Bizarre Biology -- Bone-Eating Worms

In the category of creatures that would be hard to believe if invented in fiction as aliens, meet Osedax, commonly known as bone-eating worms:

Osedax

They're marine animals, a variety of tube worms, that live on the bones of decaying corpses such as those of whales.

They don't have a mouth, a digestive system, or an anus. Instead, they absorb nourishment more like plants than animals, through the magic of symbiosis. Adult females are sessile (fixed in place). They "settle on a bone, then secrete an acid through specialized root tissues to dissolve the bone's external layers in order to access the lipids within." Their symbiotic bacteria, which aid in processing nutrients for their Osedax host, live inside the worm's "vascularized root system which penetrates bone."

Even weirder is their extreme sexual dimorphism. Anglerfish, whose males atrophy into tiny lumps permanently attached to their female partners, seem ordinary by comparison. A female Osedax hosts 50 to 100 microscopic males (producing sperm while never developing past the larval stage) that live inside the tube surrounding her body. Therefore, when females spawn, the eggs emerge already fertilized.

Water-dwelling animals with roots? If we encountered something like Osedax on an extraterrestrial planet, we might have trouble recognizing it as an animal rather than a plant. Moreover, we'd probably assume it's a female reproducing by parthenogenisis until we had a chance to examine it closely and discover the microscopic males. What if similar tube worms on an alien world had evolved intelligence? Their biology and behavior would be so different from ours that communication with them would be very difficult -- rather like talking with trees on Earth, except that at least we share the same environment with our tree neighbors.

Margaret L. Carter

Please explore love among the monsters at Carter's Crypt.

Animal Gender-Flipping

A list of some animals with reproductive patterns that deconstruct the male-female binary:

Animals That Can Change Their Sex

Many can switch from male to female or vice versa, depending on environmental or social conditions. (No mammals, though.) Famously, the clownfish, first on the list, reveals that Nemo's dad in the movie should have become his mother. Some animals are hermaphroditic, with both sexes in one body, or nonbinary. Some (e.g., the hawkfish) can even change back and forth rather than shifting to the opposite sex and sticking with it for life. Parthenogenetic species also exist, whose females can give birth without having their eggs fertilized by males. Humphead wrasse are females in youth but can change to males later in life.

Interestingly, Heinlein adopts this reproductive pattern for his Martians in STRANGER IN A STRANGE LAND. The fertile young -- "nymphs" -- are female. All fully mature Martians are male. Although only hinted at in RED PLANET and PODKAYNE OF MARS, apparently the Martians in those books have the same biology.

Such transsexual phenomena can't be classified quite the same as human transgender identity, since the physical changes are automatic in animals but voluntary in humans. Still, the examples mentioned, only a few among many, illustrate that life on Earth is stranger than we often realize. Consider the extreme sexual dimorphism of the anglerfish, where the male, much smaller than the female, attaches himself permanently to her body. He fuses with her so that he atrophies into simply a parasitic sperm cell producer.

For a deep dive, with copious references and statistics, into unconventional animal sexual behavior, check out the exhaustively thorough BIOLOGICAL EXUBERANCE (1999), by Bruce Bagemihl. He explores transsexualism, transvestism, parthenongenesis, and homosexuality, mainly the latter, in numerous species (mostly mammals and birds). The six chapters of Part I, "A Polysexual, Polygendered World," offer an overview of the field and refute arguments that have attempted to explain away homosexual behavior in nonhuman animals. Part II, "A Wondrous Bestiary," comprises a catalog of particular species observed to exhibit the behaviors discussed in Part I, with lists of sources for the information on each. The book's appendix, bibliography, endnotes, and index take up almost 100 pages.

Through natural phenomena such as these, we can find inspiration for bizarre alien reproductive biology without ever having to leave Earth.

Margaret L. Carter

Please explore love among the monsters at Carter's Crypt.

Pregnancy Alternatives

On this season of one of my favorite TV shows, CALL THE MIDWIFE, a recently married character just suffered a miscarriage. This episode and the overall premise of the series reminded me of the ways some animals seem to have an easier time with reproduction than we do. Suppose women could resorb embryos to terminate an early pregnancy, like rats and rabbits, but consciously and at will? Or wouldn't it be more convenient if we were marsupials? Imagine giving birth painlessly to tiny, underdeveloped offspring and completing gestation in a pouch, which doubles as a cradle and food source for the growing infant. Moreover, performing mundane tasks and working at a career would be facilitated by the ability to carry babies around with us, hands-free, twenty-four-seven.

