The freaks among us. Stranger Than Fiction: Considerations on the quirks of living things. The OddBalls

Transcription

1 Stranger Than Fiction: Considerations on the quirks of living things Most biologists and paleontologists look at life in a very conservative way it is the normal organisms that we think about the most when we think of life But there are many organisms living today that are really strange in form and/or behaviour. The OddBalls By looking at some of the oddballs we can gain an appreciation of the products of evolutionary change in response to the interactions of organisms with their environment through time. The freaks among us Ever Notice That The Flamingo Eats Upside Down? Few of the examples presented here will be discussed in conventional courses in biology or geology this is partly because they deviate from the concept of evolution as a straightforward process. But this is not a conventional course, right? So here we go One might think this is an awkward way of feeding, but it works!

2 Mysterious Circular Scars on Whales: CAUSE? The Cookiecutter Shark Cookiecutter shark rams into victim, twists its body right around Pygmy Sperm Whale Cuvier s Beaked Whale Gouges out a plug-like piece of flesh (thickness of plus up to twice the diameter of the mouth). The shark then may create oral suction with its thick fleshy lips, large tongue and strong throat muscles to hoover the piece of flesh out of the prey's body. Victims: Tuna, elephant seals, dolphins, whales, swordfish - plugs of fish and marine mammal flesh have been recovered from the Cookiecutter s stomach. Range: Widespread in Northeastern Atlantic, Mediterranean Sea The Art of Deception The Art of Deception Members of a certain group of freshwater clams (unionid bivalves) possess mantle flaps that mimic small fishes. Predatory fishes such as bass attack the mantle lure, rupturing larva-holding pouches that lie between the mantle flaps.

3 How to maximize your chances of being mugged by a fish. The lure can even move! Different Lures for Different Prey Amazingly, different species of this clam group mimic different species of prey (and not just fishes) Broken-rays mussel (Lampsilis reeveiana) James River in Greene County, Missouri For example, the freshwater clam Villosa iris has mantle flaps that mimic a crayfish. Adaptations such as these are the product of interactions of a multitude of generations of organisms with their environment and other organisms. In this case, each species of these freshwater clams has evolved to mimic a desired prey item of predatory fishes in their respective river systems. crayfish mantle flaps Real Crayfish Some of the clam larvae released from the marsupia by the strike attach to gills of attacker. Baby Clam Nursery The Kiwi: The Labour-Intensive Bird The clam larvae benefit from the safety of their host s gills. After some development, the larvae drop off from the host s gills and settle onto the stream floor, where they mature into adult clams. Another benefit of this reproductive strategy: larvae can be dispersed over a large area, without any effort on the part of the clam. Note: Ratis means "raft" in latin - a boat without a keel (don t need one because they are flightless)

4 Continental Rafts Modifications from flying ancestor From a common (Presumably large) ancestor the different ratite species evolved independently on different landmasses after the split-up of Gondwana approximately 80 million years ago. Ostriches in Africa Rheas in South America Emus and Cassowaries in Australia Elephant Bird (extinct) In Madagascar Moa (extinct) and Kiwi in New Zealand Major Changes in Body Form: 1. Loss of sternum otherwise used as an attachment for strong flight muscles 2. Loss of asymmetry in feathers (no need for aerodynamic design) Important Ratites The Runt of the Family In contrast, the Kiwi is about as large as a cat. The Kiwi is an oddball among the ratites. Most ratites are fairly large (e.g. ostriches, emus, rheas) and are presumed to have originated from a large common ancestor. Reduction in body size is thought to have been a good adaptation for burrowing.

5 YOUCH! The Fine Art of Zombification Stage 1: In the process of grazing vegetation for food, an amber snail (Succinea) inadvertantly ingests bird faeces. Some of this faeces can contain eggs of the flatworm Leucochloridium. One feature that the Kiwi has retained from its ancestor is its egg size A single egg can be 20 % of the body volume! Stage 2: Worm larvae hatch and infect the digestive gland of the snail. The larvae form large, sausage-like, colour- striped swellings, one or more of which can extend into the snail s tentacles. These swellings rhythmically extend and contract within the tentacles, making the tentacles a pulsating appearance Stage 3: Tentacles now resemble caterpillars in colour and movement. Birds attack the tentacles which now cannot be withdrawn due to their size.

6 Watch Your Tongue! Stage 4: Inside the bird's digestive tract the larvae change into adults A major pest of sea bass and sea bream in the Aegean Sea is the isopod crustacean called Ceratothoa oestroides Stage 5: Adult flatworms lay eggs in bird s digestive tract, completing the cycle. Females of isopod crustacean Ceratothoa oestroides invade a fish s mouth, devouring its tongue, or promoting the loss of the tongue by clamping its legs around it and restricting blood flow. The much smaller male generally resides in the cheek of the fish. Too Late It s Gone! Typical Life Cycle of a Hollywood Alien The isopod then acts as a replacement tongue, which the fish can use to grip and swallow prey The parasites can feed on the host s blood or mucous for as long as the fish is alive.

