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Phyllomedusa 11(2):117–124, 2012 © 2012 Departamento de Ciências Biológicas - ESALQ - USP ISSN 1519-1397 Annular bone growth in phalanges of five Neotropical Harlequin Frogs (Anura: Bufonidae: Atelopus) Erik Lindquist1, Michael Redmer2, and Emily Brantner1 1 Department of Biological Sciences, Messiah College, One College Avenue, Grantham, PA 17027, USA. E-mail: quist@ messiah.edu. 2 United States Fish and Wildlife Service, 1250 S. Grove Ave., Suite 103, Barrington, IL 60010, USA. Abstract Annular bone growth in phalanges of five Neotropical Harlequin Frogs (Anura: Bufonidae: Atelopus). Skeletochronological studies were conducted on museum specimens representing five species of the highly threatened Neotropical genus Atelopus (Bufonidae). We detected annular bone growth (expressed as lines of arrested growth [LAGs]) patterns in each species, and this might provide insight to understand demographic constituency in future studies. In four of the five species under consideration, LAG counts in fore and hind limb bone occurred in a 1:1 ratio, indicating that bone growth was consistent within each individual. The use of skeletochronology in understanding historic and existing populations of Atelopus might assist in situ and ex situ population managers in making informed strategic conservation plans. Keywords: age estimation, demographic constituency, lines of arrested growth, skeletochronology. Resumo Crescimento do osso anular de falanges de cinco espécies de anuros neotropicais (Anura: Bufonidae: Atelopus). Estudos de esqueletocronologia foram realizados em amostras representativas de cinco espécies do gênero Neotropical altamente ameaçado Atelopus (Bufonidae). Detectamos crescimento ósseo anular (expresso em linhas de crescimento) em todas as espécies, o que pode oferecer subsídios para entender a estrutura demográfica em estudos futuros. Em quatro das cinco espécies consideradas, as contagens das linhas de crescimento nos ossos dos membros anteriores e posteriores ocorreram em uma proporção de 1:1, indicando que o crescimento do osso foi consistente dentro de cada indivíduo. O uso da esqueletocronologia na compreensão das populações históricas e atuais de Atelopus pode auxiliar os profissionais que trabalham com manejo in situ e ex situ no delineamento de planos de conservação estratégicos bem-embasados. Palavras-chave: esqueletocronologia, estimativa de idade, estrutura demográfica, linhas de crescimento. Received 26 July 2012. Accepted 3 December 2012. Distributed December 2012. Phyllomedusa - 11(2), December 2012 117 Lindquist et al. Introduction may be tracked over a period of years. Skele- tochronology has been increasingly used to Studies on demography and longevity cons- assess individual growth and age structure within titute a disproportionately small number of populations of amphibians from tropical or works on amphibians (Duellman and Trueb subtropical areas (e.g., Guarino et al. 1998, 1986), even of “common” species. Halliday and Pancharatna et al. 2000, Khonsue et al. 2000a, b, Verrell (1988) considered two techniques reliable 2001, Kumbar and Pancharatna 2001, Morrison for estimating age in amphibians and reptiles: et al. 2004, Lai et al. 2005). In these tropical capture-mark-recapture, and skeletochronology. studies it was sometimes assumed that dry/wet Skeletochronology involves visualizing and seasonality serves as the climatological cause for counting annular lines of arrested growth, or haematoxylinophilic lines of arrested growth. “LAGs” (located between bone growth areas) Recent researchers have found that in a seasonal from cross-sectioned diaphyses of long bones habitat the LAGs formation may be under such as femora or phalanges (Halliday and genetic control rather than seasonal (Marangoni Verrell 1988, Castanet and Smirina 1990). et al. 2009). Others have found that in yearly Skeletochronological studies could be important stable environments, LAGs could be irregular or in understanding historic demographic constitu- altogether absent (Kusrini and Alford 2006, encies from populations of currently endangered Tessa et al. 2007). species. Museum collections may hold crucial Our primary objective was to determine age/longevity information in these species from whether skeletochronology could be a useful when originally collected under prior healthy method for estimating age in five species of population statuses. This would appear to be Atelopus (A. chiriquiensis, A. peruensis, A. the case in the genus Atelopus, where many zeteki, A. lozanoi, and one species not yet museum collections hold scores of specimens described). In this genus, most species are taken from individual locations at a particular threatened or endangered with extinction from point in history (pers. obs. from multiple