Archive for the ‘invertebrates’ Category

Fossorial Spiders in Georgia

July 2, 2021

2 different groups of spiders live underground in Georgia soils: trapdoor spiders and wolf spiders. Trapdoor spiders belong to the Myglamorph order which also includes tarantulas, funnel web spiders, and purse web spiders. (The latter make tube shaped webs on tree trunks.) In Georgia there are 3 families of trapdoor spiders including the Ctenizidae (ravine trapdoor spiders), the Antrodiactidae (folding door spiders), and the Eucterizidae (wafer lid spiders). Spiders in the Ummidia genus belong to the Ctenizidae family, and as their name would suggest, their preferred habitat is moist ravines located next to rivers. However, most species of trapdoor spiders seem to prefer this type of environment. 1 recent study searched for trapdoor spiders in moist ravines along the Altamaha, Savannah, and Satilla Rivers in Georgia, and the spider hunters found 51 specimens including 3 species. Along with 1 species of ravine trapdoor spider, they also found wafer lid and folding door spiders.

All trapdoor spiders construct underground burrows where they wait for prey to cross across the door. When the spider senses an insect on its door, it will seize the unfortunate prey with fangs and pull it inside the burrow where the spider feeds upon it. The families differ in how their doors are constructed. Ummidia spiders use their abdomen covered in webbing as a door. Folding door spiders pull the rims of their burrows closed, unfolding it in time to catch an insect. Wafer lid spiders have a thinly-webbed door. Incredibly, the wafer lid spider, Myrmekiaphilia, constructs its burrows inside or alongside ant nests. Some species of wasps hunt trapdoor spiders. The arachnids have a defense–they desperately attempt to hold the door shut while the wasp tries to pull it open. Somehow, they are able to tell the difference between prey and a wasp.

There are at least 8-10 known species of trapdoor spiders in Georgia. Auburn University professor, Jason Bond, has discovered 37 species of trapdoor spiders in North America, and there likely are more than 10 species living in Georgia with many undiscovered. He’s named newly discovered spiders after celebrities including Barack Obama, Tobey Maguire, Angelina Jolie, and Stephen Colbert.

The moist mesophytic slopes where trapdoor spiders occur are particularly rich habitats for all wildlife. William Bartram described walking through a “magnificent” slope forest in his Travels. (See: https://markgelbart.wordpress.com/2011/04/11/william-bartrams-magnificent-forest/ ). A forest such as Bartram described no longer exists in Georgia, but even logged over 2nd growth forests are richer on these sites because they are wetter and cooler than the surrounding habitats. During Ice Ages when much of the surrounding environment was dry scrub, these sites likely provided refuge for hardwood forests and hence relic habitat for trapdoor spiders.

This photo angle is not good enough to identify what species of spider this is in my rain gauge, but I can tell it is not a trapdoor spider as I wrongly assumed at first. I made this false assumption because I thought a trapdoor spider was using an existing structure that imitated its burrow, but that is not the case.
Photo of a ravine trap door spider in the Ummidia genus. Photo from spiderid.com.
Wolf spider from the Tigerosa genus. This is the kind of spiders I see when I dig in my garden. Photo from spiderid.com.

I often come across spiders when I dig in my garden. Until I started researching information for this blog article, I wrongly assumed they were trapdoor spiders. Instead, I learned these are wolf spiders, probably belonging to the Tigrosa genus (named for the striped appearance). Wolf spiders are in the Lycosidae family, and they also construct burrows underground. Unlike trapdoor spiders, they are not sedentary predators. They hide from predatory birds in their burrows during the day, but they leave their burrows at night and actively hunt insects. They probably attack crickets, homing in on their noisy chirping. A wolf spider’s burrow can be as deep as 3 feet, keeping them safe from inclement weather and birds, but moles can find them. Female wolf spiders carry their eggs and young on their backs when they hunt at night. They are far more common than trapdoor spiders, and worldwide there might be as many as 2000 species.

