Monday, July 16, 2018

Tadpole Legs



You may recall that we commented in Linda Bower's leeches video that the tadpoles only had hind legs. I always assumed that the front legs would start as little buds, growing larger slowly like the hind legs do. It turns out that they do, but hidden inside the gills. Notice above the bump below and behind the eye. That is the front leg awaiting its debut.  So how does a tadpole become a frog?

"Look Ma, no hands!"
"As a tadpole matures, it most commonly metamorphosizes by gradually growing limbs (usually the back legs first, followed by the front legs) and then (most commonly in the case of frogs) outwardly absorbing its tail by apoptosis. Lungs develop around the time of leg development, and tadpoles late in development will often be found near the surface of the water, where they breathe air. During the final stages of external metamorphosis, the tadpole's mouth changes from a small, enclosed mouth at the front of the head to a large mouth the same width as the head. The intestines shorten to accommodate the new diet. Most tadpoles are herbivorous, subsisting on algae and plants." Wikipedia


Front leg peeking out of gill opening
The front legs develop internally inside the gill pocket of the tadpole’s body. They don't emerge until the tadpole is almost ready to make its frog/toad debut and leave the water.  The seemingly obvious reason used to be that the delay in emergence was because the front legs would obviously slow the tadpole's swimming speed, making it more vulnerable to predators.  Recent research published in Functional Ecology has proven the common explanation wrong.
Three legs and a leg lump in the gills
This article in the Telegraph summarizes the findings.

As seen in Linda's video, front legs rarely erupted simultaneously.  Generally one leg appeared five or six hours before the other. So for a short spell the tadpoles were swimming around with three legs which common sense would say might prevent the tadpole from swimming straight.  Wrong, they swam as straight as those with two or four legs.

Right elbow out but the "fingers" still in the gills.
But of course the little legs dangling down would surely slow them down.  Wrong! They tested tadpoles having two, three or four legs to see the effect on how fast tadpoles could swim. They measured the escape or “burst speed” -  how fast a tadpole set off when startled by a jet of air from a pipette. "Tadpoles swam faster with four legs than with two. They even swam faster with three legs than with two."

Now watch in Linda's video and pay special attention starting at 2:24 and you will see the front leg on the right emerge and start functioning.

"Free at last. Time to suck up my tail and eat meat!" *
 *  Stay tuned as tadpoles complete their transition to frogdom.

Friday, July 13, 2018

Linda's Leeches




Our resident videographer, Linda Bower, has been into leeches lately.  The ones seen here are Placobdella picta, a species that specializes on juvenile amphibians.  Her two months of filming has captured their movements and especially their interesting association with tadpoles. The ones seen here in this video are on spring peeper and gray tree frog tadpoles. A time lapse shows blood moving in the leech. Note the young leech attached to the glass from 1:54 to 2:25 minutes. The white dots swimming around are mostly ostracods.

Linda has been communicating with Malcolm McCallum who has researched P. picta  and their association with tadpoles described in this paper.  P. picta is known to parasitize 12 amphibian species including salamanders, frogs and the American toad.  They find their future host by detecting vibrations from the swimming amphibians.

There is speculation that this species may be an important regulator of tadpole populations. Many frogs return to the waters where their own eggs were deposited. They are a known vector for several blood-parasites and may play an important role in amphibian declines.


This video has closeups of the leeches which have not attached to a tadpole.  It includes views of  "hanging out," "walking," reacting to copepods, and the inevitable guts moving and eliminating waste. At 3:22, the leech goes inside of an air bubble and then back into the water, which is very cool to watch.


Notice you only see hind legs on the tadpole.  More on that soon. 

Wednesday, July 11, 2018

Twitching Spider Leg


As I was sitting at my desk last week, I saw a little brown spider come out from behind some books.  I suspected the spider was a brown recluse so I used a pencil to pin down its legs while looking for an insect box to put it in.  Two of its legs fell off and started twitching, continuing for over two minutes while I got my camera to take this video.

Few spiders can be identified down to species just by their markings.  Even black widows have several species, separated by the details of their hourglass.  The identification of the brown recluse, aka fiddle spider, is "confirmed" by the fiddle marking on the dorsal thorax above.  At least, that is what we were all taught. 

