Morphological abnormality in larvae of Amblyomma oblongoguttatum (Acari: Ixodidae)

Amblyomma oblongoguttatum is a tick that is a parasite of mammals and its preferred hosts are the wild pigs, tapirs and small rodents, being collected also parasitizing domestic dogs and eventually humans. An Amblyomma oblongoguttatum larva with morphological abnormality was collected along with other specimens (larvae and females) of this species and with morphologically normal Amblyomma naponense nymphs in a wild pig Pecari tacaju in a rural area of the state of Rondônia / Brazil, during research of tick-borne disease environments. The morphologically abnormal specimen showed a bifurcation of the posterior region of the opisthosoma, without other altered morphological characters. This is the first record of morphological abnormality at the larval stage of Amblyomma oblongoguttatum.


Introduction
Morphological changes in ticks are rarely documented events. The main changes described are gynandromorphism, bifurcation and asymmetry in the idiosome, anomalies in the development of the legs, alterations in the oral parts of gnathosoma and asymmetry of peritrematous plaques. Also the appearance, in the same specimen, of two anus, three stigmas or two caudal appendages (NUTTALL, 1914;GOUVEA SOUTO, 1939;NEVEU LEMAIRE, 1938;NOWAK-CHMURA, 2012;KESKIN et al., 2016).
Cases of anomalies arising from natural processes are extremely low in natural environments (ESTRADA-PEÑA, 2001). Among the main interferences that may influence anomalous development are exposure to chemical compounds, temperature and humidity of the air, hosts sensitized with chemicals and problems in the regeneration of tissues after an injury (BUCZEK, 2000;SERRA-FREIRE;BORSOI, 2009;NOWAK-CHMURA, 2012).

Amblyomma oblongoguttatum is a tick that is widely distributed in
Brazil, being reported in the states of Amazonas, Rondônia, Acre, Roraima, Pará, Minas Gerais, Goiás, Mato Grosso, Rio de Janeiro and Espírito Santo (ANDREOTTI et al., 2108). It is a parasite of mammals and its preferred hosts are the wild pigs, tapirs and small rodents, being collected also parasitizing domestic dogs and eventually humans in rural areas of the Brazilian Amazon (LABRUNA et al., 2005).
The aim of this report is to present a case of morphological abnormality in an Amblyomma oblongoguttatum larvae collected in a wild pig -Pecari tacaju -in the rural area of the state of Rondônia, northern region of Brazil.
Despite the bifurcation in the opisthosoma, other structures were not affected in the A. oblongoguttatum larva analyzed. The specimen presents complete gnathosoma, with no duplicity and this specimen did not show duplication of anal opening.
Considering that the tick with the morphological abnormality was collected in a wild animal from the forests of the region, without occurrence of agriculture and livestock, there are only small rural dwellings the possibility of the malformation observed to be associated with exposure to chemical compounds is low. The wild pig is a natural host of the species (LABRUNA et al., 2005), and it is unlikely that the larva has been fed in a host sensitized with chemicals before being withdrawn from the animal.

Conclusion
An A. oblongoguttatum larva with posterior bifurcation of the opisthosoma was collected along with other specimens (larvae and females) of this species and with morphologically normal Amblyomma naponense nymphs in a wild pig -Pecari tacajuin a rural area of the state of Rondônia, being this the first record of morphological abnormality in the larval stage of Amblyomma oblongoguttatum in Brazil.