Sexual systems and dwarf males in barnacles: Integrating life history and sex allocation theories

Yamaguchi, Sachi; Yusa, Yoichi; Sawada, Kota; Takahashi, Satoshi

doi:10.1016/j.jtbi.2012.12.001

Cited by 23 publications

(9 citation statements)

References 26 publications

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“…The environmental effects mean that at least some of the larvae can choose their own sex according to the degree of encounters with possible mating partners, which is rather difficult to predict for the parents that release the larvae from distant places. Moreover, the supposed genetic component limits the maximum proportion of males, which agrees with a version of local mate competition theory applied for barnacles, where the male to hermaphrodite ratio varies from 0:1 (in large mating groups) to 1:1 (in very small groups) (Charnov, ; Urano et al ., ; Yamaguchi et al ., , ). Under a simple ESD system, where cues from hermaphrodites induce larvae to become males, the proportion of males may become higher than being optimal for parents under the local mate competition.…”

Section: Discussionmentioning

confidence: 99%

Sex determination in the androdioecious barnacleScalpellum scalpellum(Crustacea: Cirripedia)

Høeg

Yusa

Dreyer

2015

Biol. J. Linn. Soc.

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How androdioecy (coexistence of hermaphrodites and males) is maintained is still poorly understood. Therefore, sex determination was studied in the androdioecious barnacle Scalpellum scalpellum L. First, 247 cypris larvae from seven broods were investigated for sexual dimorphism in larval morphology and found to be all identical. Second, experiments with cyprids showed that males and hermaphrodites differ distinctly in morphology as soon as 4-5 days after settlement. Third, 14 252 cyprids were allowed to settle on the bottom of their culture cages, and all surviving larvae developed into hermaphrodites and none into dwarf males. Fourth, larvae settled in hermaphrodite receptacles (i.e. future males) were removed at increasing intervals after settlement to study if the male and hermaphrodite sexual expressions are fixed or plastic. All larvae became dwarf males if allowed to stay there for more than 8 h after settlement. But if removed within 3 h after settlement, half of them developed into hermaphrodites. We conclude that an environmental sex determination mechanism operates in S. scalpellum. Together with a 1:1 hermaphrodite/male ratio observed in previously reported experiments offering a free choice of settlement, we suggest that all larvae are potential hermaphrodites, but only 50% can settle in hermaphrodite receptacles and yield males.

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Section: Discussionmentioning

confidence: 99%

Sex determination in the androdioecious barnacleScalpellum scalpellum(Crustacea: Cirripedia)

Høeg

Yusa

Dreyer

2015

Biol. J. Linn. Soc.

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“…Since then, empirical studies on various simultaneous hermaphrodites (e.g., Annelida, Crustacea, Platyhelminthes) have generally supported the prediction (Janicke et al, ; Schärer, ). However, Yamaguchi, Yusa, Sawada, and Takahashi () pointed out that the MGS concept has two aspects, namely (a) the number of individuals to which a focal individual can donate sperm (+1 = MGS in the male function; MGSm) and (b) the number of individuals from which the individual can receive sperm (+1 = MGS in the female function; MGSf). The original MGS concept assumes that MGS does not differ between male and female functions as all individuals in the same group mate with all available individuals.…”

Section: Introductionmentioning

confidence: 99%

Different effects of mating group size as male and as female on sex allocation in a simultaneous hermaphrodite

Tamechika

Matsuno

Wada

et al. 2020

Ecology and Evolution

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Sex allocation theory predicts that the optimal sexual resource allocation of simultaneous hermaphrodites is affected by mating group size (MGS). Although the original concept assumes that the MGS does not differ between male and female functions, the MGS in the male function (MGSm; i.e., the number of sperm recipients the focal individual can deliver its sperm to plus one) and that in the female function (MGSf; the number of sperm donors plus one) do not always coincide and may differently affect the optimal sex allocation. Moreover, reproductive costs can be split into “variable” (e.g., sperm and eggs) and “fixed” (e.g., genitalia) costs, but these have been seldom distinguished in empirical studies. We examined the effects of MGSm and MGSf on the fixed and variable reproductive investments in the sessilian barnacle Balanus rostratus. The results showed that MGSm had a positive effect on sex allocation, whereas MGSf had a nearly significant negative effect. Moreover, the “fixed” cost varied with body size and both aspects of MGS. We argue that the two aspects of MGS should be distinguished for organisms with unilateral mating.

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“…Several studies have predicted that dwarf males among barnacles should evolve when mating group size is small, because sperm competition is weak in small groups (Charnov ; Yamaguchi et al. , ; see also the review of Yamaguchi et al. ).…”

Section: Discussionmentioning

confidence: 99%

Dwarf males in the epizoic barnacle Octolasmis unguisiformis and their implications for sexual system evolution

Sawada

Yoshida

Yasuda

et al. 2015

Invertebrate Biology

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Descriptions of the diversity of sexual systems in animal taxa such as the thoracican barnacles are needed to study the evolution of sexual systems. Androdioecious systems (coexistence of hermaphrodites and males) are particularly important due to their possible role as evolutionary intermediates in transitions between hermaphroditism and dioecy. In this study, we used histology to examine the sexual system of the crab-epizoic barnacle Octolasmis unguisiformis to determine if dwarf males were present or not; a previous study reported the existence of conspecific-attached individuals, but did not investigate their sexuality. All conspecific-attached individuals were dwarf males, irrespective of their attachment site. However, crab-attached individuals never acted as dwarf males even if they were small and lived together with large individuals. The result emphasizes the importance of attachment to conspecifics, but not to specific sites on conspecifics, in the evolution of dwarf males. Other individuals were hermaphroditic, indicating androdioecy in this species. However, their functional sexuality (that is, whether they actually do act as males) requires further study. The presence of dwarf males in this species supports theoretical predictions that small group size, short-lived habitats, or spatial limitation favor the evolution of dwarf males.

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Sexual systems and dwarf males in barnacles: Integrating life history and sex allocation theories

Cited by 23 publications

References 26 publications

Sex determination in the androdioecious barnacleScalpellum scalpellum(Crustacea: Cirripedia)

Sex determination in the androdioecious barnacleScalpellum scalpellum(Crustacea: Cirripedia)

Different effects of mating group size as male and as female on sex allocation in a simultaneous hermaphrodite

Dwarf males in the epizoic barnacle Octolasmis unguisiformis and their implications for sexual system evolution

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