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You are here: Home / 2018 / Archives for November 2018

Archives for November 2018

Croaking Science: Caecilians – unusual reproductive ecology

November 29, 2018 by admin

Croaking Science: Caecilians – unusual reproductive ecology

Caecilians, or blind snakes, as they are also often called, are limbless, elongate amphibians which inhabit tropical regions, with hotspots in South America and Asia (Kupfer et al., 2016; Gomes et al., 2012). Of all the groups of amphibians, caecilians are the most poorly understood, which is in part due to their secretive, fossorial lifestyle (Figure 1). They belong to the order Gymnophiona, one of three orders which comprises the Amphibia. There are currently 209 recognised species, which represents just 3% of the total 7,950 amphibian species worldwide (AmphibiaWeb, 2018). Caecilians are all ground-dwelling tropical amphibians which exhibit a wide range of reproductive modes, from laying eggs which hatch into aquatic larvae to those which hatch into miniature terrestrial juveniles. Little is known of their diverse reproductive modes but in recent years research has elucidated more information on their unusual breeding ecology.

Figure 1. Caecilians have an unusual appearance, being primarily fossorial and elongate in form. [Photo credit: Will Brown – Brown-snouted Blind Snake (Ramphotyphlops wiedii or nirgrogrescens) 3, CC BY 2.0,https://commons.wikimedia.org/w/index.php?curid=71399151]
Oviparous caecilians lay eggs, which are usually laid in a small terrestrial nest (Figure 2). The females of all these species exhibit extensive parental care, guarding their clutches of eggs against predators (Gomes et al., 2012). Eggs will hatch into either free-swimming larvae which develop in small water bodies, or terrestrial juveniles which are independent of their parents. Ichthyophis kohtaoensis inhabits the tropical forests of northern Thailand and belongs to the second largest caecilian family. In this species, breeding coincides with the rainy season with clutches of eggs laid in damp soil at the onset of the first rains (Kupfer et al., 2004). Females lay their eggs in small chambers near to temporary and permanent ponds, pools and slow flowing brooks and rivers. This allows the free-swimming larvae to readily hatch into the water to complete their aquatic development. Research suggests that females eat little or no food during the three month incubation period since the body condition of females attending young clutches is higher than those with older clutches (Kupfer et al., 2004). This, along with the small clutch size, indicates that there are costs to parental investment and attending eggs. In addition, there is a correlation between female body length and clutch size with older females being longer than young females (Kupfer et al., 2004). This implies that older, more experienced females produce larger clutches and more offspring (Kupfer et al., 2004).

Figure 2. A female caecilian guarding her brood of eggs from predators. [Photo credit: Davidvraju, Creative Commons Attribution-Share Alike 4.0 International, https://commons.wikimedia.org/wiki/File:Caecilian_guarding_its_eggs.jpg]
The ringed caecilian, Siphonops annulatus, is an unusual oviparous species inhabiting South America. The eggs hatch into poorly developed terrestrial young which feed on the skin of the female. The young possess specialised teeth which allow them to scrape skin from their mother’s back immediately after hatching (Wilkinson et al., 2008). The feeding behaviour of the young is described as being “quite frenetic with the young frequently tearing pieces of skin by spinning along their long axes and sometimes struggling over the same piece of skin” (Wilkinson et al., 2008) (Figure 3). This maternal dermatophagy is also known from a second, distantly related African caecilian species, Boulengerula taitana (Kupfer et al., 2008), which suggests that skin feeding is an ancient form of caecilian parental care and may have persisted for more than 100 million years (Wilkinson et al., 2008). In addition, Wilkinson et al. (2008) report a previously undocumented behaviour which involves the female raising herself upward, exposing her vent and releasing a clear fluid, which the young consume. This appears to be a form of feeding the young, but further studies are required to ascertain the function of this behaviour.

Figure 3. A caecilian mother with eggs which will hatch into young which feed off her skin. [Photo credit: Wilkinson M, Sherratt E, Starace F, Gower DJ (2013)]
Viviparous caecilians, which give birth to live young, represent another unusual reproductive mode for amphibians. During development inside the female, the foetuses initially obtain their nutrition from a yolk, similar to egg-developing species. After this, the developing young feed on a uterine milk, secreted from the oviducts of the female. The young obtain this through possessing specialised embryonic teeth which they use to scrape at the oviduct wall (Gomes et al., 2012). The evolution of viviparity in caecilians is poorly understood, but since both viviparous and oviparous species possess specialised teeth for scraping (either skin or oviduct milk), this suggests that all these species evolved from a common, oviparous ancestor (Kupfer et al., 2006). Gegeneophis seshachari is the only known species of viviparous caecilian from the Indo-Seychellean region (Gower et al., 2008). In this area the rainy season is short and unpredictable such that laying eggs which hatch into offspring that rely on the presence of water or a damp environment may be highly risky. Water bodies may dry up rapidly before larvae can fully develop. Therefore, Gower et al. (2008) propose that viviparity may have evolved in this species in response to short, unpredictable rainy seasons and the lack of suitable locations to lay and incubate their eggs.

