Afferents of the Frontal Cortex in the Echidna (&lt;i&gt;Tachyglossus aculeatu&lt;/i&gt;&lt;i&gt;s&lt;/i&gt;). Indication of an Outstandingly Large Prefontal Area

Divac, Ivan; Holst, M.-C.; Nelson, Jessica C.; McKenzie, Jo

doi:10.1159/000118653

Cited by 32 publications

(17 citation statements)

References 37 publications

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“…Divac et al [1987] had been unable to identify a claustrum in the echidna brain in Nissl stained material and did not find any retrogradely labeled cells in the region following injections into the frontal cortex. More recently, Butler et al [2002] re-examined this issue in both echidna and platypus brain and concluded that there was no cytoarchitectonically distinct claustrum in either brain.…”

Section: Developmental and Evolutionary Significance Of The Presence mentioning

confidence: 96%

“…Their figure 3 shows only a small, medial portion of an anterior part of the piriform lobe, although a pale region in the top edge of their figure 3D may represent the rostral part of insular claustrum. Thirdly, the unusual white matter topography of monotremes, due mainly to the large anterior commissure and its attendant commissural fiber bundles, may have made the identification of the insular claustrum difficult for previous authors [Divac et al, 1987;Butler et al, 2002]. The putative insular claustrum in the echidna is embedded in commissural fiber bundles approaching and leaving the anterior commissure.…”

Section: Developmental and Evolutionary Significance Of The Presence mentioning

confidence: 99%

“…Past [Abbie, 1940] and more recent studies [Divac et al, 1987;Butler et al, 2002] have suggested that the claustrum is missing from the brains of living monotremes (the Australian short beaked echidna -Tachyglossus aculeatus and the platypus -Ornithorhynchus anatinus). The typical laminar structure of mammalian isocortex is well developed in monotremes.…”

Section: Introductionmentioning

confidence: 99%

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The Claustrum Is Not Missing from All Monotreme Brains

2004

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Many authors have reported that the claustrum, which comprises the insular claustrum and the endopiriform nucleus, is missing from the monotreme forebrain. We used Nissl and myelin staining in conjunction with enzyme histochemistry for acetylcholinesterase and immunohistochemistry for parvalbumin, calbindin, calretinin and tyrosine hydroxylase to examine the brains of two monotremes, the short-beaked echidna (Tachyglossus aculeatus) and the platypus (Ornithorhynchus anatinus). We found that although the insular claustrum is a small structure in the echidna brain, it is nevertheless clearly present as loosely clustered neurons embedded in the white matter ventrolateral to the putamen and deep to the piriform and entorhinal cortices. Neurons in this region share the chemical features of the adjacent cortex (presence of a similar proportion of parvalbumin immunoreactive neurons and minimal activity for acetylcholinesterase and tyrosine hydroxylase), unlike the adjacent putamen and ventral pallidum. A putative endopiriform nucleus can be identified in the interior of the piriform lobe of the echidna as calretinin immunoreactive neurons embedded within the white matter. The situation is much less clear in the platypus, but our data suggest that there may be an insular claustrum deep to frontal cortex, separated from layer VI by only a thin layer of white matter. We could not identify an endopiriform nucleus in our platypus material. Our findings indicate that presence of the claustrum cannot be considered a feature confined to therian mammals and lend weight to arguments that this structure was present in the ancestral mammalian brain.

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Section: Developmental and Evolutionary Significance Of The Presence mentioning

confidence: 96%

Section: Developmental and Evolutionary Significance Of The Presence mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The Claustrum Is Not Missing from All Monotreme Brains

2004

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“…For example, the human 'record' of 33% of the neocortical area occupied by the prefrontal cortical area, is well surpassed by an egg-laying mammal (the echidna, Tachyglossus aculeatus), for which the corresponding figure is 50% (e.g. Divac et al 1987). Also, birds lack a neocortex as a distinct brain area but they show convincing signs of pain, for example, selecting feed with pain killers under circumstances that would be experienced as painful by humans (Gentle 1992, Danbury et al 2000).…”

Section: Physiological Indications Of Sentience In Fishesmentioning

confidence: 99%

Expanding the moral circle: farmed fish as objects of moral concern

Lund¹,

Mejdell²,

Röcklinsberg³

et al. 2007

Dis. Aquat. Org.

