Ken J. Sanderson

Heavy metal toxicity of kidney and bone tissues in South Australian adult bottlenose dolphins (Tursiops aduncus).

Metallothioneins (MT) concentration, renal damage, and bone malformations were investigated in 38 adult Tursiops aduncus carcasses to determine any associations with cadmium, copper, zinc, mercury, lead and selenium. Significantly higher concentrations of cadmium, copper, and zinc in the liver were observed in dolphins showing evidence of more advanced renal damage. No significant differences in metal or selenium concentrations in the liver were observed between groups differing in level of bone malformations. Some dolphins displayed evidence of toxicity and knowledge of metal toxicity pathways were used to elucidate the cause of these abnormalities. Two dolphins had high metal burdens, high MT concentrations, renal damage, and evidence of bone malformations, indicating possible severe and prolonged metal toxicity. One dolphin showed evidence of renal damage, but the lack of any other symptoms suggests that this was unlikely to be caused by metal toxicity. We recommend examining a range of metal toxicity symptoms simultaneously to aid in distinguishing metal toxicity from unrelated aetiologies.

Postnatal development of retinal projections in the brushtailed possum, Trichosurus vulpecula.

The postnatal development of retinal projections was studied in the brushtailed possum, Trichosurus vulpecula. [3H]proline was injected into one eye of 13 young possums aged 24-84 days in order to trace retinal pathways. The dorsal lateral geniculate nucleus (LGNd) can be identified in Nissl material at 19 days but not at 9-10 days. By 40 days some cytoarchitectural lamination of the LGNd is apparent and by 71 days the adult pattern of cell layers is present. At 24 days retinal fibers occupy by lateral part of the LGNd on both sides of the brain. By 38-40 days the retinal fibers fill be contralateral LGNd and the binocular part of the ipsilateral LGNd and there is a beginning of the segregation of retinal fibers into left and right eye territories. By 49-50 days a partial segregation is achieved, and complete segregation by 71 days. At 9-10 days the superior colliculus is not differentiated into layers and there is a thick zone of cell proliferation around the ventricle. By 23 days the superior colliculus has well-defined cell layers and there is still some indication of cell proliferation around the ventricle. By 40 days, the superior colliculus shows little evidence of cell proliferation. At 24 days retinal fibers fill the superficial layers of the contralateral optic tectum and are lightly distributed through the superficial layers of the rostral half of the ipsilateral tectum. By 38 days the ipsilateral retinal input is restricted to the deeper layers of the tectum. These results show that the adult pattern of retinal projections to the LGNd and optic tectum develops a number of weeks before eye opening occurs (at 90-120 days).

Perception of terrestrial and aerial alarm calls by honeyeaters and falcons

This study tested the responses to aerial and terrestrial alarm and distress calls in an avian predator, the brown falcon, Falco berigora, and two potential avian prey species, the New Holland honeyeater, Philidonyris novaehollandiae, and noisy miner, Manorina melanocephala. Calls were delivered from a computer system at intensities 5–20 dB above background, to birds held in large cages. All birds located the broad-band alarm and distress calls easily, but they had difficulty locating the narrow-band aerial alarm calls, although they were able to detect most of these. Aerial alarm calls thus reduce risk to the caller. The performance of raptors and songbirds was similar. This result suggests that there are no reliable differences in the auditory characteristics of avian predators and prey, as have been described in species from the Northern Hemisphere.

Primary Visual Cortex in the Brushtailed Possum: Receptive Field Properties and Corticocortical Connections

The corticocortical connections and receptive field properties of primary or striate visual cortex of the brushtailed possum, Trichosurus vulpecula, have been examined. In this Australian marsupial species primary visual cortex has connections with four other visual areas in the occipital lobe. In these adjacent visual areas fibers from striate cortex terminate mainly in layers 3 and 4 and in some cases also in layers 1 and 2. In all four areas return connections to striate cortex originate predominantly in layers 2 and 3, and to a much lesser extent in layers 5 and 6. Interhemispheric connections of striate cortex are limited to the boundary of striate and peristriate cortex. In addition to its cortical connections, striate cortex makes reciprocal connections with the claustrum. Most neurons in striate cortex are highly binocular. Of our sample of 113 visually responsive neurons, only 30% were orientation selective. On the basis of these observations we have compared striate cortex of the marsupial brushtailed possum with striate cortices of the American marsupial opossum and those of placental mammals.

