Use of a wireless ultrasound probe as a portable, noninvasive method for studying reproductive biology in the asp viper, Vipera aspis

Abstract

In this study, we investigated the use of wireless ultrasonography as an imaging system to study the reproductive ecology of the asp viper (Vipera aspis), a viviparous snake found in southwestern Europe. Female vipers were captured during the summer and immediately scanned to obtain an estimate of the number of embryos. Ultrasound imaging was performed with a pocket-sized wireless ultrasound probe interfaced with a tablet with a dedicated app. Vipers were then released at the exact capture site after collecting data on body size and weight. We validate wireless ultrasonography as a non-destructive, effective tool for ultrasonic investigations in the field. Wireless probes are light and compact, which facilitates carriage in rugged terrain. Moreover, the absence of cables simplifies the maneuvers to be made on a small, potentially dangerous snake. Importantly, ultrasound scans can be performed at the capture site, thus minimizing restraint time and handling of gravid females.

Keywords: Vipera; snake reproduction; viviparity; wireless ultrasonography.

Figure 1

Ultrasound examination of vipers (Vipera aspis). (a) One of the gravid females that were investigated. (b) In‐the‐field ultrasound scanning of a gravid viper. Females were examined shortly after capture and then released at the exact capture site.

Figure 2

Ultrasound images of individual “eggs” in the oviduct of Vipera aspis. In all images, the ventral side is at the top and the vertebral column (bracket) of the female is visible in the dorsal aspect. (a) An individual “egg” with embryonic skeletal elements (arrows) surrounded by a prominent mass of yolk. (b) Two contiguous “eggs” (asterisks) adjoining at the level of the dotted line. Arrows point to echogenic skeletal elements of the embryos. (c) An embryo at a later stage of development. Notice that the amount of yolk has strongly decreased and the embryo occupies most of the egg volume. The arrow likely points to the cranium.