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1.
Chemosphere ; 250: 126228, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32114339

RESUMO

The recently described Squalus albicaudus is a mesopredator shark and, as such, exposed to mercury biomagnification processes. Therefore, this study aimed to assess total Hg (THg) concentrations in S. albicaudus, a deep-water species, sampled off Southeastern Brazil and discuss ecological, reproductive, human consumption and conservation implications. Thirty-two individuals were sampled off the coast of Rio de Janeiro, including 13 gravid females carrying 34 embryos. Muscle THg concentrations were higher in all sex classes compared to liver, gonads and brain. The last three, in turn, presented THg concentrations above toxic biota thresholds. Significant correlations were observed between muscle and brain and liver, indicating systemic Hg contamination and inter-organ transport and distribution. In addition, correlations observed between organs strongly support efficient Hg blood-brain barrier crossing and maternal transfer. Maternal THg transfer was observed, with embryo THg also above toxic thresholds for fish. THg levels in muscle and liver, as well as embryos, were higher compared to other Squalus species worldwide. Hg contamination off the coast of Rio de Janeiro is of significant concern and should be further assessed. Potential human consumption risks are noted, as muscle THg concentrations were above maximum permissible levels set by regulatory agencies.


Assuntos
Monitoramento Ambiental , Mercúrio/metabolismo , Squalus/metabolismo , Poluentes Químicos da Água/metabolismo , Animais , Brasil , Cação (Peixe) , Ecologia , Feminino , Peixes , Mercúrio/análise , Músculos/química , Alimentos Marinhos , Poluentes Químicos da Água/análise
2.
Physiol Biochem Zool ; 92(6): 554-566, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31567050

RESUMO

Pacific spiny dogfish (Squalus suckleyi) have been widely used as a representative species for chondrichthyan CO2 excretion. Pacific spiny dogfish have a slower red blood cell (RBC) carbonic anhydrase (CA) isoform than teleost fishes, extracellular CA activity, no endogenous plasma CA inhibitor, and plasma-accessible CA IV at the gills. Thus, both the RBC and plasma compartments contribute to bicarbonate ion (HCO3-) dehydration at the gills for CO2 excretion in contrast to teleost fishes, in which HCO3- dehydration is restricted to RBCs. We compared CA activity levels, subcellular localization, and presence of plasma CA inhibitors in the blood and gills of 13 chondrichthyans to examine the hypothesis that the dogfish model of CO2 excretion applies broadly to chondrichthyans. In general, blood samples from the 12 other chondrichthyans examined had lower RBC CA activity than teleosts, some extracellular CA activity, and no endogenous plasma CA inhibitor. While type IV-like membrane-associated CA was found in the gills in all four of the chondrichthyans examined, S. suckleyi had three times more CA activity (183±13.2 µmol CO2 min-1 mg protein-1) in the microsomal (membrane) fraction of gills than the other three. In addition, unexpected variation in CA characteristics was observed between chondrichthyan species. Thus, in general, it appears that the pattern of CA distribution in fishes can be generally categorized as either chondrichthyan or teleost models. However, further studies should examine the functional significance of the within-chondrichthyan differences we observed and investigate whether CO2 excretion patterns exist along a continuum or in discrete groups.


Assuntos
Anidrases Carbônicas/metabolismo , Brânquias/enzimologia , Squalus/sangue , Animais , Dióxido de Carbono/metabolismo , Anidrases Carbônicas/sangue , Squalus/metabolismo
3.
J Fish Biol ; 94(6): 966-980, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30677135

RESUMO

At-sea observer programmes can provide spatio-temporal data on the sizes and quantities of fish being either discarded or retained, including for species and size categories that may not be sampled effectively during scientific surveys. Such data were analysed for English and Welsh fisheries operating on the continental shelf of the North Sea ecoregion (ICES Divisions 4a-c and 7d) and Celtic Seas ecoregion (ICES Divisions 6a, 7a-c, e-k) for the period (2002-2016). These data were collated for four main gear types: beamtrawl, nephrops and otter trawls, and nets (including gillnets, tangle nets and trammel nets). Beamtrawlers caught proportionally more smaller individuals than otter trawlers, whilst nets were the most size-selective gear for larger sharks. Size-related discarding was observed, with smaller spurdog Squalus acanthias and starry smooth-hound Mustelus asterias (< 60 cm total length, LT ) usually being discarded. Such size-based selection was not evident for lesser-spotted dogfish Scyliorhinus canicula, which was generally landed as bait. Temporal changes in the discard-retention patterns were evident for S. acanthias and porbeagle Lamna nasus, with increased regulatory discarding as management measures became restrictive. A corresponding increase in the proportion of the non-quota M. asterias retained was also observed over the study period. Knowledge of the size-based discard-retention patterns by métier can also help inform on where future studies on discard survival could usefully be undertaken.


