Functional morphology of the trunk and paw pad skin of the African palm squirrel (Epixerus ebii)

Abstract

The study was initiated to contribute to the meager knowledge of the anatomy of the African palm squirrel. Skin of the trunk and paw pads was the subject of interest. Basic gross and histological techniques were employed. The dorsal fur was grey with golden brown free endings, while the ventral fur was greyish white. The fur covered the entire trunk, extended through the dorsal surface of the distal carpal joint to the dorsal surface of the digits. Five digital pads, three inter-digital pads and two metacarpal pads were observed on the forefoot. There was no observable digital pad on the hind foot; four inter-digital and two metacarpal pads were observed. Surface grooves were evident in the cornified layer of the trunk skin, but not in the paw pad skin. The mean thickness of the cornified layer of the epidermis of the palmar pad was 75.54±3.45 μm, while the entire epidermis was 102.32±4.23 μm thick. The non-cornified layer of the trunk skin was made of only three distinct layers, as the stratum lucidum was not evident. Conversely, the stratum lucidum was evident in the paw pad skin. Dermal papillae observed in the paw pad skin were more numerous and progressed deeper into the non-cornified epidermis than those observed in the trunk skin. There were more melanocytes in the dorsal than in the ventral trunk skin. The study concluded that the trunk and paw pad skin of the African palm squirrel enable its adaptation to arboreal habitat.

Comparative morphology of the paw pad of the main arboreal Xenarthras from Amazon

“…In digitigrade animals, which rest on the fingers, such as dogs and cats, digital and metacarpal (metatarsal) pads are also present and are the only pads that make contact with the ground, despite having carpal and tarsal pads, in the palmar and plantar regions, respectively (Dyce et al, 2010; Konig & Liebich, 2016). Other wild species have, in addition to finger pads, interdigital pads, associated with metacarpals and metatarsals, as reported by Ibe et al (2020) for the species Epixerus ebii , the african palm squirrel.…”

“…Eccrine sweat glands can assume different dispositions between species. Ibe et al (2020) observed several groups of these glands in the regions of the dermis and also in the hypodermis of Epixerus ebii , which act on the friction of the paw pads, with its location in an adipose medium attributed to its metabolic function for the production of vitamin D and triglycerides. Myrmecophaga tridactyla , the giant anteater, also presented well‐defined groups of glandular acini (atrial glands) in the dermis, as well as tissue arrangement similar to the studied Xenarthra's (Ribeiro et al, 2015).…”

“…pads of the main Xenarthras in the Amazon region(B. variegatus, C. didactylus, T. tetradactyla and C. didactylus), the histological constitution proved to be similar, being found in the deepest dermis, the presence of numerous groups of eccrine sweat glands arranged linearly in this region and, in the species T. tetradactyla and C. didactylus, which presented these glands in the hypodermis, the first being observed in both.Eccrine sweat glands can assume different dispositions between species Ibe et al (2020). observed several groups of these glands in the regions of the dermis and also in the hypodermis of Epixerus ebii, which act on the friction of the paw pads, with its location in an adipose medium attributed to its metabolic function for the production of vitamin D and triglycerides.…”

Immunolocalization of Desmin, Vimentin and S-100 proteins in testis and epididymis of African striped ground squirrel (Xerus erythropus)

“…The squirrel is found across Africa, south of the Sahara and savannah countries, usually around cultivated lands (Thorington et al, 2012). It is well distributed in Nigeria particularly in North-eastern and South-eastern parts of the country (Ibe et al, 2020). Six subspecies are currently recognized, two of which are in Nigeria; Xerus erythropus erythropus and Xerus erythropus chadensis (Herron & Waterman, 2004).…”