Wednesday, February 28, 2007
Amongst a pile of old wooden planks (at (1.5,2.0) - see here) I found the little snail shown in photo 1 (click on the photo to enlarge).
Photo 2 shows a view from "the rear".
To learn something about snails I have been reading Land Snails of the British Isles, A.A. Wardhaugh (Shire Nat. Hist., 1989). Based on a very similar photo (to my inexperienced eyes at least) in this book, I believe my snail to be the Strawberry snail Trichia striolata, so-called as apparently it can become a pest on strawberries.
In reading the book above, I have been struck by just how curious an animal the snails is. A typical creature from a science fiction novel is far more mundane! Firsly there is the familiar means of locomotion: on a trail of slime. Next, the eyes-on-stalks (though it seems the latter is a feature only of the sub-class of snails, the pulmonates - the majority of British land snails. By contrast, the eyes of the (typically marine) prosobranch snails are located at the base of the stalks).
For the non-experts, I suspect a less familiar aspect of the snail's anatomy will be the shape of the snail's alimentary tract. This extends from the mouth, back into the body but then proceeds to curve round in a U-bend "(" shape to bring the anus out on top of the body, just inside the shell, at a point above the snails head. It never rains but it pours!
Finally, there are the mating habits of snails. Snails are hermaphrodites possessing both male and female genetalia. This would be odd enough, but snails have one more truely bizarre facet to their behaviour: in readiness for mating a number of snails prepare a 'love dart' - a sharpened dart of calcium carbonate (see here for some photos) - in a bodily organ known as the dart sac. During copulation the love dart is extended and then physically driven into the body of the partner, often to remain there to be internalised. An early theory to explain this phenomena was that it might be a 'gift' of calcium from one snail to the other. It seems the love dart is now thought to play a role in triggering a fertility-enhancing hormonal response in the 'punctured' snail. I cannot imagine the evolutionary value of going to such extreme lengths however (as opposed to a more 'traditional' approach to mating - exchanging pheromones; employing a mating dance; buying champagne etc. ?)
To be strictly accurate, I should say that although I have come across one paper (Koene, Muratov, Malacologica 2004, 46(1): 73-78) which refers generally to love darts in the Trichia genus, I have not been able to ascertain for certain that T.striolata in particular has a one (can anyone tell me?). Indeed, other than learning of its status as a common snail in Southern England and its fondness for strawberries, I have not been able to find very much at all specifically relating to the habits of T. striolata. My searches have mostly turned up the usual selection of subscription-only papers in online scientific journals (something always a point of irritatation to me since, fairly or otherwise, I feel as a tax payer I already make my contribution to UK university research. I don't begrude the contribution, but can't quite understand how the research results can come to be 'owned' by private publishing houses. Rant over!).
To close, two fascinating blogs with a distinct snail focus: Snail's tales and Snail's Eye View.
Saturday, February 24, 2007
A most pleasing aspect of my self-imposed mission to study the living things in my garden is that I am beginning to realise how much I have looked at things in the past, but over looked the fascinating details that are there before my eyes. I commented on this in my previous posting with regard to the shape of ivy leaves. My investigations of the primrose have led me to the 'discovery' that the flowers come in two distinct forms: 'pin' and 'thrum'. (I realise this will be this decidedly 'old news' to the botanists out there, but a delightful find for me).
Photo 1 (click on it to enlarge) shows a primrose growing in my garden (at (0.5,0.9) - see here). This is a 'pin' plant, so-called because the stigma (the 'stalk thingy' right in the centre of the flower) sticks out like a pin. By contrast, photo 2 shows a 'thrum' (a lovely word I'm sure you'll agree. Apparently a term from weaving, meaning literally 'a tuft of thread') primrose. This one is not growing in my garden, but on a roadside verge a few hundred metres from my house.
