biology zoology blog benno meyer rochow invasive species

Wanted and Unwanted Immigrants

And I don’t mean humans

A few years ago the “killer bee invasion” was feared in the USA; now it’s the “murder hornet”. I wanted to use this example for a talk I had planned to give at a conference about “invaders”, animals that arrive from somewhere and stay (or die). I also wanted to talk about the confusion and uncertainties that exist with regard to terms like autochthonous, indigenous, endemic, native, etc. It really isn’t easy to say with certainty if a species has evolved in one location or has got there from another place from where it may ultimately have disappeared and, if so, whether the colonization was the result of an accidental transport by rafting, aided by the wind or ‘hitchhiking’ on birds. I got interested in this, because on Hachijojima, a volcanic Pacific island 300 km south of Tokyo, inhabited by people who until ca. 70 years ago had their own language, I noticed a multitude of species that shouldn’t have been there: rats, ferrets, cats, etc.

But what about the non-mammalian vertebrates: two snake species; one toad and 3 species of frogs (American bullfrogs, introduced after the 2nd World War, are probably now no longer residents on the island). How did they get there? Snakes were presumably deliberately introduced to kill mice. Attempts to eradicate the Japanese toad exist, but I think it’s already too well established. Then there is the firebelly newt, a harmless species that seems to have arrived in the early 1970s and (as we were able to show by molecular studies) from one place of origin in Japan with all individuals on the island related to each other. Maybe children (or a teacher) took some eggs or a few adults from Shikoku as pets to Hachijojima and released them. The newts are now everywhere, but nobody minds as they’re harmless and quite cute.

It’s a different matter with millipedes, thousands, nay millions of them! Most people hate them and say they stink; others see them as a nuisance as their crushed bodies make the road slippery and only a few gardeners tolerate (or even like them) as they do not attack healthy plants or fruit, but shredder dead plant material and help recycling it. They are known to have come from Taiwan in 2002.  Also, from Taiwan are the now widely distributed whip scorpions. And another immigrant from Taiwan was the terrestrial leech that I readily found when looking for it (it had never before been seen by locals or scientists who had been searching for it: probably because of its similarity to earthworms it was always overlooked). Unsurprisingly, two species of nematode worms that had hitched a ride as parasites in the millipedes were also recorded for the first time. A species of earthworm known from India turned out a new find and for the first time for Japan a Canadian freshwater limpet was recorded from Hachijojima by me. The freshwater crab Geothelphusa dehaani (a non-native) must have been introduced, because people eat it; fireflies, too, were deliberately introduced, but to attract tourists to the island. Slimy and alien earthworm-eating planarian flatworms, however, (I collected 4 species) would be less attractive.

But how come all these diverse alien creatures (surprisingly many from Taiwan) can survive and thrive on Hachijojima? The main reasons are:  Hachijojima even in winter does not experience frost; there is a lack of predators and Hachijojima has had a number of volcanic eruptions, some thousands of years ago, the last one (involving only the northern region of the island) 330 years ago. Such upheavals lead to species extinctions and create ‘spaces’ for new introductions. Finally, the surprising variety of habitats on the island meant that there are niches for a large number of alien arrivals. And they, in turn, allowed me to find “my niche” as a keen observer of Nature and her inhabitants while on this wonderful island!

© Dr V.B. Meyer-Rochow and, 2020.
Unauthorized use and/or duplication of this material without express and written permission from this site’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to V.B Meyer-Rochow and with appropriate and specific direction to the original content. 

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Spots or Stripes

Which is better?

This is the question I’ve never been able to answer correctly when going shopping to buy a blouse or a jacket with my wife. If I’d say the spots look nice, she’d reply, but what about the stripes? If I then say the stripes look even better, I get to hear “but they make me look fat”. If I then suggest a patchy kind of pattern, I get told that I’m of no help. Can animal coat patterns help in cases like these? Let’s examine.

Dots and spots are surprisingly common amongst predatory animals and the leopard immediately comes to mind. Leopard, ocelot and jaguar need to approach their prey unseen and during the day in or under trees, the changing patterns of shaded and sunlit patches (caused by the movement of leaves and vegetation due to the wind) renders them almost invisible. Hunting at night under moonlight would undoubtedly make it even more difficult to see them. The cheetah is also spotted, but does not live in the jungle or amongst dense vegetation and hunts during the day. Why isn’t the cheetah sand-coloured like a lion. Hyenas also have spots, but often they don’t even hunt at all; they steal the food from others.

