Sylvacaecilia grandisonae (Taylor, 1970)
Aleku caecilian; Ethiopian caecilian
|Species Description: Taylor, E. H. 1970. A new caecilian from Ethiopia. University of Kansas Science Bulletin 48: 849–854.|
Sylvacaecilia grandisonae, commonly known as the Aleku caecilian, is a thick-bodied and short caecilian described from two specimens with a total length of 259 mm and 260 mm (Taylor 1970; Largen and Spawls 2010). A rounded snout protrudes about 1.2 mm beyond the mouth, the lateral distance from snout tip to first nuchal groove approximately 12.4 mm, which is smaller than the distance from snout tip to the second or third nuchal groove. From snout tip to rictus oris, the lower jaw is around 8 mm in length (Taylor 1970). The head slightly narrows anteriorly and the eyes are in a socket, visible below the skin and not covered by bone (Taylor 1970; Channing and Rödel 2019). In S. grandisonae, the tongue has a narrow tip, is extensively marginally free, and features distinct, lateral, and unpigmented narial plugs (Wake 1987). Furthermore, the tentacle aperture is closer to the eye than the nares, but equidistant between the line from eye to nares and edge of lip. The tentacular groove is not continuous with the eye and the external opening of the tentacle is small, barely elevated, and slightly horseshoe-shaped (Taylor 1970).
The premaxillary-maxillary series for S. grandisonae is 19 - 1 - 21, the prevomeropalatine series is 20 - 1 - 21, the dentary series is 17 - 17, and the splenial series is 5 - 5; the dentary teeth are mostly larger than the premaxillary or maxillary teeth, while the splenials are smaller or equal to the prevomeropalatine teeth (Taylor 1970).
The body itself is 4.6 - 11.5 mm in width and the length is around 20.4 - 26.9 times that (Taylor 1970; Largen et al. 1972). Following the occiput, there are two indistinctive collars, which Taylor (1970) noted to be slightly swollen in the holotype, perhaps due to a tumor in the mouth and throat. There are 84 - 95 primary annuli that follow the second collar, which are dorsally complete, but narrowly incomplete on the ventrum for a majority of the anterior half of the body. Additionally, there are 69 - 72 secondary annuli, with roughly 32 - 33 of them being complete. Sylvacecila grandisonae has several nuchal grooves on the collars. First, a distinctive lateral nuchal groove that is vague dorsally and laterally, followed by a vague transverse groove on the collar. Next, there is a nuchal groove that limits the first groove and is vague on the dorsal surface, but distinct ventrally and laterally. Lastly, there is another nuchal groove that is distinct dorsally and ventrally, which briefly fuses with the first primary ring. Beginning on the primary annuli near the first secondary annuli, scales are observable, with two to three scale rows (potentially complete ventrally) in each ring at the midbody and four to five scale rows in each ring on the last 20 mm of the body. These posterior scales vary in size, but the largest is 1.2 - 1.4 mm in width. There are no subdermal scales nor scale rows in the first secondary annuli (Taylor 1970).
Sylvacecila grandisonae has a 3 mm wide terminal shield and a sub-circular vent with elevated surrounding denticulations. From vent to terminus, the length is roughly 2 mm and the width of the body near the vent is 8.5 mm (Taylor 1970). The cloacal structure and extruded phallodeum have connective tissue ridges, visible patterns of sacs, lateral flanges, and lateral lobes (Wake 1987). In males, a fully extruded penis can be found with a length of around 12.8 mm and breadth of 6.6 mm (Largen et al. 1972).
There are visible skin glands on S. grandisonae. Elongate glands are within the grooves as well, directing forward and backward (Taylor 1970).
Wake (1987) describes a juvenile of total length 110 - 145 mm.
Sylvacaecilia grandisonae can be differentiated from caecilians in Geotrypetes, which it was previously assigned to, by its number of posterior scale rows, fewer splenial teeth, fewer primary body rings, greater number of secondary (and complete) body rings, closer proximity of its tentacular aperture to its eye rather than nares, extensively marginally free tongue with narial plugs, oviparity (where Geotrypetes is viviparous), and numerous osteological differences (Taylor 1970; Wake 1987). In addition, S. grandisonae differs from Herpele by having eyes in a socket, the tentacle between the eye and nares (rather than below as Herpele), and some osteological absences. Osteological differences, fewer splenial teeth, and a presence of larval period further separate S. grandisonae from Schistometopum and Idiocranium, which respectively lack a larval period or have direct development. Additionally, phallodeal morphology separates S. grandisonae from Schistometopum. Lastly, an unroofed eye socket and secondary annuli and scales also differentiate S. grandisonae from Boulengerula and Afrocaecilia, and splenial teeth further diagnose S. grandisonae from Boulengerula (Wake 1987). Please see Wake (1987) for an in-depth description of osteological differences.
