The Weirdest Animals on Earth: 12 Amazing Facts About Seahorses

A seahorse in all its glory. Photo by Gustavo Gerdel at Wikimedia Commons.

1. Seahorses are fish. They include about 54 different species of fish and are closely related to sea dragons and pipefish. But seahorses are not your typical fish! A baby seahorse is called a fry (like in other fish), but a group of seahorses is called a herd (like in horses).

2. Seahorses have skeletons unlike any other fish. Unlike other bony fish, seahorses have a neck, an exoskeleton, and a prehensile tail. Seahorses do not have pelvic fins, ribs or scales. Instead, their skin is stretched over a series of bony plates arranged in rings.

3. Seahorses are terrible swimmers and can die of exhaustion if the sea is rough or the current is too strong. The only fin they have to get around with it the tiny one in the middle of their back (the dorsal fin). They use even smaller pectoral fins on the sides of their head to steer. Seahorses and razorfish are the only fish to swim upright, because it is horribly inefficient. It is a good thing they have a prehensile tail to hang on to whatever is nearby.

A pygmy seahorse in camouflage.
Photo by prilfish at Wikimedia.

4. Seahorses are experts at camouflage and can change color. They are even able to grow fleshy appendages (called cirri) that help them with camouflage by giving them a weed-like appearance.

5. Seahorses have terrible smell but amazing vision. They have the fewest genes for olfactory receptors (used in other animals for smell and taste) of any ray-finned fish species known. But seahorses have excellent vision and their eyes can work independently, meaning they can look forward and backward at the same time!

6. Seahorses eat weird. They have a toothless, tubular snout, which they use to suck up small fish and crustaceans. They swallow them whole. Seahorses do not have stomachs and don't digest very well, so they have to eat constantly.

7. Seahorses are one of the ocean's deadliest predators, with a 90% kill rate. Because of the shape of their head and their slow, finless method of movement, seahorses move with near hydrodynamic silence, barely moving the water as their stealthily sneak up on their prey. Once they are within striking distance, they snap their heads and suck up their prey. 

8. Seahorses click when they're courting and growl when their stressed. 

9. Seahorses are monogamous and pair for life. Their courtship begins with a daily dance between the couple that they do for days. The final courtship dance can last eight hours before the female "impregnates" her partner.

10. Male seahorses get "pregnant". They are the only males that take on the full responsibility of pregnancy, carrying up to 2,000 babies at a time! Although they don’t have a mammalian womb and placenta, they do have an enclosed abdominal pouch specifically for the purpose of incubating the babies. The female deposits her eggs in his brood pouch, in which he fertilizes them and incubates them for 10-45 days (depending on the species). During this time, his body undergoes a number of hormonal and physiological changes. When the babies are ready to emerge as fully developed little seahorses, seahorse dads even experience contractions as they give birth! 

11. Seahorses are evolving faster than any other group of bony fishes. Scientists have sequenced the entire genome of a tiger tail seahorse, a threatened tropical seahorse species.

12. Seahorses are under threat because of the traditional Chinese medicine trade, the pet trade, and the curio trade, all of which capture seahorses from the wild, and because of habitat depletion and pollution.

Caught in My Web: Spiders!

Image by Luc Viatour at Wikimedia Commons

Spiders creep most of us out. But let’s face it: they are pretty darn amazing! For this edition of Caught in My Web, we appreciate our 8-legged friends.

1. Did you know that sea spiders use their gut as a heart?

2. And lace sheet weaver spiders make optical illusion webs to lure nocturnal moths.

3. Even our run-of-the-mill spiders are pretty amazing, when you really look at them. Watch this amazing timelapse of a garden orb web spider building a web:

4. Portia, the spider-hunting spider, is a genius with super-powers:

5. And researchers at the National University of Singapore have now found that personality affects how these smart spiders hunt.

I Know I Want to Work With Animals. Now What?

"What to do? What to do?" Photo by Dmitry Rozhkov at Wikimedia Commons. 

Does this sound familiar: “I know I want to work with animals, but I don’t know if I want to be a vet. What should I be? How do I prepare for a career if I don’t even know what I want to do?”

If this is you, don’t panic. There are many professions that work with animals, and luckily, there is a lot of overlap when it comes to qualifications for those jobs. This means that there are certain steps that you can take to make you competitive for a range of jobs that work with animals and you don’t have to decide today exactly what that job will be.

