Sagalla caecilian (Boulengerula niedeni)

Description

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Sagalla caecilian fact file

• Description
• Biology
• Range
• Habitat
• Status
• Threats
• Conservation
• Find out more
• Glossary
• References
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Sagalla caecilian description

First described as recently as 2005 ⁽³⁾, the Sagalla caecilian belongs to a highly unusual group of amphibians characterised by an elongated, limbless, externally segmented body, closely resembling that of a snake or a large earthworm. However, unlike earthworms, caecilians possess a prominent mouth, nostrils, and, uniquely amongst vertebrates, a pair of retractable tentacles, one on each side of the head, between the eye and nostril ^{(2) (4) (5) (6) (7)}. The skin is smooth, but toughened with keratin, and sometimes has fish-like scales in its folds ^{(4) (5) (6) (7)}, although these are reportedly absent in the Sagalla caecilian ⁽⁴⁾. The snout of the Sagalla caecilian is rounded, with short, globular tentacles ^{(3) (4) (7) (8)}, and a relatively large mouth, with two rows of teeth in each jaw ^(4) (6). The eyes are highly reduced, and entirely covered by bone and skin ^{(3) (4) (7) (8)}. As in many caecilians, there is virtually no tail, the body ending instead in a rounded, unsegmented ‘terminal shield’ ^{(3) (4) (5) (6)}.

The body of the Sagalla caecilian is brownish in colour, with a pinkish-red tinge, and with white markings around the body rings. The underside is lighter brown. Juveniles, in contrast, are unpigmented, other than along a dark, narrow band on the back. The Sagalla caecilian is the only Boulengerula species, other than its closest relative, Boulengerula taitana, to have a pigmented body, and can be distinguished from B. taitana by its brownish rather than bluish-black colouration, as well as by various morphological differences ^{(3) (4) (8)}.

Also known as

Sagala caecilian.

Size

Length: up to 30 cm ⁽²⁾

Body diameter: up to 0.6 cm ^{(2) (3)}

Sagalla caecilian biology

The Sagalla caecilian spends its life underground, using the strong, bony head to burrow through the soil. An extra pair of jaw-closing muscles are thought to hold the jaw firmly closed while burrowing, and the skin is fused to the underlying bones, to prevent it from shearing away during digging ^{(4) (5) (6) (7)}. Like the related B. taitana ⁽⁹⁾, the Sagalla caecilian is likely to feed mainly on earthworms and termites, as well as other soil invertebrates. Prey is located using the acute sense of smell, aided by the tentacles, which may detect both chemical and tactile signals ^{(2) (4) (5) (6) (7)}. The caecilian may lie in wait or actively hunt prey, which is seized in the strong jaws, and held fast by the inwardly curving teeth ^(4) (5). The Sagalla caecilian may itself fall prey to snakes, birds and driver ants, although its skin possesses poison glands which may make it unpalatable to many predators. The name ‘caecilian’ is derived from the Latin for ‘blind’, but, despite this species’ reduced eyes, it is still thought to be capable of detecting light ^{(4) (5) (6) (7)}.

Little is known about courtship behaviour in caecilians, but fertilisation is internal, the male transferring sperm directly to the female ^(4) (5). In this species, the female then digs an underground chamber, into which around five eggs are laid. The eggs are guarded by the female, and hatch into miniature versions of the adults, without passing through a free-living larval stage ^{(4) (7) (8)}. Like its close relative, B. taitana, the Sagalla caecilian is likely to show an extraordinary form of maternal care, in which the hatchlings feed on the outer layer of the female’s skin, which becomes modified, turning pale, and contains high levels of fat and other nutrients. The young even possess specialised teeth with which to take advantage of this peculiar food source ^{(4) (8) (10)}. Although further details of reproduction in this species are lacking, it may, like B. taitana, breed during the short rains, the young becoming subadults around a year after hatching, and reaching maturity at about two years ^(8) (10).

Sagalla caecilian range

The Sagalla caecilian is known only from a small area on Sagalla Hill in southeast Kenya. It has been found above elevations of 1,000 metres, and is believed to be restricted to an area of just 29 square kilometres, with this mountain block isolated from other similar habitats by the arid Tsavo plains ^{(1) (3) (4) (8)}.

Sagalla caecilian habitat

This caecilian is thought to have originally been a montane forest species, but much of this habitat has been replaced by shambas (smallholder farms), where the Sagalla caecilian is now commonly found in dark, moist soil beneath banana plants or under decomposing vegetation, particularly near streams ^{(1) (2) (3) (4) (8)}. The species requires moist soil, both to maintain its moist skin and as a suitable habitat for its prey, and may move into the upper layers of the soil during the rains. However, unlike many amphibians, the Sagalla caecilian lays its eggs on land, and so is not dependent on streams or other water bodies for reproduction ⁽⁴⁾.

Sagalla caecilian status

Classified as Critically Endangered (CR) on the IUCN Red List ⁽¹⁾.

Sagalla caecilian threats

Despite being relatively common in suitable habitats within its range ^(1) (4), the Sagalla caecilian is confined to a single location, and its distribution has become severely restricted, with an ongoing decline in the extent and quality of its habitat. Although it may be tolerant of small-scale farming, it is found in much higher densities near streams away from farms, and so the area of optimal habitat for the species may be small. In addition, much of Sagalla Hill is now covered with eucalyptus plantations, in which the dry, compacted soil and lack of soil invertebrates presents an unsuitable habitat for caecilians ^{(1) (2) (4)}. The species is also absent from remaining natural forest at higher elevations, which may either be above its natural range or have otherwise unsuitable conditions ^(1) (4).

