Population and reproductive patterns of the Neotropical planarian Girardia capacivasa (Platyhelminthes, Tricladida), and the influence of seasonality on its life history

LENGUAS FRANCAVILLA, MARINA; NEGRETE, LISANDRO; COLPO KARINE D.; BRUSA, FRANCISCO

ZOOLOGISCHER ANZEIGER

ELSEVIER GMBH

Año: 2018 vol. 274 p. 46 - 59

0044-5231

The biology of Neotropical freshwater planarians(Platyhelminthes) is almost unknown compared with that of their Holarcticrelatives. In this paper, we 1) studied the sequence of development ofthe reproductive system of Girardia capacivasa Sluys & Kawakatsu, 2005(Dugesiidae), to estimate the onset of sexual maturity, applying thelogistic regressions for the first time in flatworms; and 2) assessedreproductive and population patterns of this freshwater flatworm, andtheir responses to water temperature variation in a temperate Neotropicalstream. These appraisals allowed us to test if the life history traits offreshwater planarians are similar in regions with marked temperatureseasonality. According to the degree of development of the gonads andcopulatory apparatus the development of the reproductive system wasclassified in five stages. The estimated size at the onset of sexualmaturity was 12 mm. We found no relationship between the density of G.capacivasa and temperature, but planarians were more gregarious in warmermonths. The largest planarians were recorded in cold months. Thereproductive effort during the warm season was higher, but cocoons andjuveniles were found throughout the study period, indicating continuousreproduction. Hence, the temperature variation recorded in the study areawas not a limiting factor for breeding but influenced the body size andspatial distribution pattern of G. capacivasa.