Pin and thrum are apparently equally numerous in the primrose population. The flowers on any one plant are either all pin or all thrum. Furthermore, pin primroses cannot pollinate other pin's, or thrum's other thrum's: it takes a pin and a thrum to make a baby primrose! (It would be incorrect to think of either as 'male' or 'female' however - both are capable of 'giving birth' to fertile seeds).
From reading Primulas of the British Isles (J. Richards, publ. Shire Nat. Hist. 1989) I gather that the suggestion is that the benefit to primroses from all this heterostyly (literally "different styles") is that it guarantees that any one plant cannot self-pollinate: a plant requires pollen from its opposite (pin or thrum) type. Avoiding self-pollination presumably helps to keep the primrose gene pool healthy. Once again it seems a certain C. Darwin was historically involved in the debate (first robins, then goldfinches, now primroses - is there anything he didn't study!).
Another fascinating discovery for me is that primrose seeds come 'fitted' with an elaiosome. This is a fleshy 'lump' on the surface of the seed that is rich in proteins and designed to attract ants. Ants pick up the seeds and carry them away to their nests, eat the elaiosome and then 'dump' the left-over seed on a waste heap outside their nest. In this way the primrose gets its seeds not only distributed, but also planted on a nutrient rich site. I have seen plenty of TV documentaries over the years, showing strange insects in far-away jungles engaged in complex acts of partnership with exotic plants. I find it wonderful to think however, that there equally delicate 'waltzes' going on between the creatures in my garden. I am determined to have a look for ants around my primrose in the summer!
To end, a little Shakespeare? But of course, though I cannot promise a cheery quote:
Porter: I had thought to have let in some of
all professions that go the primrose way to the everlasting bonfire.
(Macbeth, Act III, Scence III)
Wednesday, February 21, 2007
Rather naively, I had not expected to find a great deal to say about the English ivy (Hedera helix). How wrong I was!
Having spent a few days investigating this wonderful plant, I am beginning to think that of all the life forms in my garden, it may be the one most steeped in history.
Ivy seems an established plant around the globe. In case anyone isn't familiar with this remarkably successful and resilient evergreen plant, photo 1 (click on it to enlarge) shows a closeup of some of mine. (For those of you following, the ivy in my garden grows at (0,2) and (2,0) (see here )) I'm fairly sure mine is the true, indigenous, English ivy. There are numerous commercial
The number of berries on a stalk is variable: I have counted as few as four and as many as thirty.
Despite having noticed ivy on innumerable occasions during country walks, I confess, until now I had never really looked at it. I had not hitherto noticed, for example, that the leaves on an ivy plant come in two basic forms: Those on non-flowering ('non-berry') branches have the classic "ivy leaf" (palmate) shape (photo 2, left). By contrast, those on flowering stems tend be be more uniformly ovate (photo 2, right). I cannot imagine what evolutionary advantage the plant can get from this?
Ivy's famous ability to climb up trees and buildings is effected by numerous small clinging ("adventitious") roots that sprout from the climbing stems (photo 3.). There seems to be some debate over whether ivy harms its host tree - something it is often accused of. I'm not qualified to comment - though I welcome the comments of readers.
This site argues that ivy is increasing its prevalence in Britain.
Ivy it seems, is much valued by wildlife. Unusually, ivy berries ripen over the winter. By February they are amongst the few berries available to birds, and are eaten by (amongst others) blackbirds, thrushes and pigeons. The dense foliage is a favourite hiding place for small nesting birds - a fact I can attest to: in the course of my 'prodding around' in my garden's ivy I found no less than four old, discarded nests.
Ivy seems capable of inducing a variety of unpleasant medical conditions in humans, but by contrast, is a favoured food of the caterpillars of the Holly Blue butterfly, seems to have been an important animal fodder in Mesolithic Europe, and even gets a mention in Shakespeare:
"...They have scared away two of my
best sheep, which I fear the wolf will sooner find
than the master: If anywhere I have them 'tis by
the seaside browsing of ivy"
(The Winter's Tale, Act III Scene III)
Ivy has had a long association with alcohol. According to my Brewers Dictionary of Phase and Fable it is dedicated to the Roman god of wine Bacchus (though there seems some doubt as to whether his is the same plant as English ivy). In consequence, it was hung above the entrance of Roman wine sellers (Bolton, J. American Folk-Lore, vol. 15, pp.44, 1902) to advertise their wares .
