Population dynamics of Aegla manuinflata Bond-Buckup and Santos 2009 (Decapoda: Aeglidae), an threatened species

Abstract

AIM: We evaluate the population density, median size of males and females, age distribution, sex-ratio, reproductive period and recruitment period of the threatened species Aegla manuinflata. METHODS: Monthly samplings were made from May 2006 to April 2007 in the Passo Taquara stream, Brazil. An extra sampling was performed at each season of the year in order to determine population density. Animals were captured with traps and handnets. All the captured specimens were sexed and had their cephalotoraccic length measured with a digital caliper (0.01 mm), and were then released back in the stream. RESULTS: A total of 888 individuals were analyzed, including 17 unsexed juveniles, 572 males, 274 females and 25 ovigerous females. A mean population density of 1.52 ind/m² was estimated. Males showed median sizes larger than females (p < 0.01). Age distribution was bimodal for both males and females. Females predominated in intermediary size-classes, while males were more abundant in the larger classes, with no differences for the lower classes. The sex-ratio, in general, followed the expected 1:1 proportion only in the months of May, October and November (p > 0.05). Males and females caught only with handnet follow the expected 1:1 proportion in all months of the year (p > 0.05), demonstrating that the sampling method clearly affects the results. Ovigerous females and juveniles were registered in all seasons of the year and there is no significant different in the proportion of these animals among the seasons (p > 0.05), indicating continuous reproduction. CONCLUSIONS: Population data of this study can be used as a basis for the creation of conservation measures of A. manuinflata, since the species is considered vulnerable.

Method of capture and population structure of Aegla georginae Santos and Jara, 2013 (Decapoda: Anomura: Aeglidae) in a tributary of the Ibicuí River in southern Brazil

“…Males have documented aggressive behavior (Cohen et al, 2011;Palaoro et al, 2013;. Females or juveniles would not enter the traps to avoid agonistic encounters with the larger males (Trevisan and Santos, 2014). Similar to this study, Dalosto et al (2014) also found that individuals were significantly greater in size in trap captures than in handnet captures.…”

“…Trevisan and Santos (2014) and Dalosto et al (2014) also analyzed capture methods in the assessment of the relative abundance for A. manuinflata and A. platensis, respectively. Differences according to capture method were found by Trevisan and Santos (2014), but not by Dalosto et al (2014). Other studies using handnets or even manual efforts in capturing aeglids also found a relative abundance of 1:1 for A.…”

“…The specimens were captured using two capture methods: 1) 25 plastic traps with beef liver randomly set along the sampling zone, and all traps were set late in the afternoon and checked for aeglid individuals the following morning and 2) a handnet (Surber sampler, 0.1 m 2 area, 250 μm mesh net) with an effort of 30 min by two researchers for each monthly sampling. The collection methods were adapted from Trevisan and Santos (2014).…”

“…Information about the population structure is important in working with decapods because the data assist in understanding the biology of the species in a given ecosystem. Population aspects in aeglids have been described by several authors in rivers located in the Atlantic Forest in Brazil such as Aegla paulensis Schmitt, 1942(Lopez, 1965, Aegla perobae Hebling and Rodrigues 1977 (Rodrigues andHebling, 1978), Aegla leptodactyla Rossi, 1977 (Noro andBuckup, 2002), Aegla castro Schmitt, 1942 (Swiech-Ayoub andMasunari, 2001;Fransozo et al, 2003), Aegla longirostri Buckup, 1994 (Colpo et al, 2005), Aegla franciscana Rossi, 1977 (Gonçalves et al, 2006), Aegla schmitti Hobbs III, 1979(Teodósio and Masunari, 2009), Aegla parana Schmitt, 1942(Grabowski et al, 2013, Aegla platensis Schmitt, 1942 (Bueno andDalosto et al, 2014), Aegla manuinflata Bond-Buckup and Santos, 2009 (Trevisan and and A. platensis, Aegla grisella Bond-Buckup and Buckup, 1994 and Aegla ludwigi Jara, 2013 (Copatti et al, 2015).…”

“…Usually, in studies of the population structure of aaeglids have not compared different capture methods, although Trevisan and Santos (2014) and Dalosto et al (2014) have considered the capture methods in the evaluation of relative abundance of A. manuinflata and A. platensis, respectively. We agree that the capture methods influence the evaluation of the population structure of aeglids.…”