Sanchez et al: Morphometry of juvenile and subadult Loligo pealei and L plei 



537 



were sorted from the trawl samples, counted, and 

 weighed. They were frozen (-20°C) on board within 

 two hours of capture to deter tissue degradation. 

 Large, more readily identifiable squids were frozen 

 separately for later use in biochemical determina- 

 tions of species-specific protein patterns, whereas the 

 smaller squids from each station were frozen to- 

 gether. All samples were sealed in polyethylene bags 

 in which the air had been squeezed out to prevent 

 freezer-burn during storage. The frozen squids were 

 placed in chilled containers for transportation from 

 the ship to the Gulf Coast Research Laboratory (GCRL), 

 Ocean Springs, Mississippi, following completion of the 

 cruise. Squids were stored at -20°C in the laboratory. 



Laboratory procedures 



Initial research efforts centered on establishing 

 nonvariant protein patterns that could be used to 

 separate the two Loligo species. Ten large specimens 

 of each Loligo species (greater than 200-mm mantle 

 length) were selected from the frozen samples and 

 tentatively identified at GCRL with the morphologi- 

 cal criteria provided by Bane and Wagner, 2 Voss 

 ( 1956 ), LaRoe ( 1967 ), Cohen ( 1976 ), and Roper et al. 

 (1984). These criteria included shape of the 

 hectocotylus in males, overall body shape, the size 

 and shape of the fins, and the dentition of the ten- 

 tacular suckers. A sample of mantle tissue was re- 

 moved from each squid, refrozen, and stored at -70°C. 

 Frozen squids were shipped on dry ice to the Na- 

 tional Museum of Natural History, Washington, D.C., 

 for confirmation of field identifications. Following 

 verification of identification of specimens based on 

 morphological criteria, mantle tissue from each in- 

 dividual was analyzed electrophoretically and diag- 

 nostic protein bands were determined. 



To evaluate morphometric parameters of potential 

 value in field separation of L. plei and L. pealei, speci- 

 mens of juvenile and subadult Loligo spp. (rc=304) 

 ranging in size from 29.0 to 238.0 mm mantle length 

 (ML) were selected from the squid samples frozen in 

 the field. Squids were selected from each of three 

 geographic areas over the complete range of depths 

 sampled (less than 18 m, 18-36 m, 37-55 m, 56-73 

 m, 74-110 m) within each area. Designation of geo- 

 graphic areas followed Nichols and Pellegrin 1 : Texas 

 (Brownsville to Galveston), West Delta (Galveston, 

 TX, to the Mississippi River), and East Delta (Mis- 

 sissippi River to Mobile, AL). Juvenile and subadult 

 squids were selected from 41 stations without regard 



to probable species or sex. Specimens were thawed, 

 individually numbered, and weighed to the nearest 

 0.1 g. Visual inspection for the presence of nidamental 

 glands or the spermatophoric sac was used to sepa- 

 rate females from males. 



The diagnostic measurements and indices used by 

 Voss ( 1956), Haefner ( 1964), Cohen ( 1976), and Hixon 

 (1980) were reviewed for their potential usefulness 

 in taxonomic resolution of the Loligo species. Eleven 

 morphometric measurements and selected indices 

 (ratios of measured characters) of potential value in 

 separating species and sex within a species were 

 determined (Table 1; Fig. 2). 



Morphometric characters were measured with digi- 

 tal calipers to the nearest 0.1 mm. Because some in- 

 dividuals were damaged, the number of measured 

 characters per individual varied. Squids > 100.0 mm 

 ML were not well represented in the sample aliquot. 

 Large males of both L. pealei and L. plei were in- 

 cluded in the aliquot, but there were few females of 

 similar size. For that reason, size limitations were 

 placed on the data used in regression analyses, with 



2 Bane, G. W., and A. Wagner. 1985. Key to important squids 

 of the northern Gulf of Mexico. Coastal Fisheries Institute, 

 Center for Wetland Resources, Louisiana State Univ., Baton 

 Rouge, LA, LSU-CFI-85-21, 10 p. 



Figure 2 



Morphometric characters measured for Loligo pealei and 

 Loligo plei : (A) ventral view, modified from Roper et al. 

 (1984); (B) head, dorsal view, from Cohen (1976); (C) 

 gladius. Abbreviations are defined in Table 1. 



