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1.
Zootaxa ; 5116(2): 253-266, 2022 Mar 18.
Artigo em Inglês | MEDLINE | ID: mdl-35391336

RESUMO

A new species of Hyphessobrycon presenting dimorphic males is described from the western Amazon basin in Brazil, Colombia, Ecuador, and Peru. The new species has been mistakenly identified in the literature with the non-congener Hemigrammus marginatus, with which shares a similar color pattern by presenting dark patches of dark pigmentation on caudal-fin lobes. It can be distinguished from the latter species, as well as from Hemigrammus durbinae, and two similar congeners, Hyphessobrycon diancistrus and Hy. otrynus, all of which sharing the same caudal fin color pattern, by the combination of presenting a dark patch of pigmentation on the dorsal fin, a single large anal-fin hook at the last unbranched anal-fin ray in mature males, and a moderately high body depth (22.432.5 % SL, mean 28.4 %). The new species is more similar to Hyphessobrycon diancistrus, which is putatively its closely related taxon. A putative close relationship with Hyphessobrycon otrynus, and with a non-congener presenting a distinct color pattern but sharing a similar sexual dimorphism on anal-fin hook morphology, Hemigrammus boesemani, is suggested.


Assuntos
Characidae , Caraciformes , Animais , Characidae/anatomia & histologia , Masculino , Pigmentação , Rios , Caracteres Sexuais
2.
Fish Physiol Biochem ; 47(3): 737-746, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32556899

RESUMO

This study interrogated factors which affect the appearance of secondary sexual characteristics, namely, fin spinelets (rigid dimorphic structure empirically associated with male sexual maturity in characids), in Astyanax altiparanae. Many variables such as the season of the year and several biotic components, including organism length, sex, phase of maturation, and the presence of gonads, were investigated. These factors were then associated with the physiological development of fin spinelets. The development of this trait is related to reproductive strategies but demonstrates considerable population variability as it is found throughout the year in some species but only during specific periods in others. Seventy-five specimens obtained from spontaneous spawn of farmed fish were arbitrarily grouped into small-, medium-, and large-sized groups in both summer and winter. Gonadal histology was performed to confirm each animal's sex and phase of maturation. Diaphanization of the fish was performed to visualize, count, and measure the fin spinelets. Finally, gonadectomization of some males was utilized to investigate the gonadal effect on the presence of fin spinelets. The present results show that the presence of fin spinelets is a secondary sexual characteristic of males which occurs independently of the season and is always present in males longer than 48 mm. However, in the summer, male specimens presented more rays with fin spinelets than during the winter. Furthermore, since fin spinelets were observed on immature males as well as spawning capable males, their presence cannot be directly associated with sexual maturity in male A. altiparanae, as previously supposed. Finally, gonadectomization resulted in an initial reduction in the length of fin spinelets. However, this trend was eventually normalized with time.


Assuntos
Nadadeiras de Animais/anatomia & histologia , Characidae/anatomia & histologia , Caracteres Sexuais , Animais , Castração , Feminino , Masculino , Ovário/anatomia & histologia , Ovário/cirurgia , Estações do Ano , Testículo/anatomia & histologia , Testículo/cirurgia
3.
J Fish Biol ; 98(1): 219-236, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32997388

RESUMO

Species delimitation is a permanent issue in systematics. The increasing recognition of geographically isolated populations as independent lineages allowed by new methods of analysis has inflated the species-populations dilemma, which involves deciding whether to consider separate lineages as different species or structured genetic populations. This is commonly observed between fishes of adjacent river basins, with some lineages being considered allopatric sister species and others considered isolated populations or variants of the same species. Pseudocorynopoma doriae is a characid diagnosed from its single congener by the number of anal-fin rays and sexually dimorphic characters of males, including distinct fin colouration. The authors found variation in the colour pattern between isolated populations previously identified as P. doriae but no variation in scale or fin-ray counts. They analysed molecular evidence at the population level and morphological differences related to life history (e.g., colour dimorphism related to inseminating behaviour). The results provide compelling evidence for the recognition of a new species of Pseudocorynopoma despite the lack of discrete differences in meristic data. The recognition of the new species is consistent with biogeographical evidence for the long-term isolation of the respective river drainages and with differences between the ichthyofaunal communities of these rivers.


