Here is a great video put together by the New York Times explaining how female fiddler crabs not only prefer males with larger claws, but also with claws that wave faster. This is based on work by Australian researchers who used robot claws to wave faster or slower. Waving is part of fiddler-crab courtship. So remember, the next time you’re in a bar or the grocery store and you see someone you’d like to court, wave your little claw off!
This week a young man in Australia was attacked by something while he was swimming in the ocean. His legs were bloodied and covered with hundreds of small bites. At the hospital, doctors were baffled about what bloodied the young man’s legs. The dad – who rocks in this story – went back into the water with a bloody steak and collected the small, flea-like animals. They were identified as amphipods, which are small crustaceans. If Sharknado has taught us anything, a movie about flesh-eating amphipods can’t be far now. Let’s see what that movie trailer might look like.
A young, beautiful mother sits on the beach and watches her charming son, who she can’t believe is growing up so fast, swim in the ocean. Gulls wheel overhead and waves roll gently. The sky blue.
Boy: Mom, watch me swim.
[cue the Jaws-theme music rip-off]
Boy: You watching?
Mom: Yes, dear.
[cue that voiceover guy]
That Voiceover Guy: Just when you thought it was safe to go back into the water again.
Cello: Duh-nuh, Duh-nuh, Duh-nuh, etc.
The boy screams and grabs his leg. His mother runs into the waves and pulls him out. His legs are bleeding but there’s nothing on them. A handsome and rugged marine biologist who looks just a little bit dangerous but you know you’d feel safe in his arms, runs over.
Mom: What did this!?
Ruggedly handsome marine biologist: They’re amphipods.
Mom: Oh my go…wait, what the heck are amphipods?
What the heck are amphipods? They are small crustaceans related to shrimp and crabs and lobsters. Typically, they aren’t larger than your thumbnail. If you’ve picked up seaweed on a beach, you’ve probably seen them. They are the small animals flipping and tumbling around like fleas. Those are amphipods. Sometimes called ‘sand fleas.’ Or ‘beach fleas.’ Or ‘beach hoppers.’ Or ‘sea fleas.’ The ‘flea’ name refers to the shape of their body (pressed from the sides) and the fact that they can flip around using their tails.
The media has used the term ‘sea lice’, but that really refers to an isopod, which can be parasitic on fish and look like the rolly-pollies (aka doodle-bugs) you find under logs.
Are amphipods the new marine menace? A pack of ravenous, flesh-eating beasts that roam the oceans looking for prey? Well, no. They do eat flesh, but typically not live flesh. We marine biologists (both the ruggedly handsome and other variety) don’t think of amphipods as predators but as scavengers that eat dead plants and animals. They’re more like tiny vultures swimming through the sea looking for something dead to stick their heads into rather than wild dogs looking to tear apart a baby deer.
I study amphipods in the salt marshes of Massachusetts and Louisiana (you can see pictures of them below). Just like on the beach, if you pick up seaweed in the marsh, hundreds of little crustaceans will flip and spring until they can hide in the grass. Not much of a terror. In terms of diet, these amphipods are more interested in a rotting veggie burger than a hunk of a marine-biologist.
Then why did they attack the young man’s legs in Australia? We’re not sure. Amphipods can bite humans – sometimes beach runners will have a bite or two – but they have rarely caused such damage. The best guess is that the amphipods were in a feeding frenzy and the young man’s legs happened to get in the way.
While I’ve been playful with this story, as a father, I too would have been worried. As a marine biologist, I am curious. It shows that we still have a lot to learn. The next time I pick up an amphipod I will check to see if it’s wearing a handkerchief and holding a knife and fork.
P.S. Now that we have flesh-eating amphipods in the news, soon I will write about zombie amphipods. Stay tuned. Duh-nuh…
P.P.S. If you enjoyed this article then please post it on Facebook, Twitter, or your favorite social media. And don’t forget to follow me.
I went down to the river today and found at least three* serpentine sunbathers draped across the branches of this bush. My best guess is that they were brown watersnakes, Nerodia taxispilota, based on my visit to the Virginia Herpetological Society’s awesome site. Can you find the three reptilian sunsoakers?
I’ll update the post later in the week with the answers.
*I say “at least three” because there could be more that I didn’t find.