7 The Body Snatchers Are Among Us "I'd love to talk now, but I find I have a mushroom sticking out of my throat X files: Firewalker Variation of the Chestburster: Alien Fungus In the real world, parasitic fungi (although not siliconbased) are widespread. Most of us don t notice them because they, and their hosts, are somewhat small. Fungal parasitism of insects are no less dramatic when we look at them from an insect s point of view. A number of fungal species will establish themselves in insect hosts, gaining nourishment from the internal (and later, external) tissues of the host. Mind Controlling Body Snatchers Parasite: Genus Tomentella 1. The stink ant inhales a microscopic spore of Tomentella 2. Inhaled fungal spore becomes seated inside the ant s head 3. Fungal threads (hyphae) penetrate brain, ultimately controlling the behaviour of the ant One type of fungus, Tomentella takes parasitism to the next level: MIND CONTROL The Victim: The Stink Ant Pachycondyla (Megaponera) analis Habitat: Rainforest of Cameroon, West Central Africa Life Habits: Forest floor dweller in leaf litter, feeds on termites Fungal spore and hyphae Head of stink ant

8 Ant Zombification Chestburster Stage For the first and only time in its life, ant leaves the forest floor and begins a long climb up the nearest tree. At top of tree, the ant, completely spent, clamps mandibles to a leaf or stem of the tree and dies. Fungus continues to consume nerve cells and remaining soft tissue of ant. Until Until After approximately two weeks, one or more fruiting bodies emerge(s) from the ant. Spores are released into the wind and rain down to forest floor to infect other ants. Closer To Home. Yes, there are also other mind-controlling parasites that many of us have a good chance of meeting without us even knowing. Toxoplasma gondii Recent work by researchers at Oxford University have noted that Toxoplasma, a common parasite in domestic cats, can occur in up to 35 % of rats in a rat population. Rats are infected by Toxoplasma by inadvertant ingestion of cat faeces. Rats are usually very wary and are experts at detecting signs of danger in their environment. The Cycle is Completed It has been found that Toxoplasma resides dormant in within the brains of the rats for long periods of time. When the parasite becomes active again, it is capable of overriding the rat s usually acute awareness of danger in its surroundings, making the rat easy prey for cats. The parasite can then live happily in the cat s gut until it is expelled in faeces. So the parasite has effectively used the predator-prey relationship of its hosts to ensure the survival of its offspring. (Note: Toxoplasma is relatively common in human brains too, but is held dormant by our immune system)

9 The Botfly Adult Larvae generally feed on carrion but occasionally parasitize living animals (yes, including humans). Larva (note barbs designed to prevent the larva from being dislodged from its host s flesh. Typical Range of Human-Infecting Botflies: Mexico, Central and South America (It s good to be Canadian, huh?) One Good Reason For Treating a Wound Early The botfly tail is a breathing tube, which can lift up, periscope-like, just above the surface at the point of entry. As it develops, the larva wriggles visibly and painfully under the skin. Removing the botfly is relatively simple - one remedy involves applying bacon to the breathing hole, so the botfly has to burrow up through it for air. Not all that relevant to the course, but I thought you d like to know. Crohn s Disease / Colitis: A 20th Century Phenomenon? Description: A chronic form of inflammatory disease of the gastrointestinal tract. Usually affects the lower small intestine or the colon, but can affect the entire gastrointestinal tract (colitis only affects colon). Symptoms: Abdominal pain, diarrhea, rectal bleeding, weight loss, fever Causes: Not presently known but possibly the result of the body's immune system reacting to a virus or a bacterium by causing ongoing inflammation in the intestine Treatment: Drugs (usually containing mesalamine - an anti-inflammatory), nutrition supplements, surgery, or a combination of these options. Some Interesting Observations on Crohn s Disease / Colitis No record of Crohn s Disease before 1930s First records of Crohn s Disease in U.S. discovered in upper class citizens of New York City (unknown among lower class until 1970s). Practically unheard of in very poor Third World countries. In Japan and Korea (two countries that have quickly gone from poverty to wealth are experiencing epidemics of the Crohn s and colitis). Crohn s sufferers often prone to other ailments associated with unusual reactions from immune system. With increase used of anti-worm medicines, Crohn s-like symptoms are occuring more frequently in livestock!

10 An Interesting Survey in Venezuela (Neil Lynch) Upper class (with running water and toilets): 43 % with allergies 10 % with light infections from intestinal worms Lower class (slums with no running water): 22 % with allergies 20 % with infections from intestinal worms Venezuelan Natives no allergies detected 88 % infected by intestinal worms Note possible implications for U.S. example (upper classes got rid of their parasites first) How Does It Fit In The Big Picture? 1. Hominids (humans and close relatives) have been living (and coevolving) with parasites for over 5 million years. 2. Hyperhygiene, Crohn s Disease and colitis only widespread since early 20th century. Parasite s Survival Strategy: 1. Reduce strength of attack by immune system (but not completely) 2. Mellowing of immune system allows bacteria and viruses to be held in check but allowing parasitic worms to survive 3. Through reduction of strength of attack by immune system, a host can live with some parasites without being harmed. So.Without the moderating effect of parasites, individuals with a hyperactive immune system have a greater tendency for gastrointestinal attacks to run AMOK! Should we really be surprised? Parasites Sometimes Get Lost Tapeworms generally first mature in a cyst in intermediate hosts such as cows or pigs before being passed to humans. If their eggs end up in a Human body they will proceed to make a home anyway. Accidental infestation of unusual hosts, is usually disadvantageous to the parasite. But accidents such as these that can lead to new habits, and ultimately new species, if the new conditions prove beneficial to the survival of the parasite. What do these oddball organisms say about evolution and biospheric dynamics? The direction of evolutionary change can be very unpredictable- the appearance of new innovations in body form and function are largely dictated by circumstance and what works. Biospheric processes interact in a complex manner both internally and externally (i.e. with other spheres of the Earth System), leading to interesting evolutionary consequences. Depending on how you look at them, you can think of organisms such as parasites as primitive or the most highly evolved organisms on Earth (it all comes down to perspective- let s change some of our perspective). To appreciate interactions in the Earth System, we have to always be mindful of the Big Picture - this is important!

11 END OF LECTURE