Role Reversal: 5 Strange Tales of Animal Male Pregnancies

(Images via: Babble, Belief Net, SACO, Flickr, Woodbridge, Mental Floss, Oregon Mag)

Male pregnancy is a rare but real phenomenon in the animal kingdom. In some instances, male pregnancy is the result of man-made chemicals having strange effects on male frogs and bass, prompting weird intersex developments. In other situations, male pregnancy is a natural part of how seahorses, pipefish and leafy sea dragons reproduce. Whatever the case, males taking the reproductive roles of females provide bizarre and surprisingly fascinating studies.

Common Weed Killer Causes Some Male Frogs to Lay Eggs

(Images via: Flickr, SF Gate, Magic Canoe, Jeremy Biggs)

Did you know that one of the most common weed killers can cause drastic changes in male frogs, transforming them into females that lay eggs? In a recent study, 40 male African clawed frogs were raised from infancy to adulthood in a solution containing the chemical Atrazine, which is found in many weed killers. According to the study’s findings, 10 percent of the 40 frogs apparently developed into females. Upon dissection, 2 of the 4 transformed frogs maintained their male DNA despite also displaying ovaries. As for the other two transformed frogs, they mated with male frogs and laid eggs that produced male offspring. Previously, Atrazine had been shown to decrease sperm and testosterone and cause some male frogs to mate with other males rather than female frogs. Now it appears that the chemical can apparently cause some males to become near female frogs, a strange development to say the least.


Feminized Fish: Intersex Development in Male Bass

(Images via: Harkness, Seqfish, Fishing Fury, Big Fish Tackle)

Just as Atrazine has a surprising effect on male frogs, other pesticides and even prescription drugs and pills have been shown to affect male species of fish after entering U.S. rivers, streams and other bodies of water. In 2004, researchers discovered male bass laying eggs (see top left and bottom right images) in the Potomac River, a strange occurrence that was attributed to contaminants that included natural hormones and were excreted by humans and livestock. According to a survey around this time period, 42 percent of male bass in the Potomac showed signs of intersex development, which refers to one sex displaying both testicular and ovarian tissue, while 79 percent displayed some sort of sexual abnormality. A year later, intersex fish were found in tributaries in West Virginia. More recently, researchers have noted how antidepressants and other wastewater compounds disrupt the endocrine systems of male fish and cause them to become feminized and lay eggs.

Seahorses: Wombs That Would Make Kangaroos Proud

(Images via: Bukisa, Wet Web Media, Dive Gallery, Fused Jaw)

Prior to these recent intersex discoveries in male frogs and bass, only a few other male animal species demonstrated pregnancy. Probably most famous among these species is the male seahorse, which takes on a reproductive role that is opposite to what is most commonly seen in nature. Male seahorses compete with each other not to impregnate female seahorses but to be impregnated. During seahorse mating, the female deposits unfertilized eggs into the male’s brood pouch. The male seahorse then fertilizes the eggs with his own sperm, thus initiating a three-week pregnancy that is marked by an inability to move around and search for food. After 3 days of labor, the male seahorse will give birth to 200 baby seahorses.


Male Pipefish Breeding: It’s All in the Genes

(Images via: Get A Huge Tank, Flickr, Cold Water Images, Top News)

A member of the same Syngnathidae family as seahorses, male pipefish also carry eggs in a protective pouch before giving birth. A few years back, researchers discovered a specific gene that supports the protective pouches and allows male pipefish pregnancies to occur. Called patristacin, this gene sustains male pipefish pouches, which help regulate the amount of saline in the womb. Interesting but not surprising, the patristacin gene is also found in seahorses and even in the kidneys and livers of other bony fish.


Male Leafy Sea Dragons: Shooting Out Their Offspring

(Images via: Sandshack, Sea Sky, KGOE, Animal Pictures Archive)

There is more to the eye when it comes to the leafy sea dragon, another relative to the seahorse. Not only looking like a piece of floating seaweed, the male leafy sea dragon cares for roughly 250 bright pink eggs that are attached to its tail via a long tube stemming from the female leafy sea dragon partner. After attaching to the male’s brood pouch, the eggs take nine weeks to hatch, changing in color to either purple or orange during this time period. When ready to give birth, the male leafy sea dragon shoots the baby sea dragons out of its tail during a 24-48 hour period. Only 5% of the leafy sea dragons survive, and those that do are pretty much independent from birth.