Nates and Felder: Growth and maturation of Lepidophthalmus sinuensis 



535 



Table 2 



Allometric coefficients measured as slopes for linear regressions I by least squares estimate, with log-transformed data) of chela 

 width on carapace length (ChW:CL), chela height on carapace length (ChH:CLi. chela width on chela height lChW:ChH). total 

 length on carapace length (TL:CL), and wet weight on carapace length (WW:CL) for male and female populations of Lepidophthalmus 

 sinuensis sampled at the Agrosoledad S. A. shrimp farm, upper Cispata estuary, Colombia, December 1991, through December 

 1995. Coefficients were determined for entire data set (All) and for data subdivided at the transition point (yielding separate 

 regressions for data points <X and data points >X, where X = size at onset of sexual maturity estimated by piecewise linear-linear 

 polynomial regression), 95'7f CI = confidence interval of coefficient. * *= allometric coefficient significantly (P<0.05) different from 

 1.0. a-u = allometric coefficients with same superscript are significantly (P<0.05) different from each other 



ChW:CL 



ChH:CL 



ChW:ChH 



TL:CL 



WW:CL 



Allom. coef. 95% CI Allom. coef 95% CI Allom. coef 95% CI Allom. coef 95% CI Allom. coef 95% CI 



Males 



All 1.577**° 



<X 1.525**'' 



>X 1.608**' 



±0.059 

 ±0.162 

 ±0.129 



1.457**<? 

 1.440**^ 



1.477**s 



Females (including those with eggs) 

 All 0.820**"'''''' ±0.039 0M9**'ff'' 

 <X 1.625**'' ±0.210 1.470**'' 



>X 0.441**'"*''' ±0.053 0.491***'/*'' 



±0.047 

 ±0.122 

 ±0.110 



±0.033 

 ±0.160 

 ±0.045 



1.085 

 1.061 

 1.106 



0.934'*'-'*' 



1.096' 



0.864**'-'*' 



±0.017 

 ±0.039 

 ±0.033 



±0.021 

 ±0.116 

 ±0.033 



0.928**"'' 



o.ges"'' 



0.618**'""° 



0.895**''"'' 



LOSl"""" 



0.693**'"'' 



±0.027 

 ±0.035 

 ±0.164 



±0.025 

 ±0.052 

 ±0.051 



3.094**" 



2.762** 



3.056**' 



2.476**'" 



3.458**" 



2.064**'''" 



tO.118 

 to. 747 

 ±0.118 



tO.090 

 tl.102 

 ±0.122 



This observation suggests that the detected sex bias 

 accurately characterizes the population sampled. 



In the course of previously reported observations 

 on populations of C. s. 1. filholi, it was noted that the 

 sex ratio was near 1:1 only when small animals were 

 included in the sample (Devine, 1966). For L. 

 sinuensis there is also a correlation between mean 

 size of animals in the monitored population and sex 

 ratio over the four years of monitoring. As noted for 

 C. s. 1. filholi, samples of smaller mean CL were 

 nearer 1:1 in sex ratio than were samples of larger 

 mean CL. The trend toward increasing frequency of 

 females reached an approximate asymptote after 23 

 months of observation, simultaneous with the trend 

 in increasing CL of males, and may indicate a point 

 at which increasing numbers of larger males estab- 

 lished a sexual equilibrium by displacing small males 

 from a limited habitat or maintained territory. This 

 increase corresponds roughly to the time when bur- 

 row densities within ponds on the farm began expo- 

 nential increase and when detrimental effects on 

 water quality and penaeid production became evi- 

 dent (equals month 38 in Figure 1 of Nates and 

 Felder, 1998). Sex ratios and mean carapace lengths 

 may thus serve to forecast potential for rapid in- 

 creases in infesting populations. 



Both the large body size and the robust chelipeds 

 of mature males could be of advantage in competi- 

 tion for limited space and available females wher- 

 ever L. sinuensis occurs in dense, mature aggrega- 



tions. Such behaviors have been suggested previously 

 to account for large numbers of possibly displaced 

 juvenile males of L. louisianensis observed periodi- 

 cally in plankton samples (Felder and Lovett, 1989; 

 Felder and Rodrigues, 1993). Similar intraspecific 

 competition for space, in which juveniles are expelled 

 to the surface, has also been postulated to occur in 

 some populations of Callianassa s. 1. japonica 

 ( Ortmann ), along with possible immigration of juve- 

 niles to other habitats (Tamaki and Ingole, 1993). 

 While not documented to occur in L. sinuensis, colo- 

 nization of mariculture ponds by such displaced ju- 

 venile males pumped in with estuarine waters could 

 account for higher percentages of males observed 

 early in our study. Such recruitment of juveniles could 

 potentially supplement larval settlement within 

 ponds to rapidly build early infestation densities. 



Ovjgerous females 



The abbreviated life cycle in L. sinuensis includes 

 only two brief zoeal stages, large numbers of which 

 occur in nocturnal plankton samples taken at the 

 study site (Nates et al., 1997). The eggs of this spe- 

 cies and its congener L. louisianensis are comparable 

 in size to those of Callianassa s. 1. kraussi Stebbing, 

 another estuarine species that exhibits markedly 

 abbreviated development (Forbes, 1973), and are 

 larger than those of many thalassinids with longer 

 larval histories and wider planktonic dispersal (see 



