Oogenic strategies in the evolution of development inPatiriella(Echinodermata: Asteroidea)

Abstract

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.

A boom–bust phylum? Ecological and evolutionary consequences of density variations in echinoderms

“…However, this is also expected, because most echinoderms have this life history. Most of the species identified in this review have small eggs, and so are likely to have high fecundity (Babcock et al 1994, Byrne et al 1999. However, most echinoderms have high fecundity, and so this would not be a unique feature of the species that undergo fluctuating population densities.…”

“…The most distinct difference between the two life histories is the direct nutritive coupling of adult, larval, and early juvenile food supply in echinoderms with lecithotrophic development. The nutrients present in the large eggs of these echinoderms provide a buffer against larval and early juvenile starvation (Byrne et al 1999, 2003, Villinski et al 2002. Much of the energetic lipid reserves present in the eggs of asteroids, ophiuroids, and echinoids with lecithotrophic development are not used for larval development, but are stored by the larva for the early juvenile (Byrne et al 1999, 2003, Villinski et al 2002, Prowse et al 2008.…”

Evolution of maternal provisioning in ophiuroid echinoderms: characterisation of egg composition in planktotrophic and lecithotrophic developers

“…Within taxonomic groups, small eggs are dominated by protein, whereas large eggs have enhanced lipid stores. This difference is reflected in egg buoyancy, with small eggs usually being negatively buoyant, while the presence of extensive lipid inclusions in large eggs increases their buoyancy (Emlet et al 1987, Emlet 1994, Jaeckle 1995, Byrne et al 1999). There may be selection for eggs of different buoyancy with respect to where fertilization occurs and larval dispersal strategy (Emlet et al 1987, Emlet 1994.…”

“…Data from asteroid and echinoid eggs shows that energy content does not scale with egg volume. Energy concentration is higher in the large eggs of species with lecithotrophic development due to increased lipid reserves, particularly energy storage lipids (Jaeckle 1995, Byrne et al 1999, McEdward & Morgan 2001, Villinski et al 2002, Prowse et al 2009, Whitehill & Moran 2012). In addition, many of the lipid reserves deposited in the eggs of echinoderms with lecithotrophic development are not used for the pelagic life phase.…”

A test of the ashߚfree dry weight technique on the developmental stages of Patiriellaspp. (Echinodermata: Asteroidea)

“…Patiriella regularis has planktotrophic development (170-m-diameter ova; AFDW and energetic content ϭ 0.42-0.60 g and 14.4 mJ, respectively). Patiriella calcar has planktonic lecithotrophic development (415-m-diameter ova; AFDW and energetic content ϭ 11.11-14.58 g and 410 mJ, respectively), and Patiriella exigua has benthic lecithotrophic development (390-m-diameter ova; AFDW and energetic content ϭ 8.72-14.06 g and 445 mJ, respectively) (Byrne et al 1999;Moreno and Hoegh-Guldberg 1999). The use of three congeneric species with eggs differing in size and biochemical profile provided the opportunity to assess how the AFDW procedure may affect different egg types and developmental stages.…”