The diminutive asterinid sea stars Patiriella vivipara and P. parvivipara incubate their embryos in the gonads to the advanced juvenile stage. Despite the small size of their eggs (135-150^ diameter), development is lecithotrophic. Development proceeds through the wrinkled blastula, gastrula, and brachiolaria larval stages. The gastrulae and larvae are uniformly ciliated and swim, propelled by the cilia, in the gonadal fluid. The brachiolaria is pear-shaped and has a vestigial brachiolar attachment complex composed of three small brachia. At no stage in development are the embryos attached to the gonad. Metamorphosis occurs as the larvae swim in the gonadal lumen. Internal development involves formation of one large enterocoel at the anterior end of the archenteron and one small posterior enterocoel on the left side of the archenteron. The archenteron closes to form the rudiment for the adult gut. As a result of the small size of the egg and the nonfeeding mode of development, the larvae of P. vivipara and P. parvivipara are minute, about 270 ^/m and 210 ^m in length, respectively. Newly metamorphosed juveniles are about 240 ^m and 3 10 /urn in diameter, respectively. Postmetamorphic development involves substantial growth of the juveniles, which leave the parent at a diameter between 1 .0 and 5.0 mm. The presence of a vestigial brachiolar complex and lecithotrophic development indicates that these species had a free-living lecithotrophic brachiolaria in their ancestry. We suggest that the evolution of viviparity in Patiriella sp. involved retention of a large egg by an ancestor that had a lecithotrophic brachiolaria followed by a secondary reduction in the size of the

The sea star genus Patiriella has the greatest diversity of life histories known for the Asteroidea. P. regularis has small eggs (150 pm diameter) and the ancestral planktotrophic larvae. P. calcar, P. gunnii, P. exigua and P. pseudoexigua have large eggs (390-440 pm diameter) and non-feeding lecithotrophic larvae. Two species with lecithotrophic larvae P. vivipara and P. parvivipara have secondarily evolved a small egg (135-150 pm diameter). We examined the oogenic strategies involved with evolution of egg size in these sea stars. Comparison of protein profiles, histochemistry and ultrastructure of the eggs of Patiriella indicated that the major changes underlying acquisition of a large egg involved enhanced deposition of lipid in some species and an increase in yolk reserves in others. The eggs of the planktotroph, P. regularis, and the benthic lecithotroph, P. exigua, contained an abundance of major yolk protein MYP. By contrast, the eggs of the planktonic lecithotrophs P. gunnii and P. calcar were dominated by lipid and the MYP appeared to be greatly reduced. The eggs of P. calcar contained an abundant protein which may be a truncated form of vitellogen. The small eggs of the viviparous species P. vivipara and P. parvivipara appear to be miniature versions of the eggs of the closely related P. exigua. Comparison of the eggs of Patiriella species with lecithotrophic development revealed among species variation in oogenesis. Depending on the species, the evolutionary modification of oogenesis appeared to be influenced by phylogenetic history and selection for egg characteristics with respect to the planktonic or benthic location of development.

The Cryptasterina group of asterinid sea stars in Australasia comprises cryptic species with derived life histories. C. pentagona and C. hystera have planktonic and intragonadal larvae, respectively. C. pentagona has the gonochoric, free-spawning mode of reproduction with a planktonic lecithotrophic brachiolaria larva. C. hystera is hermaphroditic with an intragonadal lecithotrophic brachiolaria, and the juveniles emerge through the gonopore. Both species have large lipid-rich buoyant eggs and well-developed brachiolariae. Early juveniles are sustained by maternal nutrients for several weeks while the digestive tract develops. C. hystera was reared in vitro through metamorphosis. Its brachiolariae exhibited the benthic exploration and settlement behavior typical of planktonic larvae, and they attached to the substratum with their brachiolar complex. These behaviors are unlikely to be used in the intragonadal environment. The presence of a buoyant egg and functional brachiolaria larva would not be expected in an intragonadal brooder and indicate the potential for life-history reversal to a planktonic existence. Life-history traits of species in the Cryptasterina group are compared with those of other asterinids in the genus Patiriella with viviparous development. Modifications of life-history traits and pathways associated with evolution of viviparity in the Asterinidae are assessed, and the presence of convergent adaptations and clade-specific features associated with this unusual mode of parental care are examined.

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