Immediately after hatching, the first free-living zoea larval stage is characterized by three pairs of well-developed thoracic
biramous maxillipeds located immediately posterior to the cephalic maxillary appendages (St.
Segments 2-9 with
biramous parapodia, with 5-12 simple chaetae per rami, and filiform and smooth interramal cirri.
Karliella differs fundamentally from these by having male surstyli that are deeply incised and
biramous.
First setiger uniramous, thereafter
biramous with a relatively broad gap between setal fascicles (Figure 1d).
Sex was determined by the presence of
biramous pleopods in females and uniramous pleopods in males (Morgan 1980).
The first pedigerous somite is cephalically incorporated and the three succeeding free pedigerous somites each bear a pair of
biramous swimming legs.
3N) Buds
biramous; much longer than that of 2nd stage.
Four pairs of
biramous swimming legs composed of a precoxa, coxa, basis, exopod, and endopod; with plumose setae on all exopods, endopods, coxae, and bases.
Crab sex was determined as follows: females have a gonopore on the coxa of each third pereopod and elongated
biramous pleopods, whereas males have a gonopore on the coxa of each fifth pereopod and short uniramous pleopods.
The
biramous antennules of decapods, in particular, are considered the primary sensory organs for olfactory chemoreception and exclusively contain, on the outer flagellum, the aesthetasc sensilla, each innervated by hundreds of olfactory receptor neurons (Schmidt and Mellon, 2011 ).
Segments 4 and 5 of the male abdomen are partly fused, whereas the mature female abdomen is broad with free segments and
biramous pleopods on segments 2-5.
All thoracic parapodia
biramous; thoracic postchaetal lobes of both rami inconspicuous.