Assuntos
Characidae/anatomia & histologia , Characidae/classificação , Filogenia , Animais , Feminino , Masculino , Rios , Caracteres Sexuais , Especificidade da Espécie
4.
J Comp Neurol ; 529(8): 1779-1786, 2021 06.
Artigo em Inglês | MEDLINE | ID: mdl-33070322

RESUMO

Mauthner cells are the largest neurons in the hindbrain of teleost fish and most amphibians. Each cell has two major dendrites thought to receive segregated streams of sensory input: the lateral dendrite receives mechanosensory input while the ventral dendrite receives visual input. These inputs, which mediate escape responses to sudden stimuli, may be modulated by the availability of sensory information to the animal. To understand the impact of the absence of visual information on the morphologies of Mauthner cells during developmental and evolutionary time scales, we examined the teleost Astyanax mexicanus. This species of tetra is found in two morphs: a seeing surface fish and a blind cavefish. We compared the structure of Mauthner cells in surface fish raised under daily light conditions, in surface fish raised in constant darkness, and in two independent lineages of cave populations. The length of ventral dendrites of Mauthner cells in dark-raised surface fish larvae were longer and more branched, while in both cave morphs the ventral dendrites were smaller or absent. The absence of visual input in surface fish with normal eye development leads to a homeostatic increase in dendrite size, whereas over evolution, the absence of light led to the loss of eyes and a reduction in dendrite size.


Assuntos
Evolução Biológica , Characidae/anatomia & histologia , Dendritos/ultraestrutura , Homeostase/fisiologia , Neurogênese/fisiologia , Adaptação Fisiológica/fisiologia , Animais , Escuridão
5.
J Fish Biol ; 98(5): 1281-1288, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33368326

RESUMO

A new species of Poptella is described from the Río Putumayo, Upper Río Amazon basin, Peru. The new species is distinguished from congeners by having a dense field of dark chromatophores homogeneously spread over the posterior half of the body, posterior humeral blotch extending to three to four horizontal scale rows below the lateral line, and a higher number of branched dorsal-fin rays. The new species can be readily distinguished from P. paraguayensis by having a comparatively shorter predorsal spine.


Assuntos
Characidae/anatomia & histologia , Characidae/classificação , Animais , Peru , Rios , Especificidade da Espécie
6.
Neotrop. ichthyol ; 19(2): e210048, 2021. tab, graf
Artigo em Inglês | LILACS, VETINDEX | ID: biblio-1279485

RESUMO

A new species of miniature fish of the characid genus Priocharax is described from a small lake near the rio Ipixuna, rio Purus drainage, Amazonas State, Brazil. It is distinguished from all congeners except P. pygmaeus by the lower number of teeth on the maxilla and dentary. It differs from P. pygmaeus by the presence of two postcleithra and 22-27 branched anal-fin rays (vs absence and 19-22). The new species is further distinguished from other species of Priocharax by a combination of characters involving the number of pelvic-fin rays and branched anal-fin rays, the number of postcleithra, the shape of postcleithrum 3, and the absence of the claustrum. Molecular evidence based on COI sequences of all valid species of Priocharax also corroborates the validity of this new species.(AU)


