petasma

petasma

[pə′taz·mə]
(invertebrate zoology)
A modified endopodite of the first abdominal appendage in a male decapod crustacean.
References in periodicals archive ?
The sex of the specimen was determined by observing the presence of petasma in males and thelycum in females.
1967), petasma (Sivalingam and Rao, 1968) and the abdomen form (Young, 1933; Mantelatto et al.
A case of abnormal petasma in the penaeid prawn Metapenaeus affinis (H.
Primer par de pleopodos del macho modificados, formando un petasma (organo intromitente).
Sex was determined by the presence of the petasma for males or the thelycum for females (Ohtomi et al.
In the western Atlantic Ocean, Perez-Farfante (1969, 1970, 1971a) described diagnostic characters of the genus Farfantepenaeus that allowed identification of individuals in the range of 8-20 mm CL (carapace length) on the basis of the following morphological features: 1) changes in the structure of the petasma and thelycum; 2) absence or presence of distomarginal spines in the ventral costa of the petasma; 3) the ratio between the keel height and the sulcus width of the sixth abdominal somite; 4) the shape and position of the rostrum with respect to the segments and flagellum of the antennule; and 5) the ratio between rostrum length (RL) and carapace length (RL/CL).
Identification of species was based on the morphological characters of rostrum, carapace, branchiae, antennule, antenna, third maxilliped, pereiopods, pleopods, abdomen, telson, petasma, thelycum, and the colored pattern of the whole body based on keys and diagnoses available from the current literature.
All but the two species of Litopenaeus within clade A, show a symmetrical and semiclosed petasma without distolateral projections, uninvaginated and unpaired seminal receptacles, simple spermatophore without accessories, and thelycum closed with two lateral plates (with the exception of Marsupenaeus, which shows a thelycum with one plate, and spermatophore with accessories).
Growth of the petasma, the copulatory organ of male shrimp, was significantly affected by the parasite.