In life, S. grandisonae is a near uniform dull bluish to violet/dark purplish-brown with a violet anterior from a dorsal view and paler/pinkish from a ventral view. Dorsally and laterally, the head and chin is lighter than the dorsum and grayish. Over and surrounding the eye (creating a ring), at the nostril, at the tentacle, and covering the vent area’s denticles, there is a visible light spot. The pale ring around the eye extends to the pale spot at the tentacle, which itself is bright red. A suffusion of minute pale spots are visible on all body surfaces, indicating the presence of skin glands and creating a dusty appearance, but the spots are more distinct in the grooves of the primary and secondary annuli. Anteriorly, the lateral folds have narrow and vague light edges (Taylor 1970; Largen et al. 1972; Largen and Spawls 2010).
In preservation, S. grandisonae is dark slate-gray or purple-gray dorsally and pinkish-gray ventrally, with a whitish bloom on all surfaces due to a mucous covering, and a dark brown pigmentation beneath such a layer (Largen et al. 1972).
Taylor (1970) describes variation in the secondary annuli and scales, with some caecilians lacking scales. Additionally the first few secondary annuli featured elongate glands filled with a cheese-like substance that may be the result of infection or similar glands in the primary annuli, with few scales in these regions.
Distribution and Habitat
Sylvacaecilia grandisonae is endemic to southwestern Ethiopia, within an elevation range of 1500 - 2180 m (Taylor 1970; Largen and Spawls 2010). The caecilians live under damp leaf-litters and humus on the floors of tropical deciduous forests, and are most accessible in Baad Buna Forest (Wake 1987; Largen 2001; Largen and Spawls 2010).
Life History, Abundance, Activity, and Special Behaviors
Sylvacaecilia grandisonae is more active at night and burrows rapidly, snout first. If disturbed, especially on their acutely sensitive snouts, the caecilians secrete mucus and react violently, notably making a very faint squeak or a singular, barely audible croak (Largen et al. 1972).
These caecilians swim by vigorous lateral undulations with a large amplitude, this motion keeping the head of the caecilian above the water, but adults appear unsuited for swimming as Largen et al. (1972) noted by the exhaustion of the caecilians when taken out of the water and their short swimming periods.
Sylvacaecilia grandisonae breed in streamlets and small springs, where females lay eggs in burrows close to the water, thus engaging in an oviparous system (Largen and Spawls 2010). Wake (1987) describes such ovarian eggs, within a clutch size of 25 eggs, to be relatively large and well-yolked (Largen 2001; Largen and Spawls 2010).
The Aleku caecilian feeds on oligochaetes and termites (Largen and Spawls 2010). Wake (1987) describes such ovarian eggs, within a clutch size of 25 eggs, to be relatively large and well-yolked (Largen 2001; Largen and Spawls 2010).
The aquatic larvae of S. grandisonae are free-living and feeding (Wake 1987). Their total length ranges from 57 - 120 mm, and their bodies having a maximum width of 2.5 - 5.3 mm. A more or less truncated tip of the lower jaw can be observed. The immediate anterior lower jaw is excavated so there is a visible small anterior aperture when the jaws are closed. The lips are distinctly large and fleshy. The nostrils create a slightly bowed vertical slit (Largen et al. 1972). At a slight depression closer to the eye than nares, a non-functional larval tentacle can be seen (Largen et al. 1972; Largen and Spawls 2010). The eyes of these larvae feature a thin skin covering, a round lens, and a normal nerve-retinal-muscular complement (Wake 1987).
Intra-oviducal, multi-rowed dentition with spoon-shaped crowns can be observed in the larvae and recent metamorphs, with the premaxillary-maxillary series being 9 - 1 - 9 to 10 - 1 - 10, the prevomeropalatine series is 11 - 1 - 11 to 12 - 1- 12, the dentary series is 11 - 11 to 13 - 13, and the splenial series is 2 -2 to 3 - 3 (Largen et al. 1972; Wake 1987).
On the sides of the head and body, small pits are distinct and indicate a neuromast sensory system, which has mechanoreceptive neuromasts and electroreceptive ampullary organs to help orient the larvae in murky waters (Wake 1987; Largen and Spawls 2010). Sylvacaecilia grandisonae larvae also have spiracles on each side of the neck, on the groove that separates the first and second collars, which allow water to passed over the internal gills and exit (Largen et al. 1972; Largen and Spawls 2010).
