Leaping forward for reptiles and amphibians
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Cryptobranchids are giant salamanders which inhabit cool, flowing freshwater in Japan, China and North America. They are an ancient group and are regarded as living fossils that have remained little changed for over 160 million years (Gao & Shubin, 2003). There are just three known species within two genera, all of which are classified as Threatened or Near Threatened. The Chinese giant salamander (Andrias davidianus) is the largest in the world growing to 1.7 m in length and weighing up to 60 kg (Murphy et al., 2000) (Figure 1). This species is Critically Endangered due to threats from over-harvesting and habitat destruction. The Japanese giant salamander (Andrias japonicus) is a closely related species and is slightly smaller than A. davidianus. Although classified at Near Threatened by the IUCN, its habitat is highly fragmented and populations are declining in many parts of its range (Kaneko & Matsui, 2004). The North American hellbender (Cryptobranchus alleganiensis) is the largest salamander in North America, reaching up to 74 cm in length (AmphibiaWeb, 2019). All giant salamanders live secretive lives but have similar ecology and biology, which includes extreme longevity (up to 60 years), parental care by males, and large larvae. However, there are differences in their habitats, diets, reproductive behaviour, egg size and mating strategies (Lou et al., 2018). Although various studies have been carried out on these species, their behaviour and ecology is still poorly understood, and often published research is in national languages which is not readily accessible. Also, much evidence of their behaviour is through occasional observations and not systematic studies (Lou et al., 2018). In this article we highlight some recent research findings of these unusual and important species.
All three species of giant salamander exhibit paternal care with the male guarding eggs, spending considerable time tail fanning and agitating eggs (Okada et al., 2015) (Figure 2). The first systematic study providing data on paternal from a North American hellbender nest was carried out by Settle et al. (2018). The researchers used unique underwater infra-red video cameras to the record behaviour of a male hellbender in his aquatic nest for a period of five weeks during the breeding season. In this study the male spent 98.4% of the 41.7 hours of observable footage guarding the eggs, rarely leaving them for the whole five week period (Settle et al., 2018). Interestingly, the male was observed to consume its own eggs (filial cannibalism) on seven occasions. The reasons for this are unknown but may either be due to the nutritional value of eggs to the male, or removing eggs that had been contaminated by a fungal infection (Settle et al., 2018). As in other giant salamander species, the male hellbender spent considerable time (60%) fanning the eggs. This is thought to increase oxygen levels in the water and prevent embryo mortality. Overall, this study highlights that male guarding of eggs in hellbenders increases survival of the eggs through decreased predation, increased oxygen levels and potentially removing diseased or dead eggs from the clutch. However, this high level of male guarding comes with several costs including low rate of feeding by the male and increased energy expenditure. Population declines of this North American hellbender could alter the relative costs and benefits of male parental care and impact on survival of populations (Settle et al., 2018).
Recently, a new species of leech (Placobdella appalachiensis) and an unknown species of parasitic trypanosome (Trypanosoma sp.), have been found in a population of hellbenders from eastern North America (Hopkins et al., 2014). Research by DuRant et al. (2015) showed that hellbenders infected by leeches had altered physiology compared to unaffected hellbenders. Leeches dampened the immune response of the salamanders, increasing levels of trypanosome infection. In addition, infection with leeches altered the circadian rhythms of the salamanders which impacted on metabolic processes, foraging behaviour and social interactions, particularly during the time of the year when hellbender activity increases as a result of the onset of breeding (DuRant et al., 2015). It is thought that leech saliva directly impacts on the salamander’s physiology since it is known to contain many different hormones and neurosignalling molecules that are believed to directly affect the salamander’s responses to infection. Understanding the dynamics between the leech species to hellbenders is important for conservation of hellbenders which are declining throughout its range. The findings from this study increase our understanding of the physiological effects of leeches on hellbenders and future research needs to examine the possible impacts on reproduction which may influence conservation efforts.
Understanding the longevity of declining species is crucial and provides important information for conservation, such as total lifespan, age of sexual maturity, and age structure of populations in the field (Yamasaki et al., 2017). However, research on longevity in the Japanese giant salamander is lacking since it is not possible to determine age from weight or length. The only reliable method to determine age in salamanders is through skeletochronology. This method is based on the presence of growth layers recorded in cross sections of long bones (Halliday & Verrell, 1988). By taking cross sections of toes, it is possible to count the layers and thus calculate the age of an individual (Figure 3). Yamasaki et al. (2017) are the first researchers to successfully use skeletochronology to estimate age in the Japanese giant salamander. In this study hellbenders lived up to 11 years. Anecdotal observations suggest that this species may live up to 60 years, but this is based on captive specimens. Long-lived species have slow growth rates and long generation times which means they are slow to adapt to environmental change. Therefore further studies on this species will help understand maximum life span and will have implications for conservation of this declining species.
References
AmphibiaWeb (2019) Cryptobranchus alleganiensis: Hellbender <http://amphibiaweb.org/species/3861> University of California, Berkeley, CA, USA. Accessed 21 June, 2019.
DuRant, S., Hopkins, W. A., Davis, A. K. & Romero, M. (2015) Evidence of ectoparasite-induced endocrine disruption in an imperilled giant salamander, the eastern hellbender (Cryptobranchus alleganiensis). The Journal of Experimental Biology, 218: 2297-2304. doi:10.1242/jeb.118703.
Gao, K. & Shubin, N. (2003) Earliest known crown-group salamanders. Nature, 422: 424-428.
Halliday, T. R. & Verrell, P. A. (1988) Body size and age in amphibians and reptiles. Journal of Herpetology, 22 (3): 253-265.
Hopkins, W. A., Moser, W. E., Garst, D. W., Richardson, D. J., Hammond, C. I. & Lazo-Wasem, E. A. (2014) Morphological and molecular characterization of a new species of leech (Glossiphoniidae, Hirudinida): implications for the health of its imperilled amphibian host (Cryptobranchus alleganiensis). ZooKeys, 378: 83-101.
Kaneko, Y. & Matsui, M. (2004) Andrias japonicus. The IUCN Red List of Threatened Species 2004: e.T1273A3376261. http://dx.doi.org/10.2305/IUCN.UK.2004.RLTS.T1273A3376261.en. Downloaded on 21 June 2019.
Luo, Q., Tong, F., Song, Y., Wang, H., Du, M. & Ji, H. (2018) Observation of the breeding behavior of the Chinese giant salamander (Andrias davidianus) using a digital monitoring system. Animals, 8: 161. doi:10.3390/ani8100161.
Murphy, R. W., Fu, J. Z., Upton, D. E., De, L. T. & Zhao, E. M. (2000) Genetic variability among endangered Chinese giant salamanders, Andrias davidianus. Molecular Ecology, 9: 1539–1547.
Okada, S., Fukuda, Y., & Takahashi, M. K. (2015) Paternal care behaviors of Japanese giant salamander Andrias japonicus in natural populations. Journal of Ethology, 33: 1–7.
Settle, R. A., Briggler, J. T. & Mathis, A. (2018) A quantitative field study of paternal care in Ozark hellbenders, North America’s giant salamanders. Journal of Ethology, 36: 235–242 https://doi.org/10.1007/s10164-018-0553-0.
Takahashi, M. K., Okada, S. & Fukuda, Y. (2017) From embryos to larvae: seven-month-long paternal care by male Japanese giant salamander. Journal of Zoology, 302: 24–31. Yamasaki, H., Taguchi, Y., Minami, S., Kuwabara, K. & Shimizu, N. (2017) Age determination by skeletochronology of the Japanese giant salamander Andrias japonicus (Amphibia, Urodela). Bulletin of the Hiroshima University Museum, 9: 41-47
What our animals are up to this month… July 2019 edition
In the amphibian world, newts may be seen during a period of transition in July. Some adult newts may still be present in ponds during this time, while others may be moving to terrestrial areas. Developing larvae will be exclusively in freshwater habitats until reaching metamorphosis.
In the reptile world, this is an important month for our slow-worms. Female slow-worms will be gravid and carrying developing young inside their bodies from July – September. Slow-worms bask even more than usual during this period in order to help along the development of young inside their bodies and may be found under objects that heat up from the sun’s energy. But with the strong need to bask, we may also see our legless lizards out in the open, using roads or paths to gain more warmth. Females carrying developing young will appear larger than your average slow-worm with young slow-worms being live-birthed in August to mid-September. The gold or silver juveniles, measuring only 4cm long, will break through their egg membrane and remain active until temperatures lower in the autumn.
To find out more about our species, click here.
Remember to record your sightings on our free Dragon Finder app.
Comedian, author, writer and frog enthusiast Stephen Fry has lent his voice to an emotive new animation created by international conservation charity ZSL (Zoological Society of London), hoping to raise the profile of the deadly Ranavirus threatening UK common frogs.
Introduced to Great Britain by humans in the 1980s, Ranavirus mainly affects common frogs (Rana temporaria) but also affects other amphibians and could affect fish and reptiles. Research from ZSL, which formed the basis of the film’s content, found that at least 20% of Ranavirus cases over the past 30 years could be attributed to human-caused introductions such as pond owners introducing fish, frog spawn or plants from other environments.
Stephen Price, amphibian disease expert at ZSL’s Institute of Zoology and UCL said: “Having studied Ranavirus for more than a decade, it was becoming ever more apparent that we needed to do something different to get people‘s attention and alert them to this deadly disease unfolding in their back gardens – because they can do something about it. People can help stop the spread by avoiding moving potentially infected material such as spawn, tadpoles, pond water and plants into their own pond. Disinfecting footwear or pond nets before using them in other water bodies will also help, while building wildlife ponds that mimic more natural freshwater habitats, which provide shade, will help frogs to keep cool and therefore lower the severity of the disease.”
Amphibians are vital to the world’s ecosystems, they are one of the most incredibly diverse forms of life, found almost everywhere. They are essential components of food webs; frogs and newts keep the insect and slug populations in check and serve as prey for foxes and birds. Without frogs, localised ecological collapse could follow.
Members of the public can assist by reporting sick or dead amphibians to ZSL’s Garden Wildlife Health Project, which helps track diseases affecting British garden wildlife:www.gardenwildlifehealth.org
For information on what Froglife are doing to tackle amphibian diseases, take a look here.
Take a look at ZSL’s Ranavirus fact sheet here.
Watch the animation narrated by Stephen Fry below:
This month, CJ Wildlife – Europe’s leading garden wildlife specialist and Froglife partner are reminding us that all of our gardens, no matter what size, can become bustling nature reserves for our local wildlife.
As June arrives you may start to notice a new crop of fledglings that have left the nest and are noisily making their way to independence. Young frogs and toads will start to leave ponds this month, continuing the journey from tadpole to adult, and will move into long grass and quiet corners to feed and grow until the autumn. The same areas are also used by lizards, slow worms, hedgehogs and other wildlife. It’s also a busy time for female hedgehogs as they will begin to give birth, so you may spot a hoglet or two in your garden or local area.
Things to do in your garden this month:
For more hints and tips on making the perfect wildlife garden this summer, visit www.birdfood.co.uk, plus as a Froglife supporter, you can save 10% off when you buy from CJ Wildlife, simply use discount code UKFROG18 when you order.
Fluorescence, or biofluorescence, occurs in nature when electromagnetic wavelengths from the visible light spectrum are absorbed by fluorescent proteins in a living organism, and then emitted as light at a lower energy level. It differs from bioluminescence which is the natural production of light by chemical reactions within an organism. Bioluminescence occurs commonly in species such as fireflies, glow-worms and lantern fish. Fluorescence is less common than bioluminescence but still occurs widely across the animal kingdom, most commonly in aquatic saltwater species including a range of fish, crustaceans and jellyfish. Fluorescence was first discovered in aquatic seas turtles in 2015 (Gruber & Sparks, 2015) (Figure 1). It is rare in terrestrial vertebrate species but has been documented in a species of parrot (Hausmann et al., 2003). Amphibians exhibit a wide range of skin colourations and patterns but until 2017 no amphibian species were known to exhibit fluorescence (Taboada et al., 2017).
The South American Polka-dot tree frog (Boana punctata) lives in seasonal swamps of primary and secondary
forest in Ecuador. It is an unusual amphibian in that it possesses a
translucent skin. During fieldwork, Taboada et
al. (2017) observed that living adults and juveniles illuminated with UV-A
blue light produced a bright blue/green fluorescent emission. Through chemical
analysis the authors found that the fluorescence was traceable to a class of
compounds that occur in lymph and skin glands. Under natural conditions the fluorescence
is highest under low-light conditions and enhances the brightness of
individuals. B. punctata is a
crepuscular species, being most active at dawn and dusk. Studies of the eye
structure of closely related species suggests that B. punctata may be able to detect fluorescence and the authors propose
that fluorescence has an adaptive significance and may be used in the visual
communication in this species. This is the first study to document fluorescence
in amphibians and suggests that if may be more widely spread in tropical
amphibian species.
Since 2017, fluorescence has been discovered in other amphibian species. Pumpkin toadlets are a group of small, terrestrial and diurnal frogs which live in the Atlantic forest of Brazil. Most species are brightly coloured yellow, orange or red and possess toxic skin compounds. Recently, research has found that two species, the pumpkin toadlet Brachycephalus ephippium and B. pitanga, exhibit fluorescence in the bones of the head and back, which is visible through their particularly thin skin (Goutte et al., 2019). Bone fluorescence in living animals is rare, but has been described in some species of chameleon. Brachycephalus ephippium and B. pitanga have recently been shown to be deaf to their own advertisement calls and are known to use visual communication signals involving hand-waving and mouth-gaping (Goutte et al., 2017). The authors propose that fluorescence in these pumpkin toadlets could be used to enhance visual communication between members of the same species such as attracting mates. However, the fluorescent patterns could alternatively be used to reinforce the warning coloration in these pumpkin toadlets which are highly toxic (Goutte et al., 2019).
This study adds to the growing list of documented cases of fluorescence in terrestrial amphibians. Although fluorescence is rare in amphibians, there is a high likelihood that a greater number of species utilise fluorescence, particularly in species which are crepuscular/diurnal and use visual communication. Further research is required to investigate the prevalence of biofluorescence across amphibian species and elucidate its ecological and adaptive significance.
References
Goutte, S., Mason, M. J., Christensen-Dalsgaard,J., Montealegre-Z, F., Chivers, B. D., Sarria-S, F. A., Antoniazzi, M. M., Jared, C., Sato, L. A. & Toledo, L. F. (2017) Evidence of auditory insensitivity to vocalization frequencies in two frogs. Nature Scientific Reports, 7: 12121. DOI:10.1038/s41598-017-12145-5.
Goutte, S., Mason, M. J., Antoniazzi, M. M., Jared, C., Merle, D., Cazes, L.,Toledo, L. F., el-Hafci, H., Pallu, S., Portier, H., Schramm, S., Gueriau, P. & Thoury, M. (2019) Intense bone fluorescence reveals hidden patterns in pumpkin toadlets. Nature Scientific Reports, 9: 5388. https://doi.org/10.1038/s41598-019-41959-8.
Gruber, D. F. & Sparks, J. S. (2015) First Observation of Fluorescence in Marine Turtles. American Museum Novitates, 3845, pp 7. DOI: 10.1206/3845.1
Hausmann, F., Arnold, K. E., Marshall, N. J. & Owens, I. P. F. (2003) Ultraviolet signals in birds are
special. Proceedings of the Royal Society London B, Biological Society, 270 (1510): 61–67.
Taboada, C., Brunetti, A. E.,Pedron, F. N., Neto, F. C., Estrin, D. A., Bari, S. E., Chemes, L. B., Lopes, N. P., Lagorio, M. G. & Faivovich, J. (2017) Naturally occurring fluorescence in frogs. Proceedings of the National Academy of Sciences, 114 (14): 3672–3677.
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