Only around 0.04 square kilometres of natural forest now remains on Sagalla Hill, and is under continued threat from cutting for wood and the expansion of farms. The harvesting of fallen wood may have a negative impact on the Sagalla caecilian since it prevents rotting material from enriching the soil, and also means the loss of the invertebrates that feed on it ⁽²⁾. The loss of vegetation, particularly along streams, has also resulted in severe flooding, soil erosion, and the drying out of the soil, so further degrading the caecilian’s habitat and breeding areas ^{(1) (2) (4) (8)}. Pesticides and other pollutants may also pose a threat to the species ^(1) (4). Like many amphibians worldwide, some caecilians have died from infection with a chytrid fungus ⁽⁵⁾. Although this has not yet been reported in the Sagalla caecilian, it may pose a potential future threat.

Sagalla caecilian conservation

Very little is currently known about this recently discovered species ⁽⁴⁾, and it does not occur in any protected areas ^(1) (4). However, a number of conservation initiatives are in place in the region, including a study into amphibian diversity ⁽⁴⁾. This caecilian is seen locally as an indicator of rich, fertile soil ⁽²⁾, and efforts have been underway to raise its profile amongst local communities, including a competition to find a name for the species in the local dialect ^{(4) (11)}. The Zoological Society of London’s “EDGE of Existence” campaign is also working to establish a caecilian preserve and to restore habitat for the species ^(2) (4).

Urgent priorities for the Sagalla caecilian’s conservation include stabilising the soil by restoring vegetation and improving agricultural practices, as well as careful replacement of eucalyptus plantations with indigenous trees, working with local communities, and undertaking further study into the caecilian’s ecology, to aid the creation of a Conservation Action Plan ^{(1) (2) (4) (8)}. Establishing a captive research and breeding programme may also be an additional option. Finally, since this unique amphibian has often been found in association with banana plantations, sensitive cultivation of bananas may benefit the Sagalla caecilian whilst also providing a source of income for local people ⁽⁴⁾.

View information on this species at the UNEP World Conservation Monitoring Centre.

Find out more

To find out more about this and other caecilians see:

• Gymnophiona.org:
  http://www.gymnophiona.org/
• EDGE of Existence: Evolutionarily Distinct & Globally Endangered:
  http://www.edgeofexistence.org/amphibians/species_info.php?id=548

For more information on amphibian conservation see:

• IUCN / SSC Amphibian Specialist Group:
  http://www.amphibians.org/
• Amphibian Ark:
  http://www.amphibianark.org/

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Glossary

Fertilisation

The fusion of gametes (male and female reproductive cells) to produce an embryo, which grows into a new individual.

Invertebrates

Animals with no backbone, such as insects, crustaceans, worms, molluscs, spiders, cnidarians (jellyfish, corals, sea anemones), echinoderms, and others.

Larval

Of the stage in an animal’s lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.

Montane forest

Forest occurring in the montane zone, a zone of cool upland slopes below the tree line dominated by large evergreen trees.

Morphological

Referring to the visible or measurable characteristics of an organism.

Vertebrates

Animals with a backbone, including mammals, birds, reptiles, amphibians and fish.

References

1. IUCN Red List (February, 2010)
   http://www.iucnredlist.org
2. IUCN / SSC Amphibian Specialist Group: Projects - Kenya (February, 2010)
   http://www.amphibians.org/ASG/Kenya.html
3. Müller, H., Measey, G.J., Loader, S.P. and Malonza, P.K. (2005) A new species of Boulengerula Tornier (Amphibia: Gymnophiona: Caeciliidae) from an isolated mountain block of the Taita Hills, Kenya. Zootaxa, 1004: 37-50.
4. EDGE of Existence: Evolutionarily Distinct & Globally Endangered (February, 2010)
   http://www.edgeofexistence.org/
5. Halliday, T. and Adler, K. (2002) The New Encyclopedia of Reptiles and Amphibians. Oxford University Press, Oxford.
6. Gymnophiona.org (February, 2010)
   http://www.gymnophiona.org/
7. Loader, S.P., Gower, D.J. and Wilkinson, M. (2003) Caecilians: mysterious amphibians of the Eastern Arc Mountains. Arc Journal, 15: 3-4.
8. Malonza, K.P.W. (2008) Amphibian Biodiversity in Taita Hills, Kenya. Ph.D. Thesis, Johannes Gutenberg University Mainz.
9. Gaborieau, O. and Measey, G.J. (2004) Termitivore or detrivore? A quantitative investigation into the diet of the East African caecilian Boulengerula taitanus (Amphibia: Gymnophiona: Caeciliidae). Animal Biology, 54: 45-56.
10. Malonza, P.K. and Measey, G.J. (2005) Life history of an African caecilian: Boulengerula taitanus Loveridge 1935 (Amphibia: Gymnophiona: Caeciliidae). Tropical Zoology, 18: 49-66.
11. Wojnowski, D. and Malonza, P.K. (2009) Kilima-Mrota is not a worm: the effect of conservation education and a local naming contest on the perspectives held by the peoples of Sagalla Hill, Kenya towards the Sagalla caecilian Boulengerula niedeni. Journal of East African Natural History, 98(2): 241-248.