Thomas and Moltschaniwskyi: Ontogenetic changes in size and shape of statoliths of Sepioteuthis lessoniana 



639 



the oldest individual was a 186-day-old mature fe- 

 male. Adult statolith weights ranged from 0.29 mg 

 in a 72-day-old immature male to 1.74 mg in a 144- 

 day-old mature female. 



Adult statolith weight was not a reliable predictor 

 of squid age, with only 579c (n=62) of the variation 

 in adult ages attributable to weight of the statoliths 

 (Fig. 2A). The strength of the relation between age 

 and statolith total length differed between juvenile 

 and adult squid (Fig. 2B). For juvenile squid, 859c 

 (n = 16) of the variation in age was attributable to dif- 

 ferences in statolith total length, indicating statolith 

 total length maintains a close correlation with age 

 during the first 60 days of squid growth. In adult 

 squid, the ability to predict age based on statolith 

 total length is poor, and only 579c (n =62) of the varia- 

 tion in squid ages can be explained by statolith 

 length. Statolith total length grew relatively slower 

 than ML for both adult and juvenile squid (Fig. 3A). 

 Adult statolith weight displayed positive allometric 

 growth with ML (Fig. 3B). 



200 



160 -I 

 120 



80 



40 

 



age = 63.42x + 62.70 

 r-=0.57, n = b2 



0.0 0,4 0.8 1.2 1.6 2.0 

 Statolith weight (mg) 



200 



160 Jage-24.27e0-«'"^ .,^. 

 r2 = 0.57, n = 62 " "^ 



B 



600 1,200 1,800 2,400 



Statolith total length lum) 



Figure 2 



Relationship between (A) adult statolith 

 weight and age, and iB) statolith total 

 length and age for Sepioteuthis lessoniana 

 specimens. Circles = adults; squares = 

 juveniles. 



Changes in statolith shape 



The first PCA axis described 98.6% of the variation 

 among individuals, which is due to statolith shape 

 or the size of all statolith dimensions combined. If 

 we use the PCA score on the first axis as a descriptor 

 of statolith shape, we can account for only 99c and 

 7% of the variation in statolith total length of juve- 

 nile (n = 16) and adult (??=78) squid, respectively (Fig. 

 4B). This result confirms that the first PCA axis con- 

 tains statolith shape information and not predomi- 

 nantly size information. Growth of the statolith along 

 the total length, ventrolateral and lateral dome axes 

 and in total length was relatively slow, as evidenced 

 by negative allometric growth (Table 3). In contrast, 

 gi-owth of the statolith along the dorsolateral axis 

 and in total width grew relatively faster, as evidenced 

 by the positive allometric growth (Table 3). This find- 

 ing indicates that the statoliths of juvenile squid are 

 relatively thin and elongate, becoming comparatively 



3.4 



3.2 



y=2.74 + 0.43x 

 (95%CL = 0.39-0. 

 r2 = 0. 61, n = SO 



s 3.0 



3.0 -I 



2.8 -^"J 



/■ 



y = 2.71 + 0.45x 

 r2 = 0.92, n = 2S 

 !.CL = 0.41-0.49) 



1.5 



2.0 



2.5 



0.4 



0.2 



0.0 



-0.2 



■0.4 



■0.6 



y = 0.17.i-1.49x 

 (95%CL = 1.34-1.67) 

 !^ = 0.52, n = 80 



1.0 1.5 2.0 2.5 



Log matitle length (mm) 



Figure 3 



Relation between (A) mantle length and 

 statolith total length, and (B) mantle 

 length and adult statolith weight for 

 Sepioteuthis lessoniana specimens. Circles 

 = adults; squares = juveniles. CL = confi- 

 dence limits of the slope. 



