Here we use SEM to show the morphology of feeding organs (gill, foot, labial palps and arborescent lips), and ultrastructural characteristics such as ciliation
in large specimens of two bivalve species, the sea scallop, Placopecten magellanicus, and bay scallop, Argopecten irradians.
of the body is developed on the ventral side; weakly developed on the dorsal side.
This is not uncommon among studies of larval form carried out before the functional significance of metatrochal ciliation
was known (e.g., see Pernet and Strathmann, 2011).
Anterior internal anatomy: Pedal pit shallow, <1/2 body width; foot single ridge 30 pm at widest; mouth opening ventrally at vestibule entrance; body wall musculature with weak circular and longitudinal fibers, the latter thickest ventrally; vestibular papillae one per root, few, vestibular ciliation
with two lateral tracts united posteriorly in U-shape, without frontal extension; pharynx surrounded by circular muscles; large paired anteroventral ganglia 45 [micro]m in diameter, posterior to pedal pit, with two commissures; cerebral ganglion 100 [micro]m wide, 70 [micro]m high; pharynx 65 pm long, surrounded by musculature and intercellular glands; no esophagus; unpaired, short midgut cecum.
We examined the organization and behavior of velar ciliation
in nonfeeding larvae of several species of Littorina, using light and scanning electron microscopy.
To enhance a classification of the major developmental stages of the thoracic bud, we also documented the expression pattern of acetylated tubulin as a marker for ciliation
Estimated ciliary band length-specific clearance rates are slight underestimates, as they were calculated by assuming that band length was equivalent to circumference at the prototroch, but a small portion of that circumference was interrupted by a dorsal gap in the feeding ciliation
collaris after ciliation
are in the range of 4-5 [micro]m, whereas those for the nemertean Carinoma tremaphoros, the polychaetes Nereis limbata and Polygordius sp., and the limpet Patella vulgata are 25-50, 11-22, 15, and 30 [micro]m, respectively (Maslakova et al., 2004; Costello, 1945; Woltereck, 1902; Damen and Dictus, 1994).
Despite some remarkable work in the earlier studies, important aspects have not been adequately or coherently covered, such as ciliation
, type of filament growth, and creation of junctions.
It would indeed be a very remarkable example of convergence if these structures should all have evolved convergently from an ancestral uniform ciliation
To determine the pattern of ciliation
, some hatchlings were double-labeled with phallacidin and anti-tubulin antibody.
The velum is a vestigial ridge with some ciliation
but lacks a well-organized food groove.