"You need not hang up the ivy bush over wine that sells well"
(Piblius Syrys, 45BC)
a quote later "recycled" by Shakespeare:
"Good wine needs no bush"
(As You Like It: Epilogue)
a reference in turn to the habit of decorating a pole (the 'ale-stick') with foliage (often ivy) to advertise a tavern in Britian. "The Ivy Bush" (or something similar) is still a common pub name.
Ivy has a long history of symbolism in the Christian and pre-Christian church, a familiar example of course being the Christmas carol 'The Holly and the Ivy' ("But do you have holly in your garden?" I hear you cry...watch this space!).
According my Brewer's dictionary:
In Christian symbolism ivy typifies the everlasting life, from its remaining continually green.
I have come across so many discussions and interpretations of ivy's symbolism in Christian and pagan religion on the internet however, that I've become unclear over the distinction between fact and speculation.
I'll end this posting by mentioning three sites that that I was surprised and amused to discover:
Firstly, an ivy society ; Secondly, a blog devoted entirely to the plant(!) ; and thirdly, one of the quirkiest horticultural sites I have yet encountered.
My garden gets more interesting every day!
Tuesday, February 20, 2007
Photo 1 shows a hen chaffinch on a branch of my apple tree and photo 2 the more brightly coloured cock.
In an attempt to learn something about chaffinches I have been reading Finches, Ian Newton (publ. Collins New Naturalist 1972). Some of the things I've learned:
British chaffinches rarely move more than a few km from their birthplace. In winter however, numbers in Britain are greatly increased by an influx of migrants from Northern Europe; Indeed Latin coelebs meaning bachelor is due to Linneaus who observed that those chaffinches remaining to over-winter in his native Sweden were primarily male. Chaffinches visiting Britain typically arrive in October and depart in March. I wonder whether the birds in my photo are locals or foreign visitors?
In winter chaffinches flock, but in the breeding season (typically late April to early July) they are territorial (unlike goldfinches) with pairs occupying territories of around 1000-12000 sq.m. I've crudely estimated the area of my garden as a little over 500 sq.m., so it seems I can accommodate at most half a breeding pair. (I would say however that it's not uncommon for me to see up to half-a-dozen chaffinches in my garden at one time).
The chaffinch seems to be one of the less dexterous finches, and is unable to hold or manipulate seeds with its feet (unlike the goldfinch). Despite this it is one of Britain's most successful birds with 5.4million territories in Britain (according to my RSPB Handbook of British Birds, Holden and Cleeves 2006)
With a typical life expectancy of 2.5years it seems Chaffinches get a better deal than robins. That said however, their love life is no bed of roses! To quote Dr. Newton:
"Courtship in the chaffinch is characterised by tentative ambivalent behaviour involving conflicts between fear, aggression and sexual attraction"
Despite this, chaffinches mate for life.
Cock chaffinches begin looking for territory in February. I enjoyed the description of the young cock chaffinch hopping around trees in a prospective territory examining the forks between branches (the preferred nesting site for the female he hopes to attract) first with one eye, then the other.
Males attract females by song and will sing up to 3,300 times in 24hrs. (I thought this was a lot until I read that the the Red-eyed Vireo may sing an astonishing - and I imagine potentially monotonous, if you happen to have them in your garden! - 24,000 times in the same period).
When a cock and hen are finally ready to mate the cock does a
" 'pre-copulatory dance' , in which [he] patters to and fro before the hen with short steps"
I'm not certain, but I think I may just have caught this in photo 3.
