Taking a Stroll in the Park (a Mossy Park that is) …

But you’ve got to be tiny

I remember that when I got back to Scott Base from a stroll up Observation Hill and showed our botanist Keith Thompson the photo of a cluster of moss plants he exclaimed: “Wow, you found a forest in Antarctica!” And now I wish to get a little deeper into the topic of a moss being called a forest.

Mosses are Bryophytes, usually rather small plants with thin leaves of just a single cell layer and no proper root system. Even the tallest moss, Dawsonia from New Zealand, with a spore-bearing stalk up to 50 cm tall, lacks like all of the other smaller Bryophyte  species, the typical vascular system and flowers of the higher plants. These tough little plants, with an ancestry that goes back 400 million years or more, were planet Earth’s terrestrial pioneers. With the exception of some freshwater species like Fontinalis antipyretica (there are no mosses in the sea) and those of swamps and bogs like Sphagnum, whose dead layers form the peat, Bryophytes are known to grow on almost anything that at least occasionally becomes soaked in water:  stones, tree trunks, bottles, roofs, monuments, and even other living plants and animals. The weevil Symbiopholus of Papua Niugini may support the growth of moss on its back and sloths, too, can have mosses in their fur. What is sometimes referred to as “moss caterpillars”, however, are not caterpillars with moss on their backs, but the larvae of nymphalid butterflies that possess moss-resembling protuberances on their bodies.

As a student in the Botany course many, many years ago, the plants I loved most were the true mosses (not including liverworts). The stage in their life cycle that has leaves and we recognize as a moss, has sexual organs and represents the gametophytes. Yes, mosses possess so-called antheridia  (which produce bi-flagellated sperm) and archegonia (which produce the egg cells). The reproductive organs, depending on the species, may be on the same or two different plants. The plants and thus their sperm and egg cells are haploid. To produce a fertilized egg, a sperm needs to reach archegonia where it can find an egg cell. For that ‘journey’ the sperm needs to swim and must wait until there is sufficient moisture. Once an egg cell has been fertilized, a new structure (attached to and growing out of the moss’ leafy gametophyte) develops and becomes noticeable as the thin and sometimes several cm tall, unbranched sporophyte. This structure possesses diploid cells and develops at its tip a spore-containing capsule. The spore-producing cells undergo meiosis, so that the spores are all haploid, some with male and some with female traits. When the spore capsule opens to release the spores, the wind carries them to various places or in the rare cases of species that grow on carrion or dung little flies may carry away spores. Should the spores land in a suitable spot, they grow into a thin threadlike protonema, which resembles a green alga, before changing into the more familiar moss with its little stems and green leaves. Being able to soak up water (but also surviving months without it), these moth gametophytes form a habitat for a multitude of invertebrates. 

Most famous of the latter are the cute tardigrades, champion survivors, just like the ever present rotifers and some tiny roundworms. Using a magnifying glass and even with the naked eye one would almost certainly encounter springtails, various mites, tiny eyeless arthropods known as Protura and Diplura, and probably very small flies, minute beetles, book lice (Psocoptera) and thrips. If one is really lucky, one may come across some pseudo-scorpion, a top predator in this micro-world. Easily recognizable as relatives of centipedes, but much smaller and thinner, are the multilegged and pale Symphyla and Pauropoda. Yellow Geophilus centipedes, ants and tiny micryphantid spiders would be the giants in this ‘forest’ and visible with the naked eye, but to spot the many ciliates and bacteria that are present, you’d need a microscope. Organisms like larval craneflies, caterpillars of micropterygiid mini-moths, and stigmaeid mites, feed on the mosses’ green parts and some nematodes are even known to induce the formation of tiny moss plant galls. Unfortunately, such a variety of different organisms would not have been present in my Antarctic “moss forest”, but take a clump of green moss sometime and go exploring:  take a walk on the wild side (of the mini world).     

© Dr V.B. Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com, 2022. 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 http://www.bioforthebiobuff.wordpress.com with appropriate and specific direction to the original content.

Princess Charlotte Likes Them

And I like that she likes them (Spiders!) 

Princess Charlotte was five years old when in 2020 she asked Sir David Attenborough if he liked spiders. I never met her or her lovely parents Prince William, Duke of Cambridge, and Catherine, Duchess of Cambridge, but I had met her great-grandmother Queen Elizabeth II. at a luncheon at the University of the West Indies and she, too, had some interesting questions like what I had been doing in Antarctica. Anyway, Princess Charlotte likes spiders and that delighted Sir David. And actually, why don’t more people like spiders? According to Oxford University Professor Fritz Vollrath it’s puzzling that not everybody wants to work with spiders, a view that probably my grandfather would have shared, for this grandfather of mine often led me to the local church (but never set foot in it), so that he could show me the spiders whose homes were in the cracks of the church’s brickwork and whose webs covered the bushes around the church. 

Anyway, what’s so special about spiders? Sir David would probably mention that they’ve been around virtually unchanged for millions of years (those embedded in age-old amber look no different from spiders today) and their conservative anatomy with eight legs, book lungs and/or trachea, 6 or 8 single lens eyes and an ability to produce silk has served them well. Prof. Vollrath would marvel at the incredible physical properties of the spiders’ silk and how from a tiny amount of liquid in a spider’s abdomen you could extract an amount of silk fibres to cover a football field with. Princess Charlotte might find the way an orb web spider catches a fly, wraps it in silk and pulls it to the centre of the web fascinating. And then there are some like Professor Barth and others, who are amazed at the spiders’ incredible sensitivity to vibrations, or their ability to see and to detect polarized light, their speed, their venom, the ecological niches they have been able to colonize and their behaviour. The latter includes an astonishing and mind-boggling variety of male/female positions during mating.

