Differentiating Paralithodes iarvae 

 using teison spines: A taii of two species* 



Gregory C. Jensen 

 Helle B. Andersen 

 David A. Armstrong 



School of Fisheries WH-IO, University of Washington, Seattle, Washington 98195 



Identification of larvae belonging to 

 closely related species of decapod 

 Crustacea is frequently dependent 

 upon few (often single) morpholog- 

 ical characters. Since larvae used in 

 descriptions are often the offspring 

 from a single captive, very little is 

 known about how intraspecific vari- 

 ability may affect the ability to dif- 

 ferentiate species. Two congeneric 

 decapods whose zoeae are separ- 

 ated on the basis of a single mor- 

 phological character are the red 

 king crab (RKC) Paralithodes cam- 

 tschaticus, and blue king crab 

 (BKC)P. platypus. Larvae of these 



' Contribution 867 of the School of Fisheries, 

 University of Washington. 



commercially-important species are 

 distinguished from each other by 

 the number of spines or processes 

 on the teison, RKC having 7 pairs 

 of spines and BKC 8 pairs, ex- 

 cluding a minute seta (Sato 1958, 

 Haynes 1984). However, when 

 viewed together there are other ap- 

 parent differences: BKC zoeae have 

 proportionately shorter rostrums 

 and carapace spines, larger bodies 

 at each stage, and larger eyes. 



During the course of extensive 

 plankton sampling for king crab lar- 

 vae in Herendeen Bay within Port 

 Moller, Alaska, considerable vari- 

 ability in teison morphology was 

 noted. A large proportion of zoeae 

 resembling BKC were captured 



BERING SEA 



<? 



PrtiMol IHanas 



- 56'N 



PACIFIC OCEAN 



160 W 



-r 



Figure 1 



Locations of Paralithodes spp. zoeae collections. 



having an asymmetrical pattern of 

 8-1-7 teison spines, while others, 

 also appearing to be BKC in other 

 respects, had only 7 pairs; such in- 

 terspecific character overlap had 

 not been noted with these two 

 species near the Pribilof Islands, 

 Alaska (Armstrong et al. 1985). To 

 confirm the identity of these zoeae 

 and provide additional characters to 

 separate the two species, several 

 measurements were taken on spe- 

 cimens from Herendeen Bay and 

 the Pribilof Islands to establish a 

 stronger, more quantitative basis to 

 distinguish these larvae. 



Materials and methods 



Paralithodes zoeae were collected 

 near the Pribilof Islands, Alaska, in 

 May 1983 and April 1984, and from 

 Herendeen Bay, Alaska (Fig. 1) in 

 May and June of 1990, using either 

 a 505 /jm mesh Tucker trawl or a 

 60 cm bongo net with a mesh of 333 

 or 505f/m. Samples were preserved 

 in 5% buffered formalin in seawater 

 and later sorted for target species, 

 which were transferred to a solution 

 of 70% ethanol and 5% glycerol. 

 The number of teison spines (ex- 

 cluding a minute seta) was recorded 

 for each specimen, and three mea- 

 surements were taken: tip of ros- 

 trum to the anteriormost edge of 

 the eye ("rostrum length"), anterior 

 edge of eye to the tip of the pos- 

 teriolateral carapace spines ("cara- 

 pace length"), and the longest 

 dimension of the eye ("eye length," 

 Fig. 2). Damaged or distorted spe- 

 cimens were not used for measure- 

 ments, but spine counts were re- 

 corded. A total of 608 larvae were 

 measured; 371 from Herendeen 

 Bay and the remainder from around 

 the Pribilof Islands. The ratios of 

 rostrum length to carapace length 

 were plotted against carapace 

 length for "normal" (i.e., 7-1-7 

 teison spine RKC and 8 -h 8 BKC) 



Manuscript accepted 1 July 1992. 

 Fishery Bulletin, U.S. 90:778-783 (1992). 



778 