Reference:

Stevenson, D.; and R. Godwin

“Notable Myglamorph Spiders (Aranae: Myglamorphae) Records for the Coastal Plain of Georgia”

Southeastern Naturalist 19 2020

Pleistocene Ant Lions (Myrmeleontadae sp.)

April 29, 2021

Ant lion pits line the bare soil areas next to the back wall of my house. Ant lions, as the name suggests, prey on ants, though they will eat anything small enough to become trapped in their pits. The larval stage of most species is the monster hidden just below the sand of the bottom of the pit. When an ant lion larva senses an ant walking near the edge of the pit, it flicks sand at the ant, knocking the ant into the side of the pit. The action of flicking sand destabilizes the wall of the pit, forcing the ant to fall within the reach of the ant lion’s jaws. The ant lion then injects venom and devours the ant, or rather sucks the juices out of it. Ant lion larva can live for years without eating and during winter they dig deeper down to avoid frosts. But after they’ve had a meal, they go into a cocoon stage before emerging as adults. They survive on nectar for energy in their brief adult stage spent searching for mates. Fertilized females lay eggs in sand and the cycle begins again.

Some species of flies lay their eggs in abandoned ant lion pits, and their larva use the same strategy as ant lion larva. At least 1 species of parasitic wasp allows itself to be captured. It stings the ant lion larva and lays on egg on it, thus turning predator into prey.

Ant lion adult and larva. Image from below reference. The larva prey on ants and other small arthropods.
Ant lion pits next to the side of my house. Ant lions prefer sandy soil and are common in arid environments. They likely were abundant in the southeast during Ice Ages when the climate was dry and bare soil environments predominated.

There are about 2000 species of ant lions, and there are species on every continent except Antarctica. Their closest living relatives are owl flies and lace wings. They are most common in tropical dry climates, but they thrive anywhere they can find a sandy substrate. I hypothesize they were abundant in southeastern North America during Ice Ages when arid climates prevailed, resulting in vast landscapes with sparse vegetation. Pleistocene climate changes likely increased species diversification when populations became isolated from each other during wetter climate phases that turned sandy environments into isolated refuges.

Ant lions are rare in the fossil record. Ant Lions have been found in 99 million year old amber at a site located in Burma. Scientists think ant lions first evolved about 150 million years ago, so they lived under the feet of dinosaurs. There are no dinosaurs in my yard (unless one includes birds), but their contemporaries live right up next to my house.

Reference:

Badano, D.; M. Engel, P. Basso, B. Wang, P. Cerretti

“Diverse Cretaceous Larvae Reveal the Evolutionary and Behavioral History of Ant Lions and Lace Wings”

Nature Communications (9) 257 August 2018

North American Army Ants

June 17, 2020

Most people are familiar with the army ants of South America and the driver ants of Africa featured in many nature documentaries, but few are aware army ants also occur in North America.  There are 30 species of army ants from the Neivamyrmex genus and 1 species from the Novamyrmex genus living on this continent.  North American army ants differ from those of South America and Africa.  North American army ants cross the landscape in more narrow spear-headed swarms than those of their tropical cousins.  Nevertheless, they are just as predatory.

Neivamyrmex nigrescens, Arizona

A species of North American army ant.  Notice how thick their antenna are. Years ago, I witnessed army ants tearing apart an earthworm in Columbia County, Georgia. This photo is by Alex Wild from the below link.

Army ants don’t live in permanent nests.  Instead, they alternate between foraging and stationary phases.  During foraging phases they roam across the land searching for food to feed their larva.  They mostly eat other ants and are built to subdue other species.  They have muscular bodies and thick antennas that other ants can’t bite through.  When the larva go into the pupa stage, army ants enter the stationary phase and live within a swarm of their own bodies.  Colonies produce new queens every 3 years, and the colony will split into 2 after the new queen is born.  Most army ant colonies perish when the queen dies, but some manage to track down a closely related queen and will merge with that colony.

