Seaward Orientation of Hatchling Turtles: Turning Systems in the Optic Tectum

Mrosovsky, N.; Granda, A.M.; Hay, Thomas C.

doi:10.1159/000121837

Cited by 11 publications

(2 citation statements)

References 7 publications

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“…This G16 was found very near the linear visual streak. (Bass et al, 1973;Bass, 1977;Mrosovsky et al, 1979). Topographical maps of the retinal surface (Peterson, 1978), of auditory space (Jay & Sparks, 1982), and of cutaneous receptors (Stein & Gaither, 1981) are found in the optic tectum, as well as afferents from muscle receptors (Abrahams & Rose, 1975) and from vestibular nuclei (Maeda et al, 1979).…”

Section: Optic Tectum Function and Topographical Mapsmentioning

confidence: 99%

Ganglion cell types of the turtle retina that project to the optic tectum: Intracellular HRP injections of retrogradely, rhodamine-marked cell bodies

Guiloff

Kolb

1992

Vis Neurosci

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The turtle retina has been shown to have a variety of different morphological ganglion cell types as well as distinct physiological ganglion cell types. The major projection of the retina to the brain in nonmammalian vertebrates is to the optic tectum. In this study, we address the question of which retinal ganglion cell types project to the optic tectum in the turtle.Fluorescent rhodamine-labeled microspheres were used to trace the retinal ganglion cell projection to the superficial layers of the optic tectum. The fluorescent ganglion cell somata, retrogradely marked by transport from the contralateral optic tectum, were impaled with micropipettes containing rhodamine-horseradish peroxidase solution and this dye was iontophoresed into the cells under visual control.Most of the morphological ganglion cell types described in Golgi studies (Kolb, 1982;Kolb et al., 1988) were stained. Thus, the small cell types G l , G2, G3, G5, G6, and G7; the medium-sized types G10, G i l , G12, G13, and G14; and the large-sized types G15, G16, G19, G20, and G21 project to the optic tectum in the turtle. We have added a new type, G2a, which proves to have some differences from the original G2 in branching pattern. We were unable to stain the small type G4, the medium-sized types G8 and G9, and the large cell types G17 and G18; this suggests that they might not project to the superficial layers of the dorsolateral optic tectum, at least, in the turtle.

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Section: Optic Tectum Function and Topographical Mapsmentioning

confidence: 99%

Ganglion cell types of the turtle retina that project to the optic tectum: Intracellular HRP injections of retrogradely, rhodamine-marked cell bodies

Guiloff

Kolb

1992

Vis Neurosci

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“…Experiments where parts of the visual field are occluded or stimulated give some support to this proposal [Mrosovsky and Shettleworth. 1974;Mrosovsky et al, 1979;Kingsmill, 1980]. However, while this modification of a simple phototropotactic system allows for circling toward a covered eye in individu als having a particularly strong contrala teral turning system, it does not account for the temporal aspects of this pheno menon.…”

mentioning

confidence: 99%

Sea-Finding Behaviour of Loggerhead Hatchlings: The Time Course of Transient Circling Following Unilateral and Asynchronous Bilateral Blindfolding

Kingsmill¹,

Mrosovsky²

1982

Brain Behav Evol

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Marine turtle hatchlings orient seaward by responding to photic cues that guide them toward the brightest horizon. Earlier research has suggested that they have a positive phototropotactic reaction to light but the behaviour must be more complex than this because circling both toward the uncovered and the covered eye has been observed in unilaterally blindfolded turtles. The present work resolved some of these problems by studying circling direction as a function of how long one eye had been covered prior to testing. Different groups of neonate loggerhead turtles (Caretta caretta) were tested from 10 s to 19 h after the application of a unilateral blindfold. The longer this had been on, the less the turtle circled, but beyond 1 h further changes were slight. Initially, circling was predominantly toward the uncovered eye but after the blindfold had been on for 1 h circling toward the covered eye occurred equally often.The time course of circling was also examined in asynchronously, bilaterally blind-folded turtles. One eye was covered 6 h before the other, and tests were made at various times after the second eye had been covered. Asynchronous bilateral blindfolding caused more intense circling and disrupted seaward orientation more severely than unilateral blindfolding. The time course of the decline in circling showed similarities between both treatments, suggesting that they were activating the same mechanism. Dark adaptation was examined as a possible explanation of such transient turning tendencies and previous models of sea-finding were elaborated.

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Tectoreticular pathways in the turtle, Pseudemys scripta. I. Morphology of tectoreticular axons

Sereno

Ulinski

1985

J of Comparative Neurology

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Tectoreticular projections in turtles were examined by reconstructing from serial sections axons that were anterogradely filled with horseradish peroxidase after tectal injections. Three tectoreticular pathways each contain extensively collateralized axons. The crossed dorsal pathway (TBd) contains large and small caliber axons. After leaving the tectum, TBd axons emit collaterals into the ipsilateral profundus mesencephali rostralis and then give off a main rostral branch that bears secondary collaterals in the ipsilateral interstitial nucleus of the medial longitudinal fasciculus and the suprapeduncular nucleus. The main trunks cross the midline and descend in the predorsal bundle, generating collaterals at regular intervals. These terminate mostly in the medial half of the reticular core from the midbrain to the caudal medulla. Axons in the uncrossed intermediate pathway also emit collaterals into a midbrain reticular nucleus (profundus mesencephali caudalis) and often have a thick rostral branch. The main caudal trunks, however, remain ipsilateral and travel in a diffuse, laterally placed tract, where each emits a long series of collaterals into the lateral half of the reticular core. The uncrossed ventral pathway (TBv) contains medium and small caliber axons. TBv axons often have collaterals within the tectum and apparently lack main rostral branches. Their caudal trunks run in the tegmental neuropile below the TBi where they collateralize less exuberantly than do TBd and TBi axons. The morphology of axons in all three pathways suggests that projections from disjunct tectal loci converge at many rostrocaudal levels within the reticular formation. This point was examined explicitly in experiments in which two disjunct injections were placed in one tectal lobe. Intermediate pathway axons traced from the two loci initially formed two distinct bundles but then intermingled in the reticular formation.

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Seaward Orientation of Hatchling Turtles: Turning Systems in the Optic Tectum

Cited by 11 publications

References 7 publications

Ganglion cell types of the turtle retina that project to the optic tectum: Intracellular HRP injections of retrogradely, rhodamine-marked cell bodies

Ganglion cell types of the turtle retina that project to the optic tectum: Intracellular HRP injections of retrogradely, rhodamine-marked cell bodies

Sea-Finding Behaviour of Loggerhead Hatchlings: The Time Course of Transient Circling Following Unilateral and Asynchronous Bilateral Blindfolding

Tectoreticular pathways in the turtle, Pseudemys scripta. I. Morphology of tectoreticular axons

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