty in phylogeny and the evolutionary history of reef living, we demonstrate that rates of morphological evolution are faster in reef-dwelling haemulids. The magnitude of this effect depends on the type of trait; on average, traits involved in the functional systems for prey capture and processing evolve twice as fast on reefs as locomotor traits. This result, along with the observation that haemulids do not exploit unique feeding niches on reefs, suggests that fine-scale trophic niche partitioning and character displacement may be driving higher rates of morphological evolution. Whatever the cause, there is growing evidence that reef habitats stimulate morphological and functional diversification in teleost fishes.
Sujet(s)
Écosystème , Variation génétique , Perciformes/génétique , Animaux , Poids et mesures du corps , Récifs de corail , Évolution moléculaire , Chaine alimentaire , Locomotion/génétique , Perciformes/anatomie et histologie , PhylogenèseRÉSUMÉ
BACKGROUND: The fish family Haemulidae is divided in two subfamilies, Haemulinae and Plectorhynchinae (sweetlips), including approximately 17 genera and 145 species. The family has a broad geographic distribution that encompasses contrasting ecological habitats resulting in a unique potential for evolutionary hypotheses testing. In the present work we have examined the phylogenetic relationships of the family using selected representatives of additional Percomorpha based on Bayesian and Maximum likelihood methods by means of three mitochondrial genes. We also developed a phylogenetic hypothesis of the New World species based on five molecular markers (three mitochondrial and two nuclear) as a framework to evaluate the evolutionary history, the ecological diversification and speciation patterns of this group. RESULTS: Mitochondrial genes and different reconstruction methods consistently recovered a monophyletic Haemulidae with the Sillaginidae as its sister clade (although with low support values). Previous studies proposed different relationships that were not recovered in this analysis. We also present a robust molecular phylogeny of Haemulinae based on the combined data of two nuclear and three mitochondrial genes. All topologies support the monophyly of both sub-families (Haemulinae, Plectorhinchinae). The genus Pomadasys was shown to be polyphyletic and Haemulon, Anisotremus, and Plectorhinchus were found to be paraphyletic. Four of seven presumed geminate pairs were indeed found to be sister species, however our data did not support a contemporaneous divergence. Analyses also revealed that differential use of habitat might have played an important role in the speciation dynamics of this group of fishes, in particular among New World species where extensive sample coverage was available. CONCLUSIONS: This study provides a new hypothesis for the sister clade of Hamulidae and a robust phylogeny of the latter. The presence of para- and polyphyletic genera underscores the need for a taxonomic reassessment within the family. A scarce sampling of the Old World Pomadasys species prevents us to definitively point to a New World origin of the sub-familiy Hamulinae, however our data suggest that this is likely to be the case. This study also illustrates how life history habitat influences speciation and evolutionary trajectories.
Sujet(s)
Spéciation génétique , Perciformes/classification , Phylogenèse , Animaux , Théorème de Bayes , Noyau de la cellule/génétique , ADN mitochondrial/génétique , Évolution moléculaire , Fonctions de vraisemblance , Modèles génétiques , Perciformes/génétique , Analyse de séquence d'ADNRÉSUMÉ
AKR1A1 or aldehyde reductase is a member of the aldo-keto reductases superfamily that is evolutionarily conserved among species. AKR1A1 is one of the five AKRs (AKR1A1 and 1C1-1C4) implicated in the metabolic benzo(a)pyrene (BaP) activation to reactive BaP 7,8-dione. BaP is a polycyclic aromatic hydrocarbon (PAH) widely distributed in aquatic ecosystems and its metabolic activation is necessary to produce its toxic effects. Although the presence of AKR1A1 in fish has been reported, its tissue distribution in tilapia (Oreochromis niloticus) and AKR1A1 inducibility by BaP are not known yet. Moreover, cytochrome P4501A (CYP1A) mRNA expression in fish has been used as a PAH biomarker of effect. Therefore, BaP effects on AKR1A1 and CYP1A gene expressions in tilapia, a species of commercial interest, were investigated by real-time RT-PCR. A partial AKR1A1 cDNA was identified, sequenced and compared with AKR1A1 reported sequences in the GenBank DNA database. Constitutive AKR1A1 mRNA expression was detected mainly in liver, similarly to that of CYP1A. BaP exposure resulted in statistically significant AKR1A1 and CYP1A mRNA induction in liver (20- and 120-fold, respectively) at 24 h. On the other hand, ethoxyquin (EQ) was used as control inducer for AKR1A1 mRNA. Interestingly, EQ also induced CYP1A mRNA levels in tilapia liver. Our results suggest that teleost AKR1A1, in addition to CYP1A, are inducible by BaP. The mechanism of AKR1A1 induction by BaP and its role in fish susceptibility to BaP toxic effects remains to be elucidated.
Sujet(s)
Aldose reductase/génétique , Benzo[a]pyrène/toxicité , Régulation de l'expression des gènes codant pour des enzymes/effets des médicaments et des substances chimiques , Foie/effets des médicaments et des substances chimiques , ARN messager/génétique , Animaux , Séquence nucléotidique , Amorces ADN , ADN complémentaire , Foie/enzymologie , Mâle , Réaction de polymérisation en chaine en temps réel , Similitude de séquences d'acides nucléiques , TilapiaRÉSUMÉ
Se presenta un estudio experimental que tiene por objetivo evaluar la sensibilidad y especificidad de la detección de solución de continuidad del tracto gastrointestinal con la utilización de partículas pesadas marcadas con Tecnecio 99. Se diseñó un estudio experimental prospectivo triple ciego, con un cálculo de tamaño de muestra teniendo en cuenta una sensibilidad y especificidad superiores al 95 por ciento, con un error alfa del 0.05 y una precisión de 0.05. Inicialmente se evaluaron 4 conejos de la raza Nueva Zelanda para determinar: el anestésico y la dosis a utilizar, la capacidad del estómago en mililitros; los tiempos promedios de tránsito gastrointestinal, la capacidad de la cavidad abdominal en mililitros y la biodistribución del radiofármaco (absorción gastrointestinal, diseminación y distribución hemática y eliminación renal). Se utilizaron 40 conejos de la raza Nueva Zelanda y se analizaron en tres estaciones de trabajo independientes, asignando aleatoriamente 20 conejos en cada grupo de estudio (perforados y no perforados). El radiofármaco utilizado fue Tecnecio 99 sulfuro coloidal > 100 nm, 2.5 mCi a 140 Kev de energía preparado en una dilución de solución salina al 0.9 por ciento quedando una concentración de 0.0025 mCi por mililitro. El rastreo se realizó con una sonda gamma a 10X. El análisis estadístico se realizó con el programa Episet V:1 aplicando la prueba de Chi Cuadrado.Todos los 20 conejos que tenían disrupción del estómago, presentaron una prueba positiva para detección de radioactividad en el líquido peritoneal analizado con un valor promedio de 467 y un rango de 37 a 1748. En los 20 conejos restantes que no tenían perforación de la pared gástrica la prueba fue negativa.La sensibilidad de la metodología diagnóstica fue de 0.98 y la especificidad de 0.98 con un intervalo...
Sujet(s)
Diagnostic , Fistule digestive , Radioimmunodétection , Scintigraphie , RadiochirurgieRÉSUMÉ
Contiene: Actividad económica y violencia; La dotación y la distribución de recursos; la perticipación en la producción; Las condiciones de intercambio y las posibilidades de bienestar; Las consecuencias del despojo, la exclusión y la discriminación: la pobreza; Conclusiones