seaturtle.org : MTN : ARCHIVES : Sign In

These mutations are a relatively rare phenomenon but have been reported for many different animal groups (birds: Sage 1962; mammals: Fertl & Rosel 2009; amphibians: Eagleson et al. 2010; reptiles: da Costa et al. 2013). Reports of albino and leucistic marine turtles refer mostly to hatchlings found in nests during monitoring campaigns. Most of the accounts are of a few individuals per nest, usually associated with other physical abnormalities such as supernumerary scutes or skull deformities (Türkozan & Durmuş 2001; Ibarra & Gasca 2009; Bárcenas-Ibarra et al. 2015).

For green turtles (Chelonia mydas), these accounts are uncommon but widespread throughout their distribution range (Table 1). The largest number of albino hatchlings reported from a single clutch was of 29 (including dead embryos and dead-in-shell hatchlings), from Juno Beach, Florida (Perrault & Coppenrath 2019).

Table 1. Reported cases of albinism and leucism in green turtle hatchlings, Chelonia mydas. NS = non specified.

Here we report all cases of albino and leucistic hatchling green turtles recorded at Poilão Island, Bijagós Archipelago, Guinea-Bissau. The green turtle population nesting on the Bijagós Archipelago is among the six largest in the world, with 90% of the nesting occurring at Poilão Island, where ca. 29 000 clutches are estimated to be laid annually (Catry et al. 2009). This island is protected by traditional taboos and, since 2000, by the João Vieira and Poilão Marine National Park (PNMJVP), a 495 km2 protected area that is also part of a Biosphere Reserve and a Ramsar site.

Poilão has been target of annual monitoring campaigns since 2004, organized by the “Instituto da Biodiversidade e das Áreas Protegidas” (IBAP), the governmental institution managing protected areas and nature conservation in Guinea-Bissau. Annually, about 100 randomly selected nests are monitored to obtain estimates of nesting success. These are followed throughout the incubation process until hatchling emergence, and the nest cavity is opened afterwards, or after 60 days in the case of no recorded emergence, to evaluate nest contents.

Like on other sea turtle breeding sites, we have documented unusual colorations among hatchlings during nest excavations. Throughout the years, there have been regular but isolated accounts of leucistic and albino individuals. The first is from 30 September 2009, when a single leucistic hatchling, with no visible malformations, was found in a clutch of 105 eggs (Fig. 1). The next two accounts were in 2014 (3 September and 9 October), each of a single leucistic malformed hatchling in each clutch. The first presented supernumerary scutes, while the second had a deformed mandible and skull, lacking eyes (Fig. 1).

Figure 1. a) Healthy leucistic hatchling found 30 September 2009. Its pigmented eyes and grey body indicate the presence of melanine; b) Malformed leucistic hatchling found 9 October 2014. With a highly deformed skull, this hatchling had a low chance of survival; c) Malformed leucistic hatchling found 3 September 2014 with supernumerary scutes.

Figure 2. a) Excavation of the nest with 30 healthy albino hatchlings; b) Healthy albino hatchling from the same clutch. The red eyes and pinkish skin indicate the absence of melanin; c) Comparison between an albino and a normal colored green turtle hatchling.

On 5 October 2018, 30 healthy albino green turtle hatchlings were found in a single nest (Fig. 2). The nest was excavated after 60 days without emergence, having been laid on 5 August 2018, by a 99.5 cm (curved carapace length), 97.5 cm (curved carapace width) normally pigmented female. The female was tagged with two flipper tags (10209 on left front flipper and 10210 on right front flipper) and a PIT tag (977200009430435) in the left shoulder. This female was observed nesting again on the same beach on 18 August and 3 September 2018.

During nest excavation, at 68 cm depth we found 115 live hatchlings and 8 undeveloped eggs with no embryos, comprising a clutch of 123 eggs. This is near the average clutch size at this breeding site (120.3 ±30.2 eggs, n=98, Patrício et al., 2017). All hatchlings looked healthy and had no visible malformations or scute anomalies, apart from the lack of pigment in the 30 albino turtles (Fig. 2).

We collected all 30 albino hatchlings and a random sample of 30 normally pigmented hatchlings, and used calipers to collect the following morphometric data, to the nearest 0.1mm: straight carapace length (SCL), straight carapace width (SCW) and shell height (SH) (Table 2). After measurements, a small tissue sample (ca. 5mm x 1mm) from the edge of the carapace was taken from each hatchling for future genetic analysis. All hatchlings were processed <30 min and, afterwards were kept in the shade, inside buckets with moist sand from their nest, and released on the sand near the nest after dark, simulating natural conditions.
The only difference in size was that the albino turtles were significantly wider (larger SCW, t29 = 3.622, p-value < 0.001, Table 2). Sonmez & Ozdilek (2011) reported that albino hatchlings were bigger than normal hatchlings. This suggests that, in green turtles, albinism may be associated with bigger overall size in hatchlings.