Uma nova espécie de peixe miniatura do gênero de caracídeo Priocharax é descrita de um pequeno lago próximo ao rio Ipixuna, drenagem do rio Purus, estados do Amazonas, Brasil. Ela difere de todas as congêneres, exceto P. pygmaeus pelo menor número de dentes no maxilar e dentário. Distingue-se de P. pygmaeus pela presença de dois pós-cleitros e 22-27 raios ramificados na nadadeira anal (vs ausência e 19-22). A nova espécie também difere de outras congêneres por uma combinação de caracteres como número de raios das nadadeiras pélvica e anal, número de pós-cleitros e formato do pós-cleitro 3, e ausência de claustrum. Evidências moleculares com base em sequências do gene COI de todas as espécies válidas também corrobora a validade da nova espécie.(AU)


Assuntos
Animais , Biodiversidade , Characidae/anatomia & histologia , Characidae/genética , Osteologia
7.
Arq. bras. med. vet. zootec. (Online) ; 72(6): 2186-2192, Nov.-Dec. 2020. tab, ilus
Artigo em Inglês | LILACS, VETINDEX | ID: biblio-1142325

RESUMO

This study aimed to compare the body indexes and hematological characteristics between Astyanax bimaculatus males and females. Four hundred fish were randomly distributed into four polyethylene tanks (100 fish/unit) in a recirculation system and fed four times a day (3% of biomass). After 90 days, ten fish (five ♀ and five ♂) were removed to perform blood tests and to measure weight, height, total length, height/length ratio, condition factor and index determination: vicerosomatic (VSI), hepatosomatic (HSI), and gonadosomatic (GSI). The results showed a higher average weight (g) in females (12.32±0.71) compared to males (6.98±0.75), the same happened to height (cm) = (3.01±0.07) and (2.40±0.05), total length (cm) = (3.01±0.07) and (2.40±0.05), VSI (%) = (11.43±0.81) and (3.55±1.05), HSI (%) = (0.72±0.08) and (0.30±0.04), respectively. Mean corpuscular hemoglobin (pg) was higher in females (3.72±1.20) than in males (2.99±1.51). Regarding the number of thrombocytes (103.µL-1), there was an increase in males (25.71±3.91) compared to females (17.40±6.40).(AU)


O objetivo deste trabalho foi comparar os índices corporais e as características hematológicas entre machos e fêmeas de Astyanax bimaculatus. Quatrocentos peixes foram distribuídos aleatoriamente em quatro caixas de polietileno (100 peixes/unidade), em sistema de recirculação, e alimentados quatro vezes ao dia (3% da biomassa). Após 90 dias, 10 peixes (cinco ♀ e cinco ♂) foram retirados para realização das análises sanguíneas e para mensuração do peso, da altura, do comprimento total, da relação altura/comprimento, do fator de condição e da determinação dos índices: viscerossomático (IVS), hepatossomático (IHS) e gonadossomático (IGS). Os resultados mostraram um maior peso médio (g) nas fêmeas (12,32±0,71) em relação aos machos (6,98±0,75); o mesmo aconteceu para altura (cm) = (3,01± 0,07) e (2,40± 0,05), comprimento total (cm) = (3,01±0,07) e (2,40±0,05), IVS (%) = (11,43±0,81) e (3,55±1,05), IHS (%) = (0,72±0,08) e (0,30±0,04), respectivamente. Hemoglobina corpuscular média (pg) foi maior nas fêmeas (3,72±1,20) que nos machos (2,99±1,51). Em relação ao número de trombócitos (103/µL), houve um aumento nos machos (25,71± 3,91) em relação às fêmeas (17,40±6,40).(AU)


Assuntos
Animais , Masculino , Feminino , Plaquetas , Caracteres Sexuais , Índices de Eritrócitos , Characidae/anatomia & histologia , Characidae/sangue , Pesos e Medidas Corporais/veterinária
8.
J Fish Biol ; 97(6): 1701-1712, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32914470

RESUMO

A new species of Odontostilbe is described from the rio Jaciparaná, rio Madeira basin, Rondônia, Brazil. Odontostilbe pacaasnovos differs from all its congeners, except O. pequira, by the colour pattern. Additionally, it differs from its congeners by the terminal mouth, number of cusps in the teeth of the premaxilla (5-7), number of branched rays in the anal fin (19-22), by the shape of dentary teeth (5-7 cusps with central cusp larger and longer than laterals cusps) and by the number of lamellae of the olfactory rosette (17-18 in male and 14 in female). Morphological and molecular comparisons corroborate the distinctiveness between O. pacaasnovos and its congeners, justifying its recognition as a new species.


