Intraespecific variation in the proboscis of Polymorphus trochus (Polymorphida: Polymorphidae) in two species of freshwater birds (Gruiformes: Rallidae) in the State of Mexico

摘要

Geometric and linear morphometric analyses were used to evaluate the morphological variation of the proboscis of Polymorphus trochus of Fulica americana and Gallinula galeata, both resident birds of Chimaliapan Wetland, State of Mexico. The geometric morphometric analysis revealed the existence of different morphotypes according to host species, microhabitat, sex and state of development of the parasite. The adult females were located in the ileum and showed an enlarged proboscis, unlike the young females, which were found in the jejunum and had a narrow proboscis, very similar to the males; this suggests different designs that fit the migratory movement of this group. Linear morphometric also indicated differences in the length of the proboscis and the hooks; it was also identified that the females present a larger size of these structures, as an adaptation towards a permanent attachment to an adequate maturation and subsequent release of the eggs. According to the present study, the reproduction and structure of the microhabitat are two important traits that influence the size and shape of the proboscis. Additionally, it is indicated that there are statistical differences in the sexual dimorphism in different levels: shape and size of the proboscis and length of the hooks, data not reported for this species before.