This species of assassin bug from Malaysia apparently carries its victims on its back in order to camouflage itself from predators. More via The Ark in Space:
Once its potential lunch has been incapacitated the assassin bug injects it with an enzyme. This liquefies the insides of its prey allowing the assassin bug to suck out their innards. Yet death is not the end for these hapless insects. Their exoskeletons will be put to further use as a form of armor or possibly scent masking camouflage.
Image of Lord Howe stick insects via Rod Morris. Ball’s Pyramid image via
The Lord Howe stick insect, Dryococelus australis, is a critically-endangered species of stick insect that was endemic to Lord Howe Island. The creature’s only-known home during the 20th century was Lord Howe Island. During the 1900s, the island suffered an invasion of black rats after a shipwreck. The rats feasted on the unique stick insects until there were no more to be found on Lord Howe Island. More via NPR:
[O]ne day in 1918, a supply ship, the S.S. Makambo from Britain, ran aground at Lord Howe Island and had to be evacuated. One passenger drowned. The rest were put ashore. It took nine days to repair the Makambo, and during that time, some black rats managed to get from the ship to the island, where they instantly discovered a delicious new rat food: giant stick insects. Two years later, the rats were everywhere and the tree lobsters were gone.
Totally gone. After 1920, there wasn’t a single sighting. By 1960, the Lord Howe stick insect, Dryococelus australis, was presumed extinct.
However, a tiny population of the stick insects was rediscovered on a nearby Jurassic-looking island called Ball’s Pyramid. Due to the topography of the island, it afforded only a diminutive space for the stick insects to cling on to.
Some climbers scaling Ball’s Pyramid in the 1960s said they’d seen a few stick insect corpses lying on the rocks that looked “recently dead.” But the species is nocturnal, and nobody wanted to scale the spire hunting for bugs in the dark.
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[T]wo Australian scientists, David Priddel and Nicholas Carlile, with two assistants, decided to take a closer look. From the water, they’d seen a few patches of vegetation that just might support walking sticks. So, they boated over. … They crawled up the vertical rock face to about 500 feet, where they found a few crickets, nothing special. But on their way down, on a precarious, unstable rock surface, they saw a single melaleuca bush peeping out of a crack and, underneath, what looked like fresh droppings of some large insect.
Where, they wondered, did that poop come from?
The only thing to do was to go back up after dark, with flashlights and cameras, to see if the pooper would be out taking a nighttime walk. Nick Carlile and a local ranger, Dean Hiscox, agreed to make the climb. And with flashlights, they scaled the wall till they reached the plant, and there, spread out on the bushy surface, were two enormous, shiny, black-looking bodies. And below those two, slithering into the muck, were more, and more … 24 in all. All gathered near this one plant.
They were alive and, to Nick Carlile’s eye, enormous. Looking at them, he said, “It felt like stepping back into the Jurassic age, when insects ruled the world.”
They were Dryococelus australis. A search the next morning, and two years later, concluded these are the only ones on Ball’s Pyramid, the last ones. They live there, and, as best we know, nowhere else.
How they got there is a mystery. Maybe they hitchhiked on birds, or traveled with fishermen, and how they survived for so long on just a single patch of plants, nobody knows either. The important thing, the scientists thought, was to get a few of these insects protected and into a breeding program.
You can read more at NPR about the challenges that faced conservationists in removing a handful of stick insects for a captive breeding program, the difficulties in getting these remarkable creatures to thrive and breed in captivity, and the challenges associated with reintroducing them to Lord Howe Island.
Video: Lord Howe Island Stick Insect hatching
Video: ABC news story on Lord Howe Island Stick Insect
Image: A fisherman pulls out a glob of slime, which is being produced by his catch of hagfish as a defense mechanism. Since they’re considered a delicacy by some cultures, there is a fishery for hagfish. Image via dirtsailor2003 on Flickr
Hagfish might be disgusting creatures, but they’re still fascinating. Hagfish, which are sometimes called slime eels, are eel-like primitive jawless fish, which use their exceptional ability to produce copious amounts of slime as a defense mechanism. The video below illustrates how “hagfishes are able to choke their would-be predators with gill-clogging slime.”
