Development of a True Ovoviviparous Sea Star, <i>Asterina pseudoexigua pacifica</i> Hayashi

Komatsu, Miéko; Kano, Yasuo T.; Oguro, Chitaru

doi:10.2307/1542316

Cited by 30 publications

(16 citation statements)

References 18 publications

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“…This latitudinal difference mirrors the geography of live-bearing in other asterinid lineages, in which viviparous species (especially Cryptasterina pacifica, Parvulastra vivipara, Asterina phylactica) have short geographical ranges at high latitudes on the margin of the distributions of their nonviviparous sister taxa in the same genera [24,25,30,31]. Our phylogeographic analyses were designed to investigate the history of this geographical distribution and its potential role in the phenotypic and reproductive divergence of the two species.…”

Section: Introductionmentioning

confidence: 80%

Extraordinarily rapid life-history divergence between Cryptasterina sea star species

et al. 2012

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Life history plays a critical role in governing microevolutionary processes such as gene flow and adaptation, as well as macroevolutionary processes such speciation. Here, we use multilocus phylogeographic analyses to examine a speciation event involving spectacular life-history differences between sister species of sea stars. Cryptasterina hystera has evolved a suite of derived life-history traits (including internal self-fertilization and brood protection) that differ from its sister species Cryptasterina pentagona, a gonochoric broadcast spawner. We show that these species have only been reproductively isolated for approximately 6000 years (95% highest posterior density of 905-22 628), and that this life-history change may be responsible for dramatic genetic consequences, including low nucleotide diversity, zero heterozygosity and no gene flow. The rapid divergence of these species rules out some mechanisms of isolation such as adaptation to microhabitats in sympatry, or slow divergence by genetic drift during prolonged isolation. We hypothesize that the large phenotypic differences between species relative to the short divergence time suggests that the lifehistory differences observed may be direct responses to disruptive selection between populations. We speculate that local environmental or demographic differences at the southern range margin are possible mechanisms of selection driving one of the fastest known marine speciation events.

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Section: Introductionmentioning

confidence: 80%

Extraordinarily rapid life-history divergence between Cryptasterina sea star species

et al. 2012

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“…As is characteristic of viviparous asterinids, the gonads of Cryptasterina hystera were ovotestes (Komatsu et al, 1990;Byrne, 1996). This condition is also reported in viviparous holothuroids (Miller, 1985;Frick et al, 1996).…”

Section: Discussionmentioning

confidence: 97%

Viviparity in the Sea StarCryptasterina hystera(Asterinidae)—Conserved and Modified Features in Reproduction and Development

Byrne

2005

The Biological Bulletin

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Cryptasterina hystera has a highly derived life history with intragonadal development and juveniles that emerge from the parent's reproductive tract. The gonads are ovotestes with developing eggs separated from sperm by follicle cells. C. hystera has typical echinosperm that must enter the gonoduct of conspecifics to achieve fertilization. During oogenesis, an initial period of yolk accumulation is followed by hypertrophic lipid deposition, the major contributor to the increase in egg size. 1-Methyladenine induces egg maturation and ovulation, but the spawning component of the hormonal cascade is suppressed. This is the major alteration in reproduction associated with evolution of viviparity in C. hystera. The switch to viviparity was not accompanied by major change in gonad structure, indicating there were few or no anatomical constraints for evolution of a marsupial function for the gonad. Despite their intragonadal habitat, the brachiolaria are equipped for a planktonic life, swimming in gonadal fluid. During the gastrula stage, lipid provisions are released into the blastocoel where they are stored for juvenile development. The eggs of C. hystera have light and dark cytoplasmic regions that mark animal-vegetal polarity. The dark pigment provided a marker to follow the fate of vegetal cells. Live birth is rare in the Echinodermata and the incidence of this form of brooding in the phylum is reviewed.

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“…These lineages differed by just 1.4% (tRNAs) or 2.5% (COl) in the neighbor-joining analysis, or by five steps in the parsimony analysis of tRNAs alone, though these species have different types of larval development and are currently classified in different genera. Unfortunately, we were unable to confirm the morphological identification of the A. pseudoexigua pacifica specimen, though it was collected by M. Komatsu in the same area from which development was originally described in this species (Komatsu et al 1990).…”

Section: Phylogenetic Relationshipsmentioning

confidence: 90%

“…Adults of A. pseudoexigua pacifica are small (R < 15 mm), simultaneous hermaphrodites that brood their offspring inside the ovotestis as do P. vivipara and P. parvivipara. Whereas P. vivipara and P. parvivipara brood larvae hatched from small eggs, A. pseudoexigua pacifica broods large, yolky eggs about 400 urn in diameter (Komatsu et al 1990). In addition, A. phylactica (which we were unable to include in our study) is also a small (R < 10 mm), simultaneous hermaphrodite that deposits large eggs (-500 urn) in benthic masses (Emson and Crump 1979), but the adult broods the egg mass and occasional embryos are retained inside the gonad where they undergo metamorphosis (Strathmann et al 1984).…”

Section: Life Histories Of Asterinid Starfishmentioning

confidence: 99%

Molecular Phylogenetic Analysis of Life-History Evolution in Asterinid Starfish

Hart¹,

Byrne²,

Smith³

1997

Evolution

102

108

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We analyzed phylogenetic relationships among 12 nominal species of starfish in the genera Patiriella and Asterina (Order Valvatida, Family Asterinidae), based on complete sequences for a mitochondrial protein coding gene (cytochrome oxidase subunit I) and five mitochondrial transfer RNA genes (alanine, leucine, asparagine, glutamine, and proline) (1923 bp total). The resulting phylogeny was used to test a series of hypotheses about the evolution of life-history traits. (1) A complex, feeding, planktonic larva is probably ancestral for these starfish, but this is not the most parsimonious reconstruction of ancestral larval states. (2) The feeding larval form was lost at least four times among these species, and three of these losses occurred among members of a single clade. (3) Small adult size evolved before both cases of hermaphroditism and viviparous brooding, but viviparity was not always preceded by an intermediate form of external brooding. (4) An ordered transformation series from feeding planktonic development to viviparous brooding has been predicted for starfish, but we could not find an example of this transformation series. (5) Viviparity evolved recently (< 2 Mya). (6) Both species selection and transformation of lineages may have contributed to the accumulation of species with nonfeeding development among these starfish. (7) Neither Asterina nor Patiriella are monophyletic genera. Larval forms and life-history traits of these starfish have evolved freely under no obvious constraints, contrary to the widely assumed evolutionary conservatism of early development.

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Development of a True Ovoviviparous Sea Star, Asterina pseudoexigua pacifica Hayashi

Cited by 30 publications

References 18 publications

Extraordinarily rapid life-history divergence between Cryptasterina sea star species

Extraordinarily rapid life-history divergence between Cryptasterina sea star species

Viviparity in the Sea StarCryptasterina hystera(Asterinidae)—Conserved and Modified Features in Reproduction and Development

Molecular Phylogenetic Analysis of Life-History Evolution in Asterinid Starfish

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