Not all cat predators with spots are big: some smaller ones like housecats and the Australian quoll have spots, too. But tigers always have stripes, mostly vertical ones that is. It certainly makes it more difficult to spot a tiger when it is prowling around in high grasses.  It’s probably correct to say that dark and lighter spots or vertical stripes are a form of camouflage allowing a predator to approach its prey more easily. However, even prey may have spots or possess stripes. Fallow deer and, of course, bambis have spots, but the bovid species ‘bongo’ and the small antelope ‘zebra duiker’ possess vertical stripes just like zebras. The stripes of the latter, however, are not vertical on the legs but horizontal. Horizontal stripes along the body are typical of wild piglets and young tapirs, and even emu chicks, but would that help them to remain undetected? One should think that vertical stripes would be a better camouflage.

Snakes and lizards are long and slender and that is often amplified by horizontal lines along the body and tail. This would certainly make sense if there weren’t these crass exceptions: coral snakes and sea snakes are vertically striped, possessing red or yellow bands on a black background (or black stripes on a yellow or reddish background) which does not render them cryptic, but highly visible. But is it wise to be seen, to be recognized? I suppose if you are venomous and can defend yourself (and the attacker does not die, but would remember to leave that stripy fellow alone) it would be an explanation. To explain similar body colour patterns, Batesian and Müllerian mimicry come to mind. The skunk’s black and white coat has a similar message: ”I’m not an easy prey; don’t you remember that nasty lesson I taught you the last time you tried?” Most likely the immensely colourful spots and stripes of many tropical and venomous frogs and the black and yellow spots of salamanders are warning colorations too.

And under water? An enormous variety of colours, spots and stripes  –  but no single “unifying” rule. The most gigantic fish, the whale shark, has spots. But so have many puffer fishes and tiny box fishes, for example Ostracion cubicus. Freshwater fish like trout may have spots, but also some skates and the catfish Synodontis negrita, too. Another catfish, the slender Plotosus lineatus, has horizontal stripes, but many open water species and the cryptic moray eel Gymnomuraena zebra have vertical stripes. Many  tropical angel fishes have horizontal stripes. Some cichlids and the lionfish Pterois sp. have both spots and stripes. And the reason for this piscine kaleidoscope: the flickering and constantly moving shady and lit patches created by the waves and the movement of the water above (plus the coral habitat, rocks and bottom substrate). Does this knowledge help our lady (see the beginning) to decide whether to choose the spots or the stripes?  With clothes and women, you’ll never have a satisfactory answer.

© Dr V.B. Meyer-Rochow and, 2020.
Unauthorized use and/or duplication of this material without express and written permission from this site’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to V.B Meyer-Rochow and with appropriate and specific direction to the original content. 

biology zoology blog benno meyer rochow blue

Being Blue is Beautiful but Difficult

Feeling blue is not so nice but easier

Blue is undoubtedly the most pervasive colour on our “Blue Planet”: the sky is blue (well, most of the time during the day), the sea is blue (unless polluted or full of green plankton), mountains and forests are (at least in the paintings of Higashiyama Kaii) and even horses can be blue (witness Franz Marc’s beautiful creations). However, when it comes to blue coloration in animals we have to admit that blue is quite a rare colour. As a child I often visiting the local zoo with my grandfather. I must have been really lucky, because I always stopped at the cage with a huge male mandrill Mandrillus sphinx, a monkey with a frighteningly bright red and blue nose as well as behind. The males of this African species belong to one of the few mammalian species to display bright red and blue coloration. And he does all that with a total lack of red and blue pigments, because blue pigments (with perhaps some very few exceptions like those described from so-called cyanophore cells in the skins of callionymid fishes) are unknown from vertebrates. By the way, do not believe when you find in the internet statements like, for example, the green colour in many frogs is created by yellow and blue pigments. There are no blue pigments. But if no blue pigments are there, but some vertebrates do display blue coloration, how come they are blue? And for what reason would any animal want to be blue in the first place? (That’s something for another blog). —>—>