Burkemuseum.org
The Burke Museum calls this a myth as there are other spiders that can have fiddle shaped markings.  Another myth involves an outbreak of L. reclusa  bites in California as this species only occurs in the south-central United States.  Spider identification can be narrowed down by the eyes.

Spider identification is tricky at best but it usually begins by looking at the arrangement of their eyes and comparing it to this chart.  For those of us non-arachnologists, looking one in the eye involves either a smashed spider or a camera.  In this case it was this postmortem view that put it in the Loxosceles genera, called the brown spiders.  There are eleven species of Loxosceles in the United States, but only  Loxosceles reclusa is reported in Missouri.
Loxosceles


Certain identification down to species requires a detailed examination of an adult spider's genitalia under a microscope.  And even the "fiddle" requires some magnification, something I can't do with a moving spider, so all brown spiders of that certain size are brown recluse until proven otherwise at postmortem. 

Exposed "hip joints"
Back to the twitching leg, this is a common finding when Opiliones (harvestmen) lose a leg and has been reported with Pholcids (cellar spiders).  Both groups have extremely long legs and tiny bodies, meaning that predators are most likely to grab a fragile leg.  Cowles describes this as a "flexible secondary defense." *  The leg kicking around on its own entertains the predator and may actually give it a satisfying treat while the victim makes an escape, similar to the twitching blue tail of a five-lined skink.

Opioliones actually have muscles in the trochanter that contract to prevent bleeding.  "Two pacemaker nerve ganglia within the leg are activated as soon as communication with the central nervous system is severed.  They operate independently, causing the leg to twitch and jerk.  The legs even have their own trachae which supply the disembodied legs with oxygen.  The leg can twitch for up to an hour, as opposed to 40 seconds without oxygen."*

I can't find any information on brown recluse spiders having disconnected twitching legs but I have the video and seeing is usually believing.
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* Amazing Arachnids, Jillian Cowles.

Monday, July 9, 2018

Wolf Spider



While doing a soil survey in our freshly mowed hay field, Richard Locke spotted a large spider skittering over the duff.  After multiple tries we had it in a box.  While few spiders are distinctive, this wolf spider had unique markings of a male rabid wolf spider, Rabidosa rabida.

First the eyes have it.  Wolf spiders have a distinctive row of 4 small eyes on bottom, then two large eyes above and finally medium eyes on top and a little lateral.  The palps are large, typical of male spiders.  In addition to the dramatic light and dark stripes along the large cephalothorax, there are the series of large paired light stripes on the abdomen.  Finally, R. rabida males have black front legs.

Wolf spider eye pattern
Note eyes- click to enlarge
According to Bradley* "The spider is usually found in open habitats such as pastures and prairies, and even open woodlands.  It is most common in tall grasses where it climbs in the vegetation at night."  We would likely never found this one except for the mowing.

R. rabida with babies - Ralph Arvesen CC
According to Wikipedia, "During breeding, the male performs a "dance" in front of the female, and makes a noise with its legs. If mating is successful, the female will begin to lay its eggs and build an egg sack out of silk, which she will use to carry her young. When the spiderlings are born, they ride on the mother's back until they are old enough to be on their own."



The abdominal markings looked familiar so I went back in my files and found photographs of this little lady R. rabida in 2016.   She was slowed down by her burden (some of you ladies will probably sympathize), and willingly posed on my hand, even climbing up my finger to demonstrate her hold on the egg case.  Ever the gentleman, I gently returned her and today's find to their home territory.


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* Common Spiders of North America, Richard Bradley, p. 160.

Saturday, July 7, 2018

A Beetle Moves a Mouse

Carrion beetles on a rat



This long-dead pack rat, Neotoma floridana, from our well house gave us a chance to witness a major orgy of carrion beetles.  Roughly 40 were scrambling over the carcass with more underneath it.  The 10:1 majority were the common American carrion beetle, Necrophila americana, dull black overall with a yellow anterior pronotum and a central dark spot.  Mating pairs were common with a lot of partner switching.

There is surprisingly little detailed information online about this common beetle.  Wikipedia states "It lays its eggs in, and its larvae consume, raw flesh (particularly that of dead animals) and fungi. The larvae and adults also consume fly larvae and the larvae of other carrion beetles that compete for the same food sources as its larvae."  They are primarily active in daytime.