Assuntos
Pesqueiros/estatística & dados numéricos , Tubarões , Animais , Oceano Atlântico , Cação (Peixe) , Inglaterra , Mar do Norte , Squalus , País de Gales
4.
PLoS One ; 13(12): e0207887, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30540765

RESUMO

A new deep-water catshark, Bythaelurus stewarti, is described based on 121 examined specimens caught on the Error Seamount (Mount Error Guyot) in the northwestern Indian Ocean. The new species differs from all congeners in the restricted distribution, a higher spiral valve turn count and in the morphology of the dermal denticles. It is distinguished from its morphologically and geographically closest congener, B. hispidus (Alcock), by the larger size (maximum size 44 vs. 39 cm TL, maturity size of males 35-39 vs. 21-28 cm TL), darker fresh coloration and dark grayish-brown mottling of the ventral head (vs. ventral head typically uniformly yellowish or whitish). Furthermore, it has a strongly different morphology of dermal denticles, in particular smaller and less elongate branchial, trunk and lateral caudal denticles that are set much less densely and have a surface that is very strongly and fully structured by reticulations (vs. structured by reticulations only in basal fourth). In addition, the new species differs from B. hispidus in having more slender claspers that are gradually narrowing to the bluntly pointed tip without knob-like apex (vs. claspers broader and with distinct knob-like apex), more spiral valve turns (11-12 vs. 8-10) and numerous statistical differences in morphometrics. A review of and a key to the species of Bythaelurus are given.


Assuntos
Tubarões/classificação , Especificidade da Espécie , Squalus/classificação , Distribuição Animal , Animais , Biometria , Cordados , Ecologia , Comportamento Alimentar , Feminino , Especiação Genética , Cabeça , Oceano Índico , Masculino , Pigmentação , Pele , Tronco
5.
Zootaxa ; 4444(2): 101-119, 2018 Jul 09.
Artigo em Inglês | MEDLINE | ID: mdl-30313931

RESUMO

Sharks of the genus Squalus have slow reproductive rates coupled with low genetic diversity, as is typical of deep-water sharks, making this group slow to rebound from depletion due to overfishing. The number of species within Squalus has been expanding recently due to increased attention on taxonomic revision, and a growing research focus on little-known deep-water sharks in general. Here we use genetics and morphology to describe a new species of dogfish shark, Squalus clarkae sp. nov. from the Gulf of Mexico (GoM) which replaces Squalus mitsukurii in this region, and place it in the context of congeners from the Atlantic and elsewhere. Previously, S. clarkae sp. nov. was considered a part of the Squalus mitsukurii species complex, a group of closely related but distinct species. We sequenced the mitochondrial cytochrome oxidase I and the NADH Dehydrogenase II gene of S. mitsukurii from the type location in Japan, S. clarkae sp. nov. from the GoM, as well as three closely related species (S. cubensis, S. blainville, and S. megalops) and S. cf. mitsukurii from Brazil. Squalus clarkae sp. nov. is genetically distinct from other species with significant statistical support (>98.6% bootstrap support/posterior probability), and 2.8% divergent from S. mitsukurii in the type location of Japan. Morphological estimates also revealed differences between S. clarkae sp. nov., S. mitsukurii, and other Atlantic Squalus species, with S. clarkae sp. nov. exhibiting a longer body, smaller interorbital space, shorter caudal fin, and a differently-proportioned first dorsal fin. In general, dogfish sharks in the Atlantic and GoM are characterized by similar but distinct morphology, significant genetic variation, and small species ranges.


