Parasitic nematodes of Polychrus acutirostris ( Polychrotidae ) in the Caatinga biome , Northeastern Brazil

We present data on nematode infracommunity of the arboreal lizard Polycrhus acutirostris in the semiarid Caatinga biome, northeastern Brazil. Twentytwolizard specimens collected in the municipality of Várzea Alegre in Ceará State and in the municipality of Exu in Pernambuco State were analyzed. Two species of nematodes were found, an Oxyuridae,Gynaecometra bahiensis, which had amean intensity of infection 23.5 ± 5.8 (prevalence 22%) and a Physalopteridae, Physaloptera retusa which had infection intensity of 21 (prevalence 9%). There were no significant differences between the parasitism rates of male or female lizards. Polychrus acutirostris demonstrated low richness of nematode parasites, but high levels of infection with G. bahiensis. Polychrus acutirostrisis reported here as a new host for P.retusa.

Parasitological studies are fundamental to interpreting parasite/host interactions and better understanding related biological communities (Rocha et al., 2003), by indicating environmental stress levels, aspects of the ecological web, and elucidating the characteristics of local biodiversity (Marcogliese, 2005).
The arboreal polychrotid lizard Polychrus acutirostris (Spix, 1825) is found in open vegetation formations in Argentina, Bolivia, and Brazil (Garda et al., 2012) in areas of Cerrado and Caatinga vegetation (Kawashita-Ribeiro and Ávila, 2008;Ribeiro et al., 2012b), being often found near human habitations (Vanzolini, 1974).It is a medium-sized diurnal lizard, uses a sit-and-wait foraging strategy and feeds predominantly arthropods (Coleoptera and Hymenoptera), and plant material (leaves, seeds, and flowers),with reproduction between the months of September and October (Vitt and Lacher, 1981).The present study analyzed the parasitic nematodes of P. acutirostris in two Caatinga vegetation localities in northeastern Brazil.

Material and Methods
Specimens of P. acutirostris were collected in two areas of Caatinga vegetation, one in the municipality of Várzea Alegre (6°53'S and 39°13'W) in Ceará State, and the other in the municipality of Exu (7°33'S and 39°44'W) in Pernambuco State.Both sites are located in the semiarid region of northeastern Brazil.The Caatinga vegetation at the Exu site was predominately hypoxerophilous deciduous forest, with average total annual rainfall between 700 and 900 mm (CPRM, 2005).The Caatinga vegetation at the Várzea Alegre site comprises a mixture of dense shrubs, Cerrado, spiny deciduous forest, and tropical pluvial subdeciduous forest, with an average annual precipitation rate of 965.3 mm, and average annual temperatures between 26° and 28 °C (IPECE, 2011).
The lizards were collected by hand between May/2011 in January/2012.They were subsequently euthanized by applying a lethal injection of Lidocaine, weighed using a spring scale (Pesola®), and their snout-vent lengths (SVL) measured using a digital caliper (0.1 mm precision).The specimens were subsequently fixed in 10% formaldehyde and conserved in 70% ethanol.Voucher specimens were deposited in the Coleção Herpetológica da Universidade Regional do Cariri.Individuals were necropsied and their body cavity, lungs and digestive tract were analyzed under a stereoscopic microscope for the presence of helminths.Nematodes encountered were placed in vials of 70% ethanol for latter identification.For species identification, nematodes were cleared using lactophenol, mounted on temporary slides, and analyzed under a light microscope.The nematodes were subsequently deposited in the Coleção Parasitológica da Universidade Regional do Cariri.
Infection rates as well as ecoparasitological terminology follow the definitions of Bush et al (1997).
We examined the relationships of the host mass (g) and snout-vent length (SVL) to the numbers of nematode using Pearson's linear correlation analysis.The differences in infection rates between males and females, as well as differences in their SVL, were examined using the Mann Whitney test (test -U), using Bioestat 5.0 software.
Another Caatinga lizard, Tropidurus hispidus Spix 1825, from the states of Ceará and Piauí in northeastern Brazil, was reported to have a prevalence of 33.3% (Ávila et al., 2012) with P. retusa, and the low prevalence found in the present study (9%) may have been influenced by the number of individuals examined or some aspect of the nematode community analyzed.
Five specimens (4 adult females and one adult male) of P. acutirostris had infection with the Oxyuroidea nematode Gynaecometra bahiensis, with high intensity of infection (23.5 ± 5.8; and prevalence of 22%).
The nematode G. bahiensis has only been described as a parasite in P. acutirostris, and additional studies will be necessary to better understand this association (Ávila et al., 2010, 2011).Food habits and foraging modes may influence the composition of host helmintho faunas, and omnivorous and herbivorous lizards are known to have wider and more diverse nematode than carnivorous lizards (Roca, 1999).
Polychrus acutirostris was found to have a low diversity of parasitic nematodes, which could reflect its simple intestinal system, ectothermic metabolism, and/or generalist feeding habits (Goater et al., 1987).
Little is currently known about the lifecycle of P. retusa, although studies with other Physaloptera spp.(such as Physaloptera hispida Petri (1950), Physaloptera maxillaris Molin, 1860, Physaloptera praeputialis von Linstow (1889), and Physaloptera rara Hall and Wigdor, 1918) have shown that infection are initiated by the ingestion of crickets, grasshoppers, and cockroaches contaminated with third stage larvae (Schell, 1952;Lincoln and Anderson, 1975).Polychrus acutirostris is recorded here as a new host for P. retusa.The lifecycle of G. bahiensis has not been well investigated, although other members of Oxyuridae have strictly monoxenic lifecycles (Anderson, 2000).The arboreal habit and omnivorous diet of P. acutirostris may have influenced the low number of nematode species infecting this lizard and the high infection intensities encountered.