Lots of humans seem not satisfied with just one sexual position, but sometimes want to explore other, often less comfortable, variations (the Indian love-making recipe book “The Kamasutra” comes to mind). However, much can be learnt in this field by studying how spiders do “it”. The problem with spiders is twofold: almost always the male is considerable smaller than the female he needs to approach to hand over his sperm. “Hand over” is an appropriate term, for the males do not have penises but need to fill a little bulb on a pair of feeler-like appendages (known as the pedipalps) on their head near the oral cavity with sperm from their abdominal genital opening. Once the bulb on the pedipalp contains the sperm, it needs to be transported and injected into the female’s genital opening. For most spider males that is the hardest part of the mating procedure. No wonder therefore that before a male dares to approach a female, the male (depending on the species) performs certain rituals: male jumping spiders dance, male orb weavers carefully send messages along the silk strands before they advance, in some crab spiders males hand over a nuptial present and (not trusting their females fully) tie down the female with some silk to symbolically restrain her.

But then the mating commences. There are species that mate head-to-head; in others the male creeps under the female, its head pointing towards the female’s abdomen; sometimes the female turns on her back or raises her body and stands on her tippy toes; a sideways approach is seen in some species. Incidentally, the techniques to procure food are just as varied: there are species that pounce on the prey, pursue prey, ambush it, attract it with pheromone as in the bolas spider, use trap-doors, sheet or orb webs, cast a tiny web over unsuspecting prey as Dinopis does, or spit sticky fluid over prey; even diving after prey as in Dolomedes or stealing what other species have caught (as in kleptoparasitic species) occurs. But what unites them all is the possession of silk glands on one end of their body and a venomous bite on the other end (the front). That they pre-digest their food outside their bodies has already been mentioned in an earlier blog and that Princess Charlotte, Sir David and Prof. Vollrath are correct to find spiders fantastic, should now be clear to everyone, I think.

© Dr V.B. Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com, 2022. 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 http://www.bioforthebiobuff.wordpress.com with appropriate and specific direction to the original content.

Wound Healing & Blood Clotting

Complicated in mammals, but in insects, too

When I was a PhD-student I very much enjoyed recording intracellular responses from visual cells of a variety of insect species. It wasn’t easy, but it was so rewarding when I succeeded in holding a cell for several hours and could determine its sensitivity and visual field. I then had the idea to record from the eyes of an Australian spider, but my supervisor at that time told me that it would not work, because once you’d injure a spider, its blood would coagulate and become jellylike, he said. So, I gave up the idea.

What my supervisor must have been thinking of at that time were observations on the blood of Limulus (the horseshoe crab, which isn’t a crab at all, but related to spiders). It had been studied in 1956 by Fred Bang, who established that its blood can undergo spontaneous gelation. Indeed so famous became Limulus blood that pharmaceutical companies got highly interested in it. So-called gram-negative bacteria that, for example, cause diseases like toxic-shock syndrome, meningitis and typhoid are usually killed by sterilizing medical tools. But the sterilization process does not always remove bacterial compounds from the bacterial cell wall like endotoxins. It is these chemicals that the Limulus blood reacts to. Regarding blood clotting and gelation, they must then be seen as a way to prevent harmful bacteria from entering a wound and spreading. Functionally these roles (and forming a scab over a wound) seem no different in mammals, or are they? I always liked lecturing on the physiology of blood clotting in mammals (rather than the kidney function), because it involves  a fascinating  cascade of events with inputs from vitamin K and calcium ions, but I never discussed the clotting physiology of blood like that of spiders and insects.

In mammals, tissue and blood vessel damage causes the release of thromboplastin from blood platelets and involves calcium ions, factors V and X, to change the inactive prothrombin of the blood plasma into the active thrombin. Thrombin then converts factor I (the molecule fibrinogen) into soluble fibrin strands, while the anti-haemolytic Factor XIII (which depends on fat-soluble vitamin K and is missing in people suffering from haemophilia A, i.e. the bleeder’s disease) together with Factor IX leads to platelet adhesion and in the presence of Factor XIII then stabilizes the fibrin clot, sealing the wound. But white blood cells, especially the granulocytes and eosinophils, also get in on the act, accumulate under the wound and in the case of the granulocytes, aggregate, engulf and ingest bacteria or, in the case of the eosinophils, release a crystalline protein to fight off multicellular parasites: a 2-pronged injury response.

Insects do not possess blood vessels like veins or arteries and the colourless blood in the insect’s body cavity (the haemocoel) does not contain platelets. However, the blood does contain crystal cells and haemocytes, of which granulocytes and plasmatocytes are the most significant ones. The granulocytes are generally amoeboid and one of their roles (like the granulocytes in a mammal) is to encapsulate and digest bacteria. Primarily fighting invading and unwanted micro-organisms, these mobile cells migrate to an injury, coagulate and release a “Factor VIII = vertebrate clotting equivalent”.  Factors promoting the coagulation such as trans-glutaminase are liberated from plasmatocytes (that behave like mammalian macrophages and tackle parasites larger than bacteria) and prophenoloxidase from ruptured crystal cells (a similarity to mammalian eosinophils that also contain crystals, but composed of a protein known as MBP1). A calcium-binding protein known as glutactin, which lines muscles, the central nervous system and basal epithelial cells, is produced by the fat body (= the insect’s liver) and has adhesive properties. It helps building a fibrous or gelatinous clot, sealing the wound.

What all this shows is that there’s also a clotting cascade in insects, but that it is an analogous process: it leads to the same result, but follows a different a pathway. However, that’s not the end of the story, for the clot or the scab will ultimately have to be reabsorbed, right? And that’s different. Vive la différence!

© Dr V.B. Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com, 2022. 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 http://www.bioforthebiobuff.wordpress.com with appropriate and specific direction to the original content.