![]() ![]() Lacuna vincta egg masses aresmall (about 3 mm in diameter), yellow and donut-shaped. This form of development of Ophiopholis, more typical of brittlestars, is a major contrast to the direct development of the brooding Amphipholis.Īll of the egg masses we found atSnug Harbor were in the lower intertidal, in the first 2 or 3 quadrats.They all belonged to gastropods. The sea urchin larva is called an echinopluteus, and the brittle star larva is an ophiopluteus. The sea urchin Strongylocentrotus droebachiensis and the brittle star Ophiopholis aculaeata both have a pluteus larval form. Both larvaltypes are characterized by a gel-filled, bilaterally symmetric body, a complete digestive tract, and prominent ciliated bands used in swimming and particle capture. The sea cucumber, Cucumaria miniata, produces an auricularia larva, while sea stars like Evasterias sp. Bryozoa) has a feeding cyphonautes larva. They then release nauplius larvae, which later become cyprid larvae before settling on a substrate. Barnacles Balanus and Semibalanus have a long penis, in which they use to fertilize neighboring barnacles. After the larva starts production of its shell, it settles and attaches with the pedicle, a fleshy stalk on the exterior end the extends from the hinge between the shell valves. The larvae of Terebratalia transversa (Ph. The eggs hatch into free-swimming nauplius larvae, which will develop into crab zoea, and finally into megalopae, which is the post-larval stage. Crabs including Hemigrapsus nudus and Petrolisthes sp. Indirect development: Free-swimming larvae Many species in various phyla found at SnugHarbor have planktonic larval stages. The larger-bodied species has more typical free spawning and indirect development via a planktonic larva. The smaller species has direct development and broods its young on the oral side of its body. On Cobble Beach one can find at least two distinguishable species of Henricia-one is small with orange arm tips, the other is blood red and relatively large (see photos to right) -although the taxonomy for these species complexes has not been worked out. ![]() This species of brittle star was seen pnly near the waterline on the more sheltered beach of Mitchell Bay. ![]() The sponge Halichondria and the anemone UrticinaĪmphipholis squamata, a brittle star, carries its eggs around in the bursae on the bases of its arms, which develop directly into juvenile brittle stars. ![]()
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