Light microscopic studies on the pineal organ in teleost fishes with special regard to its function

Abstract

A morphohistological study was carried out on the pineal organ in 15 species of teleosts belonging to 12 different families. In spite of a general similarity in pineal structure in different species, there is evident a systematic diversity. The majority of species possess saccular pineal organs containing photoreceptors as prominent parenchymal components. The close anatomical relationship of the pineal organs with the relatively thin cranial roof further supports the photosensory nature of this organ in most species. However, in certain species, particularly Corydoras aneus, apparent paucity of sensory cell outer segments, parenchymal proliferation, epithelial compactness and rich vascularization suggest specializations for a predominantly nonsensory and possibly secretory function. On the other hand, the preponderance of sensory cells in the pineal organ of Symphysodon aequifasciatus and Gyrinocheilus aymoneri indicates exceptional adaptations for a predominantly photosensory role. The results are discussed in the light of existing electron microscopic and biochemical investigations which support a secretory function of fish pineal. The need for proper selection of species for future research on pineal function is emphasized.There is also evident a close anatomical relationship between the pineal organ, the dorsal sac and the third ventricle in various species. The possibility of intramural functional relationship of the pineal with these structures and the brain is suggested.The presence of intrapineal neurones and an afferent (pinealofugal) innervation in majority of species is described. The tractus pinealis enters the posterior commissure area. In rainbow trout, Salmo gairdneri, some branches, right and left, leave the posterior commissure and could be seen to move toward the habenular ganglia. Their destination remains unclear. In jack smelt, Atherinopsis californiensis, a major bundle of tract fibres follows the ventral aspect of the posterior commissure reaching what may be nuclei dorsomedialis-dorsolateralis. The possibility of direct connections with the fasciculus retroflexus is suggested. No evidence could be provided supporting existence of an efferent (pinealopetal) innervation of parenchymal cells in the pineal of species studied. It is pointed out that clarification of this aspect in future is important for a proper understanding of metabolic aspects of pineal organs in fishes.The functional status of pineal organ in fishes has been a subject of intensive research and review, yet little understanding of its physiology has so far been achieved. There is general agreement that in fishes it is photosensory in function (reviews by Tilney and Warren, '19; Gladstone and Wakeley, '40; Kelly, '62; U. Holmgren, '59, '65; Van De Kamer, '65 In spite of the above information our knowledge nf comparative aspects of pineal structure and innervation is still limited and consequently generalizations concerning pineal physiology may not be necessarily valid. The present report on the morphohistology of t...

Afferent and Efferent Connections of the Pineal Organ in the European Sea Bass <i>Dicentrarchus labrax:</i> A Carbocyanine Dye Tract-Tracing Study

“…The first evidence of the pineal efferent tract was reported by Holmgren [1918] and then by Hafeez [1971], who employed methylene blue staining and a silver impregnation method, respectively. More recently, several authors have investigated pineal neural pathways in many species using cobalt chloride iontophoresis [Hafeez and Zerihun, 1974] or horseradish peroxidase tracing methods [Ekström andvan Veen, 1983, 1984;Ekström and Korf, 1986;Puzdrowski and Northcutt, 1989;Jiménez et al, 1995].…”

Ultrastructural study of the cellular types in the pineal organ of gambusia affinis (teleost)

“…This fact, in addition to the existence of a "pineal window," seems to suggest a possible photoreceptor function for the pineal gland of this teleost (Hafeez, 1971). In that there are no ultrastructural studies on the pineal organ of Gambusia affinis, we have studied its fine structure.…”

L'organe pinéal du Brochet (Esox lucius, L.). I. Etude anatomique et cytologique

“…Les études morphologiques effectuées sur l'épiphyse des Poissons Téléostéens ont conduit, très tôt, les auteurs à suggérer les adaptations de l'organe à la photorécep-tion (Studnicka, 1905 ;Hafeez et Ford, 1967 ;Omura et Hafeez, 1971). Les recherches ultrastructurales corroborent les données anatomiques (Salmo : Breuc-ker et Horstmann, 1965 ;Hartwig et Pfautsch, 1973 ; Mugil : Rüdeberg, 1966 ; Uranoscopus : Rüdeberg, 1966 ; Sardina : Rüdeberg, 1968 ;Phoxinus : Oksche et Kirschstein, 1967Kirschstein, , 1971Carassius : Takahashi, 1969 ; Scyliorhinus : Rüdeberg, 1969 ; Plecoglossus : Omura et Oguri, 1971 ;Esox : Owman et Rüdeberg, 1970; Anguilla et Lebistes : Rüdeberg,1971 ; Poecillia : Omura et Oguri,1971 ;Thunnus : Murphy, 1971 ;Pterophyllum : Bergmann, 1971 ; Oryzias : Takahashi et Kasuga, 1971 ;Urasaki, 1976a ; Astyanax : Omura, 1975 ;Herwig, 1976 Dodt, 1963 ;Morita, 1966 ;Tabata et al, 1975 ;Salmo, Plecoglossus, Mugil, Pelteo6agrus : Hanyu et al, 1969 ;Hanyu et Niwa, 1970 ; Pterophyllum : Morita et Bergmann, 1971).…”

“…Contrairement à Owman et Rüdeberg (1970) (Rüdeberg, 1970 ;Hafeez, 1971 ;McNulty, 1976 ; McNulty et Nafpaktitis, 1976) (Falcon, 1979 ;Falcon et Mocquard, 1979 Rüdeberg, 1970), une intense activité de synthèse. Comme chez Astyanax (Omura, 1975 ;Herwig, 1976) (Takahashi, 1969), Phoxinus (Oksche et Kirschstein, 1971) et Astyanax (Omura, 1975 ;Herwig, 1976) Rüdeberg, 1970, chez Esox), présentent de grandes analogies avec certaines cellules de l'organe pinéal de Scyliorhinus (Rüdeberg, 1969) Diemictylus (Flight, 1973) ?…”