The Lack of Nasolacrimal Ducts in Plethodontid Salamanders?

Abstract

Nasolacrimal ducts are a terrestrial vertebrate adaptation and appear to have co-evolved with orbital glands. Although plethodontid salamanders possess orbital glands, a recent study concluded that plethodontid salamanders lack nasolacrimal ducts. Functionally, the absence of nasolacrimal ducts closes the route for orbital gland secretion passage into the nasal and vomeronasal organ cavities. Orbital glands have been implicated in enhancement of vomeronasal function so loss could have important implications for communication. Multiple older studies depict or discuss nasolacrimal ducts in plethodontid salamanders. Interestingly, the only consensus between recent and older literature is that Desmognathus lacks nasolacrimal ducts. To determine if plethodontid salamanders truly lack nasolacrimal ducts, we sectioned plethodontid salamander heads for general histological examination of species from the majority of the plethodontid tribes. From our representative sample, we found only two species that completely lacked nasolacrimal ducts (Desmognathus fuscus and Eurycea tynerensis) and one species that possessed nasolacrimal ducts that ended blindly before reaching the nasal cavities (E. spelaea). Bayesian ancestral state reconstruction resulted in the presence of nasolacrimal ducts on the branch leading to Plethodontidae and both subfamilies within Plethodontidae, with two independent losses in Desmognathus and Eurycea. Anat Rec, 301:765-775, 2018. © 2017 Wiley Periodicals, Inc.

Development of the squamate naso-palatal complex: detailed 3D analysis of the vomeronasal organ and nasal cavity in the brown anole Anolis sagrei (Squamata: Iguania)

“…Most tetrapods, except turtles [ 6 ] and a few plethodontid salamanders [ 110 ], possess a lacrimal duct. In mammals, birds, crocodilians, Sphenodon and most amphibians, it extends from the lower eyelid and discharges into the nasal cavity near the external naris or more caudally, closer to the entrance to the VNO [ 21 , 111 – 115 ].…”

Embryology of the naso‐palatal complex in Gekkota based on detailed 3D analysis in Lepidodactylus lugubris and Eublepharis macularius

“…It is widely accepted that the lacrimal duct of squamates and other tetrapods is involved in vomeronasal chemoreception, by delivering the secretion of the Harderian gland into the VNO directly or to its vicinity (Rehorek, 1997; Rehorek et al ., 2000; Rossie & Smith, 2007). This is not true for turtles and some plethodontid salamanders in which the lacrimal duct is absent (Bellairs and Boyd, 1947; Siegel et al ., 2018) and for crocodilians and birds, in which the VNO is lost (Parsons, 1959a). It has been confirmed that in snakes ( Thamnophis ) the female pheromones are soluble in the homogenate of the Harderian gland (Huang et al ., 2006).…”

Development of the squamate naso-palatal complex: detailed 3D analysis of the vomeronasal organ and nasal cavity in the brown anole Anolis sagrei (Squamata: Iguania)

“…Most tetrapods, except some plethodontid salamanders [110] and turtles [6], possess a lacrimal duct. In mammals, birds, crocodilians, Sphenodon and most amphibians, it extends from the lower eyelid and discharges into the nasal cavity near the external naris or more caudally, closer to the entrance to the VNO [20,[111][112][113][114][115].…”