Insects that Scampered or Clambered into Amber

On purpose or unplanned?

I once sent my children to school with a big apple that was inside a glass bottle with a narrow neck. I told my children to show it to the teacher and ask her how the apple got into the bottle. The teacher said to them that your father is a scientist and he probably knew how to carefully remove the bottom of the bottle and stick it on again once he’d put the apple inside. That, of course, hadn’t been how I’d done it (I had fastened a bottle facing downward, lest water got in, over a tiny apple still on the tree, before it got big). What this has to do with amber and insects inside it? Well, how did they get there?

Amber is used in expensive jewelry, but it’s not a stone or mineral, but the hardened resin that had oozed out of conifer trees like pine and spruce millions of years ago. What interests biologists are their frequent inclusions, primarily arthropods like mites, spiders, centipedes and insects. But even bigger animals like frogs, lizards have been recorded. The oldest ambers with inclusions are those 130 million year olds from Lebanon, while those from Myanmar, known as Burmese Ambers and famous for their biological inclusions, are considered to be approximately 100 million years old. The famous Baltic Amber, used in the “Amber Room” celebrated as the “Eighth Wonder of the World” (the whereabouts of which are still lost), dates back to 34 – 48 million years ago and also contains numerous insects present at that time in Nordic forests. What has been puzzling biologists, and especially entomologists, is the presence of so many aquatic insects in the amber and a variety of suggestions have been made how these insects ended up in the sticky tree resin that ended their lives.

One possibility is that the insects happened to get stuck accidentally, but that idea can quickly be dismissed on the basis of mathematical probability and statistical evidence.  Another suggestion had been that coniferous resin flowed into water-filled tree holes and the aquatic insects living in these tiny water bodies were trapped by the resin. However, many of the trapped aquatic insects represented species that do not visit water-filled cavities of trees. Somewhat similar was the suggestion that the resin flowed down the tree’s bark and contacted on its way to (or upon reaching) small water bodies, insects that got encased by the resin. But once again there were objections to that theory just as there were to the idea that wind could have blown the insects onto the resin and caused them to adhere and get stuck never to free themselves again. The three theories have in common that the aquatic insects ended up in the resin by accident, but the fourth suggestion has it that some insects were attracted to the resin by its glistening appearance, resembling water droplets. However, what exactly attracted the dispersing, flying, aquatic species to the resin remained unknown.

To solve that question Horvath and co-workers in Hungary carried out field experiments with sticky surfaces that polarized the light, reflected from the surfaces to different degrees and angles. They then analysed the taxonomic positions and numbers of insects that had got stuck on the surfaces and concluded that it was not simply the “shininess” or “brightness” of the sticky sheets, but the degree and angle of polarization. The result does, of course, agree with the known observation that insects, which depend on water to deposit their eggs in it like mayflies, dragonflies, stone- and caddisflies, identify water bodies not by their colour or smell, but by their polarization characteristics. The result was also in agreement with the published report representing the ancient insect fauna. So, does that solve the question how water-seeking insects ended up in the resin as ‘amber inclusions’?

Perhaps not, because in a recent 2021 publication by Mario Schädel et al., the authors reported that they had examined a piece of Burmese Amber with an assemblage of over 100 specimens of immature stages of a parasitic aquatic woodlouse relative, belonging to a group known as Epicaridea. And these tiny (and of course wingless) specimens did not possess prominent eyes at all and could not fly. So, what attracted them to the resin? Was their entrapment accidental or did the resin attract them? It’s “back to the drawing board”. But that’s science (and keeps us busy)!

© Dr V.B. Meyer-Rochow and, 2021. 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.

Compulsive Hoarding

A disorder with ancient roots?

I think we all know some people who are ever so ready to throw away something they no longer fancy or to discard some item if a newer version is available. But we may also know people, who behave in exactly the opposite way: they never throw away anything but keep and store and guard even things that no longer seem useful. That kind of behaviour can be compared to what is termed “hoarding” and, if compulsive, it is now considered a mental disorder of the “obsessive-compulsive” nature. But is it an atavism, a re-surfacing of an ancient trait with roots in the animal kingdom as suggested by Sandro René Pinto de Sousa Miguel, Rodrigo Ligabue-Braun of Porto Alegre in Brazil, akin to narcolepsy and quadripedalism in humans, which have also been linked to atavisms?

Hoarding, especially of food but occasionally also of material or other items, is certainly common in the animal kingdom and helps individuals survive lean periods. And immediately La Fontaine’s famous poem “La cigale et al fourmi” that I had to learn as a pupil during my High School French lesson, comes to mind. Indeed, there are several examples of invertebrates that store or cache food or, in the case of leaf cutter ants, even collect and tend inedible leaves to grow on them edible fungi. Honey bees are so successful (unlike the equally social hornets) and survive the winter, because they prepare and store food for the cold season. Although not usually overwintering, spiders, too, can often be seen in summer to keep numerous wrapped-up insect prey in their orb-webs for later use.

