Sperm dumping in Centrobolus inscriptus Attems (Spirobolida: Trigoniulidae)

Abstract

Differential ejaculate usage was tested in the diplopod Centrobolus inscriptus. Copulation duration, postmating interval, and ejaculate volume (disintegrations per minute of H 3+ ) were analysed for single and double mating sequences. During the 24h post-mating, ejaculate volumes decline was identified. The significant drop in ejaculate volumes (dpm) post-mating (Z = 3.00, n = 6, 7, P = 0.003) indicates a female process thought to be sperm dumping.

When is the change in sperm precedence in the millipede <em>Centrobolus inscriptus</em> (Attems, 1928) (Diplopoda, Pachybolidae)?

“…This also demonstrates that successive mating produces opposite patterns on ejaculate volume and selection on female remating interval which is influenced by male sperm competition strategies as was shown in an ancient arthropod model [1,21] . Body size and reproductive performance may be related in C. inscriptus because secondmale sperm precedence is achieved by those individuals which prolong mate-guarding relative to body size based on mass [13] .…”

“…In the ladybird males which mated last were found to sire up to 72% indicating that prolonged matings by first males are essentially examples of post-copulatory mate guarding to prevent last male sperm precedence [3] . In the polygynandrous millipede Centrobolus inscriptus with sperm dumping and sperm storage, remating interval negatively relates to second copulation duration [10,11,13] . Three scenarios exist for sperm precedence, namely, first-male precedence, last-male precedence, and no order effect, although this may change with additional mating [10] .…”

Sexual conflict over the duration of copulation in Centrobolus inscriptus (Attems)

“…When species specific patterns are analysed in C. inscriptus copulations are long and perhaps even costly for males [17] . Thus in 15 of 18 of the studies of C. inscriptus I found equal evidence for syncopulatory male control in prolonged copulations and struggles also under female control [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] . Females are thought to protract the time spent with each male and hence mediate sperm competition [23] .…”

“…The literature was searched for all studies of Centrobolus inscriptus, both independent and dependent of copulation duration [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] . The author's own publication collection was consulted and relevant male versus female control was tabulated [3-10, 13-17, 20] .…”

“…Recent studies on the sexually dimorphic aposematic millipede Centrobolus inscriptus are providing insight into mating behaviour and ecology [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] . Control of mate-guarding in the spirostreptid millipede Doratogonus uncinatus proved males control the duration of copulation [19] .…”