Gnathopod 1 subchelate to parachelate; coxa small; merus and carpus not rotated; carpus short; propodus large, palm straight to convex; dactylus slightly curved, not hidden by setae.
Gnathopod 1 subchelate; basis length more than three times breadth; propodus margins subparallel.
Here I explore the role of gnathopod characteristics in male reproductive success by measuring aspects of sexual selection (pairing success) and natural selection (success in mating with larger, more fecund females) on gnathopod size in the two amphipod ecotypes.
Analysis of selection on gnathopod characteristics.-Gnathopod characteristics may affect the reproductive success of males by influencing (1) the success of males in forming precopulatory pairs with females and (2) the success of males in mating with larger, more fecund females.
I analyzed major differences between the morphotypes with analysis of variance, with populations within a morphotype as replicates and either population means (body size, size at maturity and egg size) or size-adjusted trait values (antennal segment number, spine length, egg number and gnathopod width) as data.
The size-adjusted PC1 axis, which explained 65.9% of variation in the trait matrix, had high loadings for antennal segment number (0.66) and gnathopod width (0.65).
Sexual dimorphism in amphipods: the role of male posterior gnathopods
revealed in Gammarus pulex.
The use of the male's gnathopods
during precopulation in some gammaridean amphipods.
The active manipulation of the newly spun silk threads by the gnathopods (see above) persisted throughout the process.
femorata and other ampithoids, the recently spun silk threads are additionally manipulated by pereopods 1 and 2, the gnathopods (e.g., present study; Skutch, 1926; Heller, 1968), but the functional significance of this behavior is not yet fully understood.
volutator switches to filter feeding by using the long setae on the second pair of gnathopods
to retain suspended particles brought into the tube by the pleopodal current.
of the cyprid form an oral cone, which opens to the ventral surface of the cephalon [ILLUSTRATION FOR FIGURES 1, 2, 12A OMITTED].