Experience With Animals

To get a job that works with animals, you need to be good at working with animals. Seems pretty obvious, but it can be more difficult than you think. To get good at something, you need experience, and to get experience, you need a position, and to get a position, you need to be good at it… AARRGG!

The trick is to get your foot in the door: Train your pets to compete in obedience or agility competitions. Work in a pet store, groomers, or pet boarding kennel. Volunteer at a local animal shelter, animal rehabilitation center, veterinary clinic, or zoo. If you are considering colleges, ask about clubs, internships and other opportunities that they offer to get animal experience.

It is also important to keep a record of all your animal experiences; List all of the experiences by category or position and keep track of your hours. This will be invaluable information to put on applications in the future.

Experience With People

We often forget that many positions that work with animals also require a strong ability to work with people. Veterinary clinics work with pet owners; Zoos and aquariums teach the public; Animal trainers would be more accurately called “pet-owner-trainers”. As counterintuitive as it may seem, you can improve your marketability to animal jobs by improving your people skills.

First and foremost, don’t shy away from face-to-face contact. Yes, texting and emailing is faster and easier, but an actual conversation can have a much better outcome and helps develop your people skills without a conscientious effort. Beyond that, pay attention in English classes, read books, and seek out opportunities to interface with actual people. Jobs in retail and as receptionists are good for this. Look for opportunities in the field of education, perhaps as a tutor or assistant. Volunteer to interact with people in nursing homes, hospitals, or shelters. And again… keep track of your hours.

Education

Educate yourself for the job you want.
Photo by raider of gin at Wikimedia Commons.

There are jobs that work with animals for people with all levels of education, so you may want to pursue the level of education you need for the job(s) that you want.

Before you complete high school, you may be eligible to be a: volunteer (at an animal hospital, rehabilitation center, zoo, aquarium, or animal shelter), pet store employee, pet boarding employee

With a high school diploma, you may be additionally eligible to be a: veterinary assistant, veterinary receptionist, domestic animal care staff, domestic animal trainer, animal control worker or dog warden, animal farmer or breeder

With a specialized 2-year degree, you may be additionally eligible to be a: veterinary technician or veterinary technologist

With a 4-year degree, you may be additionally eligible to be a: zoo keeper or aquarist, educator, wildlife rehabilitator, wildlife animal trainer, assistant research biologist, animal care manager, animal cruelty investigator

With a DVM, you may be additionally eligible to be a: veterinarian (at a clinic, hospital, zoo, or university), research biologist

With a PhD, you may be additionally eligible to be a: research biologist


Are you already in an animal-related career? Share your tips in the comment section below! And for more advice for working with animals, go here.

A New Key to the Story of How the Sexes Have Come to Be

In the beginning, we are all male and female… More specifically, we are all in between male and female. So what makes our embryonic selves choose and follow a developmental path to becoming the sex that we are today? New research has dramatically changed our understanding of this process.

During early embryonic development, all mammals develop a single pair of gonads that are neither testes nor ovaries, but have the potential to become either. Likewise, the external genitalia at this early stage has the potential to become either a penis and scrotum or a clitoris, vagina, and labia. Two pairs of ducts develop to connect the gonads to the undifferentiated external genitalia: One set of ducts, the Wolffian ducts, would become the epididymis, vas deferens, and seminal vesicles if this animal becomes male. The other set of ducts, the Müllerian ducts, would become the oviducts, uterus and innermost part of the vagina if this animal becomes female. So what determines if a given animal will develop male or female reproductive anatomy?

Early in development, mammalian embryos have one set of gonads that has the potential to become either testes or ovaries (here labeled as "bipotential gonad"). These gonads are connected the the developing external genitalia by two sets of tubes: The Wolffian ducts become the reproductive tracts in males and the Müllerian ducts become the reproductive tracts in females. The ducts that do not become reproductive tracts typically disintegrate. However, XX female embryos that lack the COUP-TFII protein do not dismantle their male-like reproductive tracts. Figure from Swain, 2017.