Assuntos
Cação (Peixe) , Squalus , Animais , Brasil , Golfo do México , Japão , Tubarões
6.
J Exp Biol ; 221(Pt 17)2018 09 13.
Artigo em Inglês | MEDLINE | ID: mdl-30012576

RESUMO

Elasmobranchs are a group of cartilaginous fish with no direct sympathetic innervation of the heart or gills. Fast cardiorespiratory regulation is controlled solely by the parasympathetic branch of the autonomic nervous system. Cardiovascular changes associated with ventilation are commonly present in the form of respiratory sinus arrhythmia (RSA) and as cardiorespiratory synchrony (CRS, in which there is a 1:1 beat to breath ratio). The latter has been hypothesized to maximize oxygen uptake, coupling the pulsatile flows of blood and water in the gills. Given this, we hypothesized that CRS should be more prevalent in situations of low oxygen supply and RSA should be abolished by vagotomy. To test this, we investigated the role of the vagus nerve in mediating cardiorespiratory responses to changing environmental oxygen conditions in the elasmobranch Squalus suckleyi Hypoxia and hyperoxia had little effect on heart rate but did alter breathing frequency and amplitude. Atropine yielded an overall tachycardia in all oxygen conditions and abolished all heart rate variability (HRV), suggesting that HRV solely reflects fluctuating vagal tonus on the heart. Regardless of the presence of atropine, hypoxia still induced an increase in ventilation rate and depth. CRS was only found during progressive hyperoxia post-atropine, when heart rate was uninhibited and ventilation was slowed owing to the increase in oxygen supply, suggesting that in S. suckleyi, CRS is an epiphenomenon and not actively regulated to maximize gas exchange efficiency.


Assuntos
Frequência Cardíaca/fisiologia , Oxigênio/metabolismo , Taxa Respiratória/fisiologia , Squalus/fisiologia , Nervo Vago/fisiologia , Anaerobiose , Animais , Água do Mar/química
7.
J Fish Biol ; 91(4): 1178-1207, 2017 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-28905386

RESUMO

The long-snouted African spurdog Squalus bassi sp. nov. is described based on material collected from the outer shelf and upper continental slope off South Africa and Mozambique. Squalus bassi shares with S. mitsukurii, S. montalbani, S. chloroculus, S. grahami, S. griffini, S. edmundsi, S. quasimodo and S. lobularis a large snout with prenarial length greater than distance between nostrils and upper labial furrows, dermal denticles tricuspidate and rhomboid and elevated number of vertebrae. Squalus bassi can be distinguished from all its congeners by a combination of body and fin colouration, external morphometrics, vertebral counts and shape of dermal denticles. Similar long-snouted congeners from the Indo-Pacific region, including S. montalbani, S. edmundsi and S. lalannei are compared in detail with the new species. This new species has been misidentified as the Japanese S. mitsukurii and the Mediterranean S. blainvillei due to the lack of comparative morphological analyses. The validity of the nominal species S. mitsukurii in the south-eastern Atlantic Ocean and western Indian Ocean is also clarified herein, indicating it has a more restricted geographical distribution in the North Pacific Ocean.


Assuntos
Squalus/anatomia & histologia , Animais , Oceano Atlântico , Tamanho Corporal , Feminino , Oceano Índico , Masculino , Moçambique , África do Sul , Squalus/classificação
8.
Ecotoxicol Environ Saf ; 145: 340-348, 2017 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-28759763

RESUMO

Recycled water is important for maintaining river flow in semi-arid regions. However, it has ecological risk, as suggested by comparison of habitat and white and red blood cell count in two wild fish species (Barbus meridionalis and Squalius laietanus) before and after an input of recycled water in Ripoll River (NE Spain) in 2009. Due to the lack of normal ranges for blood variables in wild fish, we surveyed seasonally the same river reaches in 2013 to test if blood alterations from 2009 compromised the viability of the fish populations. By examining other indicators of river health in baseline and polluted sites (fish abundance, mass-length relationships, and community indices in fish, diatoms and invertebrates), we tested for the superior utility of blood tests in biomonitoring. The comparison of water quality and scores of diatoms and invertebrate indices between polluted and reference sites showed that polluted sites improved from 2009 to 2013. The abundance of B. meridionalis also increased in polluted sites, but that of S. laietanus declined in 2013 compared to 2009. These results contrast with results of blood analyses in 2009, which suggested that B. meridionalis was more seriously affected by pollution than S. laietanus. The fish index did not reveal the risk of recycled water to fish health, whereas fish mass-length relationships suggested that S. laietanus individuals in 2013 had a better body condition in polluted than in reference sites. Given that the two fish species had opposite results in reference sites, and that the physical habitat was more suitable for B. meridionalis in polluted sites in 2013 than was for S. laietanus, trends in population size are not only explained by pollution. The role of phenology is suggested by peaks in blood disorders during the breeding season. However, more long-term studies combining indicators of river health at the individual and community scales are needed to fully assess the ecological risk of recycled water in this river. These studies will also help to develop blood tests as reliable health indicators in wild fish populations.


