The Pregnant Male Pipefish
Like seahorses, male pipefish are one of the select underseas species that get pregnant and carry their young in their brood until birth. A recent study has shown that pregnant male pipefishes will selectively abort their young if they feel the mother is not attractive and healthy enough. According to the study:
The conflict seems to be mediated by a strategy of cryptic choice in which males increase rates of offspring abortion in pregnancies from unattractive mothers to retain resources for future reproductive opportunities.
Or as lead researcher Kimberly Paczolt told Scientific American:
"It's almost as if he is saying, 'Are these babies worth my effort?' If he is not overly fond of the mother, the answer appears to be 'No,' and he invests fewer resources."
The pregnant male may deny nutrients to the low-quality eggs, or he may even absorb the eggs to feed himself. It seems one of the largest factors in evaluating the relative attractiveness of the female was her size: the bigger, the better.