There are over 200 species of army ants worldwide including 5 genera in the Americas and 2 genera in Africa and Asia.  A study of army ant genetics determined some genera of American army ants are closely related to African army ants.  They diverged 100 million years ago before Africa and South America drifted apart.  Other genera of army ants are not closely related to other army ants and are examples of convergent evolution.

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Range map of army ants in North America.  Map is also from the below reference.

Cold climate apparently is a limiting factor for army ant distribution, but it might not be the temperatures.  I noticed in the map of their distribution that the northern limits of their range approximately corresponds to the southern limit of Ice Age glaciers.  Like many species of trees, they simply have been unable to colonize deglaciated territory even though they can survive the cold temperatures of Iowa and Nebraska.

Reference:

Most of the information for this blog entry comes from Alex Wild, a Texas entomologist.  This links to his website.

http://www.myrmecos.net/2008/12/14/army-ants-of-the-north/

Bald Faced Hornets (Dolichovespula maculata) are Marvelous Engineers

October 5, 2019

Humans were not the first species to manufacture paper.  Wasps were building paper nests millions of years before  Homo sapiens  evolved.  The bald faced hornet builds the largest, most spectacular nest of any species of wasp, and I always love finding these in the woods.

Bald Faced Hornet

Bald faced hornet’s nest.

A mature bald faced hornet’s nest holds 400-700 workers.  A pregnant queen emerges during spring and begins building the nest but she is soon aided by workers she births. The hornets make the paper by chewing wood.  The workers are all sterile females, and sterile males also live in the nest.  Meanwhile, the queen keeps laying eggs.  By late fall these eggs become future queens and drones (fertile males).  The queens and drones leave the nest, and the latter impregnates the former.  The pregnant queens than overwinter under cover to emerge the following spring.  Bald faced hornets are carnivorous, feeding upon soft-bodied invertebrates and carrion.  They attack caterpillars, fly larva, and spiders that they then feed to their larva.  The adults get their energy from flower nectar and fruit.  People picking fruit need to be careful not to pick up a piece of fruit being enjoyed by a bald faced hornet.  They love my scuppernong grapes.  Plums are another favorite.

The bald faced hornet is not a true hornet but rather a yellow jacket wasp.  All hornets are wasps, but only some species of wasps are hornets.  Hornets are generally larger in size and less colorful than other species of wasps.  Hornets build paper nests, while most wasps build nests suspended in the air, on the ground, or underground.  But to add to the confusion, bald faced hornets do build paper nests though they are not true hornets.  The difference between true hornets and wasps involves technical anatomical differences that I am not going to cover here.

Bald faced hornet.

Bald faced hornets are widespread and adaptable.  This species expanded throughout deglaciated Canada in less than 10,000 years following the last Ice Age.

Bald faced hornet range map.  Note how they occur in the geographic region that used to be covered by glacial ice.  They’ve colonized territory all the way to central Alaska.  Amazing.

As far as I can determine, there is no Pleistocene-aged fossil evidence of bald faced hornets or their nests.  Insects are rarely preserved, and of course paper nests deteriorate rapidly when exposed to the elements.  I’m sure they were just as common during the Pleistocene as they are today.

Pleistocene Squid

February 11, 2018

The cephalopods were the most intelligent creatures on earth for hundreds of millions of years.  Nectocurus pteryx, a squid-like ancestor of all cephalopods, lived 500 million years ago during the Cambrian Age.  Fossil specimens of this species are found in the famous Burgess Shales.  Cephalopods–a group that includes squid, octopus, cuttlefish, nautiloids, and the extinct ammonites–evolved arms they can use to manipulate objects, and squid, through convergent evolution, evolved eyes quite similar to the human eye, so they can see the world like we do.  This explains how they evolved intelligence much greater than that of other invertebrates.

