Abstract text (incl. figure legends and references)

INTRODUCTION: Among the different bird species, the shape, size and structure of the stomach varies with diet (Duke, 1997). The avian stomach is composed of two definite compartments separated by a constriction: the cranial glandular proventriculus (PV) and a larger caudal non-glandular gizzard (GZ). The stomach of flesh-eating species of birds is primarily a storage organ appropriate for chemical digestion of soft diet. But, the stomach of herbivorous and omnivorous birds is adapted for mechanical degradation of tougher food materials through strong muscular development of the stomach (King and McLelland, 1975). The red-eyed dove (RD) and domestic pigeon (DP) belong to the Columbidae which feed primarily on seeds, fruits, and plants. But the domestic and wild feeding habitats of the species could influence their granivorous and omnivorous habits and subsequently impact on the structure of the stomach. Large-sized grains were specifically recovered from stomach of RD unlike the small-sized grains from the DP. Studies have been carried out on the histology of the proventriculus and gizzard in many species especially poultry (fowl, guinea fowl and turkeys, quail) and few feral species (common starlings, hooded crow and Australian passerines). Few reports have described the stomach linings of the Columbidae especially wild doves by ultrastructural evaluation. The present investigation seeks to evaluate the structural features of the proventriculus and gizzard in the wild RD and DP and related the features with dietary habits. METHODOLOGY: The work used gross dissection, stereomicroscopy, histology and scanning electron microscopy following routine protocols. Six adult RD (body weight: 148.69g) and 6 DP (body weight: 293.56g) birds of either sex were used. Humane handling and cervical dislocation for euthanasia were used. RESULTS: Gross results showed that the relationship of the stomach to the left lobe of liver, duodenum, spleen and abdominal air sacs was similar in both species. Grossly typical features of cone-shaped PV and lens-shaped GZ were present (Figs 1a-e). It was located within intestinal peritoneal sac. The total GIT weight and stomach weight for were 12.06g, 27.61g and 5.12g, 8.51g respectively for RD and DP. The stomach represented 41.4% and 30.1% of the GIT in RD and DP respectively. It showed 3.4% and 2.8% of body weight in RD and DP respectively. Under SEM (Figs 2a-f), PV formed spiral folds (plicae) around a central glandular opening and the number and anastomotic arrangement varied in the species. The glandular openings were surrounded by longitudinal and transverse mucosal folds of the epithelium. Evidence of secretory activity of mucin-like substances was apparent. Surface structures resembling variably shaped projections of membrane were in the gizzard of the birds by SEM. Histologically (Figs. 2g-i), four typical tunics were represented in the two species. Large proventricular glands were tubuloalveolar lobules with secretory ducts and arranged were in a definite row and shape in the muscularis mucosa. The koilin membrane and tunica muscularis of GZ was thicker in the RD. Simple tubular glands were with the thick muscular layers. CONCLUSION:The morphological features of the stomach did not differ significantly in the two birds indicating convergence of dietary components.

King and Mclelland (1975). Outlines of Avian Anatomy, Bailliere Tindall, London

Duke (1997). Proc. Nurt. Soc., 56, 1049-1056.