This month I wrote a guest blog for Scientific American about the first fish to leave Earth’s gravitational grip, the mummichog, Fundulus heteroclitus. You can find it here. They published only the first half of the essay; the entire essay is below.
A large mummichog, Fundulus heteroclitus, from the Great Marsh.
When you launch a human body into space, sometimes that body become sick with nausea and general disorientation in the first few days. After a time, the body is better. This is the space version of seasickness. Because gravity holds our feet to the ground, we humans basically move in two-dimensions on Earth. So it may not be surprising that when you launch our bodies into gravity-free three-dimensional movement in space that our stomachs lurch and our heads spin. In the 1970’s the National Association of Space and Aeronautics (NASA) wondered how zero gravity would affect fish, animals that moved in three dimensions on Earth. Does a fish get space sick? For this important aquatic mission, NASA needed a fish that required little care but could endure the stress of a space launch and time in space. NASA first considered the goldfish, but they were not tough enough. NASA instead chose a drab, humble minnow found in salt marshes called the mummichog, Fundulus heteroclitus. It is not a fish prized as bait or aquariums so it is not well known. But if you’ve ever waded in the Bay of Fundy in Canada or Chesapeake Bay or the Gulf of Mexico in the U.S. and saw schools of minnows darting between your legs, then you met the first fish in space.
On July 28, 1973 at 7:11 a.m., the engines on the Saturn 1B rockets fired and the ground of Cape Canaveral, Florida, trembled. As the space shuttle lifted, the thrust pressed three American astronauts – Alan Bean, Owen Garriott, and Jack Lousma – into their seats. It also pressed the world’s first aquanauts, two juvenile fish and fifty fish eggs, against the walls of their small plastic aquariums. The rockets launched the astronauts and aquanauts into space for the second manned mission for Skylab (a mission confusingly called Skylab 3), the first scientific laboratory to orbit Earth.
When the two juvenile fish arrived at Skylab, they swam in elongated loops as though they were the spinning hands of a Salvador-Dali created clock. Without gravity the fish didn’t know which way was up.
On the third day, the fish swam in regular patterns, always with their backs towards the interior lights of the Skylab. In many animals, including the two-legged kind that build rockets, gravity tugs on special cells in the inner ear and tell the animal which way is up (away from gravity). This is called the vestibular righting response. Without gravity to tug on their inner ears, mummichogs relied on artificial light to tell them what direction was up. Using fish logic this is reasonable. The sun never shines from bottom of the ocean.
Looping appeared to be the fish’s version of space sickness. Humans, like fish and other animals, rely on our inner ears for balance and orientation. When ocean waves or lack of gravity disrupts our signals, we become disoriented and often ill. As the mummichogs looped, the astronauts vomited. As the urge to vomit subsided in the astronauts, so too did the urge to loop in fish. By the fourth day in space, both human and fish had found their bearings. The fish swam in their small, plastic aquariums in space as though they had been there the whole time.
Would the unhatched fish be space sick and loop when they were born? The astronauts found out by their third week on Skylab, when 48 of the 50 eggs hatched. These tiny mummichogs did not loop. They immediately followed their older cousins and used the light for orientation. The fish fry having learned the up-is-where-the-light-comes-from-trick as embryos. Only when the astronauts shook the aquarium did the fish fry, apparently disoriented, began swimming in loops, only to return to swimming with their backs to the light.
I am a saltmarsh ecologist and know the mummichog well. It does not surprise me that the mummichog was the first fish in space. For the mummichog, space is only the next logical step for a fish that has tried to conquer land.
On a summer day 30 years after mummichogs become the first fish to swim in space, I found a female mummichog – just barely longer than my middle finger, which is large by mummichog standards – laying in the grass. Abandoned by the tide, she was as stoic as sea-glass. Death will do that to you. I picked her up and she jumped out of my hand. I startled, not expecting a dead fish to be so agile. I picked her up and marveled about how far she was from the water: at least 100 meters, what must be kilometers in fish-distance. I looked at the tacky-skinned fish in my hand. A tough and adventurous survivor. I walked to a nearby pond and drop her in. She swam away as though she’d been there the whole time.
