tribuloides reached the eight-arm stage of development, but not in earlier stages, we observed that larvae intermittently flexed their postoral
(PO) and posterodorsal (PD) arms.
A) Habitus, dorsal; B) Left antennule, ventral; C) Left antenna, posteromedial; D) Left antenna, anterolateral; E) Distal endopodal segment of left antenna, posterior; F) Left maxillule (MX1) and postoral
process (POP), ventral.
gavilanicola by having three and four accessory atrial sacs and by the absence of lateral auricular papillae and postoral
ring (reduced in L (L.
The length of postoral
rods in relation to midline body length was significantly different between food treatments for larvae from both the shallow mothers (ANCOVA for homogeneity of slopes, n = 103 means for larvae from each jar and day [as described in last paragraph of Methods], F = 33.
0 24,059 13 Day 8 4699 648 7293 65 Postoral
Day 2 3779 2140 1659 12.
By 3 days after fertilization, larvae had developed a nearly complete set of external ciliary structures: an apical tuft composed of a group of long cilia surrounded by shorter cilia, three equatorial ciliary bands (a preoral prototroch, circumoral food groove, and postoral
metatroch), and a ventral neurotroch (Fig.
4%; anterior nasal flap short; labial furrows absent; postoral
groove short, extending ventrolaterally from corners of mouth; first dorsal fin strongly raked, apex rounded, posterior margin truncate, fin larger than second dorsal fin, its origin over midbase of pelvic fin; second dorsal fin strongly raked, apex narrowly rounded, posterior margin truncate; anal fin much larger and taller than second dorsal fin, its origin ahead of origin of second dorsal fin; pectoral fin short and broad, anterior margin convex and with broadly rounded apex, posterior margin truncate, free tip broadly rounded; pelvic fins relatively small; anal fin larger than second dorsal; claspers cylindrical, elongate and reaching anal fin origin in the mature individual, surface covered with denticles except for tip.
I measured cilium lengths from the postoral
, anterolateral, and postero-dorsal arms of a seven-day-old larva with a 100x objective lens under oil immersion with DIC (see Wray 1992 for anatomical terminology).
During this period without food, larval echinoids have previously been shown to develop longer postoral
arms (Boidron-Metairon, 1988; Hart and Strathmann, 1994; McEdward and Herrera, 1999; Sewell et al.
They formed fenestrated postoral
rods characteristic of all cidaroid larvae that have skeletons.
This feeding mechanism, in which a preoral band of compound cilia (the prototroch) beats from anterior to posterior, and a postoral
band of compound cilia (the metatroch) beats in the opposite direction, trapping particles between them, was described in the larvae of serpulid annelids (Strathmann et al.
Arms arise in bilaterally symmetric pairs: the postoral
arms (POA) elongate first, and the anterolateral arm rods extend into the preoral lobe while the POA elongate (see Strathmann, 1987).