More obvious hoarders are found amongst our feathered friends and some of them behave seemingly intelligently when they attempt to hide food items and then firstly look around to make sure no other bird observes where they hide their treasures. A behaviour such as this has been reported from Corvus corax ravens by the Austrian researchers T. Bugnyar and K. Kotrschal and also the Eurasian jay Garrulus glandarius by the Cambridge University scientists E.W. Legg and N.S. Clayton. North American woodpeckers are less selfish and establish food stores that are accessible to other wood peckers, but whether shrikes like Lanius collurio allow other shrikes to access the insects, and even small mice and lizards, they store on thorns in the open, I do not know. However, policing food stores such as these, which are visible and in the open would be quite a task. Besides, hoarders with multiple caches (to reduce pilferage) run the risk of forgetting some of their troves, and in the case of forgotten and buried seeds, help spreading trees. A special facet of hoarding is that, which is represented by the New Caledonian crow Corvus moneduloides that bends twigs into hooks to extract grubs from wooden trunks with and then hides and hoards these precious tools.

Proverbial hoarders are the hamsters. It has been reported that European hamsters of the species Cricetus cricetus may have many kg of grain (up to 60 kg !) in their nests  – and it’s all for themselves (and their offspring). Packrats and squirrels, too, are well known hoarders and beavers establish food stores that can be used by anyone of their family. Some of the best-studied mammalian hoarders are shrews, especially a species by the name of Blarina brevicauda from the northeastern region of North America. To survive the winter they collect and cache food items in their burrows that can contain seeds and dry fruit, invertebrates and even small mice. It was this species of shrew that the Brazilian researchers, mentioned above, compared obsessive human hoarding with to suggest that the latter was an atavism going back to ancient evolutionary roots. The problem is, human hoarders more often than once, not just hoard food, but inedibles like coins, stamps, toys, clothes, buttons etc., and some are even known to hoard and guard some really weird and useless things like used underwear, smelly socks, cigarette buds, etc. Do animals do that also? Well, in the Statistical Manual of Mental Disorders, 5th edition (DSM-5) such behaviours in humans are now classified as a mental disorder. Maybe it’s risky then to mention I collect coins with animals on them.

© Dr V.B. Meyer-Rochow and, 2021. 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.

Giant Fishes of the Rivers

How much longer will we have them?

The vertebrate class of Pisces contains members of two major groups of fishes: the cartilaginous species and the bony fishes. The most massive (if not the longest as well) of all fish are the Whale Shark (Rhincodon typus) and the Basking Shark (Cetorhinus maximus). These two species are peaceful giants, feeding on plankton that they filter out of the ocean water with their comb-like gill rakers. However, in this blog I want to write about giant freshwater and not marine fish. Yes, river fish, for several of them are bigger than the marine bony species (with one exception: the oarfish Regalecus glesne, of which during the 1967 “Walther Herwig” South Atlantic Expedition I caught a glimpse of one 7.30 m long specimen. This midwater species is said to reach a maximal length of 13 m).

What prompted me to write this blog was the sad news that the giant Yangtze River paddlefish Psephurus gladius was officially declared extinct. It thus follows the Yangtze freshwater dolphin Lipotes vexillifer, affectionately called ‘the baiji’ in Chinese but declared extinct in 2006. In 1970 there were still 25 tons of Yangtze paddlefish caught, but the last individual was probably killed in 2007. Specimens of at least 5 m in length existed. Another Chinese giant with a length of approx. 4 m is the Chinese sturgeon Acipenser sinensis, but it may also soon be gone forever for its population decreased by 98% from 1973-2010. As of this year (2021) all commercial fishing in the Yangtze will be banned for 10 years, but as welcome a measure as this is, it cannot bring back what is lost forever.

Probably the largest with a maximum length of around 7 m of all freshwater giants is the Beluga sturgeon Huso huso of the Caspian Sea and the Sea of Azov. Because of the value of its roe (the famous “Caspian caviar”) it is farmed, but the eggs of its also farmed but only 5.5 m long relative, the Huso dauricus, are considered even tastier. In northern Europe adults of the 3 – 4 m long sturgeon Acipenser sturio used to enter rivers to reach their breeding grounds upstream, but one of the few streams where these sturgeons now still breed is the Gironde in France. Recolonisation efforts are in progress elsewhere, but so far with minimal success. A huge surprise for our professor and us students of the Zoology Class at the University of Kiel in 1968 was when an almost 2 m long catfish of the species Silurus glanis was delivered. It had been caught the day before in the small North German freshwater stream known as the Trave. The East Asian Mekong River Pangasianodon gigas catfish and South American species of river catfish are said to reach maximum lengths of 4 m and can become a danger to bathers. Of the other South American freshwater giants the Arapaima gigas with a reported maximum length of 3.4 m and the electric eel Electrophorus electricus with a length of 2.5 m need to be mentioned.

Africa’s largest freshwater fish is the Nile perch, but it hardly reaches 2 m. On the other hand there are some quite big bony fishes in the North American Mississippi-Missouri river system. There is the North American paddlefish Polyodon spathula and the fierce-looking alligator gar that can both reach a length of 3 m. Although not in imminent danger of becoming extinct, these two species are considered vulnerable and an analysis of what led to the extinction of the Yangtze River paddlefish may help save the North American species and other freshwater fish giants too. It is believed that the biggest threats to the vulnerable freshwater fish giants (but even smaller species as well) are dams that block the fish’s access to upstream spawning grounds, and furthermore overfishing, the use of illegal methods (like electro-fishing, nets with unacceptably small mesh widths, and explosives). Pollution of the river water by chemicals like insecticides, by effluents and other wastes from urban areas, and by fertilizers used in agriculture must not be forgotten. But what is certainly interesting is that rivers compared with the oceanic habitat contained more giant bony fish species than the sea. Any suggestions why?  

lication 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.

© Dr V.B. Meyer-Rochow and, 2021. 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.