Reproductive ecology and diet of Cnemidophorus ocellifer Spix 1825 (Squamata: Teiidae) in a coastal area from northeastern Brazil / Ecologia reprodutiva e dieta de Cnemidophorus ocellifer Spix 1825 (Squamata: Teiidae) em Ãrea de tabuleiro no nordeste do Brasil
Djan Zanchi da Silva
DATA DE PUBLICAÇÃO
Chapter 1:Reproduction of Cnemidophorus ocellifer was studied based on data collected from September 2009 to August 2010 in a coastal area of the SÃo GonÃalo do Amarante municipality, CearÃ, Brazil. Lizards were captured by manual collection, with the aid of pressure rifle or tourniquet and, after dead, individuals were dissected for sex determination by inspection of the gonads. Females were considered reproductive in the presence of eggs in the oviducts or vitellogenic follicles and / or corpora lutea. Clutch size was estimated by counting the number of vitellogenic follicles or eggs in the oviducts. Eggs were measured in its length and width and their volumes were estimated using the volume formula to a prolate spheroid. In males, the left testicles were removed and measured in its length and width, so their volumes were estimated using the volume formula of a prolate spheroid. Histologic sections of testes removed were made, to verify the reproductive condition of males, by identifying the stage of cell maturation in spermatogenesis. Males were considered reproductive if they were in stage IV of cell maturation, corresponding to sperm production. In both sexes the fat bodies were weighed after being drained on paper towels. The reproduction of males and females occurred throughout the sampling period, but with variation in the proportion of reproductive individuals. The reproductive peak for both sexes occurred in July/2010. Females reach sexual maturity at 51,46 mm in snout-vent length (SVL) and males with 43,39 mm SVL. Clutch size ranged from one to three eggs and was positively associated with body size of females (Spearman correlation, P <0,001, rs = 0,43). The mean egg volume was associated with body size of females (F1,9 = 9,48, P = 0,01, R2 = 0,51), however, no association between litter size and mean egg volume was found (Spearman correlation, P = 0,11, rs = 0,48). Only one female had eggs in the oviducts and vitellogenic follicles simultaneously. The frequency of male reproductive suffered from long-term precipitation and temperature, with an additive effect on precipitation. The values of testis volume and the mean seminiferous tubules diameter and germinative epithelium height of males varied little throughout the study, however, higher values occurred from May to July. The mass of fat bodies of males and females was low throughout the study period, the highest value being found in the rainy season and in August/2010. Cnemidophorus ocellifer reproduces continuously in the area of coastal tableland of northeastern Brazil, and the reproductive peak occurs at the end of the rainy season. As with other species of lizards, the SVL is an important attribute of life history shaping both the size and quality of offspring. Chapter 2: We studied the trophic ecology of the lizard Cnemidophorus ocellifer in coastal area in northeastern Brazil, aiming to describe the composition of the diet, to verify the relationship between the availability of items in the environment and what is consumed by lizards, and analyzing the possible occurrence of sexual variations, ontogenetic and seasonal diet of the species. The lizards were captured between September/2009 to August/2010. Stomach contents were screened with a stereoscopic microscope. The food items were measured in its length and width and estimated volume using the formula for the prolate spheroid volume one. The diet in this population is mainly insectivorous, composed mainly of insect larvae, termites and beetles. In the dry season there is an increased consumption of plant parts. Parts of lizards were found in the diet of some individuals of C. ocellifer. The numerical distribution of the items found in the stomachs of C. ocellifer differed from that available in the environment in the dry season (Kolmogorov-Smirnov, Dmax = 0,59, p = 0,0009) but not in wet season (Kolmogorov-Smirnov, Dmax = 0,35, p = 0,17). There was no variation in the diet of C. ocellifer between the two seasons, considering the number (Kolmogorov-Smirnov, Dmax = 0,17, p = 0,76), volume (Kolmogorov-Smirnov, Dmax = 0,25, p = 0,34) and frequency of occurrence of prey in the diet (Kolmogorov-Smirnov, Dmax = 0,17, p = 0,76). The standardized food niche breadth of C. ocellifer was higher in the rainy season (0,29) than in the dry season (0,23). No differences were found between the diet of males and females on the number (Kolmogorov-Smirnov, Dmax = 0,15, p = 0,92), volume (Kolmogorov-Smirnov, Dmax = 0,23, p = 0,49) and frequency of occurrence of prey (Kolmogorov-Smirnov, Dmax = 0,19, p = 0,72), and the average length of the food items did not differ significantly between sexes (males: 7,36 Â 3,61 mm, n = 171 , females: 8,06 Â 4,03 mm, n = 99, t test, t = 0,99, df = 160,42, p = 0,32). The standardized food niche breadth of C. ocellifer males (0,23) was equal in females (0,23). The overlap of the diet of males and females was higher when considering the volumetric values (0,92) than when considering the numerical values (0,58). The diet of young lizards and adults did not differ significantly on the number (Kolmogorov-Smirnov, Dmax = 0,31, p = 0,12) and frequency of occurrence of prey ingested (Kolmogorov-Smirnov, Dmax = 0,27, p = 0,22), however, significant differences between the volume of prey consumed by young lizards and adults were found (Kolmogorov-Smirnov, Dmax = 0,48, p = 0,0002). Prey eaten by adults had higher average length than those ingested by young lizards (adults: 7,62 Â 3,78 mm, n = 270; young: 5,14 Â 2,34 mm, n = 97, t test, t = - 6,00, df = 147,35, p = <0,001), however, prey size independent of body size of lizards did not differ among age classes (t test, t = 0, df = 146,68, p = 1). The average width of the standard diet of young lizards (0,32) was higher than the average width of the standard diet of adults (0,22). The overlap of the diet of adults and juveniles was higher when considering the numerical values of the diet (0,87) than when considering the volumetric values (0,68).
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