PEREZ FARFANTE: ROCK SHRIMP GENUS SICYONIA 



distal third of merus, followed by bright yellow 

 band crossing merus and proximal part of carpus; 

 fourth and fifth pereopods marked with orange red 

 band flanked by yellow ones extending across 

 merus and proximal part of carpus. Pleopods 

 mostly pink, lateroventral part of basis white. 



Maximum size. — Males 21 mm cl, 88.8 mm tl; 

 females 28 mm cl, 98.7 mm tl (Arana Espina and 

 Mendez G. 1978). Largest specimens examined by 

 me: males 20 mm cl, females 25.7 mm cl. 



Geographic and bathymetric ranges. — Bahia 

 Santa Maria (24°42'48"N, 112°13'54"W), to the tip 

 of Baja California Sur, Mexico, and from southern 

 Sonora, Gulf of California, southward to Pisco 

 (13°55'S), Peru(Fig. 52). 



This species has been found between 5 and 

 139-93 m, but rarely in water deeper than 65 m; 

 contrary to most of its congeners from the Ameri- 

 can Pacific, it does not seem to range beyond the 

 continental shelf. It occurs on bottoms of mud, 

 detritus, fine sand, and rock and coral, seemingly 

 with no preference. 



Abundant in the southeastern part of the Gulf of 

 California (Paul and Hendrickx 1980), it has not 

 been reported off northern Sonora or along the 

 east coast of Baja California; the present records 

 from these latter areas are the first for the species 

 north of Bahia San Lucas, a locality cited by Bur- 

 kenroad (1938). The southern limit, Pisco, Peru, 

 given here is also the first report of the presence of 

 this shrimp in waters south of San Lorenzo 

 (12°0.5'S), Peru, the southernmost locality cited 

 by Arana Espina and Mendez G. (1978). The record 

 from Pisco is based on specimens collected by M. 

 Mendez G. and J. Zeballos, at 5.5-13 m, on 5 

 November 1983 (Matilde Mendez G. footnote 3). 



Discussion. — Burkenroad (1938) was the first to 

 point out some of the differences that separate this 

 species from its closest relative S. ingentis. 

 Sicyonia disdorsalis can be distinguished from the 

 latter by having 1) a sparsely setose carapace, 2) 

 a less elevated postrostral carina, 3) a weak, al- 

 most indistinct branchiocardiac carina, 4) a pos- 

 teriorly truncate carina on the fifth abdominal 

 somite that is sometimes produced in a spine, 5) an 

 anteromedian pleural sulcus on the first abdomi- 

 nal somite which ends abruptly far from the ven- 

 tral margin, and does not continue ventrally as a 

 shallow depression, 6) a strong spine on the an- 

 teroventral extremity of the pleuron of the first 

 abdominal somite, 7) angular posteroventral 



pleural margins on the first two abdominal so- 

 mites, 8) minute telsonic spines in juveniles and 

 vestigial or indistinct ones in adults, and 9) short 

 uropodal rami that fall short of or barely surpass 

 the apex of the telson. 



Various features of the genitalia also allow the 

 separation of iS. disdorsalis from S. ingentis. The 

 distal projection of the dorsolateral lobule of the 

 petasma is curved distomesially instead of extend- 

 ing distolaterally, and is not produced in a short, 

 apical filament; and the distal projection of the 

 ventrolateral lobule does not extend so far distally 

 as the projection of the dorsolateral lobule, is 

 bifurcate laterally, and bears a conspicuous trans- 

 verse rib. In the thelycum, the breadth of the fiat 

 or concave posterolateral areas of the median 

 plate, as well as the depth of the delimiting inci- 

 sions are much less than the depressed area be- 

 tween them. Furthermore, the posterior compo- 

 nent of the median plate is sometimes slightly 

 raised posterolaterally but not forming well- 

 defined lateral bosses traversed by a suture as in 

 S. ingentis. 



The differences between S. disdorsalis and the 

 geminate western Atlantic S. dorsalis Kingsley 

 1878, were discussed in detail by Burkenroad 

 (1934a). 



Commercial importance. — Throughout its range, 

 S. disdorsalis is present in the commercial catches 

 of other penaeoid shrimps. It was recorded by 

 Rosales Juarez (1976) in those off the coast of 

 Sinaloa, in the Gulf of California, and more re- 

 cently, on the basis of its abundance in the shrimp 

 bycatch from the waters off Sinaloa and Nayarit, 

 Paul and Hendrickx (1980) suggested that this 

 shrimp has a possible commercial value in that 

 area. Arana Espina and Mendez G. (1978) recorded 

 that in 1977 it made up to 5.8% of the total catches 

 made in northern Peru, a notable increase from 

 that of previous years in which it constituted 

 <0.5%. This species is considered by them to have 

 a significant economic potential. 



Material. — 1054 specimens from 85 lots. 



Mexico— Baja California Sur: 16 29, SIO, 

 Bahia Santa Maria, 0-37 m, 8 December 1962, H. 

 C. Perkins. 16, SIO, NW of Punta Marquez, 37 

 m, 4 December 1962, H. C. Perkins and R. 

 Wisner 16 , SIO, NW of Punta Marquez, 18 m, 4 

 December 1962, H. C. Perkins. 16 29, YPM, 

 Bahia San Lucas, 5.5 m, 7 May 1936, Zaca stn 

 135D-20. 26, YPM, Bahia San Lucas, 5-17 m, 7 

 May 1936, Zaca stn 135D-18-D19. Sonora: 7c? 

 29, USNM, Bahia de Lobos (boca sur), 30 m, 18 



67 



