Not-So-True Facts About The Seahorse

Written By: | Date Posted: 01/22/2013 | 3 Comments |
Not So True Facts About The Seahorse

Original photo by Klaus Stiefel

Ze Frank just did a wonderfully funny video “True Facts About The Seahorse”. I love the True Facts videos he’s been doing; especially since they’re mostly true.

Mostly.

(Seriously, watch this; it’s some funny stuff.)

As good as the video is, there are some things as a seahorse enthusiast I know are flat out wrong, and my obnoxiously pedantic side won’t let it be. I don’t blame Ze Frank; there is just some bad information about seahorses floating around the internet. People want to believe some crazy things about seahorses because so many things about a seahorse are ridiculous and unbelievable, why not one more?

So let’s look at a few of these not-so-true facts and maybe they’ll stop getting passed around online once and for all. (I’m looking at all you iseahorses.com!)

1) Seahorses eat 3000 brine shrimp a day.

Well no, not really. Seahorses would never encounter brine shrimp (Artemia spp.) in the wild as brine shrimp come from inland saltwater pools and lakes, not the ocean. Most of the bodies of water where brine shrimp live are more or less uninhabitable except by a few extremophiles (of which brine shrimp are). They have very few aquatic predators in those waters, so the brine shrimp don’t have much by way of evasive maneuvers. Seahorses, on the other hand, are found in oceans around the world. You can see where this becomes a problem; their worlds never meet.

In captivity, seahorses are often fed brine shrimp and it’s a staple used to feed many baby fish species, seahorses included. Baby brine shrimp are an extremely easy food to culture, so they’re used for raising many fish types, both freshwater and saltwater. The 3000-a-day number is actually a misinterpretation of a protocol for raising newborn seahorses in captivity. The protocol suggested baby seahorses needed 3000-4000 newly hatched brine shrimp each day. (Yes, babies eating babies, that’s grim in its own way.)

Somehow in the early days of the internet, that got interpreted to adult seahorses eating 3000 brine shrimp a day as their natural diet; and and this “fact” has just been passed around continuously and incorrectly. Even in captivity, brine shrimp do not make the best diet for adult seahorses. Brine shrimp are often fed to adult seahorses anyway, but they can eat somewhere between 100 – 300 brine shrimp a day. In the wild, a seahorse’s diet is made up of mysids, amphipods, shrimp and crab larvae, and other small plankton. But not brine shrimp.

His conclusion though is not wrong. Because of the aforementioned lack of predator response, brine shrimp really are stunningly bad at running away.

2) Seahorses often sing while mating. Variation: Seahorses utter musical sounds while mating.

I’m not sure how this one got started but Ze Frank isn’t the first to utter this stupid fact. No, seahorses don’t sing, make musical sounds or other melodious utterances. They do produce a single sound which is best described as an audible pop or click, and is informally known as a “snick”. This noise is produced when bones in the seahorse’s head rub against one another when it stretches out its mouth and neck, such as when feeding.

While the snick is most characteristically heard when feeding, seahorses also snick when fighting, as an aggressive territorial display, when trying to clear something from their snout, and when stressed. Researchers have also put forth additional ideas about how the snick might be used, like for a seahorse to identify its mate over a distance, as well as be a way for seahorses to find a mate outside it’s visual field. However, these are just hypotheses, and it’s not clear if the snick plays any actual role in the courtship and mating of seahorses.

Any suggestions that they occasionally break into underwater Broadway-styled musical numbers has, thus far, been unsubstantiated, and should at best be considered exceedingly unlikely. However footage to the contrary would always be welcome.

3) Seahorses mate during the full moon.

No. Just no.

Many ocean fish and corals do mate during different lunar cycles, especially the full moon. Spawning of various species in captivity have been successfully achieved by simulating the full moon.

But not seahorses.

Seahorses breed much too frequently for this to be true; most tropical species bearing young every two weeks (and the diminutive dwarf seahorse H. zosterae giving birth every 10 days.) They are also mostly diurnal, and while their courtship takes most of a day, they still complete the egg transfer during daylight (or in some cases twilight) hours, the moon having no bearing.

4) Seahorses release sperm into the ocean.

I’m sure this was included in the video for effect because it’s funny. The infamous quote that Ze Frank is obviously paying homage to is “Water? I never drink the stuff, fish **** in it.” by W.C. Fields. But unfortunately, this assertion about seahorses is not exactly true. Male seahorses have a genital pore that is a few millimeters above the pouch. When the male and female spawn, he releases sperm into the water, but it is quickly whisked into the pouch along with the eggs. So the sperm only briefly touches the ocean water before entering the pouch and fertilizing the eggs. This system is so efficient that some seahorses only product around 300 sperm at a time. By comparison, most fish release millions of sperm in a single spawning event.

Of course, as said above most other fish produce millions of sperm. And many of those fish are broadcast spawners. So next time you’re taking a leisurely swim in the ocean, keep in mind that it could be teeming with fish sperm – just not from seahorses. Does that make it better, or worse?

Some other false “facts”

These two weren’t in Ze Franks video, but they’re often stated and passed around the web; many from the same sources the above “facts” came from.

5) A group of seahorses is called a herd.

I’m really not sure what a group of seahorses is called, but it’s not a herd. Colloquially, many aquarists my call a group of seahorses in their aquarium their “herd”, and that they are living in a “corral” (the aquarium), and they use “hitching posts” (holdfasts). These are fun, cutesy phrases but are not technically correct. At best, a group of seahorses would be a school or a shoal. They’re still fish afterall. However, as they don’t generally congregate in groups (some species excluded), I don’t know what you’d call them if they did. Probably just a group of seahorses.

6) Seahorses mate for life, and die when their mate dies.

This one drives me crazy. Some seahorses are seasonally monogamous (stay with the same mate for a breeding season). Some are promiscuous and breed in groups. Some are sort of monogamous and will stay with the same mate until a better one comes along. In particular, males tend to prefer their women large; and some will abandon smaller mates if a zaftig lady seahorse stumbles into their territory.

There is one species, White’s Seahorse H. whitei has been shown to maintain pair bonds over the course of several breeding seasons. However, in cases where one seahorse is lost, the “widowed” seahorse will move on and find another mate. Despite what people want to believe, they just aren’t that sentimental.

Seahorses do, however, give their mates a hug every morning during pregnancy. Well, not exactly a hug, but a greeting ritual which often involves intertwined tails and grabbing on to one another. Calling it a hug is close enough.

So Ze Frank isn’t dead on; but he does actually do a pretty okay job of explaining the absurdity of seahorse biology. Even if he does consider seahorse birthing videos porn. Hey, some people have weird kinks.

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