Assuntos
Characidae/classificação , Nadadeiras de Animais/anatomia & histologia , Animais , Brasil , Characidae/anatomia & histologia , Characidae/genética , Feminino , Proteínas de Peixes/genética , Masculino , Boca/anatomia & histologia , Pigmentação , Especificidade da Espécie , Dente/anatomia & histologia
9.
J Anat ; 237(6): 1136-1150, 2020 12.
Artigo em Inglês | MEDLINE | ID: mdl-32735750

RESUMO

Astyanax brucutu is a peculiar species of Neotropical tetra endemic from the Chapada Diamantina, a large plateau in northeastern Brazil. Individuals of this species undergo a dramatic ontogenetic shift in their diet that is accompanied by equally remarkable changes in their feeding apparatus. Whereas juveniles of A. brucutu feed mostly on algae, adults feed almost exclusively on an endemic species of hydrobiid snail and other associated living organisms that inhabit their dead shells (including infaunal invertebrates and algae). Skeletal adaptations associated with this change in diet were previously reported, but until now, the changes in the musculature remained mostly unknown. The present paper describes the facial and gular muscles, as well as the buccal ligaments of A. brucutu in different life stages, and identifies the major ontogenetic changes in these systems associated with the diet shift in the species. Such changes primarily involve expansions of specific portions of the adductor mandibulae and associated tendons and ligaments that likely represent adaptations to increase the biting power necessary to crush copious amounts of shells ingested by larger individuals of A. brucutu. Those adaptations are absent in specimens of any size of Astyanax cf. fasciatus, a sympatric congener lacking durophagous feeding habits. Anatomical comparisons and landmark-based principal components analysis (PCA) suggest that most specializations to durophagy in A. brucutu arose by peramorphosis. We also found that several of the muscular specializations of adults of A. brucutu are paralleled in species of Creagrutus and Piabina, two other characid genera distantly related to Astyanax, but that also feed on hard food items.


Assuntos
Characidae/anatomia & histologia , Dieta , Músculos Faciais/anatomia & histologia , Comportamento Alimentar/fisiologia , Ligamentos/anatomia & histologia , Adaptação Fisiológica/fisiologia , Animais , Músculos Faciais/fisiologia , Ligamentos/fisiologia
10.
J Morphol ; 281(8): 986-996, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32562593

RESUMO

Among teleost fishes, differences exist in the shape, number, and arrangement of the olfactory lamellae, the distribution of the sensory and non-sensory epithelium, as well as, the abundance of various receptor cells. The objective of this work was to describe the morphology, immunohistochemistry, and scanning electron microscopy ultrastructure of the olfactory epithelium of the bloodfin tetra, Aphyocharax anisitsi. This is the first complete description including the anatomy, histology, and immunohistochemistry of the peripheral olfactory organ from a Characiformes. Based on the external morphology of the olfactory organ, A. anisitsi was classified as a ditermous species, with an olfactory cavity containing two openings divided by a skin flap that separates the anterior and posterior nostril. This species belongs to the group of isosmates, since the presence of accessory olfactory sacs was not observed, and non-sensory ciliated cells were identified. A. anisitsi has an olfactory rosette with an arrow-shaped arrangement, with differences in length between the anterior and posterior lamellae. In the olfactory epithelium, three types of olfactory receptor neurons were identified using histology and confirmed by immunohistochemistry, that is, ciliated olfactory receptor neurons in the basal region of the epithelium, microvillar olfactory receptor neurons in the middle region; and Crypt cells, in smaller numbers compared to the other neuronal types, present in the apical region. Sensory and non-sensory areas were scattered and mixed along the lamellar lateral surface but the nasal cavity and the midline raphe lacked olfactory receptor neurons. The presence of abundant kinocilia in the non-sensory cells could be related in A. anisitsi with ventilation and quality control of water entering the olfactory cavity. The spatial organization of the sensory and non-sensory areas in A. anisitsi was similar to that observed in other species that also inhabit still and slow-flowing bodies of water with high-density vegetation.