I was in the Great Marsh in Massachusetts. At low tide, the Great Marsh exposes its broad mudflats. In tidal creeks, the water may be shallow as a big toe is deep. In the rivers and bays, water may be only deep enough for small jon boats. During this time mummichogs and other fishes and shrimps wait in what crowded pockets of water they can find. Competition for food is intense. As the tide rises into the rivers and creeks, mummichogs who have been waiting in the deeper waters of the subtidal, follow the leading edge of the water in a crowded, confused mass. In fact, the name ‘mummichog’ is a Narragansett word meaning ‘going in crowds.’ As the creeks and rivers fill, the crowded fish twist their bodies as they bite the mud for small snails and worms. On the larger spring tides the water overtops the marsh and pushes into the expansive, grassy marsh. Here the fish spill into the marsh and spread out an army raiding a village. The grasses offer a menu not available in the muddy creeks and rivers: insects and spiders and small crustaceans. A fish who takes advantage of this easy protein grows faster than those that remain in the muddy creeks and rivers.
A flooded marsh is a land available to any fish willing to use it. But a fish can get greedy and forage far from the safety of a river and lose track of time and tide. This greedy fish can be trapped in a net of interwoven grasses and dilly-dallying. A fish that can breathe air survives. A fish that can’t, won’t.
Ever since the first fish, which didn’t really look like a fish, found itself in the Cambrian ocean 500 million years ago, it had to occupy a niche, that space in the world where it can make a living. It’s not always a perfect fit. Some fish, like the tuna, found their niche in the big, blue water. Some, like the deep-sea anglerfish, went to the big black water of the abyss. Some fish found themselves pushed against a new habitat, one strange to those with fins and gills, land.
Over time, fish watched the crustaceans conquer this new habitat, which gave them a roadmap to do the same. The first step? Learn to breathe air. The ancestors of the mummichog developed a gill that drew oxygen from both water and air. Mummichogs have retained this ancestral trait, which is why after any given spring tide in the warmer months, it is not uncommon to find the grasses of the salt marsh sprinkled with these finger-length fish. A mummichog can withstand a land no longer underwater if there is just the slightest bit of moisture to wet its gills. In this way, a mummichog can make do on regular air until it is rescued by the following tide. I have accidentally left a small mummichog at the bottom of a bucket with so little water that it lay on its side. The next day it did not complain and when I plopped it into an aquarium it swam as though it had been there the whole time.
Mummichogs can be stranded not only on land, but also in water. Mummichogs take refuge from the snapping jaws of stripers and flesh-shredding teeth of blue fish (Pomatomus saltatrix) in the ponds that pock the marsh. These ponds are only flushed during the spring tides of the new and full moons. In the interim, the oxygen levels in these ponds, particularly in the summer, can plummet to nearly zero. Most other fish species die. The mummichog gulps at the water’s surface and survives.
Mummichogs use their intertidal life to incubate their eggs in the safety of grass blades and shells high in the intertidal. During the spring and summer months, a female mummichog may lay her clutch high on grass stems during the highest spring tides. As the eggs are cradled in the crook of a grass blade, they are well above the ebb and flood of hungry mouths. The eggs develop slowly and will persist in even the strongest of summer swelters. Once the sea rises enough to wet them, possibly even a month later, big-eyed and translucent fry emerge and swim away within minutes. This habit of egg-laying and hatching is so coded in the mummichog’s genes that eggs never exposed to air do not hatch.
Terrestrial life began first as an aquatic one and then an amphibious one. Intertidal fish like the mummichog conquered the first challenge of an amphibious life, air breathing. Conquering land required, quite literally, another step. The first animal with a bony skeleton to crawl from the water to see the trees and find dry soil under it, was possibly the recently found fossil, Tiktaalik. This fossil is commonly called the ‘fishapod’ because it looks like a fish flattened from the top and bottom that has fins like short, stubby legs. Among evolutionary biologists, it is a most famous and celebrated fish. The mummichog is not a jealous fish, but it may take some satisfaction in knowing that while anyone can walk to an east coast salt marsh and admire a living example of the first fish in space, one has to go to a museum to see the now extinct Tiktaalik.
Fish are not supposed to live on land. Just as humans aren’t supposed to live in space. Yet today we find fish that can live on land, even if only for a little while just as we can live in space, if only for a little while. In the halls of NASA and living rooms of dreamers, we talk about living on Mars, an inhospitable planet compared to our own. Yet we hope to conquer and inhabit this planet. To make it our own. This sense of exploration and colonization is not a strictly human condition; if we look back far enough we can see it’s in our fishy genes.
