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Reproduction in seven species of Microlophus (Squamata: tropiduridae) from South America.

Article Excerpt
Abstract.-Information on the reproductive cycles of seven species of Microlophus (M. koepckeorum, M. occipitalis, M. peruvianus, M. stolzmanni, M. theresiae, M. thoracicus and M. tigris) from coastal northern South America gathered from a histological examination of gonadal material is presented. All species exhibited extended reproductive activity present in both austral spring-summer and autumn. Histological evidence is presented that M. peruvianus may produce multiple clutches in the same year. Comparisons are made with the reproductive cycles of other species of Microlophus.

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The genus Microlophus consists of some 20 species and is restricted in distribution to South America and the Galapagos Islands (Peters & Donoso-Barros 1986). Microlophus koepckeorum, M. peruvianus, M. theresiae, M. thoracicus, M. tigris are endemic to Peru (Lehr 2002). Microlophus occipitalis is known from southwestern Ecuador and northern and central Peru, and M. stolzmanni is known from northwestern Peru and possibly southwestern Ecuador (Peters & Donoso Barros 1986). Information on reproduction of M. peruvianus, M. theresiae, M. thoracicus and M. tigris (all as Tropidurus) are in Dixon & Wright (1975) and M. (as Tropidurus) occipitalis is in Watkins (1996). The purpose of this paper is to add information on the reproductive cycles of seven species of Microlophus lizards from coastal northern South America.

MATERIALS AND METHODS

Histological examinations were performed on 313 museum specimens of seven species of Microlophus on deposit with the Natural History Museum of Los Angeles County (LACM), Los Angeles, California (Table 1). Counts were made of oviductal eggs or enlarged follicles (> 4 mm length). The left testis and epididymis were removed from males; the left ovary was removed from females for histological examination. Tissues were embedded in paraffin and cut into sections at 5[micro]m. Slides were stained with Harris' hematoxylin followed by eosin counterstain (Presnell & Schreibman 1997). Testis slides were examined to determine the stage of the male cycle; ovary slides were examined for the presence of yolk deposition. Histological slides of most gonads from 45 juveniles: M. koepckeorum (n = 4), M. occipitalis (n = 6), M. peruvianus (n = 3), M. stolzmanni (n = 13), M. theresiae (n = 6), M. thoracicus (n = 8), M. tigris n = 5) were made to determine the minimum size at which maturity was reached. In cases where the gonads were extremely small, immaturity was assumed and no histology was performed. The relationship between female SVL and clutch size was examined by linear regression analysis and an unpaired t test was used to compare male and female mean body sizes (SVL) (Instat vers. 3.0b, Graphpad Software, San Diego, CA).

Table 1. Sample sizes (n), mean sizes...

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