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| Poster #130 In situ hybridization analysis for the expression of olfactory receptors in the olfactory organ of red-bellied short-necked turtle, Emydura subglobosa |
| Shoko Nakamuta, Takuya Yokoyama, Yoshio Yamamoto, Nobuaki Nakamuta Iwate University, Lab of Veterinary Anatomy, Morioka, --, Japan |
Turtle olfactory organ consists of upper (UCE) and lower chamber epithelium (LCE). The UCE, equipped with associated glands, and the LCE, devoid of glands, line the dorsal and ventral portion of nasal cavity, respectively. Generally, ciliated olfactory receptor neurons (ORNs) express odorant receptors (ORs) and microvillous ORNs express vomeronasal receptors in vertebrates. However, although UCE contains ciliated ORNs and LCE contains microvillous ORNs in many turtles, most ORNs express ORs regardless of whether they are ciliated or microvillous. To date, studies on turtle olfactory receptor expression are limited to hidden-necked turtles. Thus, a side-necked turtle, Emydura subglobosa, was examined to clarify the origin of LCE containing OR-expressing microvillous ORNs. In E. subglobosa, most ORNs expressed GNAL and CNGA2, suggesting the expression of ORs or trace amine-associated receptors (TAARs). Among ORs, class I ORs were mainly expressed in the LCE, while class II ORs in the UCE. In addition, all TAARs except TAAR1, including TAAR2, 4, 5, 7, and 9, were mainly expressed in the LCE. Present results suggest that most ORNs in both UCE and LCE of side-necked turtle express ORs, as in hidden-necked turtles. The olfactory organ containing OR-expressing ciliated ORNs in both UCE and LCE, as in side-necked turtle, has been demonstrated in soft-shelled turtles among hidden-necked turtles. Possibly, LCE in the common ancestor of turtles might have contained OR-expressing ciliated ORNs and, after the divergence of soft-shelled turtles, ORNs in the LCE of other hidden-necked turtles might have changed from ciliated to microvillous, leaving the expression of olfactory receptors unchanged. |