Licht-im-Terrarium: Literaturdatenbank

Chloe Davies, Richard Brown, Luiza Passos: School of Biological and Environmental Sciences, LJMU, Liverpool

Introduction

The Status of global amphibian populations continues to deteriorate; they are considered the most threatened class of vertebrates by the IUCN. —40% of known species are threatened With extinction and it is estimated that 170 are already extinct amongst wild populations (Gonzålez-deI-PIiego et al., 2019).

Localised declines have been noted since the 70s, especially in the tropics regions. Major "die-offs" are now being found in both temperate and tropical populations. Viable ex situ populations are therefore required urgently which will require greater understanding of their specific environmental and nutritional needs (Baines et al., 2016).

Importance of UV

UVA (350 nm)
within the visual range of amphibians, used to identify ,members of the same species and food items (Moehn 1974; Fleishman et al. 1993; Honkavaara et al. 2002).

UVB (290 - 315 nm)
allows for the conversion of 7-dehydrocholesterol (7DHC) to pre-vitamin D3 in the Skin, and later metabolised to Vitamin D3 and calcitriol (an important endocrine hormone responsible for controlling calcium metabolism).

Direct effects on the Skin
modulation of the cutaneous immune system, antibacterial, strengthening of Skin barrier functions and increasing pigment formation (McGuigan et al. 2012).

Excessive exposure to UV must be avoided, high doses can result in eye and Skin damage, reproductive failure and sometimes death.

Study Species

1. Blue-legged mantella (Mantella expectata)
• Distribution: Sandstone landscape of Isalo National park, Madagascar and the areas to the south of it.
• Habitat: near temporary, rocky Streams and quiet open Canyons
• Status: Endangered (EN)
• Threats: prolonged drought, habitat loss and destruction, Over-exploitation from the pet trade, floods, disease, anthropogenic activity (Adreone et al., 2008).

2. Brown mantella (Mantella ebenaui)
• Distribution: Endemic to Northern Madagascar, One of the few species of mantella that has a reasonably wide distribution.
• Habitat: Rain forests and secondary tree plantations.
• Status: Least Concern (LC).
• Threats: habitat loss, deforestation, disease, anthropogenic activity.

Methods

Experiment 1
• 20 M.ebenaui randomly allocated into one of two equal Size groups, With each frog kept in its own terrartum.
• Group I: no UV
• Group 2: exposure to recommended UV levels (Fergusson zone 2:2-6% UV-B fluorescent tube).
• After 3 months, treatments will be swapped (repeated measures design).

Experiment 2
• 25 M. expectata placed in a large "ExoTerra" terrarium
• Fergusson zone 2 UV-B fluorescent tubes and daylight bulbs placed on different sides of terrarium, separated by UV-block screen
• Passive behavioural Observations using security cameras for 2 months.
• CORT and cutaneous bacterial diversity swabs will be taken at the start of the experimental period and at the end.

Summary

This Study will investigate whether the provision of artificial UV to captive frogs provides health benefits such as:
Reduced number of bacteria found on the epidermis due to anti-bacterial properties; thus, reduces the likelihood of contracting illnesses/diseases in captivity.
Reduced Corticosterone Levels.
Prevents metabolic bone disease (MBD).
Increased vibrancy = better reproductive rates.
Results from the described experiments into these benefits are expected in July, 2024.

BESCDAV1@ljmu.ac.uk