The vomeronasal organ and associated structures of the fetal African elephant,Loxodonta africana(Proboscidea, Elephantidae)

Abstract

 Abstract Göbbel, L., Fischer, M.S., Smith, T.D., Wible, J.R. and Bhatnagar, K.P. 2004. The vomeronasal organ and associated structures of the fetal African elephant, Loxodonta africana (Proboscidea, Elephantidae). -Acta Zoologica (Stockholm) 85 : 41-52The vomeronasal organ (VNO) is a chemosensory structure of the nasal septum found in most tetrapods. Although potential behavioural correlates of VNO function have been shown in two of the three elephant species, its morphology in Loxodonta africana has not been studied. The development of the VNO and its associated structures in the African elephant are described in detail using serially sectioned material from fetal stages. The results show that many components of the VNO complex (e.g. neuroepithelium, receptor-free epithelium, vomeronasal nerve, paravomeronasal ganglia, blood vessels, vomeronasal cartilage) are well developed even in a 154-day-old fetus, in which the VNO opens directly into the oral cavity with only a minute duct present. However, the vomeronasal glands and their ducts associated with the VNO were developed only in the 210-day-old fetus. Notably, in this fetus, the vomeronasal-nasopalatine duct system had acquired a pathway similar to that described in the adult Asian elephant; the VNOs open into the oral cavity via the large palatal parts of the nasopalatine ducts, which are lined by a stratified squamous epithelium. The paired palatal ducts initially coursed anteriorly at an angle of 45 ° from the oral recess and /or the oral cavity mucosa, and merged into the vomeronasal duct. This study confirms the unique characteristics of the elephant VNO, such as its large size, the folded epithelium of the VNO tube, and the dorsomedial position of the neuroepithelium. The palatal position and exclusive communication of the VNO with the oral cavity, as well as the partial reduction of the nasopalatine duct, might be related to the unique elephantid craniofacial morphogenesis, especially the enormous growth of the tusk region, and can be seen as autapomorphies.

Organisation and chemical neuroanatomy of the African elephant (Loxodonta africana) olfactory bulb

“…The absence of an accessory olfactory bulb in the adult African elephant Given the reports of the occurrence of a vomeronasal organ in foetal African elephants (Göbbel et al 2004) as well as adult and newborn Asian elephants (Rasmussen and Hultgren 1990;Johnson and Rasmussen 2002); and a number of behavioural studies indicating chemical communication between elephants (Rasmussen et al 2003;Vidya and Sukumar 2005), it was expected that the African elephant would possess an accessory olfactory bulb; however, this structure was not observed in serial sagittal sections of whole olfactory bulbs (Fig. 7).…”

“…In the elephant it is large (Rasmussen and Hultgren 1990;Rasmussen et al 2003) and relatively well developed even in foetal and newborn elephants (Johnson and Rasmussen 2002;Göbbel et al 2004). Chemical communication in elephants has been well documented and is believed to be vital to maintain the highly organised and stable elephant society (Rasmussen et al 2003).…”

“…The chemoarchitecture of the MOB has yet to be described and it is also unknown if elephants posses an AOB. Elephants are known to possess a vomeronasal organ and to communicate through chemical signals, suggesting the presence of a vomeronasal system, and by extension, an AOB (Rasmussen and Hultgren 1990;Johnson and Rasmussen 2002;Göbbel et al 2004); however, it has also been suggested that elephants are descended from an aquatic ancestor (Gaeth et al 1999). If this is the case, elephants may lack an AOB due to a historical adaptation to an aquatic environment.…”

Nuclear organization of the rock hyrax (Procavia capensis) amygdaloid complex

“…In addition to this, the hyrax represents a baseline from which comparisons to other members of the Afrotheria can be drawn. For example, the African elephant olfactory bulb lacks the accessory olfactory bulb (Ngwenya et al 2011), but the elephant appears to have both a functional vomeronasal organ (Johnson and Rasmussen 2002;Gobbel et al 2004) and exhibits behaviours related to pheromonal stimulation (Rasmussen et al 2003(Rasmussen et al , 2005Bagley et al 2006). Within the amygdaloid complex, the medial nuclei are involved in the processing of olfactory cues from the vomeronasal organ (Bergan et al 2014), thus we can question whether these nuclei will be present or atrophied in the elephant amygdaloid complex.…”

Communication in a Small Herd of Semi-Domestic Elephants another Interpretation of their Social Organization, Social Contract and World View

“…The vomeronasal organ attached to the base of the brain is considered to be for the careful investigation of strong, pertinent or unfamiliar smells [44]. It is uniquely large in the elephant and has paired palatal ducts, a folded epithelium and a dorso-medial position of the neuro-epithelium indicating its complexity and links to the cerebral cortex [45], and elephants perform flehmen which is associated with the vomeronasal gland [46]. They have cutaneous glands around the temple and inter-digital glands that produce steroids as well as other secretions and have been found to secrete pheromones related to sexual status.…”