Animals that change sex
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Animals That Change Sex — Daily trivia Saturday, April 11, 2026: questions and answers
All 10 questions with answers and explanations. Play this daily
Q 01Male-to-female sex change is common in fish and molluscs but absent from which group?
- ATerrestrial vertebrates
- BFreshwater crustaceans
- CMarine gastropod molluscs
- DDeep-sea teleost fishes
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Terrestrial vertebrates
Terrestrial vertebrates never switch from male to female, though the common frog Rana temporaria sometimes changes the other way, female to male.
Q 02What term describes an organism that produces male and female gametes at different stages in its life?
- ASimultaneous hermaphroditism
- BParthenogenesis
- CSequential hermaphroditism
- DAsexual reproduction
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Sequential hermaphroditism
Sequential hermaphroditism is usually cued by social structure or by reaching a certain size or age; botanists call the plant version dichogamy.
Q 03Which term describes clownfish starting life as males and becoming females?
- AGonochorism
- BParthenogenesis
- CProtandry
- DSimultaneous hermaphroditism
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Protandry
Protandry runs the clownfish anemone: the breeding female is the largest fish, and if she dies the breeding male becomes the female and the largest non-breeder the male.
Q 04What is it called when an animal starts life as a female and later changes to a male?
- AGonochorism
- BGynogenesis
- CAndrogenesis
- DProtogyny
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Protogyny
Protogyny is by far the commoner direction in fish: about 75% of the roughly 500 known sequentially hermaphroditic fish species change from female to male.
Q 05In species like the bluehead wrasse, what typically triggers the largest female to change sex?
- ARemoval of the dominant breeder
- BChemical pollutants in the water
- CA seasonal change in day length
- DA drop in food availability
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Removal of the dominant breeder
Removal of the dominant breeder is the cue: when terminal-phase males are taken away, more females turn into males, a change that takes around 8 days and can't be reversed.
Q 06From which sex does the Asian sheepshead wrasse (kobudai) typically transition to become a male?
- AFrom a non-breeding male
- BFrom a female
- CFrom an immature male
- DFrom a simultaneous hermaphrodite
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From a female
After the transition the fish grows its famous bulbous forehead and turns aggressive, though it keeps some ovary-like gonad tissue from its female years.
Q 07What term describes fish that can switch sex back and forth between male and female?
- AMonogamous hermaphroditism
- BBidirectional hermaphroditism
- CUnidirectional hermaphroditism
- DAcyclic hermaphroditism
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Bidirectional hermaphroditism
Bidirectional hermaphroditism lets a fish switch sex either way, potentially repeatedly, which suggests there may be no inherent advantage to whichever sex it starts as.
Q 08Beyond social cues, what environmental factor influences sex determination in some fish and reptiles?
- ALight intensity
- BTemperature
- CAmbient noise levels
- DWater salinity
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Temperature
Temperature settles sex in most turtles and some teleost fish, and near the 'pivotal' temperature, where its influence is equivocal, mixed sex ratios appear.
Q 09Which leading hypothesis says animals change sex because each sex reproduces best at a different growth stage?
- AThe size-advantage hypothesis
- BThe metabolic rate hypothesis
- CThe ecological niche hypothesis
- DThe genetic diversity hypothesis
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The size-advantage hypothesis
The size-advantage hypothesis holds that each sex breeds best at a certain size: big bodies make more eggs, favouring male-first, but where a big male guards a harem, female-first pays.
Q 10Which key enzyme lets sex-switching fish convert androgens into oestrogens to transform their gonads?
- AAmylase
- BProtease
- CLipase
- DAromatase
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Aromatase
Aromatase is the enzyme that turns androgens into oestrogens, and in some fish it turns up in the ovaries whether sex was set by genes or by temperature.
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