Morfologia da cloaca e do aparelho copulador de Cairina Moschata (Anatidae: Anseriformes) com implicações sistemáticas

Abstract

The cloacae and the phallus of 12 specimens of the Muscovy duck Cairina moschata were studied in order to identify and describe the main morphological characteristics, determine its mechanism of erection of the phallus and identify characters that can contribute to phylogenetic analyzes of birds within the amniotes. The studies were conducted from dissections, vascular injections of gelatin and routine histological techniques. The cloacae of C. moschata are divided into three compartments, coprodeum, urodeum and proctodeum separated by coprourodeal and uroproctodeal folds. The coprodeum is dilated and continued with the rectum. The wall is formed by mucosa, submucosa and muscular tunics. This compartment is coated by single cylindrical epithelium with goblet cells and a well-developed muscular layer of the mucosa. The urodeum walls have similar structure to coprodeum. In this compartment the ureter opens in a rounded ostium and the vas deferens opens through a conical papilla. The proctodeum is coated by cylindrical pseudo stratified epithelium of secretory type and abundant goblet cells and shows muscular mucosa. In adult specimens the cloacae bursa is completely regressed. On the floor of this compartment is located the phallus within a fibrous bag. The phallus is formed by base, ejaculatory cavity, vascular bodies and tubular portion of the phallus. This is formed by fixed and aversively portions. The base is sustained by fibro cartilaginous body. The erect phallus averted in spiral form through the vent. Caudally, the proctodeum opens to the outside through the vent orifice. Seventeen morphological characters that were used for the preparation of phylogenetic trees were identified. An evolutionary scenario and three phylogenetic analyzes based on the most recent phylogenetic studies of Amniota was made. The nomenclature and the morphological changes of the cloacae and the copulatory organ of amniotes are discussed.