Assuntos
Cyprinidae/crescimento & desenvolvimento , Monitoramento Ambiental/métodos , Rios/química , Squalus/crescimento & desenvolvimento , Poluentes Químicos da Água/análise , Animais , Biomarcadores/sangue , Cyprinidae/sangue , Diatomáceas/crescimento & desenvolvimento , Ecossistema , Invertebrados/crescimento & desenvolvimento , Densidade Demográfica , Reciclagem , Espanha , Squalus/sangue , Águas Residuárias , Qualidade da Água
9.
J Comp Physiol B ; 187(8): 1155-1161, 2017 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-28444441

RESUMO

Elasmobranchs possess a specialised organ, the rectal gland, which is responsible for excreting sodium chloride via the posterior intestine. Previous work has indicated that the gland may be activated by a number of hormones, some of which are likely related to the salt or volume loads associated with feeding. Furthermore, evidence exists for the gland being glucose dependent which is atypical for an elasmobranch tissue. In this study, the presence of sodium-glucose co-transporters (SGLTs) in the rectal gland and their regulation by feeding were investigated. In addition, the hypothesis of glucose dependence was examined through the use of glucose transporter (GLUT and SGLT) inhibitors, phlorizin, Indinavir, and STF-31 and their effect on secretion by the rectal gland. Finally, the effects on rectal gland activity of insulin, glucagon, and glucagon-like peptide-1, hormones typically involved in glucoregulation, were examined. The results showed that sglt1 mRNA is present in the gland, and there was a significant reduction in sglt1 transcript abundance 24 h post-feeding. An almost complete suppression of chloride secretion was observed when glucose uptake was inhibited, confirming the organ's glucose dependence. Finally, perfusion with dogfish GLP-1 (10 nmol L-1), but not dogfish glucagon, was shown to markedly stimulate the activity of the gland, increasing chloride secretion rates above baseline by approximately 16-fold (p < 0.001). As GLP-1 is released from the intestine upon feeding, we propose that this may be the primary signal for activation of the rectal gland post-feeding.


Assuntos
Glândulas Exócrinas/metabolismo , Peptídeo 1 Semelhante ao Glucagon/metabolismo , Glucose/metabolismo , Squalus/metabolismo , Animais , Cloretos/metabolismo , Glucagon/metabolismo , Insulina/farmacologia , Ácido Láctico/metabolismo , Masculino , Reto , Transportador 1 de Glucose-Sódio/genética
10.
Gen Comp Endocrinol ; 247: 46-52, 2017 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-28093310

RESUMO

Elasmobranchs (sharks, skates, and rays) are a primarily carnivorous group of fish, consuming few carbohydrates. Further, they tend to exhibit delayed responses to glucose and insulin administration in vivo relative to mammals, leading to a presumption of glucose-intolerance. To investigate the glucoregulatory capabilities of the spiny dogfish (Squalus suckleyi), plasma glucose concentration, muscle and liver glycogen content, and glucose transporter (glut1 and 4) mRNA levels were measured following intra-arterial administration of bovine insulin (10ngkg-1) or an approximate doubling of fasting plasma glucose concentration. Within 6h, following glucose administration, approximately half of the introduced glucose load had been cleared, with control levels being restored by 24h post-injection. It was determined that plasma clearance was due in part to increased uptake by the tissues as muscle and liver glycogen content increased significantly, correlating with an upregulation of glut mRNA levels. Following administration of bovine insulin, plasma glucose steadily decreased through 18h before returning toward control levels. Observed decreases in plasma glucose following insulin injection were, however, relatively minor, and no increases in tissue glycogen content were observed. glut4 and glycogen synthase mRNA levels did significantly increase in the muscle in response to insulin, but no changes occurred in the liver. The responses observed mimic what occurs in mammals and teleosts, thus suggesting a conserved mechanism for glucose homeostasis in vertebrates and a high degree of glucose tolerance in these predominantly carnivorous fish.


