The Jupiter Theft

“Ah, but it does!” Dmitri said. “Same body structure—but the legs have atrophied because it needs them only for clinging, and the ‘head’ has regressed to its only function: to suck blood. No eyes, because a parasite doesn’t need them, and if I dissected it I would find no digestive organs, because it gets its meals predigested. But the gonads, you can be sure, are well developed, as they are in all parasites. It is perfectly adapted to its way of life.”

“What a filthy thing!” Beth said.

“Filthy?” Dmitri said, in genuine puzzlement. “Perhaps to us. To the Cygnans, perfectly natural. Nature always provides rewards to encourage reproduction—rewards in the form of pleasure, or at least release from compulsion.” He nodded toward the struggling Triad, whose body contractions had grown rhythmic and violent. “That poor creature is in torment.”

“But a parasitic mate!” Liz said. “Isn’t that a bit farfetched?”

“There are any number of terrestrial examples,” Dmitri said. “Trichosomoides crassicauda. It’s a parasitic worm, like the Cygnans’ distant ancestors. The male lives as a parasite within the uterus of its own mate. Edryolychnus. It’s a deep-sea fish, very ugly. The male’s a tiny appendage that attaches itself to the female early in life. Its eyes and other sense organs atrophy. Its blood vessels fuse with hers. I could go on.”

“Strange way to perpetuate a species,” Omar said.

“No stranger than ours. Males aren’t very important in the scheme of things. They’re just a mechanism for exchanging gametes. Female spiders eat their mates when they’ve finished their job. This thing in my hand is a gene package, not a lover. A Cygnan’s emotional equivalent of a mate is the other female she trades males with.”

Jameson became thoughtful. “Dmitri, how would it work biologically?”

Dmitri looked around happily. “There’s an almost precise, terrestrial analogy. A mite that’s parasitic on moths: Lasioseius lacunosus. About one egg in twenty hatches as a male. The male is born first. That’s so it can be an obstetrician for its sisters. It helps in the birth of the females by pulling them out of the mother’s body. It lives as an ecoparasite with the mother for a brief time—it can’t survive removal itself. But before its sisters leave home, it impregnates them.”

“But the Cygnan male doesn’t impregnate its own sister?” Jameson said.

“No, it simply becomes a parasite on her. Let’s say it works like this. Suppose the Cygnans have multiple births, or hatchings, or buddings, or whatever. The male can’t survive on its own, any more than Lasioseius lacunosus can. It must immediately hook itself into the bloodstream of one of its much larger sisters or die. The attachment of a first male probably stimulates production of a hormone or chemical trigger that prevents the other male siblings from implanting themselves—”

“The way an ovum becomes impervious to other sperm after the first one reaches it,” Janet said, looking up from her work of bandaging Ruiz’s head.

“Yes, yes,” Dmitri said impatiently. “At any rate, it’s the fittest that tend to survive.”

“The courtship mechanism…” Jameson prompted.

Dmitri nodded. “What you call ‘courtship’ is two females pairing of and eventually exchanging their parasitic males. It must be as charged with emotion for them as sex is for humans. The exchange is an evolutionary survival mechanism which prevents inbreeding. Presumably there’s a hormone or body-chemistry block which ordinarily prevents a parasite from impregnating its sister-host. The courtship ritual, on the other hand, must release pheromones—repare the endocrine systems of both the hosts and the parasites to accept the switch, just as a foreplay prepares both human sexes for sex.”

Jameson’s eyes strayed toward Triad. The involuntary contractions of her body looked as if they were causing her physical pain. With each wave her rubbery body compressed by a third, then stretched out again like taffy. He was unable to imagine what she was feeling but clearly she was in the grip of a powerful biological imperative.

Her own tiny brother was already within the body of the dead Tetrachord, presumably dead or dying itself. The other half of the exchange must have been interrupted by the alarm. The squirming thing in Dmitri’s hand was animated by its own biological imperative. If it failed to make contact with Triad soon, then the union of Tetrachord and Triad would produce no young.

Did Cygnans mate for life?

One of the Struggle Brigade stalwarts, a sinewy fellow with close-set eyes and bristly black hair brushed forward over his forehead, had retrieved the hoe and was prodding Triad with the handle. Jameson reached him in three swift strides.