The Galápagos pink land iguana: possible sources of risk.

Three species land iguanas (Conolophus subcristatus, C. pallidus and C. marthae) exist in the Galápagos. All are endemic to that archipelago and recognized endangered, as result of direct and indirect human impact on the wildlife of the islands. The recently discovered and described species C. marthae (the pink land iguana from the Galápagos) is still waiting for the proper assignment to a IUCN risk category, although first available data suggested to include the species in the “critically endangered” species list. Here, we illustrate some possible sources of risk for C. marthae. Some of these are generated by the restricted area of occurrence (about 25Km2) and small population size (Nc and Ne). Additional risk is related to the presence, in the area of occurrence, of rats and cats, which prey on eggs and juveniles. The impact of these recently-introduced predators on the recruitment of the population is still unknown, but it could be not negligible as we have observed no pink iguana juvenile so far, since the first field trip in the 2005. Complete eradication of these pests, successful in other islands of the archipelago, is most likely impossible in Isabela, due to the large area of this island. We also consider the possible risk associated with high parasite load observed in C. marthae. In fact, the northern side of volcano Wolf (Isabela island), area of occurrence of C. marthae (WM) and a population of C. subcristatus (WS), hosts a very large population of ticks, feeding on land iguanas and giant tortoises. Ticks are also vectors of the haemoparasite Hepatozoon (Apicomplexa) which, in a haematological survey, we found in the blood of the three species of Galápagos land iguanas. This raised some concern as the infection by this haemoparasite (known in mammal, birds, reptiles and amphibians) may cause anemia or blood cell abnormalities, resulting in reduced juvenile’s survival, immunosuppression, reduction of growth, reduced reproductive fitness. Comparison between values of parasitemia (number of infected individuals) and prevalence (number of parasites per individual) for the two populations of volcano Wolf (WS and WM) shows that C. subcristatus is characterized by a high prevalence and medium parasitemia whereas C. marthae shows very high prevalence and low parasitemia. The analysis of white blood cell count for individuals parasitized shows significant differences in eosinophils and monocytes between WS and WM (that share the same formula) and the other populations. Unexpectedly, however, the altered leucocytic formula observed in WS and WM does not correlate to the presence of Hepatozoon in the blood of iguanas. Thus, data suggest that in volcan Wolf particular environmental factors occur, that causes the same alteration of leucocytic formula in C. subcristatus and C. marthae. These (still unknown) factors might also explain the same pattern of variation of the microbiota (Enterobacteriaceae) observed in WM and WS. This scenario is compatible with the hypothesis of a massive infection by an endoparasite. Furhter investigations are urgently needed to clarify the demographic trend and health status of C. marthae