Rato C, Marques V, Paracuellos M, Tortolero J, Nevado JC, Carretero MA (2021) Alborán Island, a small meeting point for three invasive lizards, whose geographic origin is uncovered by molecular analysis. BioInvasions Records 10(4): 977–990.

https://www.reabic.net/journals/bir/2021/4/BIR_2021_Rato_etal.pdf

Francisco J. Diego-Rasilla, John B. Phillips; Evidence for the use of a high-resolution magnetic map by a short-distance migrant, the Alpine newt (Ichthyosaura alpestris). J Exp Biol 1 July 2021; 224 (13): jeb238345. doi: https://doi.org/10.1242/jeb.238345

Newts can use spatial variation in the magnetic field (MF) to derive geographic position, but it is unclear how they detect the ‘spatial signal’, which, over the distances that newts move in a day, is an order of magnitude lower than temporal variation in the MF. Previous work has shown that newts take map readings using their light-dependent magnetic compass to align a magnetite-based ‘map detector’ relative to the MF. In this study, time of day, location and light exposure (required by the magnetic compass) were varied to determine when newts obtain map information. Newts were displaced from breeding ponds without access to route-based cues to sites where they were held and/or tested under diffuse natural illumination. We found that: (1) newts held overnight at the testing site exhibited accurate homing orientation, but not if transported to the testing site on the day of testing; (2) newts held overnight under diffuse lighting at a ‘false testing site’ and then tested at a site located in a different direction from their home pond oriented in the home direction from the holding site, not from the site where they were tested; and (3) newts held overnight in total darkness (except for light exposure for specific periods) only exhibited homing orientation the following day if exposed to diffuse illumination during the preceding evening twilight in the ambient MF. These findings demonstrate that, to determine the home direction, newts require access to light and the ambient MF during evening twilight when temporal variation in the MF is minimal.

Diego-Rasilla, F.J., Luengo, R.M. Magnetic compass orientation in common midwife toad tadpoles, Alytes obstetricans (Anura, Alytidae). J Ethol (2020). https://doi.org/10.1007/s10164-020-00653-3

https://rdcu.be/b4AFq

We provide the first evidence for y-axis magnetic compass orientation in Alytes obstetricans. Evidence for wavelengthdependent effect of light on magnetic compass orientation is also shown. In the first series of experiments, two groups of tadpoles were tested shortly after being collected from a pond with a natural shoreline and a clearly defined y-axis under two different lighting conditions (full-spectrum and long-wavelength light). Magnetic bearings from tadpoles tested under full-spectrum natural skylight displayed bimodal distribution along an axis that coincided with the magnetic direction of the y-axis in their home pond, while those tested under long-wavelength light failed to exhibit a consistent overall direction of orientation relative to the magnetic field, although a subset of tadpoles exhibited magnetic compass orientation that was rotated about 90° counter-clockwise of the magnetic direction of the y-axis in their home pond. In the second series of experiments, tadpoles were collected from a watering trough without a defined y-axis, trained to learn the direction of the y-axis in tanks with an artificial shore at one end and tested under full-spectrum natural skylight. Tadpoles from the two trained groups showed bimodal magnetic compass orientation along the shore–deep water magnetic axis of their respective training tanks. The present findings widen the number of species with y-axis magnetic compass orientation to include Alytidae, a family of primitive semiterrestrial frogs.