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Petasma

A complex genital structure attached to the mesial margins of the protopodites of the first pair of pleopods in male penaeidean shrimps. [Chace and Hobbs, 1969]
Abdominal appendage modified as gonapophysis in males of some eucarids, syncarids, and stomatopods. [Moore and McCormick, 1969]
Abdominal structure developed from male pleopods, used in copulation. [McLaughlin, 1980]
Anterior abdominal pleopod modified for sperm transfer in the Dendrobranchiata. [Brusca and Brusca, 2002]
Complex genital structure attached to the inner margins of protopodites of the first pair of pleopods on male penaeidean shrimps. [Butler, T. H.]
Copulatory organ of male penaeid shrimps that is formed from the first abdominal appendages (pleopods); used by the male to thrust the spermatophore against the thelycum of the female. [Bliss, 1982]
Endopodite of first pleopods in male Penaeidae; a complicated membranous plate bearing coupling hooks mesially which interlock with those on member of opposite side; may terminate distally in various complex-shaped lobes. [Williams, 1984]
Male genital structure comprising the enlarged and coupled endopods of pleopods 1 (Dendrobranchiata); usually composed of complex lobes and lobules. [Poore, 2004]
The male genital structure consisting of the much enlarged and coupled endopods of the first pair of pleopods. The presence or absence of a petasma, or in juveniles, the position of the first endopods (situated more distally in females than in males), is the easiest means of distinguishing between the sexes in penaeidean shrimps (Fig. 1, 4B).
(pl. petasmata) [Perez Farfante and Kensley, 1997]
The modified endopodite of the first pair of pleopods of male euphausiids. [Mauchline, 1984]
(Taxon-specific: Order Decapoda) In reproductive system of male in shrimp-like (natantian) decapod, expanded structure formed by modified inner branches (endopods) of first pair of pleopods; may bear series of distal lobes (e.g., distolateral, distoventral, distomedian lobes) and other processes. Functions in transferring spermatophores into thelycum of female. [Stachowitsch, 1992]
(Taxon-specific: Order Stomatopoda) In male reproductive system, copulatory structure on each appendage (pleopod) of first abdominal somite (pleomere). Located on inner branch (endopod) and pleuropod; consists of hook-shaped and tubular processes. [Stachowitsch, 1992]
(Taxon-specific: Superorder Syncarida) In male, copulatory structure formed by first two pleopods. [Stachowitsch, 1992]
(Taxon-specific: Order Euphausiacea) In male, one of first two pairs of pleopods modified as copulatory structure. Inner branch (endopod) basically consists of four lobes (auxiliary = additional, internal, median, setiferous lobes), each bearing a variety of projections (blades, heel, processes, setae, spines). Serves to transfer spermatophores into thelycum of female. [Stachowitsch, 1992]