This blog article, like my entry about Pleistocene spiders, is entirely speculative because cephalopods have soft bodies that are also rarely preserved.  During Ice Ages sea levels receded and dry land extended across the continental shelf, today inundated by ocean water.  It seems likely deep water species of squid inhabited waters adjacent to the shore because steep drop-offs existed much closer to land during these climatic stages.  Giant squid (Architeuthis dux), reaching lengths of 43 feet, and colossal squid (Mesonychoteuthis hamiltoni), almost as long, probably lurked near the coast, whereas today they are normally restricted to deeper waters far out to sea.

The Gulf Stream current that keeps land temperatures moderate in the northern hemisphere often shut down or was greatly reduced during episodes of glacial meltwater influxes known as Heinrich Events.  These must have had an impact on squid migration.  Many species of squid migrate long distances to spawning grounds, and Heinrich Events must have altered their paths of movement, species abundance, and species composition.  Large die-offs probably occurred in some species, while others may have benefitted from the chaos.

Squid are an important food source for marine mammals, and deep sea species of whales likely ventured closer to shore in search of squid during Ice Ages.  Seals then living on the shores of the Atlantic Coastal Plain fed on squid.

The composition and species abundance of squid during various stages of the Pleistocene will forever remain a mystery.  There are over 300 known species of squid in the world today, but scientists know little about squid species abundance of the present day, let alone of the distant past.  One study of squid off the eastern coast of Florida determined eye flash squid (Abralia cf veranyi), flying squid (Ommastrephidae sp.), and shortfin squid (Illex sp.) were the 3 most abundant genera or families.

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Eye flash squid are 1 of the most common species found off the coast of eastern Florida.

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Shortfin squid–another common species.

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Flying squid shoot out of the water to escape predators.  

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Sperm whales feed mostly on squid.  Individuals can be distinguished by scars from battles with giant squid.

I’m not impressed with the flavor of calamari.  I’ve had it in a Vietnamese pho soup.  The soup itself was delicious, but the calamari was rubbery and tasteless.  I’ve tried fried calamari but this too had no flavor.  The best squid I’ve ever eaten was a canned Korean product.  The squid, packed like sardines, were seasoned with soy sauce and sugar.  The seasoning would’ve made anything taste good.  However, the squid were not cleaned, and I had to be careful chewing so I wouldn’t break a tooth on the hard beaks.

Reference:

Erickson, Carrie; Clyde Roper and Michael Vecchione

“Variability of Paralarval-Squid Occurrence in Meter-net Tows from East of Florida, USA”

Southeastern Naturalist 16 (4) 2017

 

Spider Romance or How to Eat your Mate

October 25, 2017

Halloween decorations often include mock spider webs  because many people think of spiders as creepy.  I don’t.  I think they are fascinating.  There are over 44,000 known species of spiders in the world with about 400 new species named every year.  Most spiders trap their prey in the sticky substance produced in their abdomen, then they quickly pounce on the struggling insect and inject a paralyzing venom that liquefies the insides.  After their prey is subdued the spider sucks the juices from the helpless victim.  I suppose that is an horrifying fate for insects, but people have nothing to fear from such a small organism so vulnerable to a rolled up newspaper.  (I never kill spiders.  Instead, I catch and release them, if they invade my house.)  The spider’s strategy of trapping prey in a web poses a dilemma for males seeking a mate.  It is difficult for a female spider to discern the difference between food and potential sex.  Male spiders must tap on the web in a certain way, communicating to the female they are a sperm donor, not a trapped fly. Mistakes are occasionally made.

Female spiders are larger than male spiders, but in some genera sexual dimorphism is extreme.  Evolution has led to female gigantism among orb-weaving spiders.  Nature has selected for large females and small males in orb-weavers for 4 reasons: a) large females are more fertile and produce more eggs, b) larger females are less likely to fall prey to predators, c) small males reach sexual maturity at an earlier age, and d) small males are better climbers and can reach females faster than others when journeying up the web.  If after sex, a female spider eats a male, there is no great loss.  The female has already been fertilized, and the male is more useful as extra nutrition.  This reproductive strategy is not satisfactory for lampshade spiders.  Female lampshade spiders have larger bodies than males, but the males do have longer legs.  This gives male lampshade spiders the ability to escape after mating, so they can impregnate other females.

