Nates and Felder: Growth and maturation of Lepidophthalmus sinuensis 



537 



nual cycles in availability of nu- 

 trition may determine potential 

 for vitellogenesis and success of 

 larvae (Zimmerman and Felder, 

 1991: Mouton and Felder, 1995). 

 Although temperature was not 

 subject to marked fluctuation in 

 the shrimp farm habitat of L. 

 sinuensis, it did vary slightly 

 with the annual changes in rain- 

 fall patterns that determined sa- 

 linity of the upper estuary (Fig. 

 4A). The annual decline in salin- 

 ity from April through October 

 reflected increased input of nu- 

 trient-loaded waters from the 

 nearby Rio Sinii which was re- 

 ported to result in periodic eleva- 

 tion of penaeid shrimp growth 

 rates on the Agrosoledad farm 

 (MogollonM. Similarly, such low 

 salinity periods may have pro- 

 duced improved conditions for vi- 

 tellogenesis inL. sinuensis. Peak 

 development of ovaries in the 

 first quarter of the typical year 

 either coincided with or shortly 

 followed lowest mean salinity 

 during the last quarter of the pre- 

 vious year, and fell markedly just after salinity 

 peaked. The abundance of ovigerous females peaked 

 almost simultaneously with salinity in most years of 

 the study and a decrease in mean ovarian width im- 

 mediately followed, indicating that the abundance 

 of females with spent ovaries was not offset by other 

 females simultaneously undergoing vigorous ovarian 

 development. Reduced vitellogenesis following the 

 high salinity period was also suggested by the mark- 

 edly reduced mean number of eggs per clutch found 

 in those ovigerous females that occurred from May 

 through July. 



Growth and sexual maturation 



Among callianassids and other thalassinid shrimp, 

 the major chela is used commonly for aggressive in- 

 teractions between captured individuals that are held 

 together or among individuals encountering one an- 

 other where burrows intersect in laboratory fossoria 

 (MacGinitie, 1934; Pearse, 1945; Rodrigues, 1976; 

 Tunberg, 1986; Felder and Lovett, 1989; Pillai, 1990; 



20 4 8 



Carapace length (mm) 



Figure 7 



Linear regression ( by least squares estimate for untransformed data) of wet weight 

 (W^\') on carapace length (CD for males (A) and females (B) in sampled Colom- 

 bian populations o( Lepidophthalmus sinuensis, December 1991 through Decem- 

 ber 1995. The transition point at which data are subdivided, estimated by piece- 

 wise linear-linear polynomial regression, was positioned to minimize the sum of 

 squares of residuals. 



' Mogollon, J. V. 1995. Agrosoledad S. A., Playa de la Artillena 

 no. 33-36. Cartagena. Columbia. Personal comniun 



Rowden and Jones, 1994). Contrary to the case with 

 many other genera, both males and females of Lepi- 

 dophthalmus have one chela enlarged, but the ma- 

 jor chela of mature males is much more strikingly 

 developed than that of mature females (Felder and 

 Rodrigues, 1993; Felder and Manning, 1997). Sexual 

 dimorphism of the chelae in decapods is generally 

 thought to reflect adaptations for their use. especially 

 by males, in combat, display, and courtship (Hartnoll, 

 1974). The enlarged chela can play a role in intermale 

 competition during the precopulatory phase of the 

 life cycle, and marked change in its allometric growth 

 rate is frequently related to functional sexual matu- 

 rity (Grey, 1979; Aiken and Waddy, 1989; Claxton and 

 Govind, 1994; Gu et al., 1994; Robertson and Kruger, 

 1994). This is likely also the case in L. sinuensis, even 

 though we can only speculate as to the exact role 

 this appendage plays in such fossorial populations. 

 A striking transition takes place in rate of relative 

 growth for the major chela in L. sinuensis. and there 

 is an allometric divergence between males and fe- 

 males in the shape of this appendage at sizes that 

 exceed a defined, transitional carapace length. For 

 the most part, the relationships of slopes above and 

 below these transition or maturation points are simi- 

 lar to relationships previously reported in monitored 



