Nates and Felder: Growth and maturation of Lepidophthalmus stnuensis 



533 



35 

 30 

 25- 



20 



15H 



10 



5 







E 

 E^ 



_i 

 u 



f 



O 



Lovett, 1989), as well as in 

 populations of western Pacific 

 intertidal thalassinideans such 

 as Trypaea australiensis Dana 

 (Hailstone and Stephenson, 

 1961), Callia?}assa s. 1. filhoU 

 Milne Edwards (Devine, 1966). 

 and sexually mature adult popu- 

 lations of Neotrypaea califor- 

 niensis (Dana) and Upogeblci 

 pugettensis Dana (Dumbauld et 

 al., 1996). Populations were 

 male-biased in sampled popula- 

 tions of Callianassa s. 1. subter- 

 ranea Montagu from subtidal 

 European waters (Rowden and 

 Jones, 1994). 



Observance of skewed sex ra- 

 tios in thalassinidean samples 

 may reflect actual bias in the 

 population or an artifact of col- 

 lecting methods that do not 

 sample sexes equally within 

 the vertical profile of burrows 

 or across horizontal beach 

 transections, especially when 

 collections must be restricted to 

 readily accessed reaches of 

 shoreline sediments. Move- 

 ment of ovigerous females to- 

 ward the surface for egg release 

 or to optimally ventilate eggs 

 could lead to greater probabil- 

 ity of their capture when bur- 

 rows are aspirated with yabby 

 pumps. Likewise, sampling re- 

 stricted to shorelines may re- 

 flect differential positioning of 

 sexes within the burrow along 

 tidal or wave agitation clines. 

 Such effects could account for 

 previous observations in which 

 populations of Callichirus 

 islagrande were female-biased 

 on high wave-energy beaches 

 but not on nearby protected 

 beaches, or for ratios that dif- 

 fered markedly from month to 

 month in some populations of 

 L. loiiisianensis from the Gulf 



of Mexico (Felder and Griffis, 1994). In the present 

 study, mudflats along margins of drainage canals 

 were fully accessible to sampling during periods of 

 low pond discharge, samples were not limited to 

 shorelines, and burrows were not as deep as reported 



E 



Figure 5 



Pooled monthly measures for salinity, temperature, and reproductive indices in 

 sampled Colombian populations of Lepidophthalmus stnuensis: for A, monthly tem- 

 perature data were pooled from December 1991 through December 1993, and monthly 

 salinity from January 1992 through December 1995; for B, monthly data were pooled 

 from January 1992 through December 1995; for C, monthly data were pooled from 

 January 1993 through December 1995; for A, C. and D, vertical lines define 95Tf CI; 

 for B, vertical lines define range. (A) Morning surface salinity i solid circles, continu- 

 ous line I at farm intake pump in upper estuary, and afternoon surface temperature 

 (open circles, broken line) at outlet in pond 1. expressed as means of daily measures; 

 (B) frequency of ovigerous individuals among mature oll.O mm CL) females of 

 populations; lC> relative ovarian development (OW/CLi; iD) mean number of eggs 

 in clutches of ovigerous females. 



for above mentioned populations of C islagrande and 

 L. loiiisianensis. From resin casts (Fig. 4 in Nates 

 and Felder, 1998), it was observed that almost all 

 burrows were <1 m in depth, thus encompassing 

 water volumes readily extractable with yabby pumps. 