Assuntos
Characidae/anatomia & histologia , Mucosa Olfatória/anatomia & histologia , Mucosa Olfatória/citologia , Animais , Cílios/ultraestrutura , Feminino , Imuno-Histoquímica , Masculino , Mucosa Olfatória/ultraestrutura , Neurônios Receptores Olfatórios/metabolismo
11.
J Exp Zool B Mol Dev Evol ; 334(7-8): 405-422, 2020 11.
Artigo em Inglês | MEDLINE | ID: mdl-32488995

RESUMO

Carotenoids are lipid-soluble yellow to orange pigments produced by plants, bacteria, and fungi. They are consumed by animals and metabolized to produce molecules essential for gene regulation, vision, and pigmentation. Cave animals represent an interesting opportunity to understand how carotenoid utilization evolves. Caves are devoid of light, eliminating primary production of energy through photosynthesis and, therefore, limiting carotenoid availability. Moreover, the selective pressures that favor carotenoid-based traits, like pigmentation and vision, are relaxed. Astyanax mexicanus is a species of fish with multiple river-adapted (surface) and cave-adapted populations (i.e., Tinaja, Pachón, Molino). Cavefish exhibit regressive features, such as loss of eyes and melanin pigment, and constructive traits, like increased sensory neuromasts and starvation resistance. Here, we show that, unlike surface fish, Tinaja and Pachón cavefish accumulate carotenoids in the visceral adipose tissue. Carotenoid accumulation is not observed in Molino cavefish, indicating that it is not an obligatory consequence of eye loss. We used quantitative trait loci mapping and RNA sequencing to investigate genetic changes associated with carotenoid accumulation. Our findings suggest that multiple stages of carotenoid processing may be altered in cavefish, including absorption and transport of lipids, cleavage of carotenoids into unpigmented molecules, and differential development of intestinal cell types involved in carotenoid assimilation. Our study establishes A. mexicanus as a model to study the genetic basis of natural variation in carotenoid accumulation and how it impacts physiology.


Assuntos
Carotenoides/metabolismo , Characidae/genética , Animais , Evolução Biológica , Carotenoides/análise , Cavernas , Characidae/anatomia & histologia , Characidae/metabolismo , Cromatografia Líquida de Alta Pressão , Mapeamento Cromossômico , Olho/anatomia & histologia , Feminino , Gordura Intra-Abdominal/química , Masculino , Análise de Sequência de DNA , Análise de Sequência de RNA , Transcriptoma
12.
J Fish Biol ; 97(3): 776-784, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32535919

RESUMO

Resource partitioning has an essential role in interspecific relations, especially in congener species, which share many morphological traits. In some places, small characids coexist through resource partitioning, which may reduce their interspecific competition. Astyanax species (e.g., Astyanax minor, Astyanax gymnodontus and Astyanax bifasciatus), for example, coexist in different water bodies from the Iguaçu River basin. These species have high phenotypic plasticity and many morphologic specializations that allow them to live in different habitats. Based on evidences that these species modified their feeding habits because of changes in resource availability in Iguaçu River, this study tested two hypotheses: (a) there are differences in head morphology, number of teeth and number of gill rakers among the species of Astyanax; and (b) there are differences in gill arch and gill raker morphology among the species of Astyanax, which may favour their trophic resource partitioning in Iguaçu River. The head morphological traits and quantitative morphological characters were summarized in a principal coordinates analysis (PCoA), and the analysis of similarities (ANOSIM) showed significant differences among species. Gill morphological measurements were analysed through analysis of covariance (ANCOVA), and it also showed significant differences in gill arch and gill raker morphology among species. Therefore, the analysis of ecomorphological traits related to trophic habits revealed some differences that may suggest a tendency of reducing competition for trophic resources in the Iguaçu River basin.


