The evolution of egg trading in simultaneous hermaphrodites

Mapping Intimacies ◽

10.1101/460386 ◽

2018 ◽

Author(s):

Jorge Peña ◽

Georg Nöldeke ◽

Oscar Puebla

Keyword(s):

Mating System ◽

Analytical Model ◽

Egg Production ◽

High Probability ◽

Rare Occurrence ◽

Male Role ◽

Encounter Rates ◽

Simultaneous Hermaphrodites

AbstractEgg trading, whereby simultaneous hermaphrodites exchange each other’s eggs for fertilization, constitutes one of the few rigorously documented and most widely cited examples of direct reciprocity among unrelated individuals. Yet how egg trading may initially invade a population of non-trading simultaneous hermaphrodites is still unresolved. Here, we address this question with an analytical model that considers mate encounter rates and costs of egg production in a population that may include traders (who provide eggs for fertilization only if their partners also have eggs to reciprocate), providers (who provide eggs regardless of whether their partners have eggs to reciprocate), and withholders (“cheaters” who only mate in the male role and just use their eggs to elicit egg release from traders). Our results indicate that a combination of inter-mediate mate encounter rates, sufficiently high costs of egg production, and a sufficiently high probability that traders detect withholders (in which case eggs are not provided) is conducive to the evolution of egg trading. Under these conditions traders can invade—and resist invasion from—providers and withholders alike. The prediction that egg trading evolves only under these specific conditions is consistent with the rare occurrence of this mating system among simultaneous hermaphrodites.

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Courtship, copulation, and sperm trading in the sea slug, Navanax inermis (Opisthobranchia: Cephalaspidea)

Canadian Journal of Zoology ◽

10.1139/z85-406 ◽

1985 ◽

Vol 63 (12) ◽

pp. 2719-2729 ◽

Cited By ~ 51

Author(s):

Janet L. Leonard ◽

Ken Lukowiak

Keyword(s):

Mating System ◽

Temporal Relationship ◽

Trading System ◽

Male Role ◽

Sexual Role ◽

Sea Slug ◽

Sexual Roles ◽

And Function ◽

Simultaneous Hermaphrodites ◽

Over Time

Navanax inermis are internally fertilizing, simultaneous hermaphrodites that normally mate in pairs. Copulations usually occur in bouts with active alternation of sexual roles and function. Over the study, individuals copulated equally often and for equal periods of time as each sex. The sequence of behaviors involved in courtship, copulation, and role switching is described. While the sequence of behaviors associated with each sexual role is quite stereotyped, the temporal relationship between the behaviors of the two partners is variable. A mating bout is initiated when one individual assumes the male role, finding and following a conspecific mucous trail, and then courts and copulates as a male. Each individual initiated approximately one-half of the copulatory bouts in which it was involved; size played no role in determining which individual initiated the bout. Our observations suggest that in N. inermis, individuals are always willing to be female, while willingness to be male varies over time. The mating system of N. inermis is based on sperm trading. Individuals apparently act as males, donating sperm, to obtain sperm, and are more willing to be fertilized than to fertilize, in violation of Bateman's principle. In N. inermis, females control fertilization and therefore copulation involves greater risks for males than females. The sperm-trading system is "enforced" by the maintenance of intromission until the partner shows courtship behaviour.

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Experience and relatedness influence mating interactions in a simultaneously hermaphroditic snail, Physa gyrina

10.1101/865170 ◽

2019 ◽

Author(s):

Thomas M. McCarthy

Keyword(s):

Chemical Cues ◽

Simultaneous Hermaphrodite ◽

Male Role ◽

Female Role ◽

Behavioral Dynamics ◽

Physa Gyrina ◽

Current Partner ◽

Mating Interaction ◽

Resistance Rates ◽

Simultaneous Hermaphrodites

AbstractThe means by which animals assess potential mates is an important issue in studies of reproductive systems. I tested whether an individual’s previous experiences and the relatedness of mates affected mating behavior in a simultaneous hermaphrodite snail, Physa gyrina. Previous work with this species showed reduced reproductive success resulting from both strong outbreeding and inbreeding. Thus, I predicted that individuals should prefer partners of intermediate relatedness. During activity trials, snails moved longer distances when exposed to chemical cues from conspecifics of lesser relatedness. Furthermore, during mating interactions, behavioral responses to relatedness varied with gender-role: male-role behaviors did not vary across relatedness treatments, while snails paired with either closely related or highly dissimilar partners increased their female-role resistance behaviors as interactions escalated. Experiences with their current partner also affected behavioral dynamics. Familiar pairs had fewer matings and longer latency times until a mating occurred than unfamiliar pairs. Snails acting in the female role also exhibited higher resistance rates in familiar pairs than in unfamiliar pairs. Previous, brief exposure to chemical cues in a non-mating context also influenced behavior during a subsequent mating interaction. Snails that were previously exposed to chemical cues from unfamiliar individuals tended to be more likely to occupy the male role following an encounter, and had significantly lower copulation frequencies and higher female-role resistance rates (i.e. were choosier) than those previously exposed to cues from familiar individuals. Overall, the results show that: 1) relatedness, past exposure to conspecific chemical cues, and experience with a current partner all influence mating behaviors in these snails; and 2) in these simultaneous hermaphrodites, an individual’s responses depend on whether it is occupying the male or female role.