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Female and male banana spiders (Nephilia clavipes).  Evolution has selected for large females and small males in spiders.  

Lampshade spiders construct webs in the shape of a lampshade, hence the name.  Females are larger than males in this species as well, but the males have longer legs, so they can escape after mating.

Humans are not as different from spiders as one might think, especially considering risky sex.  People aware of sexually transmitted diseases, including deadly AIDS, are still often willing to have unprotected sex with strangers.  Men and women cheat on their significant others, even though they realize their jealous partner might shoot or stab them, if their indiscretion is discovered.  And some people, mostly men, pay dominatrixes to bind them, putting them in a situation not dissimilar from male orb-weaver spiders.

Many men are attracted to woman who are larger than they are.  My personal preference is for women with really large breasts and buttocks, and I don’t mind if a woman is heavier than I am.  But some men have a fetish for extremely large women…in fact unrealistically giant women, known as giantesses.  They fantasize about a woman who can hold them in the palm of their hand.  The desire male spiders have for gigantic female spiders evidently exists in some human males as well.  Though psychological triggers in the environment probably influence this fetish, there must be something deep inside the mating urge, providing the platform for it to develop in people.  This template is something we share with spiders and likely goes back to a common ancestor over 500 million years ago.

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Many men are turned on by women who are much larger than they are.  Some even fantasize about giantesses.

The association of sexual excitement with fear of being eaten is another characteristic some humans share with spiders and other creatures.  I’m 55 years old, and I thought I was aware of every sexual fetish, but I first learned about the vore fetish within the last year.  Vore is short for devour–some people are sexually excited by the thought of being eaten by their sexual partner.  I don’t really understand this fantasy.  How, for example, does one reach sexual satisfaction after they’ve been eaten?  I think maybe this fantasy has something to do with being in the warm amniotic sac of a woman’s tummy.  Or maybe some are really thrilled with the thought sex might lead to their consumption.  Nevertheless, deep down inside, humans are like spiders in more ways than we would like to admit.

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People are not as different from spiders as one might think.  Some people get sexually excited at the thought of being eaten by their mate.  It’s known as a vore fetish.

Reference:

Kuntac, Matjaz; Jonathan Coddington

“Discovery of the Largest Orb-Weaving Spider Species: The Evolution of Gigantism in Nephilia”

Plos 1  October 2009

Disjunct Populations of Western Insects Occur on Black Belt Prairies of Southeastern North America

September 4, 2017

The Black Belt Prairie region extends through Alabama and Mississippi with additional isolated patches in Georgia and Tennessee.  There is a different Black Prairie region in east Texas.  The chalky soils of Black Prairies favor grass over trees, and in the southeast they produce a mosaic of forest and prairie.  Western species of plants such as little bluestem grass grow on Black Prairie landscapes, and they attract species of insects not normally found in southeastern North America.  At least 15 species of insects that occur on western grasslands exist as disjunct populations on the Black Prairies located in southeastern North America.  This includes the white bee (Tetralonella albata)–a pollinator of prairie clover–as well as 4 species of long-horned beetles and 10 species of moths.  The red-femured long-horned beetle (Tetraodes femorataand the Texas long-horned beetle (T. texanus) feed upon milkweed.  Most of the moths are hosts on flowers in the aster family.

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Map of Black Belt prairie region in southeastern North America.  (Shaded orange.)  Although the map doesn’t show it, some isolated pockets of Black prairie occur in Georgia as well.

Bee on Dalea - Tetraloniella albata

The white bee occurs in disjunct populations in Mississippi and Arkansas.  The main population occurs from Colorado and Illinois to California.