Assuntos
Characidae/anatomia & histologia , Cadeia Alimentar , Rios , Animais , Brasil , Brânquias/anatomia & histologia , Estado Nutricional , Especificidade da Espécie , Clima Tropical
13.
J Exp Zool B Mol Dev Evol ; 334(7-8): 511-517, 2020 11.
Artigo em Inglês | MEDLINE | ID: mdl-32436310

RESUMO

The lateral line is the primary modality fish use to create a hydrodynamic image of their environment. These images contribute to a variety of behaviors, from rheotaxis to escape responses. Here we discern the contributions of visual and lateral line modalities in hunting behavior of larvae that have developed under different photic conditions. In particular, cave animals have a hypertrophied sense of mechanosensation, and we studied the common animal model cavefish Astyanax mexicanus and its closest related surface relative. We raised larvae in a diurnal light-dark regimen and in complete darkness. We then examined the distribution of neuromasts in their lateral lines, and their hunting performance in light and dark conditions, with and without the contribution of the lateral line. We report that all larva depend on the lateral line for success in hunting and that surface fish raised in the dark have a greater dependency on the lateral line.


Assuntos
Adaptação Fisiológica/fisiologia , Characidae/anatomia & histologia , Animais , Comportamento Animal/fisiologia , Cavernas , Characidae/fisiologia , Escuridão , Meio Ambiente , Lateralidade Funcional/fisiologia , Larva , Comportamento Predatório/fisiologia
14.
J Fish Biol ; 96(6): 1444-1453, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32166742

RESUMO

Hyphessobrycon chiribiquete n. sp. is described from the Río Caquetá drainage in Colombia and the Río Ucayali drainage in Peru, western Amazon. The new species is diagnosed from its congeners by having the following combination of characters: a conspicuous narrow midlateral stripe, starting on the sides of the body behind the opercle near the lateral line; lateral stripe overlapped anteriorly with a vertically elongated humeral blotch; inner premaxillary teeth pentacuspid; margin of anal fin falcate in mature males.


Assuntos
Characidae/anatomia & histologia , Characidae/classificação , Nadadeiras de Animais/anatomia & histologia , Animais , Colômbia , Masculino , Peru , Rios
15.
J Exp Zool B Mol Dev Evol ; 334(7-8): 530-539, 2020 11.
Artigo em Inglês | MEDLINE | ID: mdl-32017448

RESUMO

Studying how different genotypes respond to environmental variation is essential to understand the genetic basis of adaptation. The Mexican tetra, Astyanax mexicanus, has cave and surface-dwelling morphotypes that have adapted to entirely different environments in the wild, and are now successfully maintained in lab conditions. While this has enabled the identification of genetic adaptations underlying a variety of physiological processes, few studies have directly compared morphotypes between lab-reared and natural populations. Such comparative approaches could help dissect the varying effects of environment and morphotype, and determine the extent to which phenomena observed in the lab are generalizable to conditions in the field. To this end, we take a transcriptomic approach to compare the Pachón cavefish and their surface fish counterparts in their natural habitats and the lab environment. We identify key changes in expression of genes implicated in metabolism and physiology between groups of fish, suggesting that morphotype (surface or cave) and environment (natural or lab) both alter gene expression. We find gene expression differences between cave and surface fish in their natural habitats are much larger than differences in expression between morphotypes in the lab environment. However, lab-raised cave and surface fish still exhibit numerous gene expression changes, supporting genetically encoded changes in livers of this species. From this, we conclude that a controlled laboratory environment may serve as an ideal setting to study the genetic underpinnings of metabolic and physiological differences between the cavefish and surface fish.


