Oral presentation- Open Session 12th International Mammalogical Congress

Morphology and evolution of the oral shield in marsupial newborn pouch young. (#439)

Yamila Gurovich 1 2 , Nanette Y Schneider 3
  1. CIEMEP , CONICET-UNPSJB., Esquel, Chubut, Argentina
  2. Faculty of Medicine, School of Medical Sciences, University of New South Wales, Randwick, New South Wales, Australia
  3. Centre des Sciences du Goût et de l’Alimentation (CSGA), Université de Bourgogne-Franche-Comté, Dijon, France

Newborn marsupials can be arranged into three grades of developmental complexity based on their external form, on their organ systems and their cytology. The dasyurids are considered the least developed at birth, while didelphids and peramelids are intermediate and macropods are the most developed. Currently there is still little information on caenolestid and microbiotherid development at birth. Developmental stages can be graded as G1, G2 and G3, with G1 being the least developed at birth, and G3 the most developed. Marsupials are also characterized by having an extremely developed craniofacial region at birth compared to therians, with the oral region varying in development between different marsupial groups at birth. The oral shield is a morphological structure observed during late embryological development and is retained until shortly after birth. Morphological variation of the oral shield can be arranged by developmental complexity from greatly developed, reduced to vestigial. In its most developed state, the lips are fused, forming together with the rhinarium, a flattened ring around the buccal opening. We observe the oral shield in newborn marsupials (dasyurids, peramelids, macropods and didelphids), including the newborn monito del monte young (Dromiciops gliroides). The adaptive value of the oral shield structure is reviewed and appears to be exclusively present in Marsupialia. We observe that a well-development oral shield may be related to ultra altricial development at birth, large litter size (more than 2) and is present in most species that lack a pouch or have a less developed pouch with some exceptions.