Milkweed Longhorn Beetle (Tetraopes sp.) - Tetraopes femoratus

The red-femured long-horned beetle ranges from the Great Basin to Mexico.  Disjunct populations occur in the Blackland Prairie Region.

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Epiblema iowana–another western species found in the Black Belt prairie region plus 1 site in Florida.

A grassland corridor formerly must have connected the Great Plains grasslands with the Black Belt prairies of the southeast.  Some scientists speculate that before the last Ice Age this corridor may have existed along the Grand Prairie of Arkansas or through the Arkansas River Valley.  The Mississippi River was lower then and interspersed with lightly vegetated sandbars that allowed for insect passage between the 2 regions.  After the last Ice Age glacial meltwater expanded the Mississippi River, blocking insect passage, but a grassland corridor between the Great Plains and the southern Black Belt Prairie may have existed through cedar glades in Tennessee to Kentucky to Illinois where the Mississippi River was more narrow. Currently, the Mississippi River and forested habitat separate the 2 grassy regions.

During Ice Ages the Black Belt prairies may have served as a refuge for many species of grassland insects found in the Great Plains today.  Forests of jack pine and spruce replaced Great Plains grasslands during glacial phases.  Summers were cooler and shorter.  Species of insects that preferred grassland communities and long warm summers retreated to the Black Belt prairies and Gulf Coast grasslands of southeastern North America.  Populations considered disjunct today may actually be seed populations that replenish Great Plains insect fauna following the end of Ice Ages.

Reference:

Peacock, Evan; and Timothy Schauwecker

“Blackland Prairies of the Gulf Coastal Plain”

University of Alabama Press 2003

 

Pleistocene Oysters (Crassostrea virginica)

March 14, 2017

Before humans harvested them, oysters lived longer, grew larger, and produced denser quantities of offspring.  Scientists compared oyster shells from Pleistocene-age oyster reefs with those from Native-American archaeological sites and modern harvests.  Pre-human contact oysters lived as long as 30 years, while oysters since human colonization never live longer than 6 years.  Pleistocene oysters grew up to 10.2 inches, pre-historic oysters from Native-American middens grew to 7.4 inches, and modern oysters reach 6.1 inches.  Native-Americans harvested oysters in a sustainable way, but populations of oysters since European colonization have been reduced by over 99%, despite restoration efforts.  Pollution and overharvesting have destroyed oyster numbers.  This is unfortunate because oyster reefs are a productive natural community, providing habitat for at least 303 species that have co-evolved with oysters over the past 135 million years, ever since these bivalves first evolved. Scientists estimate the original oyster population of Chesapeake Bay was capable of filtering the entire contents of this estuary in just a few days, so they help clean the water as well.  Modern day estuaries are suffering without more abundant populations of oysters.

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Ancient oyster midden.

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Pelican in front of a Georgia oyster reef at low tide.

A representative of every species living in oyster reefs could fill a big city aquarium.  Barnacles, mussels, clams, and bryozoans attach themselves to the reefs and live out their lives filter feeding just like their hosts.  Mud crabs (Eurypanopeus depressus) graze on the algae and detritus that accumulates on the reefs and sometimes feed upon the smaller oysters.  Oyster pea crabs (Pinnotheres) depend upon reefs for their very survival. The seashore springtail (Anurida maratima), unusual salt water insects, prey on microorganisms living on the reefs.  Amphipods, worms (Polydora and Polychaetas), anemones, mites, and hydroids are commensal animals dependent upon the existence of oyster reefs.  Boring sponges (Cliona) and starfish directly prey on the oysters.

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The seashore springtail is a true insect that lives on oyster reefs.

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The depressed mud crab grazes on algae, detritus, and small oysters on oyster reefs.

Many small species of fish swim in and around oyster reefs during low tide because the structure affords protection from predators.  Species of fish commonly found in Georgia oyster reefs include in order of abundance naked goby (Gobiosoma bosci), feather blenny (Hypoblennius hentzi), skilletfish (Gobiosox strumosus), seaboard goby (Gobiosoma ginsbingi), striped blenny (Chasmodes bosguianus), oyster toad fish (Opsanus sp.), and the crested blenny (Hypleurochilus geminatus).  During high tide larger fish such as sheepshead, black drum, and croakers move in and feed upon the shellfish and smaller fish living on the reef.

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The naked goby is the most common fish living in Georgia oyster reefs.  They feed upon worms, crustaceans, and dead open oysters.

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The skillet fish clings to oysters with its sucking mouth.

Land vertebrates forage oyster reefs during low tide.  Raccoons and wading birds find many a meal on the reefs.  Oyster catchers (Haematopus palliatus) specialize on feeding upon the oysters and other bivalves growing here.  Even boat-tailed grackles exploit oyster reefs–they eat the amphipods and pea crabs crawling over the reef.

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The American oystercatcher thrives on oyster reefs.

Oysters have a complex life cycle.  They expel sperm and eggs into the ocean water, and when these sex cells meet by chance they form larva.  (Oysters change sexes, so that males become females and vice-versa.  Some individuals are hermaphroditic  and expel sperm and egg at the same time.)  The larva lives in the zooplankton until they develop a foot.  The oyster senses pheromones from other oysters on a reef and will attach its foot to the structure where it will remain for the rest of its life, filter feeding upon diatoms, dinoflagellates, inorganic particles, bacteria, and marsh plant detritus.

Oyster reefs also have life cycles.  When oysters begin colonizing an area it is known as the clustering phase.  Oysters attach to each other and on old dead oyster shells during the accretionary stage, building reefs.  Eventually, oysters reach a vertical limit and start building the reef horizontally during the senescent phase.  Large reefs block sediment and shell debris carried by tidal currents and this action can create islands.  Little Egg Island in the middle of the Altamaha River mouth is an example of an island created by an oyster reef.

References:

Bahr, Leonard, William Larsen

“The Ecology of Intertidal Oyster Reefs of the S. Atlantic Coast: A Community Profile”

U.S. Geological Survey 1981

Lockwood, R.; K. Kusperck, S. Bonanani, and Gratt, A.

“Reconstructing Population Demographics and Paleoenvironment of Pleistocene Oyster Assemblages: Establishing a Baseline for Chesapeake Bay Restoration”

North American Paleontological Convention 2014

Rick, Turbin; et. al.

“Millenial-scale Sustainablity of the Chesapeake Bay Native American Oyster Fishery”

PNAS 2016

Wharton, Charles

The Natural Environments of Georgia

Georgia Department of Natural Resources 1978

The Amazing Fishing Spiders (Dolomedes sp.) are Greater than Jesus

March 6, 2017

Fishing spiders are more amazing than the so-called “amazing” Spider-Man. Fishing spiders really exist and have persevered for millions of years, while Spider-Man is a fictional character created by Steve Ditko in 1962.  Fishing spiders are greater than Jesus Christ because there is proof they can walk on water whereas there is little evidence the semi-fictional legend even existed.  The story of Jesus walking on water was invented by the unknown author of Mark, the oldest New Testament gospel, and it was plagiarized by the unknown authors of Matthew and John.  Their stories were so ridiculous they were too ashamed to attach their real names to them. Instead, they forged other people’s names to their scrolls, hoping to avoid ridicule.  Jesus could not walk on water.  The laws of physics as we understand them in the present day demonstrate he would sink.  But fishing spiders use hairs on their legs to stride on the surface tension of water, a feat I’m sure Jesus could not actually accomplish in real life.

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The striped fishing spider (Dolomedes scriptus) is large, growing up to 3 inches long.

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Fishing spider with dinner.

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Fishing spiders walk on water…like Jesus Christ allegedly could do.

Fishing spiders mostly hunt aquatic insects on top of the water, but they can also dive underwater to seize minnows, tadpoles, frogs, and crayfish.  They carry an air bubble with them attached to the hairs on their body when they dive underwater.  Their venomous fangs quickly deliver a mortal bite to their prey and the buoyant air bubble carries them back to the surface.  Fishing spiders are able to sense their prey the same way web-spinning spiders do.  Spiders detect vibrations made by insects captured in their web; fishing spiders feel vibrations made by prey moving through water.  Fishing spiders don’t need webbing to sense prey because water serves as their web.

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An Okefenokee fishing spider (D. okeefenokensis) with a crayfish.  I wonder how they get past the claws. They also prey on small frogs.

There are 9 species of fishing spiders native to North America in the Dolomedes genus.  8 of them are aquatic–the lone exception lives in trees.  The Okefenokee fishing spider lives in south Georgia and Florida but there are several species that occur as far north as southern Canada.  Striped fishing spiders were able to expand their range north following the end of the last Ice Age.  It would be interesting to know how long it took for this dispersal to take place.  It would also be interesting to know the evolutionary relationship between the 9 species and other closely related spiders.  It’s likely they evolved from terrestrial ancestors.  Alas, as far as I can determine, scientists have not yet studied Dolomedes genetics.

 

The Continent Conquering Human Flea (Pulex irritans)

January 8, 2017

A flea can jump 160 times its own body length–the equivalent of a 6 foot tall human jumping the length of over 3 football fields.  Most of the known 2500 species of fleas are ectoparasites that use this phenomenal jumping ability to leap from the ground to an host or from one host to another.  Scientists believe the human flea was originally a parasite of wild cavies, species of rodents native to South America.  9,000 years ago, South American Indians began domesticating a species of cavy, either Cavia tschudii or C. aperearesulting in the well known household pet, the guinea pig ( C. porcellus ).  The domestication process may have been instigated by the cavies rather than humans.  Cavies likely were attracted to the shelter of human dwellings where they fed on vegetal kitchen scraps.

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The human flea expanded to many times its size. Their toes serve as a lever that helps them jump many times their body length.

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The guinea pig is thought to be the original host of the human flea.  Fur traders spread the flea from South America to North America and across the Bering Strait to Asia.

By 7,000 years ago, guinea pigs were commonly raised in many South American Indian households.  Maintaining a population of 20 individuals yielded about 12 pounds of meat per month, so they served as a valuable source of food, lessening the need to hunt wild animals.  Fleas from guinea pigs made the leap to man and from there they conquered 5 continents.  According to the lead author of the below referenced study, they advanced through a “step by step gift exchange of furs from South to North America and over the Bering Strait.”  Fur traders slept on their skins and left flea larva living in the detritus of flea feces, dried blood, and human skin flakes that accumulated on their unwashed beds.  After mature fleas feed on blood, they lay their eggs in this detritus.  Human fleas were carried along Asian trade routes and they conquered Egypt by 6000 BP.  The Roman armies carried fleas from Egypt to southern Europe, and the Vikings may have carried fleas from North America to northern Europe.

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Roman legions and Vikings carried fleas with them to Europe.  Bubonic plague carried by fleas from rats to humans and back depopulated Europe.  Fleas were responsible for far more deaths than Romans and Vikings.

Human fleas made a colossal impact on human history.  Fleas jumping back and forth between rats and humans spread bubonic plague, a disease that killed an estimated 30%-60% of the European population during the years 1347-1350.  Much of Europe reverted back to wilderness following this depopulation.  The Romans and the Vikings thought they had conquered the world, but they are long gone.  Human fleas are still here and can be found in just about every hotel, even in the finest, most expensive chains.

Reference:

Panagiotakopulo, Eva; and Paul Buckland

“A Thousand Bites–Insect Introductions and Late Holocene Environments”

Quaternary Science Reviews November 2016