Nicrophorus tomentosus with mites (upper left) and Necrophila americana

In the writhing mass I could occasionally spot a gold-necked carrion beetle, aka tomentose burying beetle, Nicrophorus tomentosus, named for the dense yellow hair on its pronotum.  We wrote about them with an emphasis on the mites they carry extensively in this blog last October.  We will return to them below.

RCB - note tooth on femora
Occasionally in the swirling mass of beetles I got a glimpse of another beetle I hadn't seen before.  It stayed mostly under the rat and I finally caught one to photograph.  This was a red-lined carrion beetle (RCB), Necrodes surinamensis.  Aside from the orange markings they also have a distinctive  expanded hind femora with a large tooth.

 Bugguide says "Rather nocturnal and is found at lights, unlike related genera. Adults locate carrion and mate on or near a carcass. They feed on fly larvae there. Eggs are laid on soil near the carcass. Larvae feed on fly larvae and carrion and pupate in soil. Adults overwinter in under litter."

All of these carrion beetles have a foul smell (no surprise their considering their life style) but that is due to the defensive chemicals they produce like all carrion beetles and their larvae.  RCB is even more sophisticated.  "It can eject anal fluid as a spray rather than an ooze. The abdominal tip, which projects beyond the posterior margins of the elytra, serves as a revolvable turret by which ejections are actually aimed."  Unlike bombardier beetles who spray from a dedicated gland, the RCB is unique as its spray is from the anus, a mixture of toxin and fecal matter, adding insult to injury. * (Editor's note: the author is a retired gastroenterologist.)

Unlike the other carrion beetles, there is detailed information on RCB in this paper by Brett C. Rattcliffe.  While the details of how they feed on the fly maggot was too much for even me, it is interesting that they are frequently canabalistic on their larvae.


Just as I finished this blog, my nephew Jon found beetles on a long-dead mouse.  When he came back 40 minutes later, the carcass had been moved 2 feet and he could see it twitching.  He watched as a Nicrophorus tomentosus beetle (with the orange jagged markings) would scout ahead, then come back and get under the mouse and start moving it again.  Berndt Heinrich recently described their technique of crawling under the animal lying on their back and using their legs to propel the victim forward.

Jon called me to the crime scene and I videoed the action.  Warning: This video is very graphic- do not watch before eating.  See it here on Youtube

3mm fly and a small rove beetle
You can see most of the other insects that feed on carrion as described in this Entomologytoday.org link crawling on and in the mouse.  The mouse has lost lots of it hair already and several holes allow them access to the body cavity. In addition to the usual beetle suspects, there are metallic green blow flies, black and white striped Sarcophagidae flies, slender black rove beetles and a variety of small oval black beetles, ants, and lots of tiny orange 3mm flies that were flying in and out of the picture.

The Nicrophorus tomentosus beetles that are moving the mouse in little jerks are lifting 20 times their own weight, a prodigious feat, all done to provide a home for their larvae.  They will protect their eggs, parent their offspring and even may share a carcass with other beetles.  You have to love a beetle like that, or at least respect it.

Thursday, July 5, 2018

Water Snake Fishing for Hognose

Heads up for a breath of fresh air
Last week we spent a 96 degree afternoon by the swimming hole in the shade of a sycamore.  Kids snorkeling and water fights were occasionally interrupted by the sight of a northern water snake poking its head out of a hole in the rock shelf to catch a breath and look around.  It was very patient and allowed us to get within a few feet for photographs.

Moving down the body to a head first grip
Quick, find the snake!
Later that afternoon, our nephew Jon followed it along the far shore line and saw it duck its head into the water and come up with a fish.  It swam to shore where its camouflage helped it remain inconspicuous.  Jon got an Iphone and captured this video of the snake swallowing a  juvenile northern hog sucker (Hypentelium nigricans).  The fish is the same diameter as the snake, but snakes can dislocate their jaws to engulf far larger prey.  You can watch as it bites it multiple times before maneuvering it around to get a head first grip.  Then it is "down the hatch" as you watch it move down the snake's body.
Beautiful visitor to our deck
Cruel fate
We discussed the northern water snake in this previous blog.  Over the years we regularly swam with a larger one which even came out on our deck 12 feet above the creek last year.  Unfortunately it was killed by a well-meaning visitor a few months later.  He saw it in the swimming hole near some children and thought it was a water moccasin, a species that we have never found in our creek.  All we have left now is its skin and fond memories.  It pays to be able to identify snakes for safety as well.  Ironically, this same swimming hole was the site of a misidentified copperhead snake bite in 2011 as described in this blog.

