Morphology of rhinoceros platelets

Abstract

Basic hematological information about rhinoceros species is limited. In this study, we have determined the platelet counts and described the platelet morphology of free‐living white (Ceratotherium simum) and black (Diceros bicornis) rhinoceros using light and electron microscopy. The platelet counts of the two species were similar, but there were significant differences in platelet size as well as morphology between the species. The presence of large, nondiscoid platelet forms, resembling proplatelet or stress platelet forms, were observed in both, although not as often in the white rhinoceros as in the black rhinoceros. J. Morphol. 239:245–253, 1999. © 1999 Wiley‐Liss, Inc.

Ultrastructural observations on the platelets of the Arabian oryx (Oryx leucoryx)

“…Typically, most platelets of the Arabian oryx, exhibited between 1–2 electron‐dense bodies (Figure ), similar to the number found in the Arabia tahr (Johnson et al, ) but unlike those in humans and camels with 5–7 electron‐dense bodies per cell (Gader et al, ) Electron‐dense bodies have also been reported in other wild and domestic animal species including the white and black rhinoceros (Du Plessis et al, ) and buffalo (Du Plessis et al, ). They are characterized as being clear vesicles with an electron‐dense core.…”

“…This cytoskeleton structure gives rigidity and maintains the discoid shape of the platelets (Patel‐Hett et al, ). Approximately, 2 per cent of the platelets exhibited pseudopodia, as described for platelets from humans (van Rooy & Pretorius, ),and infrequently in platelets of impala (Du Plessis, Botha, & Stevens, ) and white and black rhinoceroses (Du Plessis et al, ).…”

“…This coat is composed of mucopolysaccharides and glycoproteins that play important roles in haemostasis (Fritsma, ).). The platelets of the Arabian oryx exhibited generous quantities of cytoplasm, as described in many other animal species, but in contrast to the platelets of the white and black rhinoceros, which have a paucity of cytoplasm (Du Plessis, Botha, & Stevens, ). Mitochondria, cytoplasmic reticulum and glycogen particles were frequently present, however, ribosomes and Golgi elements were rarely observed.…”

“…Unlike the platelets from humans (Sharda & Flaumenhaft, ) and the Arabian tahr (Johnson et al, ), there was no evidence for the presence of nucleoids. The α granules from the Arabian oryx are surrounded by a membrane as those of humans, white rhinoceroses and the tahr, however, those of the black rhinoceros do not have membranes (Du Plessis et al, ). More than 300 soluble proteins have been identified in human α granules.…”

“…An open canalicular system (OCS) is a membranous tortuous channels that communicate directly to the surface membrane of platelets and is generally considered a hallmark feature of platelets in most animals (Choi, Karim, & Whiteheart, ).It was not however, observed in the platelets of the oryx, nor those from horses (Segura et al ), buffalo (Du Plessis et al, ), impala (Du Plessis et al, ), tahr (Johnson et al, ) and camels (Gader et al, ). Two rhinoceros species, white and black, have poorly developed OCSs (Du Plessis et al, ). The OCS is one of the major structures of human circulating platelets (Selvadori & Hamilton, ) and is described as playing an important role in endocytosis and secretions (Escolar, Lopez‐Vilchez, Diaz‐Ricart, White, & Galan, ), calcium concentration regulation (Davlouros, Xanthopoulou, Mparampoutis, Giannopoulos, Defterous, & Alexopoulos, ) and it communicates with the surrounding medium.…”