Assuntos
Proteínas Facilitadoras de Transporte de Glucose/metabolismo , Glucose/farmacologia , Insulina/farmacologia , Squalus/metabolismo , Animais , Glicemia/metabolismo , Bovinos , Glucose/administração & dosagem , Transportador de Glucose Tipo 4/metabolismo , Glicogênio/metabolismo , Glicogênio Sintase/genética , Glicogênio Sintase/metabolismo , Insulina/administração & dosagem , Fígado/efeitos dos fármacos , Fígado/metabolismo , Masculino , Músculo Esquelético/efeitos dos fármacos , Músculo Esquelético/metabolismo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo
11.
Syst Parasitol ; 94(1): 91-96, 2017 01.
Artigo em Inglês | MEDLINE | ID: mdl-28062996

RESUMO

Trebius Krøyer, 1838 currently consists of 15 accepted species all infecting elasmobranchs. Apart from two species, i.e. T. caudatus Krøyer, 1838 and T. latifurcatus Wilson, 1921, that have been reported from ten and eight host species, respectively, the other 13 species have each been reported from only one or two host species. Trebius benzi n. sp., collected from Squalus acutipinnis Regan, is described and illustrated after examination through stereo- and compound microscopes. This species can be distinguished from the other known species by a combination of characters including an abdomen that is shorter than the genital complex, a maxillule with an endite that consists of a single-tined dentiform process, sternal furca tines that are blunt and as long as the base, and the innermost spine of the last exopodal segment of leg 1 the shortest.


Assuntos
Copépodes/classificação , Squalus/parasitologia , Animais , Copépodes/anatomia & histologia , África do Sul , Especificidade da Espécie
12.
Syst Parasitol ; 94(2): 275-291, 2017 02.
Artigo em Inglês | MEDLINE | ID: mdl-28130671

RESUMO

Both sexes of a new species of pandarid copepod are described from sharks of the genus Squalus L. (Squaliformes: Squalidae). Specimens of Pseudopandarus cairae n. sp. were collected from Squalus bucephalus Last, Séret & Pogonoski and S. melanurus Fourmanoir & Rivaton in New Caledonian waters, the first parasitic copepod to be described from either host species. This is the eighth nominal species of Pseudopandarus Kirtisinghe, 1950 and the first to be described from a shark of the order Squaliformes. Pseudopandarus cairae n. sp. is easily distinguished from P. australis Cressey & Simpfendorfer, 1988, P. longus (Gnanamuthu, 1951) Cressey, 1967, and P. pelagicus Rangnekar, 1977 in having the female genital complex concealed beneath an elongate dorsal genital shield with a trilobed posterior margin. It can be distinguished from P. gracilis Kirtisinghe, 1950 and P. scyllii Yamaguti & Yamasu, 1959 by the armature of the leg 4 endopod and by the proportions of the dorsal genital shield. The new species is unique among known species of Pseudopandarus in its possession of only 1 setal element on the distal endopod segment of leg 4. In addition to describing the new species, the host associations of all species of Pseudopandarus are reviewed and observations are made regarding sexual dimorphism and mode of attachment. A key to the species considered valid is provided.


