YANG ET AL.: CULTURE EXPERIMENTS OF LOLIGO OPALESCENS 



the nidamental gland was observed in a 101-d-old 

 female (23 mm ML) in L.0. 1981. The penis was first 

 recognizable in a 93-d-old male (29 mm ML, 1.15 g 

 WW), and the nidamental gland was observed in a 

 92-d-old female (33 mm ML, 1.71 g WW) in L.0. 

 1982. Figure 15 shows that females become mature 

 at approximately 60 mm ML. This maturation in- 

 dex is based upon reports by Hixon (1980a) and 

 Macy (1982) in which the ratio of nidamental gland 

 length to mantle length is >0.20. Squid this size 

 could produce fully formed egg capsules. The 

 smallest male with spermatophores was 71 mm ML 

 in L.O. 1982. 



In L.O. 1981, first mating activity was observed 

 on day 193. A pair was swimming together, a sec- 

 ond male interrupted, and a third male grasped the 

 female in the midmantle area but she jetted away. 

 On day 197 another pair was swimming together at 

 the end of the RW and a brief head-to-head mating 

 was observed. They separated for about 1 min, then 



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20 40 60 80 100 120 

 MANTLE LENGTH (mm) 



Figure 15.— Maturation index for females from pooled data of 

 L.O. 1981 and 1982. Dots with circles indicate sexually mature 

 females in which the ratio of nidamental gland length to mantle 

 length is >0.20. See text. 



the male grabbed the female by the arms for a sec- 

 ond time. Drew (1911) illustrated this copulating 

 position in Loligo pealei. A second mating position 

 was observed on day 226. A male grasped a female's 

 mantle one-third of the way from the posterior tip 

 of the mantle, then he gradually moved to the 

 female's head near the mantle opening and then let 

 go. This was done very swiftly and it was impossible 

 to see if a spermatophore was passed. Freshly dead 

 females had spermatophores attached around the 

 sperm receptacle below the mouth after head-to- 

 head matings. Mating activity was not as closely 

 monitored in L.O. 1982, but first observations were 

 several weeks earlier (before day 175). 



Spawning started on day 196 and lasted till day 

 239 in L.O. 1981. Of 151 egg capsules, 24 (16%) were 

 unfertilized (Table 4). Squid kept in the CT system 

 (3°C higher temperature from day 125) spawned 

 first on day 185, 11 d earlier than the RW system, 

 but none were fertile. Spawning occurred earlier in 

 L.O. 1982, beginning day 175 and ending day 222. 

 All of the 199 spawned capsules were infertile. The 

 maximum number of spawned capsules in a single 

 day was 27 on day 203 (Fig. 13B). Most eggs were 

 collected in the morning indicating that spawning 



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