Sulikowski et al.. The reproductive cycle of Amblyro/a radiata 



541 



60 



CD 



Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 



40 



35 



25 S 



20 



Figure 3 



Comparisons between male and female thorny skate (A. radiata) 

 reproductive parameters over the course of the sampling period: 

 (A) GSI; (B) diameter of the two largest follicles and percentage of 

 spermatocysts (SVIl and; (C) shell gland weight and percentage of 

 spermatocysts (SVI). 



very limited because studies have focused on changes 

 in morphological parameters (i.e., Richards et al., 1963; 

 Craik, 1978) or steroid hormone analyses (i.e., Sumpter 

 and Dodd, 1979; Rasmussen et al., 1999) in females. To 

 our knowledge, the only two species in which quantita- 

 tive methods were used to describe annual reproductive 

 patterns in males were H. ocellatum (Heupel et al., 

 1999) and L. ocellata (Sulikowski et al., 2004). These 

 two species exhibit contrasting strategies in their re- 

 spective reproductive cycles. For example, similar to 

 male thorny skates from the present study, male winter 

 skates appear capable of continuous production of ma- 

 ture spermatocysts throughout the year (Sulikowski et 

 al., 2004). In contrast, examination of the testes and 

 circulating hormone concentrations in H. ocellatum 

 indicated that sperm production and androgen concen- 



tration display a concurrent seasonal cycle that peaks 

 from June to October (Heupel et al., 1999). 



The lack of correlation between GSI or HSI and stage 

 of spermatogenesis in the thorny skate was not surpris- 

 ing because studies do not support the assumption that 

 relative gonad size (or storage products in the liver) 

 and reproductive readiness are positively correlated 

 (Teshima, 1981; Parsons and Grier, 1992; Maruska et 

 al., 1996). For instance, neither peak sperm production 

 (Maruska et al., 1996) nor the pattern of testosterone 

 concentration was correlated with GSI in Dasyatis sa- 

 bina (Snelson et al. 1997) or L. ocellata (Sulikowski et 

 al., 2004). 



Relatively few studies have assessed whether cycli- 

 cal patterns of reproductive morphological parameters 

 or hormone concentrations are coordinated between 



