Some bivalve species with populations living in turbid environments have been found to have larger ctenidium and LP areas than populations living in less turbid environments, including the blue mussel (Mytilus edulis) (Theisen 1982), the oyster (Crassostrea gigas) (Barille et al.
Ordinary filaments Tube-shaped filaments that make up most of the ctenidium. Principal filaments Modified, U-shaped filaments that are found between adjacent plicae of heterorhabdic ctenidia.
All femora with ventral ctenidium, inconspicuous on fore and hind pair.
Legs mainly black without ventral ctenidium on hind femur and without erect posterior bristles medially on hind tibia.
Fore and mid tibia with inconspicuous ctenidium on anteroventral side and hind tibia without erect posterior bristles medially.
Fore coxa with 22 brown setulae on anterior surface; fore tibia with ctenidium of 10 or 11 short, sharp black spinules.
Fore coxa with 9 brown setulae on anterior surface; mid coxa with 8 brown setulae; fore tibia with ctenidium of 12 spinules.
Fore coxa with 8 diminutive brown setulae on anterior surface; mid coxa with 2 very strong, lateral, ventrally-directed black setae, 1 very strong medial seta and 5 brown setulae; fore tibia with 4 strong setae on lateral margin, the second basal seta of similar length to other three, with ctenidium of 9 or 10 short, sharp, black spinules, separated from each other by one or more basal spinule widths.
Fore coxa with 9 brown setulae; mid and hind coxa silver-yellow pruinose, mid coxa with 3 brown setulae; hind coxa with 2 brown setula; fore tibia usually with 4 strong setae on lateral margin, the second basal seta of similar length to other three, with ctenidium of 7-9 short, sharp black spinules.
cancellata, we compared the relationships between ctenidium area and body mass in T.
We used reduced major axis (Model II) regression to describe the relationships between ctenidium area and body mass for the three species (LaBarbera, 1989).
Bacterial symbionts are, however, abundant in the abfrontal region of the ctenidium
[ILLUSTRATION FOR FIGURE 2D-F OMITTED] AND [ILLUSTRATION FOR FIGURE 3 OMITTED].