Assuntos
Copépodes/classificação , Squalus/parasitologia , Animais , Copépodes/anatomia & histologia , Feminino , Masculino , Nova Caledônia , Especificidade da Espécie
13.
Zootaxa ; 4133(1): 1-89, 2016 Jul 04.
Artigo em Inglês | MEDLINE | ID: mdl-27395700

RESUMO

Squalus is a genus of reportedly cosmopolitan shark species that have a high taxonomic complexity due to difficulties in their morphological differentiation; many of its species need revision. Currently, there are 26 valid species of Squalus, which have been divided into three species-groups according to overall morphological similarity, the S. acanthias, S. megalops, and S. mitsukurii groups. Loss of type specimens, propagation of erroneous identifications in the literature, and difficulties in obtaining representative series for comparison are secondary challenges that have impeded a global taxonomic revision of the genus. This problem applies clearly to species from the Southwestern Atlantic Ocean, including species that occur off Brazil. Following a current global tendency, a regional taxonomic revision of Squalus was conducted in order to investigate which species are valid in the Southwestern Atlantic Ocean and provide diagnostic morphological characters that can be efficiently used for identifying species. Comparative detailed analysis of external (e.g. morphometrics, dentition, and color pattern) and skeletal morphology (primarily meristic data, neurocrania and claspers) of specimens of Squalus from the region revealed four new species that are herein described (S. albicaudus sp. nov., S. bahiensis sp. nov., S. lobularis sp. nov., and S. quasimodo sp. nov.), as well as S. acanthias, which is redescribed from the region based on new material. Comparisons are offered based on examinations of congeneric species; this work is part of a global systematic revision of Squalus.


Assuntos
Squalus/anatomia & histologia , Squalus/classificação , Animais , Oceano Atlântico , Feminino , Masculino , Especificidade da Espécie
14.
Parasitology ; 143(10): 1340-6, 2016 09.
Artigo em Inglês | MEDLINE | ID: mdl-27225942

RESUMO

Predicting how elevated temperatures from climate change alter host-parasite interactions requires understandings of how warming affects host susceptibility and parasite virulence. Here, the effect of elevated water temperature and parasite exposure level was tested on parasite prevalence, abundance and burden, and on fish growth, using Pomphorhynchus laevis and its fish host Squalius cephalus. At 60 days post-exposure, prevalence was higher at the elevated temperature (22 °C) than ambient temperature (18 °C), with infections achieved at considerably lower levels of exposure. Whilst parasite number was significantly higher in infected fish at 22 °C, both mean parasite weight and parasite burden was significantly higher at 18 °C. There were, however, no significant relationships between fish growth rate and temperature, parasite exposure, and the infection parameters. Thus, whilst elevated temperature significantly influenced parasite infection rates, it also impacted parasite development rates, suggesting warming could have complex implications for parasite dynamics and host resistance.


Assuntos
Acantocéfalos/isolamento & purificação , Mudança Climática , Doenças dos Peixes/parasitologia , Helmintíase Animal/parasitologia , Squalus/parasitologia , Acantocéfalos/fisiologia , Animais , Suscetibilidade a Doenças , Interações Hospedeiro-Parasita , Carga Parasitária , Prevalência , Squalus/crescimento & desenvolvimento , Squalus/fisiologia , Temperatura
15.
J Morphol ; 277(7): 896-905, 2016 07.
Artigo em Inglês | MEDLINE | ID: mdl-27106538

RESUMO

The coronary circulation is of great importance in maintaining cardiovascular function and consequently it has been extensively studied in many mammalian species. However, much less attention has been paid to the coronary circulation in other vertebrates. For example, while elasmobranch fishes are of special interest as they are the most ancient lineage of vertebrates to possess a coronary circulation, only qualitative studies exist on their coronary circulation and most concern the architecture of the large arteries. Our study tested the prediction that the coronary circulation of sharks is better developed than previously thought. However, to test this idea, a methodology was needed to quantify vascularity, vessel morphology and oxygen diffusion distances in a heart with predominantly spongy myocardium. Here, we describe this methodology using dogfish and rainbow trout and suggest that the dogfish spongy myocardium appears to rely predominantly on the coronary circulation for its oxygen supply, an arrangement that contrasts with the spongy myocardial tissue of rainbow trout. In support of this suggestion, the density of the microvasculature of the spongy myocardial tissue of dogfish exceeded that of their compact tissue. Although vascularity in the compact myocardium of dogfish was significantly lower than trout, intervascular distances were similar on account of a significantly larger vessel diameter in dogfish, which corresponds to a larger red blood cell size of the dogfish when compared to trout. J. Morphol. 277:896-905, 2016. © 2016 Wiley Periodicals, Inc.