Better yet, wouldn't it be nice if fathers shared the burdens of gestation? Seahorses, of course, fertilize their mates' eggs in a pouch on the male's body where the eggs are sheltered until they hatch. TV Tropes has a page about this phenomenon in various media:

Mister Seahorse

Remember the TV series ALIEN NATION? The Tenctonese (who have three sexes, female and two types of males, but that's a different topic) transfer the pod holding the fetus from mother to father partway through gestation. The father undergoes all the typical experiences of pregnancy, including birth. If human beings had evolved this system, imagine the radical differences that might have historically existed in women's political rights and career opportunities.

Laying eggs like Dejah Thoris (John Carter's wife in Edgar Rice Burroughs's Mars series) would be a less attractive alternative. Even with high-tech incubators, parental care after hatching would be intensive and prolonged. The babies would be small and helpless, probably more so than real-life human newborns because of the limitations of an egg rather than a womb. The only advantage of oviparous over viviparous reproduction would be that both parents could share the work equally.

How about artificial wombs? In my opinion, they're never likely to become universal and replace natural reproduction as in BRAVE NEW WORLD, in the absence of some catastrophic fertility crisis. As long as the natural method remains viable, the expense and technical complications of in vitro gestation would surely far outweigh the potential convenience, except maybe for the very wealthy. Robert Heinlein's PODKAYNE OF MARS includes a less drastic technological modification of the human reproductive cycle. Some couples (those who can afford the cost, I assume) choose to go through pregnancy and birth at the optimal physiological age for healthy reproduction but bring up the children at the optimal economic stage of the parents' life. They achieve this goal by having newborn infants placed into cryogenic suspended animation until parental career and income factors reach the desired point.

Would I want to have done this, if possible? I'm not sure. Getting through college and graduate school would have been easier without babies and toddlers. On the other hand, young parents probably have more energy for chasing after kids than they would in their thirties or forties, and there's something to be said for "growing up with" one's children. Having given birth four times over the span from age nineteen to age thirty-four, I've experienced both ends of that range.

Margaret L. Carter

Carter's Crypt

Eggs and Equity

Recently on a wildlife program in the PLANET EARTH series I viewed a segment about clownfish. In addition to their sexual mutability, which enables the largest male in a group to transform to female if the adult female dies, they display interesting parental behavior. Clownfish live in symbiotic partnerships with sea anemones, nesting among the anemone's tentacles, deadly to most other sea life. The anemone "fortress" shelters the fertilized eggs, for which the male takes responsiblity, tending and guarding them. If the dominant female doesn't find his level of care acceptable, though, she'll reject him in favor of one of the rival males lurking in wait. So the devoted father in FINDING NEMO is true to life in a way.

As far as paternal child care in marine life is concerned, everybody knows about the prime example, the seahorse. The female lays eggs in the male's pouch, where he fertilizes them and carries them until they hatch. Mr. Seahorse, not his mate, undergoes pregnancy. They appear to practice monogamy through at least one breeding season.

On another episode of the same series (PLANET EARTH, BLUE PLANET, etc.) a tiny tree frog is shown depositing his mate's fertilized eggs in small water reservoirs in leaves. To provide nourishment, the female lays an unfertilized egg in the water drop, while the male guards the eggs and tadpoles.

Most people have probably watched documentaries about penguin parents raising their young on the Antarctic ice. The father keeps the single egg warm on top of his feet while his mate is feeding out at sea. When she returns, she relieves him and takes over the care of the chick while he goes in search of food.

Some birds, rather than tending their chicks as monogamous partners, practice polyandry. The female controls a large territory in which she mates with several males, each one incubating a clutch of eggs in a different nest. She helps each of her mates defend his individual nesting territory.

These animals and many others illustrate the fact that in oviparous species the female isn't "tied down" by pregnancy and lactation. When the young hatch from eggs, either parent or both can guard and care for the eggs and offspring. If otherwise convenient, the female can leave parenting duties entirely to the male without jeopardizing the welfare of their children. Therefore, a society of intelligent, oviparous aliens might practice very different sexual and child-rearing customs from ours. In a high-tech culture, the option of sheltering the eggs in an incubator, terrarium, or aerated aquarium (depending on the species) could even allow both parents to combine childrearing with other pursuits. They might have completely egalitarian gender roles or even female dominance.

Margaret L. Carter

Carter's Crypt