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Selectivity matters: rules of thumb for management of plate-sized, sex-changing fish in the live reef food fish trade

10.1101/098624 ◽

2017 ◽

Author(s):

Holly K. Kindsvater ◽

John D. Reynolds ◽

Yvonne Sadovy de Mitcheson ◽

Marc Mangel

Keyword(s):

Population Dynamics ◽

Life History ◽

Mating System ◽

Egg Production ◽

Somatic Growth ◽

Fishing Effort ◽

Relative Effect ◽

Total Biomass ◽

Food Fish ◽

Fish Trade

AbstractEffective management of fisheries depends on the selectivity of different fishing methods, control of fishing effort, and the life history and mating system of the target species. For sex-changing species, it is unclear how the truncation of age structure or selection of specific size or age classes (by fishing for specific markets) affects population dynamics. We specifically address the consequences of plate-sized selectivity, whereby sub-mature, ‘plate-sized’ fish are preferred in the live reef food fish trade. We use an age-structured model to investigate the decline and recovery of populations fished with three different selectivity scenarios (asymptotic, dome-shaped, and plate-sized) applied to two sexual systems (female-first hermaphroditism and gonochorism). We parameterized our model with life-history data from Brown-marbled grouper (Epinephelus fuscoguttatus) and Napoleon fish (Cheilinus undulatus). ‘Plate-sized’ selectivity had the greatest negative effect on population trajectories, assuming accumulated fishing effort across ages was equal, while the relative effect of fishing on biomass was greatest with low natural mortality. Fishing such sex-changing species before maturation decreased egg production (and the spawning potential ratio) in two ways: average individual size decreased, and, assuming plasticity, females became males at a smaller size. Somatic growth rate affected biomass if selectivity was based on size-at-age because in slow growers, a smaller proportion of total biomass was vulnerable to fishing. We recommend fisheries avoid taking individuals near their maturation age, regardless of mating system, unless catch is tightly controlled. We also discuss the implications of fishing post-settlement individuals on population dynamics and offer practical management recommendations.

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Quick Consult: Quick Consult: Acromioplasty

Guides Newsletter ◽

10.1001/amaguidesnewsletters.2002.mayjun03 ◽

2002 ◽

Vol 7 (3) ◽

pp. 4-5

Keyword(s):

Glasgow Coma Scale ◽

Outcome Assessment ◽

High Probability ◽

Vegetative State ◽

Behavioral Impairment ◽

Whole Person ◽

Ordinal Scales ◽

Probability Of Death ◽

The Individual ◽

Assessment Scales

Abstract Different jurisdictions use the AMA Guides to the Evaluation of Permanent Impairment (AMA Guides) for different purposes, and this article reviews a specific jurisdictional definition in the Province of Ontario of catastrophic impairment that incorporates the AMA Guides. In Ontario, a whole person impairment (WPI) exceeding 54% or a mental or behavioral impairment of Class 4 or 5 qualifies the individual for catastrophic benefits, and individuals who do not meet the test receive a lesser benefit. By inference, this establishes a parity threshold among dissimilar injuries and dissimilar outcome assessment scales for benefits. In Ontario, the Glasgow Coma Scale (GCS) identifies patients who have a high probability of death or of severely disabled survival. The GCS recognizes gradations of vegetative state and disability, but translating the gradations for rating individual impairment on ordinal scales into a method of assessing percentage impairments cannot be done reliably, as explained in the AMA Guides, Fifth Edition. The AMA Guides also notes that mental and behavioral impairment in Class 4 (marked impairment) or 5 (extreme impairment) indicates “catastrophic impairment” by significantly impeding useful functioning (Class 4) or significantly impeding useful functioning and implying complete dependency on another person for care (Class 5). Translating the AMA Guides guidelines into ordinal scales cannot be done reliably.

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The Effect of Outcome Probability on Generalization in Predictive Learning

Experimental Psychology (formerly Zeitschrift für Experimentelle Psychologie) ◽

10.1027/1618-3169/a000429 ◽

2019 ◽

Vol 66 (1) ◽

pp. 23-39 ◽

Cited By ~ 1

Author(s):

Hadar Ram ◽

Dieter Struyf ◽

Bram Vervliet ◽

Gal Menahem ◽

Nira Liberman

Keyword(s):

High Probability ◽

Lower Probability ◽

Perceptual Similarity ◽

Learning Paradigm ◽

Predictive Learning ◽

Lightning Bolt ◽

Outcome Probability

Abstract. People apply what they learn from experience not only to the experienced stimuli, but also to novel stimuli. But what determines how widely people generalize what they have learned? Using a predictive learning paradigm, we examined the hypothesis that a low (vs. high) probability of an outcome following a predicting stimulus would widen generalization. In three experiments, participants learned which stimulus predicted an outcome (S+) and which stimulus did not (S−) and then indicated how much they expected the outcome after each of eight novel stimuli ranging in perceptual similarity to S+ and S−. The stimuli were rings of different sizes and the outcome was a picture of a lightning bolt. As hypothesized, a lower probability of the outcome widened generalization. That is, novel stimuli that were similar to S+ (but not to S−) produced expectations for the outcome that were as high as those associated with S+.

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