The Follicle Cells of Styela Plicata (Ascidiacea, Tunicata): A Sem Study

Villa, L.; Patricolo, Eleonora

doi:10.2108/zsj.17.1115

Cited by 7 publications

(7 citation statements)

References 19 publications

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“…Styela plicata is a broadcast spawning, solitary ascidian and a simultaneous hermaphrodite (although self-sterile) (65). S. plicata is thought to be invasive to eastern Australia, is common on made-made structures (growing both in isolation and in clumps), and in vitro fertilization by strip-spawning techniques is straightforward (66).…”

Section: Methodsmentioning

confidence: 99%

Gamete plasticity in a broadcast spawning marine invertebrate

Crean

Marshall

2008

Proc. Natl. Acad. Sci. U.S.A.

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Sperm competition has classically been thought to maintain anisogamy (large eggs and smaller sperm) because males are thought to maximize their chance of winning fertilizations by trading sperm size for number. More recently it has been recognized that sperm quality (e.g., size, velocity) can also influence sperm competition, although studies have yielded conflicting results. Because sex evolved in the sea, debate has continued over the role of sperm competition and sperm environment in determining both sperm and egg size in externally fertilizing broadcast spawners. Remarkably, however, there have been no direct tests of whether broadcast spawners change the traits of their gametes depending on the likelihood of sperm competition. We manipulated the density (and thus, sperm environment) of a broadcast spawning ascidian (Styela plicata) in the field and then determined whether the phenotype of eggs and sperm changed. We found that sperm from adults kept at high density were larger and more motile than sperm from low-density adults. In vitro fertilizations revealed that sperm from high-density adults also lived longer and induced less polyspermy. Adult density also affected egg traits: eggs from high-density adults were smaller targets for sperm overall but produced larger ovicells than eggs from low-density adults. This suggests that broadcast spawning mothers balance (potentially conflicting) pre-and postzygotic selection pressures on egg size. Overall, our results suggest that sperm competition does not represent a strong force maintaining anisogamy in broadcast spawners. Instead, sperm limitation seems to select for large eggs and smaller, more numerous sperm.anisogamy ͉ sperm competition ͉ adaptive maternal effect ͉ transgenerational plasticity T he fundamental difference between the sexes is that males produce numerous, tiny sperm, and females produce relatively fewer, large eggs (anisogamy). Classic theory suggests that anisogamy most likely evolved by, and is maintained through, sperm competition (whereby sperm from 2 or more males compete to fertilize an egg) because males producing a greater number of sperm have a competitive advantage (refs. 1 and 2; but see ref. 3 for an alternative). In species with internal fertilization, competition for fertilizations can therefore be viewed as a ''raffle,'' whereby males that have the highest representation of sperm in the pool have the greatest chance of fertilizing eggs (4, 5). More recently, however, it has been proposed that sperm quality (e.g., sperm size, velocity, and longevity) can also influence the outcome of sperm competition (6, 7). Furthermore, because a male's sperm supply is limited (8, 9) and each mating opportunity may carry a variable risk of sperm competition (10), males must make decisions on the optimal allocation of both sperm number and quality for each mating event. The optimal allocation of sperm size and number within an ejaculate remains a source of intense debate (reviewed in refs. 7 and 9).The prediction that males should increase the ...

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Section: Methodsmentioning

confidence: 99%

Gamete plasticity in a broadcast spawning marine invertebrate

Crean

Marshall

2008

Proc. Natl. Acad. Sci. U.S.A.

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“…8), which probably exerts an attracting role during fertilization. 13 Several mitochondria are detected in the cortical ooplasm; although many of them occur singly or in clusters, others surround the cortically placed lipid droplets (Fig. 3).…”

Section: Controlsmentioning

confidence: 98%

Effects of tributyltin(IV) chloride on fertilization of Styela plicata (Ascidiacea: Tunicata): II. Scanning and transmission electron microscopy studies

Mansueto

Villa

D'Agati

et al. 2003

Applied Organom Chemis

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The morphological aspects of Styela plicata fertilization after treatment with tributyltin(IV) chloride are described by means of scanning and transmission electron microscopy investigations. Alterations have been shown both on female and male gametes; spermatozoa, all the egg envelopes and the mitochondria of the egg cortical cytoplasm are modified in relation to incubation time. As a consequence, the damage to gametes blocks sperm-egg interaction and fertilization does not occur.

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“…This fits with previous research that has found ascidian follicle cells assist in sperm aggregation and attraction (Kawamura et al 1988;Villa and Patricolo 1993). In particular, the follicle cells of S. plicata are thought to function as a sperm attractant and to facilitate sperm penetration through the vitelline coat (Villa and Patricolo 2000). In high sperm concentrations, we suggest that large follicle cells increased fertilization success by reducing polyspermy.…”

Section: Discussionmentioning

confidence: 78%

“…Styela plicata eggs consist of the main ovicell (size range of ovicell area = 14-28 × 10 3 µm 2 ), surrounded by large, columnar follicle cells (size range of follicle cell area = 11-26 × 10 3 µm 2 ) (Villa and Patricolo 2000;Crean and Marshall 2008). Fertilization can be replicated in the laboratory using established, standardized protocols (Crean and Marshall 2008;Crean et al 2012).…”

Section: Study Speciesmentioning

confidence: 99%