[Histology and morphometry of the in the freshwater Paracheirodon axelrodi (Characiformes: Characidae)]. 2009

Mario O Tovar, and Martha J Obando, and Edwin Gómez, and María L Caldas, and Hernán Hurtado
Facultad de Ciencias Básicas, Universidad Militar Nueva Granada, Colombia. mario.tovar@unimilitar.edu.co

The visual system of Teleost fishes has a wide range of adaptations. The eye has suffered modifications, mainly towards better sensitivity and visual resolution according to specific environmental conditions. In that way, this organ is so important for survival. In spite of being the most commercialized Orinoquia species, and one of the most important ornamental fish worldwide, there are almost no studies on the communication systems of P. axelrodi (including vision). We studied the eye in ten individuals of P. axelrodi, with a mean total length of 2.7 cm (SD = 0.2, n = 20). We measured eye relative size (TRO) after sacrifice. Heads were processed for hematoxylin-eosin, and 8 microm thick sections were obtained. Images were digitalized for histological identification and morphometrics. The relation between TRO and body length was 9.8% (SD= 1.1, n= 20); lens was spherical with a relative size of 64.3% (SD = 4.9, n = 20). Rete mirabilis choroid was composed mainly by capillaries, while sclera was composed of cartilaginous tissue. Retina with eight layers and two membranes. An areae centrales was observed in the posterior retina. Iris covered by a simple cubic epithelium. Cornea of endotelial tissue with two membranes. Pupil almost circular, with a naso-caudal elongation. Measures of retina thickness were as follows: lateral retina 144.5 microm (SD = 5.4, n = 20), temporal retina 210.4 microm (SD = 14.8, n = 20). Lens measurements were: dorso-ventral 759.6 microm (SD = 31.7, n = 20), antero-posterior 763.4 microm (SD = 30.7, n = 20). Cornea thickness was 27.6 microm (SD = 4.3, n = 20); iris thickness was 18.9 microm (SD = 1.9, n = 20); rete mirabilis choroid 22.2 microm (SD = 3.2, n = 20) and sclera: 15.9 microm (SD = 1.2, n = 20). This species has a typical Teleost eye conformation. The retina was thicker in the posterior area, probably related to the presence of neuron groups. This modification allows for a better sharpness and visual resolution. The TRO, areae centrales in the retina, and thin cornea, suggests the need of a well developed visual system resulting from a predatory diet.

UI MeSH Term Description Entries
D005123 Eye The organ of sight constituting a pair of globular organs made up of a three-layered roughly spherical structure specialized for receiving and responding to light. Eyes
D005399 Fishes A group of cold-blooded, aquatic vertebrates having gills, fins, a cartilaginous or bony endoskeleton, and elongated bodies covered with scales.
D005618 Fresh Water Water containing no significant amounts of salts, such as water from RIVERS and LAKES. Freshwater,Fresh Waters,Freshwaters,Water, Fresh,Waters, Fresh
D000222 Adaptation, Physiological The non-genetic biological changes of an organism in response to challenges in its ENVIRONMENT. Adaptation, Physiologic,Adaptations, Physiologic,Adaptations, Physiological,Adaptive Plasticity,Phenotypic Plasticity,Physiological Adaptation,Physiologic Adaptation,Physiologic Adaptations,Physiological Adaptations,Plasticity, Adaptive,Plasticity, Phenotypic
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D017753 Ecosystem A functional system which includes the organisms of a natural community together with their environment. (McGraw Hill Dictionary of Scientific and Technical Terms, 4th ed) Ecosystems,Biome,Ecologic System,Ecologic Systems,Ecological System,Habitat,Niche, Ecological,System, Ecological,Systems, Ecological,Biomes,Ecological Niche,Ecological Systems,Habitats,System, Ecologic,Systems, Ecologic

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