The relative sexual size dimorphism of Centrobolus inscriptus compared to 18 congenerics

Abstract

Millipedes illustrate reversed sexual size dimorphism (SSD) as females are larger than males. SSD was calculated in 18 species of the genus Centrobolus and illustrated as a regression. The approximate relative position of C. inscriptus is shown. The size of C. inscriptus was 2245mm 3 : 1841 mm 3 : (females: males; n=88) and logged (x = 3.351216; y = 3.265054) and plotted. The mean volume ratio for C. inscriptus was 1.219446. Sexual size dimorphism was visible with the naked eye.

Relative sexual size dimorphism in Centrobolus fulgidus (Lawrence) compared to 18 congenerics

“…Figure 1 shows the finding for Centrobolus where mean volume ratios ranged from 0.63-2.72 with the regression of log male volume on log female volume was highly significant with a positive slope less than 1; showing females get larger than males with an increase in body size [4,7,9] . The 1.251 ratio was at the middleupper end of the trend for the genus.…”

“…C. fulgidus (Lawrence) were collected at Richards Bay Minerals (February 1996) and St. Lucia Estuary (December 1996) in South Africa. Millipede SSD was also calculated in the genus Centrobolus [4,7] . A regression of male volume on female volume was used to show the position of 18 species and the size of C. fulgidus was taken as a volumetric measurement and inserted into a Microsoft (MS) Excel spreadsheet and converted using the logorithmic (mathematical) equation.…”

“…Millipedes illustrate reversed sexual size dimorphism (SSD) and females are larger than males [4][5][6][7][8][9] . SSD in forest millipedes has successfully been understood as volumetric measurements using Centrobolus to corrobrate Rensch's rule [4][5][6][7] . Based on the assumption of equal developmental rates in males and females, the proximate cause for Rensch's rule is sexual bimaturism [10][11] .…”

“…Based on the assumption of equal developmental rates in males and females, the proximate cause for Rensch's rule is sexual bimaturism [10][11] . The general trend of SSD has been calculated for Centrobolus and sexual bimaturism shown [7,11] . The present study was aimed to illustrate the trend of SSD for the genus Centrobolus and pinpoint the position of C. ruber relative to 18 congenerics in order to determine whether males and/or females follow the trend of Rensch's rule.…”

Size matters in myriapod copulation

“…These factors may be interdependent [3] . In millipedes, size and SSD are related to copulation duration [4][5][6] . Here the present study tested the presence of a relationship between male length and copulation duration in second matings.…”