Assuntos
Characidae/metabolismo , Transcriptoma/fisiologia , Adaptação Fisiológica/genética , Adaptação Fisiológica/fisiologia , Animais , Cavernas , Characidae/anatomia & histologia , Characidae/genética , Escuridão , Meio Ambiente , Feminino , Perfilação da Expressão Gênica , Luz , Fígado/anatomia & histologia , Fígado/metabolismo , Alinhamento de Sequência , Análise de Sequência de RNA , Transcriptoma/genética
16.
J Fish Biol ; 96(4): 950-955, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32048289

RESUMO

A new species of Brachychalcinus is described from the Rio Trombetas basin, Brazil. It differs from congeners by possessing a conspicuous rounded second humeral spot. Additionally, our new species differs from Brachychalcinus nummus, B. orbicularis and B. reisi by having a higher number of branched dorsal-fin rays, and from Brachychalcinus parnaibae by having a lower head depth.


Assuntos
Characidae/anatomia & histologia , Characidae/classificação , Nadadeiras de Animais/anatomia & histologia , Animais , Brasil , Cabeça/anatomia & histologia , Rios , Especificidade da Espécie
17.
J Exp Zool B Mol Dev Evol ; 334(7-8): 450-462, 2020 11.
Artigo em Inglês | MEDLINE | ID: mdl-32030873

RESUMO

Life in complete darkness has driven the evolution of a suite of troglobitic features in the blind Mexican cavefish Astyanax mexicanus, such as eye and pigmentation loss. While regressive evolution is a hallmark of obligate cave-dwelling organisms, constructive (or augmented) traits commonly arise as well. The cavefish cranium has undergone extensive changes compared with closely-related surface fish. These alterations are rooted in both cranial bones and surrounding sensory tissues such as enhancements in the gustatory and lateral line systems. Cavefish also harbor numerous cranial bone asymmetries: fluctuating asymmetry of individual bones and directional asymmetry in a dorsal bend of the skull. This asymmetry is mirrored by the asymmetrical patterning of mechanosensory neuromasts. We explored the relationship between facial bones and neuromasts using in vivo fluorescent colabeling and microcomputed tomography. We found an increase in neuromast density within dermal bone boundaries across three distinct populations of cavefish compared to surface-dwelling fish. We also show that eye loss disrupts early neuromast patterning, which in turn impacts the development of dermal bones. While cavefish exhibit alterations in cranial bone and neuromast patterning, each population varied in the severity. This variation may reflect observed differences in behavior across populations. For instance, a bend in the dorsal region of the skull may expose neuromasts to water flow on the opposite side of the face, enhancing sensory input and spatial mapping in the dark.


Assuntos
Evolução Biológica , Characidae/anormalidades , Anormalidades Craniofaciais/veterinária , Animais , Anoftalmia/veterinária , Cavernas , Characidae/anatomia & histologia , Escuridão , Ossos Faciais/anormalidades , Imageamento Tridimensional , Característica Quantitativa Herdável , Crânio/anormalidades , Crânio/anatomia & histologia
18.
J Fish Biol ; 96(4): 868-876, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31995227

RESUMO

Hemigrammus xaveriellus sp. nov. is described from the upper Río Vaupés basin (Amazon basin), Departamento Guaviare, Colombia. It is distinguished from all congeners by the combination of the following characters: presence of a conspicuous, dark, longitudinal midlateral stripe extending along the body; presence of a conspicuous rounded, horizontally elongated humeral blotch anterior to the beginning of the dark midlateral stripe; seven scale rows between the dorsal fin and lateral line (vs. five to six); and five scale rows between the lateral line and pelvic-fin insertion (vs. three to four). The single mature male of He. xaveriellus possessed a well-developed urogenital papilla, an unusual feature among characids. The presence of an enlarged urogenital papilla in the family is discussed, and comments regarding the putative relationships of the new species are presented.


