Evolution of Intragonadal Development in the Diminutive Asterinid Sea Stars Patiriella vivipara and P. parvivipara with an Overview of Development in the Asterinidae

Abstract

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

A molecular and morphological review of the asterinid, Patiriella gunnii (Gray) (Echinodermata: Asteroidea)

“…Eastern and Western Australian specimens of P. 'brevispina' were found to be conspecific in this study. Byrne (1995Byrne ( , 1996, Byrne and Cerra (1996), and Long and Byrne (2001) have reported on the reproductive and developmental biology of P. gunnii (as P. 'brevispina').…”

“…Eastern Australian specimens are confirmed by molecular and morphological evidence and described here as Patiriella oriens sp. nov. Byrne (1991Byrne ( , 1992Byrne ( , 1995Byrne ( , 1996, Byrne and Anderson (1994), Byrne and Cerra (1996), Cerra and Byrne (2001), and Long and Byrne (2001) reported extensively on the reproductive and developmental biology of Patiriella 'gunnii'. Since this research was based on material collected from Clovelly (M. Byrne, pers.…”

Chromosomes of Japanese Starfishes

“…While extensive morphological (Fisher, 1911(Fisher, , 1928(Fisher, , 1930Hayashi, 1940Hayashi, , 1943Hayashi, , 1973Spencer and Wright, 1966;Fell, 1963;Heddle, 1967;Blake, 1987;Downey, 1973;Clark and Downey, 1992), developmental (Oguro et al, 1976;Komatsu et al, 1979;McEdward, 1992;Chia et al, 1993;Byrne and Cerra, 1996), biochemical (Kubo, 1961;Schopf and Murphy, 1973;Mochizuki and Hori, 1980;Matsuoka, 1981, Matsuoka et al, 1994, and molecular (Lafay et al, 1995;Wada et al, 1996;Knott and Wray, 2000) studies have been systematically carried out on starfishes, cytogenetic studies have not yet been applied to asteroid phylogeny.…”

Strong character incongruence and character choice in phylogeny of sea stars of the Asterinidae

“…We collated data on the early life histories and breeding systems of asterinids from the literature and from unpublished obsersvations (Byrne 1992(Byrne , 1996Byrne & Cerra 1996;Hart et al 1997;Byrne et al 1999;Carvalho & Ventura 2002;M. Byrne, unpubl. data; R. Ventura, unpubl.…”

“…Here we give a simple quantitative analysis of congruence between early life history characters and mitochondrial DNA (mtDNA) sequences for asterinid sea stars (including new sequence data for five species). Many asterinid species share apparent derived forms of reproduction, larval morphology, and brood protection that may reflect either homology or convergence (Byrne & Cerra 1996;Hart et al 1997;Byrne et al 1999). We use this quantitative analysis to illustrate the extreme conflict between early life history and nucleotide characters, the risks associated with phylogenies based on such characters, and the scant benefits of including certain early life history characters in total evidence analyses.…”