microanatomy, morphometric, morphostructure, ovary, pangolin
D Ofusori. The Morphostructure Of The Ovary Of African Tree Pangolin Manis tricuspis. The Internet Journal of Veterinary Medicine. 2007 Volume 4 Number 1.
Little is known about the reproductive biology of pangolin, most especially the female sex organ. Hence, the need to study its ovary. Ovaries from ten female pangolins were used for this study. The animals were decapitated and a lower mid-line abdominal incision performed to have access to the ovarian tissues. The microanatomy of the left and right ovaries was compared. Similarly some morphometric parameters were also analyzed. The result present a morphostructural difference between the left and right ovaries; with the left conforming to the basic structure unlike the right. This preponderance feature of the left ovary over the right is also reflected in the morphometric analysis which present a significant difference (p<.05) when the data were compared. Hence the left ovary could be the principal sex organ of reproduction in African tree pangolin
African tree pangolin
Few researches have been conducted on some aspect of this animal. Ofusori et al. (2007a) in their work on the morphometric study of the stomach of African pangolin reported that the corpus of pangolin’s stomach is metabolically more active than the other parts of the stomach. Also, Adenowo and Caxton-Martins (2000) found from their investigation that the pineal gland of pangolin is markedly different from the human bovine pineal glands histologically.
One ovary or the other produces one egg per month during reproductive life in human. The ovary's spongy medulla is a mass of vessels in a loose connective tissue stroma. It fades into the cortex, where the eggs are. Cortical fibroblasts are arranged in dense cellular whorls, and are called “ovarian stroma”. After ovulation, the granulosa cells and the theca interna become the corpus luteum, a new endocrine organ which makes estrogen and progesterone last until the end of the cycle, and even longer if pregnancy takes place. The wall of the follicle collapses into folds which are mirrored into the structure. Blood and lymph vessels invade at once. The granulosa cells expand greatly (“luteinize”) and become steroid-secreters. At the center is the blood from ovulation, which organizes into scar just like in wound healing. The scar will remain as a wiggly corpus albicans . The corpus luteum is maintained by LH from the pituitary and (if pregnancy occurs) chorionic gonadotropin (hCG) from the trophoblast.
A thorough search into the literatures revealed that only little is known about the reproductive biology of this species. Hence, the need to comparatively investigate the morphostructural differences in the left and right ovaries of
Materials And Methods
Care of the animals
Ten female African pangolin average weights (1.35kg) were procured from Asejire, a local town in the northwest region of Osun state. The animals were examined and confirmed to be presumably free from any pathological assaults. They were kept in the animal holdings of the department of Anatomy, Igbinedion University Okada, Nigeria, and fed with termites and water
Excision of the ovary
The animals were decapitated and the left and the right ovaries of each of the pangolin excised following a lower mid-line abdominal incision. The ovaries were rinsed in physiological saline and blotted dry on a filter paper.
The ovaries of the animals in group A were fixed in 10% formol saline for a period of 48 hours. They were then processed accordingly for routine paraffin embedding. This included the dehydration in graded alcohol, clearing in xylene, infiltration in paraffin wax and finally embedded in paraffin wax for 24hours. The embedded tissues was sectioned at 5µm thickness and subjected to Heamatoxylin and eosin (H&E) staining procedure. The right and left ovaries were then studied for any microstructural differences.
The left and right ovaries of the animals in group B were subjected to morphometric assessments which included taking the wet weights using a Metler (P153) balance. The length, diameter and thickness were determined using digital Vernier Calipers and the volume by adopting water displacement method earlier described by Ofusori et al. 2007b.
Data were express as mean ± S.E.M. The data were analysed by student t-test using the statistical soft ware STATISTICA VERSION 5. p<0.05 is considered significant.
The left and right ovaries were observed to be spherical in shape and encapsulated by tunica albuginea. Further macroscopic examination of the two ovaries revealed that the average weight of the left is somewhat higher than the right. This was evident when the relative weights were compared (Table 2). A significant difference was again recorded when the diameters were compared (Table 2). The length of the left ovary 1.45±0.05 was observed to be significantly different (p<0.05) from the right ovary 0.89 ± 0.08. The volume of the two ovaries differ significantly (p<0.05) when compared (Table 2). The mean value of the thicknesses of the right and left ovaries also present a significant difference as shown in Table 2.
The results of the microstructural investigation of the right and left ovaries revealed some microanatomical differences in the two ovaries. The left ovary which is the larger of the two was observed to conform to the basic microstructural organization having both the cortex and medulla (Fig 3a). Few capillaries, fibroblast and smooth muscle cells were observed in its cortical region with follicles in various sizes and states of development (Fig 2a & 3a). This is however different from the right which has its entire stroma dominated by connective tissue fibers as well as smooth muscle cells without any clear demarcation into cortical and medullary regions (Fig 2b and 3b).
Our morphostructural study in this investigation demonstrates morphometric and microanatomical differences between the left and right ovaries of the African tree pangolin
The right ovary on the contrary has a uniform stroma without any clear demarcation in to cortical and medullary parts (Fig 2b & 3b). The entire stroma which is dominated by connective tissue fibers as well as smooth muscle cells makes it more or less rudimentary in contrast to the left.
In conclusion, the comparative morphometric and histological study reveals some differences between the left and right ovaries of
The authors are very grateful for the technical assistance of Kola Oyewole, Oluwaseun Timothy and Iniola Gbela of the Obafemi Awolowo University, Ile-Ife, Osun state, Nigeria.