 Northern hogsucker - Brian Gratwicke CC
Now back to the poor northern hogsucker, the Rodney Dangerfield "get no respect" of the fish world.  Other names are now better, "hog molly" and "box head."  They are abundant in the Ozarks, generally found below riffles in streams of all sizes.  Its oversized head comes equipped with a vacuum cleaner mouth pointed downward.

The MDC Field Guide describes it as "An energetic feeder, overturning rocks and stirring up the bottom as it forages for immature aquatic insects and other bottom life with its fleshy, sucking lips.  Other fishes, especially the smallmouth bass, longear sunfish, and various minnows, commonly follow foraging hogsuckers to feed on the small organisms exposed by the hogsuckers' energetic rooting."

These hogsuckers live in clear water with gravel bottoms, the perfect description of our 8 foot deep swimming hole.  They are one of my favorite snorkel prey and they lay still on the bottom as you glide overhead, trying to spot it.  I rarely can find one until I am directly over it and it suddenly scoots away, not realizing that I am harmless. 

A good resource for the snakes of Missouri is on this Missouri Department of Conservation web page.

Sunday, July 1, 2018

Ostracod Diner



Linda Bower has produced one of her finest water macro videos, matching action with music in a way that Beethoven would be proud of.  This one is of the larvae of a predaceous diving beetle that seems built to feed on ostracods.  For those of us unfamiliar with these species, this will take a lot of explaining.  First I am taking this directly from our 2017 blog posting about ostracods in a fountain.

Ostracods, a.k.a. seed shrimp, are tiny crustaceans that live in water.  They are an ancient species with 70,000 species identified but "only" 13,000 that have survived extinction.  They are common in fresh water, frequently in temporary pools and ponds.  Their eggs resist dehydration and can wait for months or many years before hatching with their next hydration.
Click to enlarge - Pionocypris vidua, - bumblebee.org

Their flattened bodies lie within a bivalve structure similar to a mollusc.  They swim with their legs extended but can contract them and close their "shell" to protect themselves.  They lack a distinct abdomen and circulatory system but have antennae to seek out food (diatoms, bacteria and detritus) and mandibles and maxilla to obtain it.  I will leave the anatomical details to Wikipedia.


Here are what 5th grade WOLF students would call "Fun Facts"* although some might be R-rated.
  • Although fish eat ostracods, some may survive the passage through the gut.  One study showed that 26% of those eaten by a bluegill passed out the rectum alive. Who counts these things?
  • Many species reproduce parthenogenetically, i.e. without male fertilization, but some species have the largest sperm in the animal kingdom, up to 3.6 times longer that the adult's body.
  • Ostracods are the most abundantly preserved arthropod in the fossil record (500 million years) and boast the oldest known example of a fossilized penis, 425 million years ago.
  • Some species are bioluminescent, a defense mechanism seen in this video.  During WWII, Japanese troops collected and dried specimens, then rehydrated them to provide a dim light for map reading without giving away their location.
We described predaceous diving beetles back in 2013 when we were young(er) and innocent (sorta) in this blog.  We were describing large and menacing beetles with 2" larvae that can put a major hurt on a naive naturalist's finger.  At that time I impulsively grabbed a larva and had throbbing finger and swelling to remember it by.  These in Linda's video belong to a genus of 1-3 mm beetles that probably couldn't penetrate my skin but are genuinely ferocious under Linda's microscope.

Desmopachria beetle larva
It is hard remember that these larvae, resembling alligators are actually tiny.  In the video you will see them grabbing the ostracods and opening the bivalve "shell" like an oyster.   Once open they pull out the "meat" with the panache of a seafood gourmet at an oyster festival.  I almost expected to see it wipe its mandibles with a bib napkin.  The Desmopachria larva looks like it was designed to prey on ostracods.

 Desmopachria dispersa - Mike Quinn CC
Linda has identified these tiny beetle larvae as being in the genus Desmopachria.*  There are way over 100 species in this genus with more identified each year.  They can be collected by their attraction to black lights and mercury vapor lamps.  Only the adult beetles can be identified by species, the larvae are all just Desmopachria sp.