Assuntos
Vasos Coronários/anatomia & histologia , Oncorhynchus mykiss/anatomia & histologia , Squalus/anatomia & histologia , Animais , Circulação Coronária , Oncorhynchus mykiss/fisiologia , Squalus/fisiologia
16.
Mitochondrial DNA A DNA Mapp Seq Anal ; 27(6): 4522-4523, 2016 11.
Artigo em Inglês | MEDLINE | ID: mdl-26539656

RESUMO

We present the complete mitochondrial genome sequence (16 555 bp) of the Philippines spurdog, Squalus montalbani, currently listed as Vulnerable due to population declines and fishing pressures. A phylogenetic analysis was carried out on S. montalbani and representative shark mitogenomes. Squalus montalbani was placed within the Squaliformes as a sister taxon to Squalus acanthias and Cirrhigaleus australis.


Assuntos
Genoma Mitocondrial , Squalus/genética , Animais , DNA Mitocondrial/química , DNA Mitocondrial/isolamento & purificação , DNA Mitocondrial/metabolismo , Proteínas de Peixes/classificação , Proteínas de Peixes/genética , Proteínas de Peixes/metabolismo , Funções Verossimilhança , Fases de Leitura Aberta/genética , Filipinas , Filogenia , RNA Ribossômico/química , RNA Ribossômico/genética , RNA de Transferência/química , RNA de Transferência/genética , Análise de Sequência de DNA
17.
Artigo em Inglês | MEDLINE | ID: mdl-26686463

RESUMO

The North Pacific spiny dogfish (Squalus suckleyi) is a partially euryhaline species of elasmobranch that often enter estuaries where they experience relatively large fluctuations in environmental salinity that can affect plasma osmolality. Previous studies have investigated the effects of altered salinity on elasmobranchs over the long term, but fewer studies have conducted time courses to investigate how rapidly they can adapt to such changes. In this study, we exposed unfed (no exogenous source of nitrogen or TMAO) spiny dogfish to hyper- and hypo-osmotic conditions and measured plasma and tissue osmolytes, nitrogen excretion, and changes in enzyme activity and mRNA levels in the rectal gland over 24h. It was shown that plasma osmolality changes to approximately match the ambient seawater within 18-24h. In the hypersaline environment, significant increases in urea, sodium, and chloride were observed, whereas in the hyposaline environment, only significant decreases in TMAO and sodium were observed. Both urea and ammonia excretion increased at low salinities suggesting a reduction in urea retention and possibly urea production. qPCR and enzyme activity data for Na(+)/K(+)-ATPase did not support the idea of rectal gland activation following exposure to increased salinities. Therefore, we suggest that the rectal gland may not be a quantitatively important aspect of the dogfish osmoregulatory strategy during changes in environmental salinity, or it may be active only in the very early stages (i.e., less than 6h) of responses to altered salinity.


Assuntos
Osmorregulação/fisiologia , Osmose/fisiologia , Squalus/fisiologia , Amônia/metabolismo , Animais , Cloretos/metabolismo , Salinidade , Glândula de Sal/metabolismo , Glândula de Sal/fisiologia , Água do Mar , Sódio/metabolismo , ATPase Trocadora de Sódio-Potássio/metabolismo , Squalus/metabolismo , Ureia/metabolismo , Equilíbrio Hidroeletrolítico/fisiologia
18.
Physiol Biochem Zool ; 87(5): 623-39, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-25244375

RESUMO

The effects of acute moderate (20% air O2 saturation; 6-h exposure) and severe (5% air O2 saturation; 4-h exposure) hypoxia on N-waste, acid-base, and ion balance in dogfish sharks (Squalus acanthias suckleyi) were evaluated. We predicted that the synthesis and/or retention of urea, which are active processes, would be inhibited by hypoxia. Exposure to moderate hypoxia had negligible effects on N-waste fluxes or systemic physiology, except for a modest rise in plasma lactate. Exposure to severe hypoxia led to a significant increase in urea excretion (Jurea), while plasma, liver, and muscle urea concentrations were unchanged, suggesting a loss of urea retention. Ammonia excretion (Jamm) was elevated during normoxic recovery. Moreover, severe hypoxia led to disruptions in acid-base balance, indicated by a large increase in plasma [lactate] and substantial decreases in arterial pHa and plasma [Formula: see text], as well as loss of ionic homeostasis, indicated by increases in plasma [Mg(2+)], [Ca(2+)], and [Na(+)]. We suggest that severe hypoxia in dogfish sharks leads to a reduction in active gill homeostatic processes, such as urea retention, acid-base regulation and ionoregulation, and/or an osmoregulatory compromise due to increased functional gill surface area. Overall, the results provide a comprehensive picture of the physiological responses to a severe degree of hypoxia in an ancient fish species.