At metamorphosis, when the snout-vent length is roughly 105 - 120 mm, the spiracles close, the neuromast system disappears, the fleshy lips disappear, and the ventral edges of the nostril’s vertical slit fuse so the now slightly oval nostrils are horizontal. In addition, the tentacle, which has been gradually moving forward during development, accelerates its movement to the mid-way between the eye and nares and becomes more externally visible as the tentacle perforates to the exterior side (Wake 1987; Largen et al. 1972; Largen and Spawls 2010).
In life, the larvae are more pale brown than adults. The heart and blood vessels are visible in very small specimens from a ventral view. Pale-edged pits can be seen on the sides of the head and body too. In preservation, the larvae are gray-brown dorsally and dirty yellow ventrally, with darker pigmentation as size increases (Largen et al. 1972).
When larvae hatch, they burrow into water-saturated, soft mud to seek shelter during the day, and presumably feed on aquatic invertebrates in the dark (Largen et al 1972).
Trends and Threats
The development of housing, urbanization, logging/wood-harvesting, annual and perennial agriculture, and pollution effluents from agriculture and forestry all threaten S. grandisonae by altering the general soil moisture and temperature in its environment. Sylvacaecilia grandisonae can be found in the protected area of UNESCO-MAB Kafa Biosphere Reserve, but its remaining montane forest habitats need further protection from exploitation (IUCN 2016).
Possible reasons for amphibian decline
General habitat alteration and loss
Originally, Taylor (1970) described S. grandisonae as Geotrypetes grandisonae, but noted this placing was tentative. Later, Wake (1987) placed the caecilian in Sylvacaecilia due to numerous osteological differences, soft tissue morphological differences, and life history differences. The same evidence was used to propose Geotrypetes and Schistometopum as sister groups, with Sylvacaecilia as an outgroup (Nussbaum and Wilkinson 1989).
The genus Sylvacaecilia was named after “sylva”, a Greek word meaning “forest”, referencing its tropical deciduous forest habitat, and “caecilia”, referencing its taxon (Wake 1987).
The species epithet, grandisonae, is in honor of Miss Alice G.C.Grandison, the Curator of Herpetology at the British Museum, who provided two of these caecilians to Taylor (1970) for his study (Taylor 1970).
Channing, A., & Rödel, M. O. (2019). Field guide to the frogs & other amphibians of Africa. Penguin Random House South Africa.
Frank, N., & Ramus, E. (1995). A complete guide to scientific and common names of reptiles and amphibians of the world. NG Publishing, Inc.
IUCN SSC Amphibian Specialist Group. 2016. Sylvacaecilia grandisonae. The IUCN Red List of Threatened Species 2016: e.T59598A16944802. https://dx.doi.org/10.2305/IUCN.UK.2016-1.RLTS.T59598A16944802.en. Accessed on 4 April 2023.
Largen, M. J. (2001). Catalogue of the amphibians of Ethiopia, including a key for their identification. Tropical Zoology, 14(2), 307-402. [link]
Largen, M. J., Morris, P. A., & Yalden, D. W. (1972). Observations on the caecilian Geotrypetes grandisonae Taylor (Amphibia Gymnophiona) from Ethiopia: Pubblicazioni del centro di studio per la faunistica ed ecologia tropicali del CNR: LX. Monitore Zoologico Italiano. Supplemento, 4(1), 185-205. [link]
Largen, M., & Spawls, S. (2010). The Amphibians and Reptiles of Ethiopia and Eritrea. Edition Chimaira. Frankfurt am Main, Germany.
Nussbaum, R. A., & Wilkinson, M. (1989). On the classification and phylogeny of caecilians (Amphibia: Gymnophiona), a critical review. Herpetological monographs, 3(1989), 1-42. [link]
Taylor, E. H. (1970). A new caecilian from Ethiopia. University of Kansas Publications. [link]
Wake, M. H. (1987). A new genus of African caecilian (Amphibia: Gymnophiona). Journal of Herpetology, 6-15. [link]
Originally submitted by: Hong Nguyen (2023-04-21)
Description by: Hong Nguyen (updated 2023-04-21)
Distribution by: Hong Nguyen (updated 2023-04-21)
Life history by: Hong Nguyen (updated 2023-04-21)
Larva by: Hong Nguyen (updated 2023-04-21)
Trends and threats by: Hong Nguyen (updated 2023-04-21)
Comments by: Hong Nguyen (updated 2023-04-21)
Edited by: Ann T. Chang (2023-04-27)
Species Account Citation: AmphibiaWeb 2023 Sylvacaecilia grandisonae: Aleku caecilian; Ethiopian caecilian <https://amphibiaweb.org/species/1945> University of California, Berkeley, CA, USA. Accessed Dec 5, 2023.
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Citation: AmphibiaWeb. 2023. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 5 Dec 2023.
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