The pineal complex: a morphological and immunohistochemical comparison between a tropical (Paracheirodon axelrodi) and a subtropical (Aphyocharax anisitsi) characid species.

LAURA RINCÓN CAMACHO; LEONEL MORANDINI; AGUSTINA BIRBA; LUCIANO CAVALLINO; FELIPE ALONSO; FABIANA LO NOSTRO; MATIAS PANDOLFI

JOURNAL OF MORPHOLOGY

WILEY-LISS, DIV JOHN WILEY & SONS INC

Lugar: New York; Año: 2016

0362-2525

Cardinal tetra Paracheirodon axelrodi and bloodfin tetra Aphyocharax anisitsi are two species of characins characids with high trade value as ornamental fish in South America. Although both species inhabit middle water layers, cardinal neon exhibits a tropical distribution and bloodfin tetra a subtropical one. In this work, we carried out an anatomical, histological and immunohistochemical study of the pineal complex of P. axelrodi and A. anisitsi, in order to better understand the pineal morphology. In both species, the pineal complex consisted of three components, the pineal and parapineal organs, and the dorsal sac (DS). The pineal organ was in turn composed of a short, thin pineal stalk (PS), vertically disposed with respect to the upper surface of the telencephalon, and a pineal vesicle (PV), located at the distal end of the PS and attached to the skull by connective tissue. The pineal window (PW), translucent at the dorsal surface of the skull, is the spot where the luminal information access the pineal organ. In the epidermis of P. axelrodi?s PW, club cells (known to be associated with the release of alarm substances) were identified, but were not observed in the epidermis of A. anisitsi?s PW. With respect to the DS, it appeared to be folded on itself, and was bigger and more folded in A. anisitsi than in P. axelrodi. Immunohistochemical assays revealed the presence of cone opsin-like and rod opsin-like photoreceptor cells in the PS and PV. These results provide a first insight into the morphological assembly of the pineal complex of both species, and contribute to a better understanding of the integration and transduction of light stimuli in characids.