Sadly, however, gastric-brooding frogs are probably extinct. Their unusual mode of reproduction is known only from some photographs or written accounts of observations, so the chance exists that no other living human will be able to witness one of nature’s most extraordinary events. I don’t believe that video exists showing the female frogs give birth through the mouth. However, if you know of video, then please share the information.
The reason(s) for the disappearance of this species remains unknown (Tyler and Davies 1985b). Populations were present in logged catchments between 1972 and 1979. Although the species persisted in the streams during these activities, the effects of timber harvesting on this aquatic species were never investigated. Its habitat is currently threatened by feral pigs, invasion of weeds (especially mistflower Ageratina riparia), and altered flow and water quality due to upstream disturbances (Hines, Mahony and McDonald 1999). However, from what is known from similar declines and disappearances elsewhere in the world, the disease chytridiomycosis must be suspected.
However, a new, efficient automated system, which seems to be exceptionally accurate, may locate any gastric-brooding frogs that might still be in existence by listening for them. Via ABC Science Online:
Citizen science and computer software are being harnessed as a low-cost way of tracking Australian native bird species in order to monitor environmental change.
The Queensland University of Technology software is also being used on the frontline in the battle to stop cane toads marching on to Groote Eylandt in the Northern Territory.
The program uses automatic acoustic sensors, voice recognition technology and expert birdwatchers to reduce the number of hours ecologists have to spend in the field observing wildlife.
Researcher Jason Wimmer, a PhD student, says experiments show the automatic system is actually more effective in capturing the presence or absence of birds than standard observation.
Under the project, sensors are placed in the bush to record environmental sounds that are then transmitted to an online digital library.
To overcome the need to sit through hours of recordings to listen for bird sounds, Wimmer and his team developed a software program to filter the audio and identify potential bird noises.
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Wimmer says the potential of the automatic system was highlighted by a 2 am recording of the call of a rarely sighted species, Lewin’s Rail (Lewinia pectoralis).
“That is just one example of the impact this system can have,” he says.
The system is also going to be used to find the Gastric Brooding Frog, a native frog that has not been seen for 20 years with sensors to be placed in the Conondale Range, north-west of Brisbane.
Wimmer says the technology is also helping protect native quolls on Groote Eylandt from eating cane toads. The island is currently free of cane toads.
“We’ve put in sensors as an early-warning system for cane toads,” he says. “The sensors are all 3G (mobile phone)-based and timed to record and analyse data automatically.”
The sensor turns on every 30 minutes and if it hears the distinctive canetoad calls is programmed to send SMS alerts to various people.
To prevent digestive juices from destroying the eggs and tadpoles, both the eggs and tadpoles produced or were associated with a “substance [that] had the ability to turn off the production of hydrochloric acid in the [frog's] stomach.” After some time, developing within their mother’s stomach, fully-formed froglets emerge from the mother’s mouth (though some accounts note that one of the species gave birth to tadpoles — not fully-formed froglets). More on the reproductive habits of Rheobatrachus silus via the IUCN:
Females brood young within the stomach and give birth through the mouth (Tyler and Carter 1982). Fertilized eggs or early stage larvae are presumably swallowed by the female and complete their development in the stomach (Tyler and Carter 1982). The number of eggs in gravid females (approximately 40) exceeds the number of juveniles found to occur in the stomach (21-26) (Tyler 1989). It is not known whether or not the excess eggs are digested by the female or whether or not they are simply not swallowed (Tyler 1989). The production of hydrochloric acid in the stomach of the female ceases during brooding (Tyler et al. 1983). Tadpoles develop in a manner similar to the aquatic tadpoles of other species though, as they feed off egg yolk, the labial teeth are absent and the intestines form at a later stage of development (Tyler 1989). After 6-7 weeks the females give birth to up to 25 young (Tyler and Davies 1983a). Young emerge from the female’s mouth as fully formed frogs and after four days the digestive tract returns to normal and the female recommences feeding (Tyler and Davies 1983b). Ingram (1983) reported minimum brooding periods from two individuals of 36 and 43 days and suggested that the duration was such that females were unlikely to breed twice in one season.