Caecilians possess interesting and unusual reproductive modes, much of which is poorly understood. In addition, many of these species are threatened or Data Deficient and in regions which are undergoing large habitat loss and fragmentation. More primary data are required to fully understand caecilian reproductive ecology and evolution, which will help inform much needed improvements in conservation assessments for these species.

 

References

AmphibiaWeb (2018) https://amphibiaweb.org. University of California, Berkeley, CA, USA. Accessed 15 Nov 2018.

Gomes, A.D., Moreira, R.G., Navas, C.A., Antoniazzi, M.M. and Jared, C. (2012). Review of the reproductive biology of caecilians (Amphibia, Gymnophiona). South American Journal of Herpetology, 7 (3): 191-202.

Gower, D.J., Giri, V., Dharne, M.S. and Shouche, Y.S. (2008) Frequency of independent origins of viviparity among caecilians (Gymnophiona): evidence from the first ‘live-bearing’ Asian amphibian. Journal of Evolutionary Biology, 21: 1220–1226.

Kupfer, A.K., Nabhitabhata, J. and Himstedt, W. (2004) Reproductive ecology of female caecilian amphibians (genus Ichthyophis): a baseline study. Biological Journal of the Linnean Society, 83: 207-217.

Kupfer, A., Müller, H., Antoniazzi, M.M., Jared, C., Greven, H., Nussbaum, R.A. and Wilkinson, M. (2006) Parental investment by skin feeding in a caecilian amphibian. Nature, 440 (13 April 2006), doi:10.1038/nature04403.

Kupfer, A., Wilkinson, M., Gower, D.J. Müller, H. and Jehle, R. (2008) Care and parentage in a skin-feeding caecilian amphibian. Journal of Experimental Biology, 309A: 460–467.

Kupfer, A., Maxwell, E., Reinhard, S. and Kuehnel, S. (2016) The evolution of parental investment in caecilian amphibians: a comparative approach. Biological Journal of the Linnean Society, 119: 4–14.

Wilkinson, M., Kupfer, A., Marques-Porto, R., Jeffkins, H., Antoniazi, M.M. and Jared, C. (2008) One hundred million years of skin feeding? Extended parental care in a Neotropical caecilian (Amphibia: Gymnophiona). Biological Letters, 4: 358–361.

doi:10.1098/rsbl.2008.0217

Filed Under: Uncategorized Tagged With: Amphibians, caecillian, Croaking Science, Croaks, egg laying, reproductive ecology, terrestrial juveniles

Froglife Training 2019

November 19, 2018 by admin

Froglife Ecological Services training programme for 2019 has been released and can be viewed here.

Our expertise in amphibians and reptiles, conservation projects and habitat management enables us to deliver a range of courses to a wide variety of audiences at all levels of experience.

Our current courses include:

  • Introduction to Amphibians
  • Great Crested Newt Survey: Working Towards a Licence
  • Introduction to Reptiles
  • Reptile Ecology and Survey Techniques
  • Habitat Creation, Restoration and Enhancement for Amphibians

Our courses are designed to offer something for everyone, from complete beginner to more experienced naturalist or Environmental professional.

Most of our courses involve an element of field work or site visits. Largely the courses run on a single day, however our Great Crested Newt: Working Towards a Licence course does require a site visit the following morning.

In addition to our standard courses we are able to offer bespoke training courses to cater to groups such as NGOs, Charities, Government Departments, volunteer groups, ‘Friends of’ groups and Councils.

Courses are run from our Peterborough location, however if you would like to book a bespoke training course we are able to run this from your group’s own venue so long as there are suitable facilities available. We also occasionally offer courses at our London and Scotland locations. We have excellent facilities and an in-depth knowledge of the sites used offering the opportunity to get a close up view of these species and explore their habitats.

Get in touch with our Science & Research Manager, Laurence Jarvis to discuss and book your training course laurence.jarvis@froglife.org

More information about the services provided by Froglife Ecological Services can be found at www.fles.org.uk

Filed Under: Uncategorized Tagged With: 2019, Amphibians, ecology, FES, GCN, habitat, Licence, Monitoring, reptiles, survey, training

Vote for Froglife in the Charity Film Awards!

November 5, 2018 by admin

Froglife are in with a chance of winning a Charity Film Award thanks to an incredible film made by our River Nene Dragon Finder trainee, but we need your help!

Visit the Charity Film Awards Website and vote for us! Remember to tell your family and friends!

Voting closes on 14th Dec!

 

Filed Under: Uncategorized Tagged With: Charity Film Awards, Film, Froglife, River Nene, trainee, Vote

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