Assuntos
Oxigênio/metabolismo , Squalus acanthias/fisiologia , Ureia/metabolismo , Equilíbrio Hidroeletrolítico , Anaerobiose , Animais , Concentração de Íons de Hidrogênio , Masculino , Squalus
19.
Artigo em Inglês | MEDLINE | ID: mdl-24518388

RESUMO

Dogfish are considered stenohaline sharks but are known to briefly enter estuaries. The acute response of North Pacific spiny dogfish (Squalus suckleyi) to lowered salinity was tested by exposing sharks to 21‰ salinity for 48 h. Temporal trends in blood pH, plasma osmolality, CO2, HCO3(-), Na(+), Cl(-), K(+), and urea concentrations, and in the rates of urea efflux and O2 consumption, were quantified. The rate of O2 consumption exhibited cyclic variation and was significantly depressed by lowered salinity. After 9 h, plasma [Cl(-)] stabilized at 9% below initial levels, while plasma [Na(+)] decreased by more than 20% within the first 12 h. Plasma [urea] dropped by 15% between 4 and 6 h, and continued to decrease. The rate of urea efflux increased over time, peaking after 36 h at 72% above the initial rate. Free-swimming sharks subjected to the same salinity challenge survived over 96 h and differed from cannulated sharks with respect to patterns of Na(+) and urea homeostasis. This high-resolution study reveals that dogfish exposed to 21‰ salinity can maintain homeostasis of Cl(-) and pH, but Na(+) and urea continue to be lost, likely accounting for the inability of the dogfish to fully acclimate to reduced salinity.


Assuntos
Salinidade , Squalus/fisiologia , Animais , Artérias/metabolismo , Dióxido de Carbono/sangue , Cloretos/sangue , Concentração de Íons de Hidrogênio , Concentração Osmolar , Consumo de Oxigênio , Oceano Pacífico , Potássio/sangue , Sódio/sangue , Squalus/sangue , Fatores de Tempo , Ureia/sangue
20.
Folia Parasitol (Praha) ; 59(2): 107-14, 2012 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-22779111

RESUMO

A new species of tetraphyllidean cestode in the genus Trilocularia is described from an undescribed shark species, Squalus cf. mitsukurii, off the coast of South Africa. Trilocularia eberti sp. n. is the second known member of its genus, and like its congener, T. gracilis (Olsson, 1866-1867) Olsson, 1869, is extremely hyperapolytic, dropping proglottids from its strobila while they are still very immature. Characteristic of the genus, it possesses a distinctive scolex with triloculated bothridia, but differs conspicuously from its congener in its possession of an anterior loculus that is much larger in width relative to the paired posterior loculi, and also in its possession of an anterior, enlarged region of its free proglottids that is triangular with a slit-like ventral aperture, rather than rounded and cup-like. This anterior region of the free proglottid is used in attachment, and its development is described. For assessment of fecundity, an attempt was made to record all free proglottids of all ages found in both host individuals, and yielded an average estimate of 362 free proglottids being produced per individual worm of T. eberti sp. n. Both Trilocularia species parasitize sharks of the genus Squalus, and given the host specificity typically exhibited by tetraphyllideans and preliminary examinations of other members of this shark genus, it is likely that other Squalus species will be found to host additional new Trilocularia species.


Assuntos
Cestoides/classificação , Infecções por Cestoides/veterinária , Doenças dos Peixes/parasitologia , Squalus/parasitologia , Animais , Cestoides/anatomia & histologia , Cestoides/fisiologia , Infecções por Cestoides/epidemiologia , Infecções por Cestoides/parasitologia , Fertilidade , Doenças dos Peixes/epidemiologia , Microscopia Eletrônica de Varredura/veterinária , Oceanos e Mares/epidemiologia , Reprodução/fisiologia , África do Sul
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