Her video features guest appearances by flatworms (they look blue under the LED lights) and a Nematode in the last clip.  For the big show you are now ready to see Desmopachria and the Ostracods!
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Much more on fascinating ostracods 30 Interesting Ostracod Facts.
 * For more details on Desmopachria, download Water Beetles of Florida  5.53 This is a large comprehensive PDF.  For the Desmopachria basics, see this page 5.53.
Photographs are taken from Linda Bower's video.

Wednesday, June 27, 2018

Gray Treefrog

Lightning beetle flirting with death - Linda Bower
Linda Bower sent me this video of a gray treefrog clinging onto her kitchen window.  A firefly can be seen crawling around in striking distance.  Flashing an insectivore is probably not a good survival strategy.  The frog is obviously annoyed as the firefly tickles its belly.


Measuring two inches, they are elusive unless less you can sneak up on one that is calling.  It produces a short trill which you can hear on this MDC link.  Gray treefrogs are frequently found on windows as they take advantage of the insects attracted to light.

The "lightning beetle" referred to above is no mistake.  They are Coleoptera (beetles), misnamed as bugs or flies just like "lady bugs" and other beetle examples.  I was going to expand on fireflies but Bug Lady has beaten me to it in this highly recommended blog posting.

Tuesday, June 26, 2018

Leaf-foot Bug Birth

 
I was photographing an alien-looking bug when I noticed a small cluster of insect eggs on the underside of a leaf.  I stored them safely in a bug box, hoping to video their births.  

The creature was a common leaf-footed bug, characterized by the leaf-shaped tibias on the hind legs.  These are plant-sucking bugs, similar to stink bugs, commonly considered garden pests. This one was easily identified as Acanthocephala terminalis, (AT). The genus name comes from the Greek akanth- 'thorn/spine' + kephale 'head', and refers to the spine on the front of the head.  Terminalis comes from the bright yellow-orange terminal segment of the antennae.




Egg - Click to enlarge
I gently moved the eggs onto the sticky part of a post-it note for handling.  We watched the eggs daily and noticed a change in color on day 16.  They were a little cloudy and had developed some red streaks.  This was a sign on maturation of the larva.  Unfortunately by the next morning the little stinkers had emerged overnight.


Empty eggs - Click to enlarge.
Now we could see the eggs with a lid cut out by the nymph.  The first instar is very distinctive with orange streaks that we had seen through the translucent eggs the day before.  I was amazed that an infant that size can emerge from a tiny egg overnight, but my wife reminded me of how compact our children were packaged before she gave birth.  Once the body of these unfolded their size was mostly the gangly legs.  There are even better photographs on Buggtracks.




The upward curve of the abdomen is common to a lot of different bug nymphs.  As they age by going through sequential molts the later instars of AT darken and develop a spiny back.  There is a series of pictures of one molting at Bugguide.  The one on the right was initially misidentified as an assassin bug nymph.


Later instar - Bugguide








Unlike beetles with their chewing mouth parts, bugs have a proboscis that resembles a hypodermic needle. Their feeding is more complex than just sucking up juices. They first inject their saliva with enzymes into the tissue, then suck up the digested liquid. Assassin bugs attack insects and other prey, while plant bugs like our AT suck the juices of leaves and fruit. It can be difficult to separate some plant bugs from their assassin brethren so it is best not to pick them up with bare hands. Although a few leaf-footed species can be listed as agricultural pests, our AT is not a problem.

Sunday, June 24, 2018

Swinging Spider


In our house on Bull Creek, cellar spiders are a daily presence.  They tend to hang out along the walls and windows, inconspicuous until you look closely at them.  They are also called vibrating spiders for a good reason.  Touch one or its web and you have instant entertainment as seen in this short video in our sink.

Resting after a long spin.  The body is only1/4" long
Cellar spiders are also called daddy long-legs spider and other related names.  They are often mistaken for harvestman species, which are a separate order of Opiliones.  Spiders have a separate cephalothorax (head+chest) and abdomen while harvestman combine the head, thorax and abdomen all in one package.

Harvestman
Spider










We have developed a "live and let live" relationship with our long-legged friends.  Before we get hate mail from Acrophobes United, let me explain their virtues. There is evidence that they can eat other spiders such as widows and recluses, populations that we want to keep in check.  They cause us no harm, we don't usually walk into their flimsy webs, and they can entertain guests with their acrobatic performances.

Today we just wanted to share their talents as swingers.  You can find more details in this 2015 blog.