. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. Figure 4. Scanning electron micrographs of the central ciliary tuft of (A) Mulinia laterals and (B) Rungui eiineaiu larvae. Note the pres- ence of both terminal discs and discs distal to the cilia tip (see arrows) in M. laleralis. Scale bar = fact that interspecific comparison is confounded by mi- nor differences in morphometry, size, and, we suspect, specific gravity of larval stages, it is evident that the pres- ence of discocilia and paddle cilia in M. lalcralis and 5. solidissima. respectively, does not apparently confer
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. Figure 4. Scanning electron micrographs of the central ciliary tuft of (A) Mulinia laterals and (B) Rungui eiineaiu larvae. Note the pres- ence of both terminal discs and discs distal to the cilia tip (see arrows) in M. laleralis. Scale bar = fact that interspecific comparison is confounded by mi- nor differences in morphometry, size, and, we suspect, specific gravity of larval stages, it is evident that the pres- ence of discocilia and paddle cilia in M. lalcralis and 5. solidissima. respectively, does not apparently confer higher rates of vertical displacement when compared with R cituccita. We did not compare absolute velocity (that which describes movement along the helical path rather than just vertical displacement) in the swimming study. Nonetheless, the ecologically meaningful value for vertical displacement (see discussion in Mann. 1986) suggests that the presence of modified cilia is not accom- panied by greater ability to depth regulate in stratified water columns, an arguable advantage to any larvae en- countering estuarine or shallow coastal environments. Examination of previous descriptions of larvae or lar- val velar morphology for Crassostrea virginica Gmelin (Elston. 1980). Ostrca eclnlis Linne (Waller, 1981), and Airiica isltuulica Linne (Lutz cl al., 1982) have failed to demonstrate the presence of velar paddle cilia or discoci- lia—although in fairness only Waller (1981) provides micrographs of sufficient magnification and appropriate content for definitive statements. The taxonomic sig- nificance of these structures is also debatable. A signifi- cant component of bivalve taxonomy has historically fo- cussed on adult shell characteristics and the present focus of larval taxonomy is on valve morphometry and hinge ultrastructure (see comments in Lutz et a/.. 1982). Yet within one family, the Mactridae, we have examined three phylogenetically associated species and demon- strate
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
