Perceived risk of sperm competition affects sperm investment in a mate-guarding amphipod

Ejaculate Characteristics Depend on Social Environment in the Horse (Equus caballus)

“…Such plasticity has been intensely studied in invertebrates [ 3 ] and has been found at the level of sperm production [ 10 , 11 ] and at the level of sperm allocation (i.e. the investment into a particular mating; recent studies include Arudell et al [ 12 ], and Kimura and Chiba [ 13 ]). Sperm number may be the trait that is most likely to be phenotypically plastic, as suggested by Kelly and Jennions [ 3 ] in their recent meta-analysis.…”

Fluctuating asymmetry, parasitism and reproductive fitness in two species of gammarid crustacean

“…Male G. duebeni were dissected for sperm counts as described in Arundell et al (2014). Briefly, the testes were dissected from the body cavity using spring-loaded scissors, and watchmaker's forceps.…”

Unusual male size vs sperm count relationships in a coastal marine amphipod indicate reproductive impairment by unknown toxicants

“…It has been noted that larger amphipods have an advantage to pair with larger females in a process known as mate guarding (Elwood and Dick, 1990), so it is important to study whether this advantage is only because of the size or if sperm quality of larger males is also higher than sperm quality of smaller males. Positive correlations between adult male size and sperm counts have also been reported in amphipods, for example, in Echinogammarus marinus (Yang et al, 2008), Gammarus pulex (Galipaud et al, 2011) and Gammarus duebeni (Arundell et al, 2014). However, no relationship between these parameters were reported in G. duebeni (Dunn et al, 2006), G. pulex (Lemaître et al, 2009) and Gammarus roeseli (Couchoux et al, 2018).…”