well- habitat fragmentation and degradation, over- known and substantial collections in the United collection and especially from chytridiomycosis States). (La Marca et al. 2005). Many species like A. A central, and now widely demonstrated and senex (Costa Rica), A. chiriquiensis (Panama accepted, assumption of skeletochronology is and Costa Rica), A. lozanoi (Colombia), A. that seasonal dormancy or inactivity leads to peruensis (Peru), and A. ignescens (Ecuador) are LAG formation. Thus, the technique is suitable already presumed to be extinct (La Marca and for age estimation of individual amphibians and Reinthaler 1991, La Marca et al. 2005, J. Lynch reptiles from populations occurring in seasonal pers. com.). A few others (e.g., A. zeteki) are climates (Halliday and Verrell 1988, Morrison et presumed extinct in the wild, but are sustained al. 2004, Matsuki and Matsui 2009). Skele- through ongoing ex situ conservation efforts, tochronology was first applied widely to anurans (e.g., captive breeding in zoological facilities) occurring in seasonal climates in Europe (Gagliardo et al. 2008, Mendelson 2011). Due to (Hemelaar 1985, Castanet and Smirina 1990, the critically imperiled status of much of this Castanet et al. 1993, Smirina 1994) and North genus, skeletochronological analysis of am- America (Bastien and LeClair 1992, Sagor et al. phibian tissues from museum collections may 1998, Redmer 2002). Skeletochronology may be provide some insights into historic demographic used as an effective non-lethal technique to constituency of populations, species, and could sample age of anuran populations at chosen or also assist in planning or management of captive successive points in time, thus, demographic populations, as well as founder wild populations parameters (such as age of reproductive adults) if reintroduction is attempted in the future. Phyllomedusa - 11(2), December 2012 118 Annular bone growth in phalanges of five Neotropical Harlequin Frogs genus Atelopus If the primary objective could be met, then A. lozanoi, and A. chiriquiensis were obtained the secondary objective of this study was to from prior studies under natural field conditions provide evidence in the literature to which by EDL and Carlos Navas in 1994 and 1995 (see reseachers and museums could refer, to make the Lindquist and Swihart 1997, Lindquist et al. case for wider, yet minimally destructive 1998). Unfortunately, only male specimens of sampling of Atelopus. This would help con- Atelopus sp. from Parque Nacional Nusagandi servation and captive managers better assess were available. The A. zeteki specimens came current population status and constituency by from specimens of limited information from the comparing to historic ones. Field Museum of Natural History. Specimens We examined histologically prepared cross- used for this study were legally obtained through sectioned and stained Atelopus phalanges in field collection and museum collections. order to determine whether annular growth is detectable in this genus. We also attempted to Histology determine if periodical growth rings and LAGs are present in a one-to-one ratio in penultimate One finger and one fourth toe were amputated phalanges from toes and fingers. from each specimen. Digits were fixed for a minimum of 24 hr in 10% formalin, rinsed 12 hr Materials and Methods in tap water, and stored in 70% ethanol. The penultimate phalanx from each digit was Species decalcified for 24 hr in Kristensen’s formic acid solution, and then rinsed for 24 hr in running tap Histological sectioning was conducted on water. Phalanges were automatically cleared and preserved specimens of five Neotropical species stained (V.I.P. Tissue-Tek® Machine), then of Atelopus: (1) A. chiriquiensis (2:7; N = 9) embedded in small paraffin blocks. The tissues from the highland cloud forests (2,200 m asl) of were sectioned to 10 µm with a rotary microtome. western Panama, A. peruensis (6:8; N = 14) from Mid-diaphyseal cross sections were mounted on the puna and sub-puna northern Peruvian Andes microscope slides with adhesive gelatin. Tissues (2,800–4,200 m asl; study specimen elevation were dehydrated with a series of alcohol steps, unknown), A. zeteki (2:2; N = 4) from the low to stained for 12 minutes with Shandon® Instant middle elevation moist forests (1,000 m) of Regressive Hematoxylin, and brought to water, central Panama, A. lozanoi (3:2; N = 5) from the at which time they were covered with Permont® high elevation páramo (3,000–3,300 m asl) of mounting medium and glass coverslips. Parque Natural Nacional Chingaza, Colombia, and Atelopus sp. (7:0; N = 7) (Nusagandi), from Skeletochronological Evaluation the lowland rain forest (600 m asl) of Parque Nacional Nusagandi, Kuna Yala, Panama. The Cross sections were

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