Comparative morphology and histochemistry of the uropygial gland of the endangered and endemic Hooded Grebe (Podiceps gallardoi, Podicipediformes)

Abstract

The Hooded Grebe is an endangered and endemic species of Podicipediformes of Argentina. Many aspects of this bird's biology are still unknown including the uropygial gland. This is the first morphological and histochemical description of the uropygial gland for this species in a comparative context. The uropygial gland of these birds had parallel arranged lobes with a kidney-like shape, a conical papilla and a feather tuft in a sub-terminal position. The lobes were composed of tubular adenomers with a straight course that lead to secondary chambers. The capsule and connective tissue around the adenomers had elastic fibres. It showed a positive reaction to AlcianBlue/Periodic Acid Schiff and several lectins indicating the presence of glycoconjugates. The uropygial gland of the Hooded Grebe shares morphological characteristics with other aquatic species (e.g. secondary chambers) and the presence of glycoconjugates might suggest protective functions against microbes as previously proposed. The sub-terminal position of the feather tuft is a unique characteristic of this species indicating that this position leaves the tuft in a dorsal location and could be involved in parent-chick recognition mediated by odour transmission. Further studies are needed to increase our knowledge on some behavioural aspects of this species related to the biochemical composition of the uropygial secretion.