Table 2. Morphometric measurements (mm) of all measured hatchlings from the clutch reported in this study. Values are presented as mean ±SD (range). SCL = rectilinear carapace length; SCW = rectilinear carapace width and SH = shell height. *** indicates significant difference between groups (see text).

The complete absence of visible malformations on the albinos of such a large clutch makes this report unusual, and the first of its kind for green turtles. Perrault & Coppenrath (2019), who reported a similar case of 23 live green turtle albino hatchlings found in a single nest laid on Juno beach, Florida, found that some albino hatchlings had scute abnormalities (Table 1). The only other published case of a single clutch having a large number of albino hatchlings with no malformations comes from Marcovaldi et al. (1995) who reported 22 live albino loggerheads (Caretta caretta) from a nest laid in Brazil.

In the context of the Brazilian loggerhead albinos, Godfrey & Mrosovsky (1995) suggested that “if (…) albinism is caused by a single locus homozygous recessive allele, a cross between two heterozygous parents would result in 25 % of the offspring having an albino phenotype.” This implies that a clutch with ~25% of albino hatchlings would probably belong to a single father, and possibly to two related parents, and may describe the parental contributions in the two cases of large numbers of green sea turtle albino hatchlings, from Florida (25% albinos, Perrault & Coppenrath 2019) and Poilão Island (24% albinos, this study). Multiple paternity is common in green turtles (Chassin-Noria et al., 2017; Lee et al. 2018), and its incidence tends to be highest in rookeries with higher numbers of nests (Lee et al., 2018). The possible occurrence of a single paternity event in a nesting population as numerous as the one in Poilão is not necessarily unexpected, and the frequency of such cases in this population is still unknown. Multiple paternity studies will help to clarify if single paternity is common at this site or a rare event much like albinism.

Apart from the embryo/hatchling stages, albino and leucistic marine turtles are rarely seen in the wild (Fletemeyer 1977, cited in Türkozan & Durmuş 2001; Limpus et al. 1979; Restrepo & Valverde 2019). This could be because of the usually associated malformations, or because albino and leucistic individuals are easier to detect by predators (Childs 1953; Krecsak 2008) or unable to survive for long without protective coloration (Wood et al. 1999). Still, in 2018 two apparently healthy leucistic adult green turtles nested successfully at Tortuguero National Park in Costa Rica, indicating that it is possible for some of these individuals to reach adulthood (Restrepo & Valverde 2019). Some authors have pointed out that the lack of pigmentation in the retina could hamper the vision and/or seafinding ability of albino individuals (Guillery 1986; Godfrey & Mrosovsky 1995; Perrault & Coppenrath 2019). We did not test this specifically, but when returning them to the sea, we noticed no difference between the albino hatchlings and their normally pigmented siblings: all went straight to the sea.

Acknowledgements. We thank the IBAP for all the logistic and field support, and all the local collaborators, always eager to learn and help in the field. We also thank the MAVA foundation who financed this work.

BÁRCENAS-IBARRA, A. H. DE LA CUEVA, I. ROJAS-LLEONART, F.A. ABREU-GROBOIS, R.I. LOZANO-GUZMÁN, E. CUEVAS & A. GARCÍA-GASCA. 2015. First approximation to congenital malformation rates in embryos and hatchlings of sea turtles. Birth Defects Research Part A - Clinical and Molecular Teratology 1033: 203-224.

CATRY, P., C. BARBOSA, B. PARIS, B. INDJAI, A. ALMEIDA, B. LIMOGES, C. SILVA & H. PEREIRA. 2009. Ecology and conservation of sea turtles in Guinea-Bissau. Chelonian Conservation & Biology 82: 150-160.

CHASSIN-NORIA, O., R. MACIP-RÍOS, P.H. DUTTON & K. OYAMA. 2017. Multiple paternity in the East Pacific green turtle (Chelonia mydas) from the Pacific coast of Mexico. Journal of Experimental Marine Biology and Ecology 495: 43-47.

CHILDS, H.E. 1953. Selection by predation on albino and normal spadefoot toads. Evolution 73: 228.

DA COSTA, J. de N., A.B. BARROS, R.M. DE MIRANDA, E.J. ALMEIDA & D.J. RODRIGUES. 2013. Record of leucism in Pseudoboa nigra Serpents: Dipsadidae) in southern Amazon, Brazil. Herpetology Notes 61: 81-82.

EAGLESON, G.W., R.A. VAN DER HEIJDEN, E.W. ROUBOS & B.G. JENKS. 2010. A developmental analysis of periodic albinism in the amphibian Xenopus laevis. General and Comparative Endocrinology 1682: 302-306.

ERICKSON, J. & I.L. KAEFER. 2015. Multiple leucism in a nest of the yellow-spotted Amazon River turtle, Podocnemis unifilis. Salamandra 513: 273-276.