Assuntos
Characidae/anatomia & histologia , Characidae/classificação , Sistema Urogenital/anatomia & histologia , Animais , Brasil , Colômbia , Masculino , Rios , Especificidade da Espécie
19.
J Exp Zool B Mol Dev Evol ; 334(7-8): 438-449, 2020 11.
Artigo em Inglês | MEDLINE | ID: mdl-31930686

RESUMO

Astyanax mexicanus consists of two forms, a sighted surface dwelling form (surface fish) and a blind cave-dwelling form (cavefish). Embryonic eyes are initially formed in cavefish but they are subsequently arrested in growth and degenerate during larval development. Previous lens transplantation studies have shown that the lens plays a central role in cavefish eye loss. However, several lines of evidence suggest that additional factors, such as the retinal pigment epithelium (RPE), which is morphologically altered in cavefish, could also be involved in the eye regression process. To explore the role of the RPE in cavefish eye degeneration, we generated an albino eyed (AE) strain by artificial selection for hybrid individuals with large eyes and a depigmented RPE. The AE strain exhibited an RPE lacking pigment granules and showed reduced expression of the RPE specific enzyme retinol isomerase, allowing eye development to be studied by lens ablation in an RPE background resembling cavefish. We found that lens ablation in the AE strain had stronger negative effects on eye growth than in surface fish, suggesting that an intact RPE is required for normal eye development. We also found that the AE strain develops a cartilaginous sclera lacking boney ossicles, a trait similar to cavefish. Extrapolation of the results to cavefish suggests that the RPE and lens have dual roles in eye degeneration, and that deficiencies in the RPE may be associated with evolutionary changes in scleral ossification.


Assuntos
Characidae/embriologia , Olho/embriologia , Cristalino/embriologia , Epitélio Pigmentado da Retina/embriologia , Animais , Cavernas , Characidae/anatomia & histologia , Characidae/crescimento & desenvolvimento , Olho/crescimento & desenvolvimento , Anormalidades do Olho/embriologia , Feminino , Cristalino/crescimento & desenvolvimento , Masculino , Epitélio Pigmentado da Retina/anatomia & histologia , Epitélio Pigmentado da Retina/crescimento & desenvolvimento
20.
J Exp Zool A Ecol Integr Physiol ; 333(3): 171-180, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-31904195

RESUMO

Together, the complex geological history and climatic diversity of Mesoamerica create a rich source of biodiversity from which evolutionary processes can be studied. Here, we discuss highly divergent morphs of lake-dwelling fishes distributed across Mexico and Central America, originally recognized as members of different genera (Astyanax and "Bramocharax"). Recent phylogenetic studies, however, suggest these morphs group within the same genus and readily hybridize. Despite genetic similarities, Bramocharax morphs exhibit stark differences in cranial shape and dentition. We investigated the evolution of several cranial traits that vary across morphs collected from four lakes in Mexico and Nicaragua and discovered an ecomorphological cline from northern to southern lakes. Northern populations of sympatric morphs exhibit a similar cranial shape and tooth morphology. Southern populations of Bramocharax morphs, however, showed a larger disparity in maxillary teeth, length and frequency of unicuspid teeth, an elongated snout, and a streamlined cranium compared to Astyanax morphs. This divergence of craniofacial morphology likely evolved in association with differences in trophic niches. We discuss the morphological differences across the four lake systems in terms of geological history and trophic dynamics. In summary, our study suggests that Bramocharax morphs are likely locally adapted members derived from independent Astyanax lineages, highlighting an interesting parallel evolutionary pattern within the Astyanax genus.


Assuntos
Characidae/anatomia & histologia , Characidae/classificação , Crânio/anatomia & histologia , Dente/anatomia & histologia , Animais , Ecossistema , Geografia , Lagos , México , Nicarágua , Filogenia
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