More on the reproductive habits of Rheobatrachus vitellinus via the IUCN:
It is an aquatic species largely restricted to the shallow section of fast-flowing creeks and streams in rainforest. It is one of only two known species to brood its offspring within its stomach. Females deposited their eggs, and then swallowed them. While in the stomach, tadpoles excreted some form of enzyme that inhibited the female’s gastric digestion, and then proceded to develop into fully formed froglets. The froglets were then regurgitated through the female’s mouth.
In the gastric brooding frogs, Rheobatrachus silus and Rheobatrachus vitellinus, brooding of eggs and/or larvae occurs in the stomach of the female; in one species, froglets emerge after metamorphosis, whereas in the other species, tadpoles are released by the female. Development in those frogs is supported entirely by yolk contained in the eggs (Crump, 1995; McDonald and Tyler, 1984). In contrast to Rhinoderma rufum, male Rhinoderma darwinii brood their tadpoles in their vocal sacs until metamorphosis occurs (Crump, 1995).
I couldn’t find information on whether the females of either species of gastric-brooding frogs stop feeding during gestation. However, it seems that more eggs were typically produced and swallowed than the number of froglets that were actually hatched or regurgitated by the female, so either the females digested some or all of the eggs, or the tadpoles and froglets consumed some or all of the unfertilized eggs while in the stomach, or perhaps some combination of both behaviors existed. There must have been some mechanism in place to utilize or dispose of unfertilized or bad eggs. Perhaps, the tadpoles practiced cannibalization as well. Tadpoles are known to practice cannibalism.
Video (this video plays automatically): In this video, a Southern gastric-brooding frog swims about a tank, and there’s a still image showing a froglet in adult’s mouth. Via ARKive
However, one species of frog, still in existence, uses a somewhat similar mode of reproduction to the gastric-brooding frogs of Australia. Darwin’s frog (Rhinoderma darwinii) is a species that’s “endemic to the austral forest of Chile and Argentina.” The species is considered vulnerable, and its population is in decline. Via the IUCN:
Recent surveys within the range of Rhinoderma darwinii in Chile reveal that some populations (including those in national parks and other preserved areas) have disappeared entirely (M. Crump and A. Veloso pers. comm.). In other areas, the density of frogs is much lower than 10 or 20 years ago (M. Crump pers. comm.). Forestry operations have destroyed large areas where northern populations were found. However, it was still abundant in at least some southern Chilean localities in 2003; indeed, it appears that the species reaches its highest densities in regions of the Archipelago, where habitat disturbance is minimal (M. Crump pers. comm.). In Argentina, this is a scarce species and appears to have declined at one site (Puerto Blest, Río Negro Province) during the past 50 years.
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In the north, the main threats are drought and pine forestry, while in the south it is clear-cutting of forest. Declines that have taken place in suitable habitat could be the result of other threats, such as climate change or disease (possibly chytridiomycosis, although this normally impacts species that are associated with water, and it has not previously been reported from Chile).
This species of frog exhibits a highly unusual form of parental care in that the tadpoles spend part of their life developing in the vocal sac of their father, where they ‘hitch a ride’ to a pool of water in their father’s vocal sac where they complete their development from the tadpole to the frog form.
Video: In this video, it’s possible to see the movement of tadpoles within the vocal sacs of the Darwin’s frog.
Video (this video plays automatically): A male Darwin’s frog releases fully-formed froglets from his vocal sac. Via the BBC.
This species of assassin bug from Malaysia apparently carries its victims on its back in order to camouflage itself from predators. More via The Ark in Space:
