An update on the physiology of two- and three-toed sloths

Physiological and pharmacological research undertaken on sloths during the past 30 years is comprehensively reviewed. This includes the numerous studies carried out upon the respiratory and cardiovascular systems, anesthesia, blood chemistry, neuromuscular responses, the brain and spinal cord, vision, sleeping and waking, water balance and kidney function and reproduction. Similarities and differences between the physiology of sloths and that of other mammals are discussed in detail.

Xenarthra; sloths; Bradypus; Choloepus; physiology

Authorship

D.P. Gilmore

University of Glasgow, Institute of Biomedical and Life Sciences, Glasgow, UKUniversity of GlasgowUKGlasgow, UKUniversity of Glasgow, Institute of Biomedical and Life Sciences, Glasgow, UK

C.P. Da-Costa

Universidade Federal de Pernambuco, Departamento de Fisiologia e Farmacologia, Recife, PE, BrasilUniversidade Federal de PernambucoBrasilRecife, PE, BrasilUniversidade Federal de Pernambuco, Departamento de Fisiologia e Farmacologia, Recife, PE, Brasil

D.P.F. Duarte

SCIMAGO INSTITUTIONS RANKINGS

University of Glasgow, Institute of Biomedical and Life Sciences, Glasgow, UKUniversity of GlasgowUKGlasgow, UKUniversity of Glasgow, Institute of Biomedical and Life Sciences, Glasgow, UK

Figures

Figures (5)

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Figure 1
- Distribution of two- and three-toed sloths throughout Central and South America (A, B) (for further details see Wetzel (3)).

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Figure 2
- Changes in arterial blood pressure (BP) in Bradypus variegatus in response to the approach of a human. A, A slight rise and B, a fall.

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Figure 3
- Distribution of ganglion cell densities in the right retina of a three-toed sloth Bradypus variegatus (A) and of a two-toed sloth Choloepus didactylus (B). Numbers next to each isodensity line represent cells/mm² divided by 1000. The cross marks the position of the optic disc. Note the different position of the region of maximum cell density (area centralis) between the sloth species. In both instances the presence of a visual streak in the retina is indicated by the elongated contours of the isodensity lines representing intermediate densities around the area centralis, this being 0.8 x 10³ in Bradypus variegatus and 0.4 x 10³ in Choloepus didactylus.

Thumbnail

Figure 4
- Distribution of ganglion cell diameters in two different quadrants of the retina in Bradypus variegatus (A) and Choloepus didactylus (B). The relative frequency was obtained by subtracting the number of cells in the inferior temporal retina (IT) of the area centralis in Bradypus variegatus and in the superior temporal retina (ST) of Choloepus didactylus from the regions of lowest cell density in the superior nasal retina (SN) of both species. An excess of cells for each region of the area centralis over the nasal temporal retina is indicated by the portion of the histogram above the 0% line and the excess of cells for each region of the superior nasal retina over the inferior temporal retina is indicated by the portion of the histogram below the 0% line. C is a histogram obtained by subtracting the relative frequency of cell diameters in the region of the area centralis (ST) of the retina in Choloepus didactylus from those in the IT and inferior nasal (IN) quadrants.

Thumbnail

Figure 5
- a, Typical sequence of locomotion of Bradypus variegatus along a branch inclined at approximately 30^o (A-F) and along another in the horizontal position (G-K). (Reproduced with permission from Mendel, 56). b, Typical sequence of locomotion of Choloepus hoffmanni along a branch inclined approximately 30^o in relation to the horizontal. (Reproduced with permission from Mendel, 57).

Figure 1 - Distribution of two- and three-toed sloths throughout Central and South America (A, B) (for further details see Wetzel (3)).

Figure 2 - Changes in arterial blood pressure (BP) in Bradypus variegatus in response to the approach of a human. A, A slight rise and B, a fall.

Figure 3 - Distribution of ganglion cell densities in the right retina of a three-toed sloth Bradypus variegatus (A) and of a two-toed sloth Choloepus didactylus (B). Numbers next to each isodensity line represent cells/mm² divided by 1000. The cross marks the position of the optic disc. Note the different position of the region of maximum cell density (area centralis) between the sloth species. In both instances the presence of a visual streak in the retina is indicated by the elongated contours of the isodensity lines representing intermediate densities around the area centralis, this being 0.8 x 10³ in Bradypus variegatus and 0.4 x 10³ in Choloepus didactylus.

Figure 4 - Distribution of ganglion cell diameters in two different quadrants of the retina in Bradypus variegatus (A) and Choloepus didactylus (B). The relative frequency was obtained by subtracting the number of cells in the inferior temporal retina (IT) of the area centralis in Bradypus variegatus and in the superior temporal retina (ST) of Choloepus didactylus from the regions of lowest cell density in the superior nasal retina (SN) of both species. An excess of cells for each region of the area centralis over the nasal temporal retina is indicated by the portion of the histogram above the 0% line and the excess of cells for each region of the superior nasal retina over the inferior temporal retina is indicated by the portion of the histogram below the 0% line. C is a histogram obtained by subtracting the relative frequency of cell diameters in the region of the area centralis (ST) of the retina in Choloepus didactylus from those in the IT and inferior nasal (IN) quadrants.

Figure 5 - a, Typical sequence of locomotion of Bradypus variegatus along a branch inclined at approximately 30^o (A-F) and along another in the horizontal position (G-K). (Reproduced with permission from Mendel, 56). b, Typical sequence of locomotion of Choloepus hoffmanni along a branch inclined approximately 30^o in relation to the horizontal. (Reproduced with permission from Mendel, 57).

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An update on the physiology of two- and three-toed sloths

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