Last week I saw fuzz on my windshield. My car does not suffer from the disease of cleanliness . I smudged the fuzz across my windshield, which added to the decor of bird poop, glass chips and cracks. More fuzz. Just as my thumb went into action, I paused. I recognized that fuzz. I leaned closer and focused on the fuzz. It wasn’t fuzz, but several strands of what looked like thin monofilaments of fishing line with slim, yellow jelly beans hanging at the end of it. There was about a dozen jelly beans dangling from my windshield (and at least one smeared).
This was not fuzz. This was eggs (yes, I know it’s not gramatically correct). Eggs of the green lacewing (Family Chrysopidae). I had left my windows down overnight so the interior could enjoy the fresh night air (read: air it out because I left some unknown food in the floorboard). The green lacewing was drawn to my car as the perfect nesting sight. No predators there. For the past week they have gone with me to work. Little jelly beans stuck at the end of a frozen bungee cord. They sitting there in my line of sight, me wondering when they will hatch and what they will eat when they do (I should have left the food in there!).
The lacewing is a delicate and beautiful insect that is well-named. And the aesthetics of its egg-laying habits serves a more important purpose than beauty. Just like a Kit-Kat is safer from me when it’s on top of the fridge instead of on the counter, tethered lacewing eggs are safer from predators than those laid on directly on the leaf.
And this is what they will look like when they emerge (courtesy of http://www.bugguide.net/).
A fat, white goose lives on the lake. I think he must be domestic and possibly someone’s pet goose because he is here all winter. In winter, he stands in the lakeside yard of his choosing and to honk that this is his lake. From emergent logs of long-ago fallen trees he makes his proclamations to the cormorants who stand on other logs with their wings held out to dry. The fat, white goose roams like a bachelor around the lake. Your yard is his yard and he greedily accepts your handouts.
I have assigned the goose as a ‘he’ because he seemed grumpy and while a lady goose can be mean and disapproving, I don’t think she would be grumpy.*
With spring come other waterbirds, mostly mallard ducks. When two or three splash down into the lake the goose swims over to them. At first I assumed to chase them off, but he only swims with them. Maybe they exchange gossip (a slip of the fingers and I accidentally typed ‘goosip’ and then tittered at my clever fingers). When the mallards swim or fly away the fat, white goose finds another log pulpit upon which to preach and honk, using the lake surface as a megaphone. Perhaps he is grumpy because he is lonely.
About a month ago the goose abandoned loneliness. The goose had a family. A mallard hen and eight fuzzy ducklings had adopted and been adopted by the goose. They followed him around the pond as he honked, like was a tour guide highlighting the best features of the lake. Indeed, he led them into yards to forage. He showed them the best docks to sleep on for sun. And when any perceived danger arrived – say a curious kayaker or neighbor with a camera – he honked an alarm, splashed into the water with small ducklings plopping in after.
Yesterday while fishing I saw the goose with two of his flock. They were no longer fuzzy ducklings but had mature feathers, but not quite grown bodies. Teenagers. As I drifted by in my kayak the goose decided I was too close and honked for the two mallards to follow. As he went around the bend, they did not follow. They went in the exact opposite direction. I watched the goose – probably thinking the two teenagers were behind him – swim father away. When he turned and saw they had not followed he honked loudly and rapidly. The two mallards ignored him and did not answer. He honked and looked for them. They did not perceive the same danger and did as they wanted to. When the goose found them and rejoined them, I would like to say that he gave them a good goose scolding. But he didn’t. He simply followed them, doing the best that he could help them make the right decisions.
My own duckling is almost a year old. When I crawl on the floor, he follows me. When I walk into another room, he follows me. He trusts me completely. He wants to be near me and doesn’t question my decisions. I know one day that will change. I can only hope that when that day comes that I have the patience of a goose.
*It is possible that the goose is a ‘she’ but the themes are the same even if not the gender. There are plenty of mom’s who act as fathers and do a fine job.
In the Great Marsh of Massachusetts
A house remembers.
Golden vases hold insect secrets.
Rivers flow into hopefulness.
In the Little Sippewissett Marsh of Massachusetts
Aprons clutch to broods.
In the Goodwin Island marshes of Virginia
Crabs of purple that hide in mud are still found.