#SensoryBiology

Our study on star-nosed moles was recently accepted in the Journal of Experimental Biology! In it we (myself and Kevin Campbell from University of Manitoba) present on a curious observation that the fleshy, tentacled nose of the star-nosed mole does not show much evidence for elevated blood flow, even when the moles encounter warm temperatures. Indeed, the highly mechanosensitive nasal rays of the star-nosed mole thermo-conform closely with ambient temperature thereby minimizing heat loss without apparent changes in sensory performance. Because this was a non-invasive study, we have to use thermo-conformation as a proxy for blood flow, and discover that they really don’t have high blood flow to the rays!

Abstract of the study

The star-nosed mole (Condylura cristata) is renowned for its densely innervated 22 appendage star-like rostrum (‘star’) specialised for tactile sensation. As a northerly distributed insectivorous mammal exploiting aquatic and terrestrial habitats, these vascularized nasal rays are regularly exposed to cold water and thermally conductive soil, leading us to ask whether the star surface temperature, a proxy for blood flow, conforms to the local ambient temperature to conserve body heat. Alternatively, given the exquisite sensory nature of the star, we posited that the uninsulated rays may be kept warm when foraging to maintain high mechanosensory function. To test these hypotheses, we remotely monitored surface temperatures in wild-caught star-nosed moles. While the tail acted as a thermal window exhibiting clear vasoconstriction/vasodilation, the star varied passively in surface temperature, with little evidence for thermoregulatory vasomotion. This thermoconforming response may have evolved to minimize conductive heat loss to the water or wet soils when foraging.

Gallery Images

Close-up image of the star of the star-nosed mole. © Joel Sartore/Photo Ark

Note: WordPress may have mangled the videos. Looking into fixing….

Bottom view of the star-nosed mole searching the ground with its star. Blink and you’ll miss it.

Bottom view of a star-nosed mole foraging on an earth worm. One of the world’s fastest eaters!

A rare video / timelapse of a star-nosed mole standing still. In this case it is grooming. This is the only time we observed the star showing any evident “body heat” warming up the star itself. Watch up to the end to see the brief vasodilation to the star before the mole walks off scene. Usually the star remains at or slightly below ambient temperature.

Backstory

This work took place in Northern Ontario in the summer 2022, as the first sabbatical project I took on board this past year. Kevin Campbell was hosting two film crews out at his field site, and invited me to “tag along” (i.e. research) with the group. My lab been interested in the inter-play between temperature and sensory functions (plus a 4th year course I teach concerns neuro-ethology and sensory ecology/physiology, so this was a fun way to explore teaching/research overlap). Best (and only) two weeks I have ever spent working in a garage/film set. Also, no trip to northern Ontario would be complete without a picture of the resident loon from the cottage.

Citation

Tattersall, GJ and Campbell, KL. 2023. Thermoconforming rays of the star-nosed mole. J Exp Biol 2023; jeb.245127. https://doi.org/10.1242/jeb.245127

Link to the paper (50 free clicks)

Acknowledgements

We thank Josh Campbell for assistance with mole capture, and the British Broadcasting Corporation Studios Natural History Unit for accommodating this study. This research was supported by NSERC Discovery Grants to GJT (RGPIN-2020-05089) and KLC (RGPIN-2016-06562) and an NSERC Research Tools and Instrumentation Grant to GJT (NSERC RTI-2021-00278).

Data Repository

The data from the paper are shared in the following open repository: http://hdl.handle.net/10464/16980

Exposure to ultraviolet (UV) light has both physiological benefits as well as costs. Many lepidosaur reptiles can behaviourally self-regulate their exposure to UV light in order to take advantage of the benefits of UV light while minimizing the costs. Furthermore, lepidosaur scales have been conceptualized by some as a barrier to the penetration of UV light.

In a recently published study, we (Nick Sakich, recent graduate from the lab) examine regulation of self-exposure to UV light in three different phenotypes of Bearded Dragon (Pogona vitticeps): wild type, animals exhibiting scales of reduced prominence (‘Leatherback’), and scaleless animals (‘Silkback’). These scaleless mutants have arisen in the captive reptile husbandry industry. All phenotypes were tested in a 3 chamber system, offered 3 different intensity of standard basking lamps to assess how long they spent under each UV lamp.

Silkbacks on average chose to expose themselves to lower levels of UV light irradiation than Leatherbacks or wild types did, which suggests that the ability for UV to penetration through the skin is diminished in normal scaled phenotypes.

Simultaneously, we tested their self-exposure behaviour while they were able to choose cold or warm temperatures. Bearded Dragons of all scalation phenotypes received higher UV irradiation when they were in the cold section of a UV gradient apparatus compared to when they were in the hot section of the apparatus. This either demonstrates that Bearded Dragons under higher UV irradiances choose cooler temperatures or demonstrates that Bearded Dragons at cooler temperatures choose higher UV irradiances. The relationship between chosen temperature and chosen UV light irradiance was not affected by scalation phenotype.

This study highlights external influences on the mechanism that regulates UV self-exposure behavior in lepidosaur reptiles. Scales are apparently a barrier to UV absorbance, and thus scaleless lizards need to adjust their time exposed to UV light.

One logical interpretation the temperature sensitive UV seeking behaviour shows evidence that when cold, lizards may adopt UV seeking behaviour in an attempt to bask (i.e. an attempt to warm up) as would happen in the wild when basking in the sun. In our study, the UV bulbs were fluorescent bulbs and not radiant bulbs, and thus lizards may spend preferentially more time exposed to UV as part of their natural basking behaviour.

Figures and citation are provided below:

*Leatherback phenotype of bearded dragon (juvenile)*

*Silkback phenotype of bearded dragon (juvenile)*

Ultraviolet light test chamber involve 3 separate ‘basking’ sites partitioned within a circular chamber. Bearded dragons were free to move between the partitions due to gaps underneath the vertical baffles. The floor was kept at the preferred temperature (35°C) within the red zone, and allow to fall to room temperature (22-24°C) outside of that zone. This created allowed us to track the UV preferences while lizards were selecting warm or cool temperatures.

For those wishing to see a pdf of our article, for the next 50 days, free access is available at the following link: https://www.ichthyologyandherpetology.org/ihbjbb/ovh2020134ug688044yq

Alternatively, please request access to a pdf from Researchgate.

Citation

Sakich, N and Tattersall, GJ. 2022. Regulation of exposure to ultraviolet light in bearded dragons (Pogona vitticeps) in relation to temperature and scalation phenotype. Ichthyology and Herpetology, 110: 477-488. https://doi.org/10.1643/h2020134

Tattersall Lab (TEMP)

Thermoregulatory, Evolutionary, Metabolic Physiology

Star-nosed moles have chilly stars

Ultraviolet Sensing Behaviour in Bearded Dragons