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Until recently fish welfare attracted little attention, but international and national legislation and standards of fish welfare are now emerging and an overview of these developments is presented in this study. Whereas animal welfare legislation is based on public morality, animal ethics does not automatically accept public morality as normative and elaborates arguments regarding the way humans should treat animals (referred to as moral standards). In this study we present the most common animal ethics theories. For most of these, sentience is considered a demarcation line for moral concern: if an animal is sentient, then it should be included in the moral circle, i.e. receive moral consideration in its own right and some basic welfare should be ensured. As for fish, research has revealed that the sensory system of teleosts can detect noxious stimuli, and that some kind of phenomenal consciousness, allowing the fish to feel pain, seems to be present. This raises the ethical question as to how much evidence we need in order to act on such indications of fish sentience. A simple risk analysis shows that the probability that fishes can feel pain is not negligible and that if they do indeed experience pain the consequences in terms of the number of suffering individuals are great. We conclude that farmed fish should be given the benefit of the doubt and we should make efforts that their welfare needs are met as well as possible. Finally, the way forward is briefly discussed: efforts must be made to understand what fish welfare means in practical fish farming. This will involve the development of research and education, greater accountability and transparency, compliance with and control of policies, and quality assurance schemes.

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“…Many aspects of echidna neurobiologye.g. their high degree of cortical gyrification, enlarged pre frontal cortex, and apparent absence of SI1 [Pirlot and Nel son, 1978;Divac et al, 1987; Krubitzeret a!., 1995] -point to a peculiar, yet highly advanced central nervous system organisation. Indeed, the proportion of brain volume occu pied by the cerebral cortex in Tachyglossus (43%) is similar to that in eutheria mammals such as prosimians (54%) [Pir lot and Nelson, 1978].…”

Section: Introductionmentioning

confidence: 99%

Cyto- and Myeloarchitectonic Organisation of the Spinal Cord of an Echidna (Tachyglossus aculeatus)

Ashwell¹,

Zhang²

1997

Brain Behav Evol

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We have studied the cyto- and myeloarchitectural organisation of the spinal cord of an echidna (Tachyglossus aculeatus) with the aid of Nissl staining, darkfield examination and p-phenylenediamine staining. We have also examined the distribution of unmyelinated afferents by labelling with a peroxidase-conjugated lectin derived from Griffonia simplicifolia (B₄ isolectin). The cytoarchitectural features characterising the laminar organisation of the spinal cord in eutherian mammals were broadly applicable to the spinal cord of this monotreme. In addition, we identified a distinct group of large neurons in the ventral part of lamina X, extending into the ventral funiculus, that we have called the median nuclear group. We were unable to identify a central cervical nucleus in this echidna on the basis of cytoarchitectural criteria, although all other spinal cord nuclei found in eutherians could be found in this monotreme. Lectin labelling with the Griffonia simplicifolia isolectin B₄ revealed a subpopulation of dorsal root ganglion cells similar to those labelled in Eutheria. In this echidna, labelling of unmyelinated fibres was found in Lissauer''s zone and laminae I and II, as seen in rats (Rattus norvegicus); there were also deeper patches extending into laminae III to V and what appeared to be commissural axons approaching the dorsal grey commissure, which have not been seen in Eutheria. Fibre calibre in the dorsal and ventral roots of this echidna was similar to that reported in Eutheria, suggesting similar proportions of afferent fibre classes and α and γ motoneurons. In the echidna, mean diameter of myelinated dorsal root axons was 4.65 µm at T₁ and 5.22 µm at L₃, with a clear bimodal distribution in the L₃ dorsal root showing distinct groups at 1 to 5 µm and 6 to 12 µm. These made up approximately 45 and 55% of the total myelinated axon population, respectively. Myelinated fibres in the ventral root at L₃ showed two major peaks in distribution. These were at 1 to 4 µm (approximately 32% of the total myelinated fibre population) and at 7 to 14 µm (approximately 58% of the total myelinated fibre population). The cross-sectional area of the dorsal columns of this monotreme was comparable to that of a eutherian mammal of similar body weight, and myelinated axon calibre was similar to that seen in the domestic cat. Our findings indicated that spinal cord cytoarchitectural organisation is highly conserved across class Mammalia, although the lectin labelling findings suggested that termination of unmyelinated afferents in echidnas may differ from that found in Eutheria. The dorsal column system appears to be as anatomically well developed in this monotreme as in those eutherian mammals considered to have a pronounced discriminative tactile sense.

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Afferents of the Frontal Cortex in the Echidna (<i>Tachyglossus aculeatu</i><i>s</i>). Indication of an Outstandingly Large Prefontal Area

Cited by 32 publications

References 37 publications

The Claustrum Is Not Missing from All Monotreme Brains

The Claustrum Is Not Missing from All Monotreme Brains

Expanding the moral circle: farmed fish as objects of moral concern

Cyto- and Myeloarchitectonic Organisation of the Spinal Cord of an Echidna (Tachyglossus aculeatus)

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