FERTL, D. & P.E. ROSEL. 2009. Albinism. In: Würsig, B., W.F. Perrin & J.G.M. Thewissen (Eds.). Encyclopedia of Marine Mammals, 2nd Ed. Academic Press, Burlington MA, USA. pp. 24-26.

FOWLER, L.E. 1979. Hatching success and nest predation in the green sea turtle, Chelonia mydas, at Tortuguero, Costa Rica. Ecology 605: 946-955.

GUILLERY, R.W. 1986. Neural abnormalities of albinos. Trends in Neurosciences 9: 364-367.

HEWAVISENTHI, S. 1990. Abnormal hatchlings of green and olive ridley turtles, Victor Hasselblad hatchery, Sri Lanka. Marine Turtle Newsletter 50:15-16.

IBARRA, A.B. & A.M. GASCA. 2009. Malformations in embryos and neonates of olive ridley sea turtle (Lepidochelys olivacea) in Nuevo Vallarta, Nayarit, Mexico. Veterinaria México 404: 371-380.

JOSEPH, J.D., R.G. ACKMAN & G.T. SEABORN. 1985. Effect of diet on depot fatty acid composition in the green turtle Chelonia mydas. Comparative Biochemistry and Physiology B: Comparative Biochemistry 801: 15-22.

KASKA, Y., R. DOWNIE & R.W. FURNESS. 2000. Abnormal development in sea turtle embryos. In: Abreu-Grobois, F.A., R. Briseño-Dueñas, R. Márquez-Millán & L. Sarti-Martínez (Comps.). Proceedings of the 18th International Symposium on Sea Turtle Biology and Conservation. NOAA Tech Memo MFS-SEFSC-436. pp. 271-272.

KRECSAK, L. 2008. Albinism and leucism among European Viperinae: a review. Russian Journal of Herpetology 152: 97-102.

LEE, P.L.M., G. SCHOFIELD, R.I. HAUGHEY, A.D. MAZARIS & G.C. HAYS. 2018. A review of patterns of multiple paternity across sea turtle rookeries. Advances in Marine Biology 79: 1-31.

LIMPUS, C.J., K. MILLER & E. MCLACHLAN. 1979. A record of a breeding amelanic loggerhead turtle. Herpetological Review 10: 6.

MARCOVALDI, M., E.P. LIMA & R. PENTEADO. 1995. Albino sea turtle hatchlings in Brazil. Marine Turtle Newsletter 69:10.

PATRÍCIO, A.R., A. FORMIA, C. BARBOSA, A.C. BRODERICK, M.W. BRUFORD, C. CARRERAS, P. CATRY, C. CIOFI, A. REGALLA & B.J. GODLEY. 2017. Dispersal of green turtles from Africas largest rookery assessed through genetic markers. Marine Ecology Progress Series 569: 215-225.

PERRAULT, J.R. & C.M. COPPENRATH. 2019. Albinism In Florida green turtle (Chelonia mydas) hatchlings: ratio-based evidence of basic Mendelian recessiveness. Marine Turtle Newsletter 156:38-40.

Restrepo, J. & R.A. Valverde. 2019. Leucistic adult female green sea turtles (Chelonia mydas) successfully nesting at Tortuguero, Costa Rica. Marine Turtle Newsletter 159:23-25.

RODRÍGUEZ-PINILLA, Q. & M.J. GÓMEZ-MARTÍNEZ. 2011. Leucismo incompleto en Turdus fuscater Passeriformes: Turdidae) en los Andes Colombianos. Boletin Científico Centro de Museos de Historia Natural 151: 63-67.
SAGE, B.L. 1962. Albinism and melanism in birds. British Birds 56: 201-232.

SCHWARTZ, F.J. & C. PETERSON. 1984. Color and teratological abnormalities of green turtle, Chelonia mydas, hatchlings from North Carolina. Florida Scientist 471: 65-68.

SÖNMEZ, B. & S.Y. ÖZDILEK. 2011. Morphologic characters of albino green turtle (Chelonia mydas) hatchlings on Samandag Beach in Turkey. Marine Turtle Newsletter 131:46-47.

TRINDADE, J. 2015. First observation of albino green turtle (Chelonia mydas) hatchlings on Vamizi Island, Mozambique. African Sea Turtle Newsletter 4: 38-39.

TÜRKOZAN, O. & H. DURMUŞ. 2001. Albino loggerhead and green turtle (Caretta caretta and Chelonia mydas) hatchlings in Turkey. Zoology in the Middle East 241: 133-136.

TURNER, G.S. 2011. Hypomelanism in Irwins turtle, Elseya irwini, from the Johnstone River, North Queensland, Australia. Chelonian Conservation & Biology 102: 275-281.

WOOD, J.M., K. JIMBOW, R.E. BOISSY, A. SLOMINSKI, P.M. PLONKA, J. SLAWINSKI, J. WORTSMAN & J. TOSK. 1999. What’s the use of generating melanin? Experimental Dermatology 82: 153-164.