Rediscovery, natural history, and conservation status of Idiocranium russeli Parker, 1936 (Amphibia: Gymnophiona: Indotyphlidae)

Abstract

The indotyphlid caecilian amphibian Idiocranium russeli Parker, 1936 is the only nominal species in its genus. Apart from two additional, largely overlooked locality records that we consider to be of an undescribed species, I. russeli is known with certainty from only a single collection of c.50 specimens from a single locality in 1933. We report new material from fieldwork in 2012 carried out in the vicinity of the type locality. Digging surveys at 34 sites for a total of >2000 person minutes found 50 I. russeli at 15 of these sites, extending the known range of the species by more than 40 km south and from an elevation of c.670 m to 104–820 m. The species probably occurs in nearby Nigeria and in some protected areas, is tolerant of some human disturbance, and is likely to move from Data Deficient to Least Concern on the IUCN Red List. Males have relatively longer and wider heads than females. Total length measured for preserved specimens is less than for freshly anaesthetized specimens, by up to 14.1%. Previously, preserved I. russeli were reported as having a maximum length of 114 mm, but the new sample includes specimens with total lengths of 145 mm in preservation and 167 mm when fresh. The sex of the smallest independent specimens (total length 62 mm in preservation) could be determined from examination of the gonads, hatchlings are c.30 mm, and I. russeli is confirmed as one of the smallest known caecilian species.

Keywords:

• abundance
• caecilian
• Cameroon
• Mamfe
• reproduction
• size

Acknowledgements

This work was funded primarily by the US Fish & Wildlife’s Wildlife Without Borders – Amphibians in Decline scheme, Zoological Society of London’s EDGE Fellowship scheme, Conservation International’s Lost Amphibians scheme, and The Royal Geographical Society, all of which we gratefully acknowledge. Additional funding that contributed to the work presented here was granted by the Zoological Society of London (Erasmus Darwin Barlow Grant), the Royal Zoological Society of Scotland, the Natural History Museum, London and the Institute of Zoology, London.

We are greatly indebted to many Cameroonian people of Mamfe Division who helped us with logistics and generously provided field assistance and hospitality. We thank the people of the villages of Ote, Kakpenyi, Tinta, Makamune, Atolo, Bashou, Nyang, Akwa, Bakebe, Tali and Nta-Ali. We particularly acknowledge the assistance of Apa Eric Ongbanya and Anya Aaron Sassa (Makamune), Tata Eric Tunda (headteacher, Tinta), Augustin and Gabriel (Kakpenyi), Wilfred and Rafael (Tinta), Joseph (Atolo), John (Bashou), Essa Leonel (Akwa), Ashu Thomas Takwa (Nyang), Emmanuel Abunga (Mukonyong), Ojong Phillipe Tabot (Eshobi), Regent (Tali), Peter (Bakebe), Joseph (Mfainchang), Njouki George and Asho Smith (Nta-Ali).

We also thank Gespo for looking after us in the field, Helen Meredith, Jeff Dawson and Cath Lawson for work on MTK’s EDGE fellowship, Simon Loader for his fieldwork with us in Cameroon in 2008, and Ngane Benjamin Kome and Nono Gonwouo for support throughout. Peter Giere provided information on Sanderson’s material in the Hubrecht Collection, Berlin, and Hendrik Müller staged the embryos and measured some hatchlings.