ctenidium

(4') If ctenidia are present 7 on abdominal tergites V-VII; ctenidium on tergite VIII anterior to spiracle (Fig.

The ctenidium is bipectinate with a short afferent membrane and thus the free portion is long.

Mussels, for example, have a filibranchiate homorhabdic ctenidium with large compound laterofrontal cirri (Atkins 1938, Owen 1978) that could account for the reported high CE of particles in the 4- to 10-[micro]m size range (Riisgard 1988, Rosa et al.

Only the coverage of Ctenidium molluscum was about 4% on average.

Legs yellow, except coxae dark brown to black; femora dark brown to black medially and distal tarsomeres brown; hind trochanter with slender ventral bristles; all femora with ventral ctenidium and hind femur with posterior row of short black bristles and a pair of subapical anterior and posterior black bristles; tibiae without apical bristles and hind tibia with two erect posterior bristles.

When suspension feeding, the primary role of the radula is to grab and direct mucus ropes of food collected on the ctenidium to the mouth (Shumway et al.

Fore coxa silver-yellow pruinose with two moderately strong, brown, ventrally-directed preapical setae and comb of finer setulae medially, with 8-10 brown setulae on anterior surface; mid and hind coxa yellow-grey pruinose, mid coxa with 2 very strong, lateral, ventrally-directed, black setae and comb of finer setae medially and 3 brown setulae; hind coxa with 1 weaker lateral black seta and 1 brown setula; femora, tibia and tarsi uniform dirty yellow; all tibiae with preapical seta; fore tibia with 4 strong setae on lateral margin, the second basal seta shorter than other three, with ctenidium of 10-12 short, sharp, black spinules, separated from each other by one or more basal spinule widths.

They are characterized by a single, external ctenidium on the right side, rolled rhinophores, and a flattened shell (Willan, 1983; Schmekel, 1985; Willan, 1987).

For most gastropods, the ctenidium, or gill, functions solely as a respiratory organ.

Fore coxa with 14 brown setulae on anterior surface; mid coxa with 7 brown setulae; fore tibia with ctenidium of 13 spinules.

2 and 3) may have stemmed from previous differential adaptations or compensations to local conditions, such as changing relative sizes of ctenidium and labial palp (e.g., Essink et al.

To briefly summarise, features of the African Pacycerina that are immediately striking include: (1) tiny ocellar setulae ('ausserordentlich klein' [extraordinarily small] in Becker's (1895: 250) words), (2) incurved anterior fronto-orbital bristles (reclinate in most Afrotropical lauxaniids, except Chaetolauxania Kertesz), (3) bulging prefrons and lateral black spots (other Afrotropical lauxaniid genera lack such a tumid prefrons and maculation), (4) elongated postpedicel, (5) two acrostrichal bristle rows on mesoscutum, (6) no profemoral ctenidium, (7) usually dark brown protibia and protarsi (relative to yellow meso- and metatibiae and tarsi), (8) the presence of paired black spots on T6 in some species, and (9) the absence of an aedeagus in the male of all species.

In treated females, the arrangement of these male copulatory organs was similar but differed in the distance between the penis sheath and the penis: the penis sheath in females was located at the edge of the ctenidium at the mantle skirt, at a distance from the penis.

For example, there is potential to resolve differences in feeding behavior and/or metabolism that result from genetic variation between stocks of the same species (e.g., Hawkins et al 2000), or to account for adaptations or compensations that may include changes in relative sizes of ctenidium and labial palp (e.g., Essink et al 1989, Barille et al 2000).

Jorgensen and Ockelmann (1991) suggested there is a coordination of activity of the lateral cilia of the gill (ctenidium) with the adductor and retractor muscles, as well as, the exhalant siphonal sphincter.