Fecundity of Hoplopleura scapteromydis (Phthiraptera : Anoplura, Hoplopleuridae), ectoparasite of Scapteromys aquaticus (Rodentia : Muridae) in Rio de La Plata marshlands, Argentina

Density and age structure of Lice collected from captured Scapteromys aquat icus rodents were studied to estimate the fecundity of Hoplopleura scaptero mydis. The number of eggs with a visible embryo inside (E), nymphs (N), adu lt males (AM), and adult females (AF) were recorded for each rodent. For th e ith rodent, the fecundity of H. scapteromydis, F(i), was estimated as F(i ) = {[E(i) + N(i)]/2}/AF(i)/T, where T represents the period of preimaginal development (unknown and arbitrarily considered as T = 1), and the sex rat io of the preimaginal stages was supposed to be 1:1. In order to look for d ensity-dependent effects, F(i) was plotted against AM(i), this being an ind ependent estimation of infrapopulation density. The number BE rodents suita ble for AF and AM calculations was 38 (57% of the parasitized animals). Alm ost 95% had a low-to-moderate louse burden (1 < AM < 30) and were captured every season, whereas only 3% had a heavy (61 < AM < 70, captured in winter ) or very heavy (AM > 80, captured in summer) louse burden. The extreme val ues of F were 0.63 and 18 (1.3 and 36 if both sexes were considered). High- to-moderate F-values (F > 5) were estimated in only 5 rodents that exhibite d low louse density, whereas low F-values (F < 5) were found at all louse d ensities. Notwithstanding the tendency toward an inverse relationship betwe en fecundity and infrapopulation density, the correlation was not significa ntly different from 0.