538 



Fishery Bulletin 94(3). 1996 



the limits dependent upon the size-frequency distri- 

 bution of the specimens. Size-class ranges for tests 

 of sexual dimorphism were from 50.0 to 150.0 mm 

 ML for L. pealei and from 40.0 to 110.0 mm ML for L. 

 plei. When characters and indices were compared be- 

 tween the two species, squids from 20.0 to 150.0 mm 

 ML were used in the analyses. Both individual charac- 

 ters and indices were regressed against mantle length 

 to determine their potential value in differentiating spe- 

 cies, or sex within a species, for squids of a given size. 



After external measurements were recorded for 

 each squid, the mantle was opened and the gladius 

 removed. Drawings of the gladii were made by means 

 of photocopies of the actual gladii as patterns. A piece 

 of mantle tissue was taken from each squid, frozen 

 immediately, and stored at -70°C. Specimens were 

 re frozen and stored at -20°C. 



Isoelectric focusing (IEF), a technique which sepa- 

 rates proteins according to their isoelectric points 

 along a continuous pH gradient ( Righetti et al. , 1990 ), 



was used to characterize mantle protein patterns. 

 Mantle tissue was minced and then homogenized in 

 BSS buffer (0.05 M Tris at pH 7.5, 0.25 M sucrose, 

 0.01 M KC1, 0.01 M MgCl 2 , 0.001 M CaCl 2 , 0.001 M 

 phenylmethylsulfonyl fluoride) with an Ultra- 

 Turex™ (Type TP 18/10 SI) homogenizer. The ho- 

 mogenate from each squid was centrifuged separately 

 at 14,000 RPM (23,460 RCF) for 20 minutes at 4°C 

 with a Beckman™ Model J-21C refrigerated centri- 

 fuge. The supernatants were recovered and frozen 

 separately at -70°C. Total protein in each supernate 

 was measured (Bio-Rad™ Bradford Protein Assay 

 Kit) in order that the same amount of protein (35 ug) 

 was loaded in each lane of the gel. 



Isoelectric focusing separations were made in 0.5- 

 mm polyacrylamide gels with an LKB Ultraphor™ 

 apparatus. Proteins were separated with ampholytes 

 of the 4.0-6.5 pH range by using 0. 1 M glutamic acid 

 as the analyte and 0.1 M beta-alanine as the 

 catholyte. The gels were prefocused at 2,000 V for 30 