A Comparative Analysis of Distress Call Structure in Australian Passerine and Non-Passerine Species: Influence of Size and Phylogeny

Distress vocalisations were recorded from 65 species of Australian birds, including passerines, parrots and raptors while held in the hand or entangled in mistnets. Distress vocalisations were shown to have similar structural properties in many species: a noisy and/or harmonic structure with a wide frequency range. The finding that distress calls from a range of Australian species have similar physical characteristics that appear to be convergent fits well with Marlers (1955, 1957) classic analyses of mobbing and aerial alarm calls in a variety of European passerines. The spectral structure and high amplitude of distress vocalisations also demonstrate that they are designed for ease of location and effective transmission over long distances. Incidence and rate of calling showed both intraspecific and interspecific variation, with a higher proportion of larger species calling more often. There were significant relationships found between mass and various distress call parameters; larger birds produced louder distress calls which were longer in duration with lower minimum and dominant frequencies.

Metabolic Rates Associated with Distress and Begging Calls in Birds

Rates of oxygen consumption during begging behaviour in nestlings of seven species and distress call behaviour in adults of eight species of Australian birds were measured. A transparent mask coupled to an open‐flow respirometry system was used, and calling was elicited by the presentation of food or by the perceived threat of a predator. Distress calling significantly increased oxygen consumption above the measured resting levels in six of the species of birds tested. The factorial increase in oxygen consumption during distress calling was independent of body mass. In most cases, begging behaviour in juvenile birds caused a significant increase in metabolic rate, with some individuals showing factorial increases over fourfold. There was a significant negative correlation between body mass and the factorial cost of begging behaviour.

The Vocal Repertoires of Six Honeyeater (Meliphagidae) Species from Adelaide, South Australia

Honeyeaters (Meliphagidae) are prominent members of the avifauna in Australia, typically with four to five resident species in any area. We recorded vocalisations from six species resident around Adelaide in South Australia: the Red Wattlebird Anthochaera carunculata, Little Wattlebird Anthochaera chrysoptera, Noisy Miner Manorina melanocephala, White-plumed Honeyeater Lichenostomus penicillatus, New Holland Honeyeater Phylidonyris novaehollandiae and Crescent Honeyeater Phylidonyris pyrrhoptera. The larger honeyeaters (Red and Little Wattlebird) produced characteristically harsh vocalisations covering a wide range of frequencies. Crescent and White-plumed Honeyeaters had a varied and complex repertoire of calls and songs which were quite musical in nature. Noisy Miners and New Holland Honeyeaters produced vocalisations dominated by simple single note whistles. Each species had specific vocalisations emitted in different contexts: alarm, distress, begging and contact calls as well as song. Alarm and distress calls of the six species had common characteristics and typically induced responses from other honeyeater species.

Retinogeniculate Patterns in Diprotodont Marsupials

The pattern of retinogeniculate connections has been examined in a range of diprotodont marsupials, including wallabies, possums, forest wombat and koala. The lateral geniculate nucleus (LGd) in most species has alternating bands of ipsilateral and contralateral retinal terminal fields, with considerable interspecific variability. The number of terminal bands of retinogeniculate input varies from eight to eleven in most species, with little binocular overlap. By contrast in one species, the feather-tailed glider, the most significant feature of LGd organisation is binocular overlap. No relationship is apparent between LGd organisation and the life-style of the animals.

Transneuronal transport of tritiated fucose and proline in the visual pathways of the brushtailed possum, Trichosurus vulpecula

Abstract Tritiated fucose and proline after injection into one eye are transported transneuronally to the primary visual cortex in the brushtailed possum Trichosurus vulpecula . On the contralateral side in layer IV a continuous band of label extends throughout primary visual cortex. On the ipsilateral side in layer IV a lighter band of label extends through the binocular part of the visual cortex. Ocular dominance columns cannot be demonstrated in Trichosurus visual cortex using these methods.

Neurogenesis in a Marsupial: The Brush-Tailed Possum (Trichosurus vulpecula)

The times of origin of neurons in the visual and auditory systems were studied in a marsupial, the brush-tailed possum, using tritiated thymidine autoradiography. Within the subcortical visual pathways, most neurons are generated between postnatal days 5 and 21, and the neurons of the primary visual cortex up to postnatal day 68. In the subcortical auditory pathways, most neurons are generated between postnatal days 5 and 28, and all auditory cortex neurons have appeared by postnatal day 46. Neurons in a single layer of cerebral cortex are generated during a period of about 2 weeks. Thus cortical neurogenesis in marsupials extends over a period similar to that seen in primates.