INTESTINAL GROWTH IN ALTRICIAL EUROPEAN STARLING (STURNUS-VULGARIS) AND PRECOCIAL JAPANESE-QUAIL (COTURNIX-COTURNIX-JAPONICA)

This paper introduces the comparison of altricial and precocial birds as a model system for the study of patterns of intestinal growth. It r eports on comparative morphometric and cytokinetic studies of intestin al growth in altricial European starling (Sturnus vulgaris) and precoc ial Japanese quail (Coturnix coturnix japonica). Morphometric data of five gut segments of neonates and adults of both species are provided to evaluate the growth of the intestine. A double labelling technique combining H-3-thymidine autoradiography with 5-bromo-2'-deoxy-uridine immunohistochemistry gives labelling index, length of S-phase, and tis sue turnover time for hatchlings and adults of both species. The resul ts of morphometry show a similar pattern of intestinal growth in both species, a strong dependency of intestinal growth on body size, and a clear topographic separation of areas of cell proliferation from the f unctional mucosal epithelium. The results of the cytokinetic experimen ts indicate a constant length of the S-phase independent of species, d evelopment, and age. The H-3-thymidine labelling index is significantl y higher in neonate quail than in neonate starling. Between adult anim als of both species, the labelling index does not differ significantly except for the duodenum which has a higher index in starling. The tur nover time necessary to replace the mucosal epithelium is 3 days in ha tchlings of both species and ranges between 10 and 17 days in adults. A diurnal pattern of cell proliferation, as previously reported in adu lt quail, is not present in neonate quail. Thus, differences in intest inal growth among altricial and precocial birds are primarily based on size differences of proliferation areas whilst cellular proliferation rates have only minor impact on intestinal growth. The short turnover time and the high rates of cell proliferation suggest that the intest ine is a flexible organ that may be adjusted in size and function to t he actual needs of the growing bird.