The sex of a mammal is determined by the combination of sex chromosomes it has. If the mammal has two X chromosomes, it will likely become female, and if it has an X chromosome and a Y chromosome, it will likely become male. The story physiologists have been telling for decades is that there is a single gene located on the Y chromosome, called the SRY gene, that single-handedly makes an embryo become a male. When expressed, the SRY gene produces a protein, called testes-determining factor, which interacts with the cells of the undifferentiated gonads to turn them into testicular cells. These newly formed testicular cells produce two key hormones: testosterone, which causes the Wolffian ducts to become the epididymis, vas deferens, and seminal vesicles, and anti-Müllerian hormone (AMH), which causes the Müllerian ducts to degenerate. In other words, if an animal has a Y chromosome, it will typically have an SRY gene that will trigger the sequence of events that causes the animal to develop into a male. If the animal does not have the Y chromosome, it will typically become female. However, it is not just the lack of a Y chromosome that can make a female; Any disruption of this pathway (such as an SRY gene that is not expressed, or the lack of testicular hormones) typically causes the animal to develop into a female. For this reason, females in mammals have been called the default sex. The scientific understanding since the 1950s has been that, in mammals, the development of a male reproductive system is an active process and the development of a female reproductive system is a passive process. However, a new study reveals that the process of becoming female mammal is not as passive as we have thought.

Fei Zhao, Humphrey Yao and their research team at the National Institute of Environmental Health Sciences and Baylor College of Medicine discovered a critical role for a specific protein, called COUP-TFII, in the active process of becoming a mammalian female. The research team examined female mouse embryos (which lack a Y chromosome, and hence an SRY gene) that had been genetically modified to lack a particular protein called the COUP-TFII protein. They compared these genetically modified XX embryos to genetically typical XX mouse embryos. When the unmodified XX embryos had developed to have only Müllerian ducts (the “typical” female reproductive pathway), the XX embryos without COUP-TFII protein retained both Müllerian and Wolffian ducts! Unfortunately, these XX mice that lacked the COUP-TFII protein died shortly after birth, so it was difficult to tell if this developmental process would have continued. The research team cultured reproductive organs of XX mice with and without COUP-TFII protein and found that this developmental trajectory likely would have continued after birth.

Images A and B show the reproductive tract from the side (A) and as a cross-section (B) in a "typical" XX female mouse embryo. Images D and E show that XX females that lack the COUP-TFII protein retain both Müllerian (pink arrows) and Wolffian (blue arrows) ducts. Figure from Zhao et al., 2017.

We know that testosterone helps promote the development of Wolffian ducts in XY males, so the most likely explanation of what they witnessed is that the lack of COUP-TFII protein somehow increased action of testosterone in these genetically modified XX embryos. The researchers ran a number of tests to explore this possibility. Testosterone is mostly produced by the gonads, so they compared the gene expression and enzymes of ovaries of unmodified XX mice with the ovaries of XX mice that lacked the COUP-TFII protein, and they found no differences that pointed to differences in testosterone production. They then considered the possibility that testosterone was produced somewhere else in the body, but the XX mice that lacked the COUP-TFII protein did not have more masculine body features compared to the unmodified XX mice. Finally, the researchers gave extra testosterone to the mother mice that were pregnant with unmodified XX mice and XX mice that lacked the COUP-TFII protein. The extra testosterone did not affect any of the mouse pups; it did not cause the Wolffian ducts of the XX mice that lacked the COUP-TFII protein to regress. Together, the researchers found that no, XX embryos that lack COUP-TFII protein do not have any more testosterone-like activity than their non-genetically modified XX sisters. This means that testosterone alone is not enough to keep Wolffian ducts.

This research has shown us that for the Wolfian ducts to go away during the reproductive development of a mammalian female, they need to be actively dismantled using a biochemical process (similar to how AMH dismantles Müllerian ducts during male reproductive development). COUP-TFII protein appears to be the chemical in charge of triggering this process. Female mammals are not the passive result of simply not becoming male, as has been taught in physiology classes for decades. Becoming a female mammal requires a process all its own, and we are only now starting to learn what that is.


Want to know more? Check these out:

F. Zhao et al. Elimination of the male reproductive tract in the female embryo is promoted by COUP-TFII in mice. Science. Vol. 357, August 18, 2017, p. 717. doi: 10.1126/science.aai9136

A. Swain. Ductal sex determination. Science. Vol. 357, August 18, 2017, p. 648. doi: 10.1126/science.aao2630