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Morphometric differentiation in 

 small juveniles of the pink spotted shrimp 

 iFarfantepenaeus brasi/iensis) and 

 the southern pink shrimp (f. notialis) 

 in the Yucatan Peninsula, Mexico 



Marco A. May-Ku 



Uriel Ordonez-Lopez 



Omar Defeo 



Centra de Investigacion y de Estudios Avanzados, CINVESTAV 



Unidad Merida 



Carretera Antigua a Progreso Km. 6, A P 73 



Cordemex, 97310 Menda, Yucatan, Mexico 



E-mail address (for M A Kay-Ku) mayfa^mdacinvestavmx 



The morphometric and morphologi- 

 cal characters of the rostrum have 

 been widely used to identify penaeid 

 shrimp species (Heales et al., 1985; 

 Ball et al., 1990; Pendrey et al., 1999). 

 In this setting, one of the constraints 

 in studies of penaeid shrimp popu- 

 lations has been the uncertainty in 

 the identification of early life history 

 stages, especially in coastal nursery 

 habitats, where recruits and juve- 

 niles dominate the population (Ball 

 et al., 1990; Perez-Castaiieda and 

 Befeo, 2001). In the western Atlantic 

 Ocean, Perez-Farfante (1969, 1970, 

 1971a) described diagnostic charac- 

 ters of the genus Farfantepenaeus 

 that allowed identification of indi- 

 viduals 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 pe- 

 tasma 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). In addition, she 

 classified Farfantepenaeus into two 

 groups according to the shape and 

 position of the rostrum with respect 

 to the segments and flagellum of the 

 antennule and the ratio RL/CL: 1) 



F. duorarum and F. notialis: short 

 rostrum, straight distally, and the 

 proximodorsal margin convex, usu- 

 ally extending anteriorly to the end of 

 distal antennular segment, sometimes 

 reaching to proximal one-fourth of 

 broadened portion of lateral antennu- 

 lar flagellum, with RL/CL <0.75; and 

 2) F. aztecus, F. brasiliensis, F. paiilen- 

 sis, and F. subtilis: long rostrum, usu- 

 ally almost straight along the entire 

 length, extending anteriorly beyond 

 the distal antennular segment, some- 

 times reaching to the distal one-third 

 of broadened portion of lateral anten- 

 nular flagellum, with RL/CL >G.80. 

 Perez-Farfante stressed that, for the 

 recognition to species level of juveniles 

 <10 mm CL, all the characters listed 

 above should be considered because 

 occasionally one alone may not prove 

 to be diagnostic. However, the only 

 characters that could be distinguished 

 for small juveniles in the range 4-8 

 mm CL are those defined on the ros- 

 trum. Therefore, it has been almost 

 impossible to identify and separate 

 small specimens of Farfantepenaeus 

 (Perez-Farfante, 1970, 1971a; Perez- 

 Farfante and Kensley, 1997). 



Pink spotted shrimp (F. brasilien- 

 sis) and southern pink shrimp (F. 

 notialis) have a wide geographic dis- 

 tribution in coastal environments of 

 the Atlantic Ocean. The pink spot- 

 ted shrimp is distributed within the 

 western Atlantic from Cape Hatteras, 

 North Carolina, to Cabo Frio, Brazil 



(22°00'S, 42°00'W; Perez-Farfante, 

 1969), including the southwestern 

 Gulf of Mexico and the Caribbean 

 coasts of Mexico (Perez-Farfante, 

 1971b). The southern pink shrimp 

 ranges from the northwestern Yu- 

 catan Peninsula, Mexico (20°45'N, 

 90°25'W; Perez-Castaiieda and Be- 

 feo, 2000), to Rio de Janeiro (Brazil) 

 in the western Atlantic, including 

 Cuba and the Virgin Islands in the 

 Caribbean Sea. The species is also 

 reported from Mauritania to Angola 

 in the eastern Atlantic Ocean (Perez- 

 Farfante, 1969; Perez-Farfante and 

 Kensley, 1997). 



The current identification keys 

 show that, for shrimps >8 mm CL, 

 the pink spotted shrimp has a pro- 

 portionately longer rostrum than 

 the southern pink shrimp. However, 

 there are no scientific data to sepa- 

 rate these species at individual sizes 

 <8 mm CL (Perez-Farfante, 1970, 

 1971a). This is particularly impor- 

 tant where both penaeid shrimps are 

 found in the same region, mainly 

 between the Yucatan Peninsula and 

 along the Caribbean coast of Mexico, 

 Puerto Rico, and Colombia. In this 

 geographic region, small juveniles of 

 both species have been almost impos- 

 sible to separate and have been clas- 

 sified only to genus level (Stoner and 

 Zimmerman, 1998; May-Kii, 1999; 

 Perez-Castafieda and Befeo, 2001; 

 Criales et al., 2002). In this note we 

 provide quantitative and qualitative 

 information that allows separation of 

 the sympatric F. brasiliensis and F. 

 notialis in the range of 4-8 mm CL 

 based on shrimp collected in the Rio 

 Lagartos and Yalahau coastal lagoons 

 of the Yucatan Peninsula, Mexico. 



Materials and methods 



Shrimp were collected by using a 

 Renfro beam trawl (1.6x0.5 m mouth, 

 1.5 m total length, and 1.0-mm mesh), 

 which was hand hauled in two coastal 

 lagoons of northeastern Yucatan 

 Peninsula (Fig. 1). The Ri'o Lagartos 



Manuscript submitted 8 March 2005 

 to the Scientific Editor's Office. 



Manuscript approved for publication 

 22 August 2005 by the Scientific Editor. 



Fish. Bull. 104:306-310 