In all, the chaffinch apparently has twenty-one songs. Chaffinch song is partly innate, but the young learn to add 'flourishes' to the basic song patterns. This means that not only are the voices of individual chaffinches distinct but that regional 'dialects' develop. I shall be listening out for the Oxfordshire accents of those in my garden.
Monday, February 19, 2007
Having failed to conclusively establish the identify of the small fungus/slime mould on my bird table, I thought I ought to try to redress the balance by posting an example of a small fungus that I am fairly confident to have identified correctly (until someone makes me eat my words that is!):
Last summer my garden hosted (at (1.2,2.0)) a patch of nettles (Urtica dioica - more in future postings). Over winter these have died back to bare woody stems and it is on these I am finding a tiny orange fungus (photo 1 - you'll need to click on it to enlarge it and make out the fungus).
Based on a similar photo in The Encyclopedia of Fungi (M. Jordan, publ. Francis Lincoln 2004), and other photo's I've found on the web, and although I wasn't able to find any spores under the microscope (normally a strong help in identifying fungi), I'm fairly confident in naming my fungus as Calloria neglecta.
From what I can ascertain C. neglecta grows only (?) on the stems of nettles. This seems a remarkably niche existence to me, but then, having recently read Fungi (Spooner and Roberts, Collins New Naturalist, 2005) and discovered that there are some fungi that live only in the intestines of woodlice I suppose a nettle stem is positively suburban!
Strictly, most images I've found of C. neglecta show the fungal bodies rising to some extent from their nettle stem, whereas under a hand lens mine seem to be simply orange coloured patches of negligible thickness. Since the description in the book above however, includes the statement:
"The conidial stage... [of C. neglecta]...is more commonly encountered"
(For those not familiar with this term, 'conidial' refers to a form of asexual reproduction that some fungi are able to undertake)
and since also the (very nice) photos on the web page of Piotr Perz are referred to as images taken
"...one month after the conidial stage Cylindrocella urticae"
I'm going to take a guess and say my diffuse orange spots are the conidial stage of Calloria neglecta (though I've not been able to find an explicit description or photo of this as yet). I'll leave it to the experts out there to correct me!
Saturday, February 17, 2007
Given my status as an untrained amateur, it has always been inevitable that during my mission to identify all the living things in my garden life I would meet things that stump me. Today's post marks one.
I have an old wooden bird table in my garden. Growing along one edge is the fungus seen in photo 1 (click on it to enlarge).
In a blatant display of plagiarism (see here !) I'd be pleased if any reader can "Name That Mushroom!"
The fungal bodies are small (~1-5 mm) 'blobs' that lack any obvious sign of a structure (stalks, cups etc.) under a hand lens. Until recently they were a more vivid red/orange. Old age and recent bout of snow has left them past their best.
Under the microscope the fungal mycelia are clear (photo 2, 1000x, 1 small division=1micron) . (For anyone reading not familiar with fungi: the mycelia are the 'spaghetti-like' threads. These make up the body of the fungus).
I am not at all expert on the microscopic caracterisitics of fungi, but I think the mycelia are uniseptate (again, for the unfamiliar: looking on the photo just above "7.5" on the graticule, you'll see a thin cross wall - a 'septum' - in the mycelial thread). There was no obvious blue reaction with Melzer's reagant.
A further puzzle is that despite a considerable time spent carefully scanning samples under the microscope I failed to find a single spore or ascus (='tube' full of spores). I am used to seeing large numbers of spores if ever I view larger, more familiar mushrooms. I'm not sure whether my failure to find any in this case is due to there being a greater skill/element of timing in finding them for the smaller fungi, or whether it is that I'm not correctly interpreting what I am seeing. I read, for example, that some smaller fungi spread by 'thallic conidiogenesis' (see here for some nice animations illustrating what this means). For all I know, maybe this is happening and perhaps even visible in the photo to the experts out there.
Saturday, February 10, 2007
I am attempting to identify all the life in my garden. In this posting I am continuing to work my way through my garden's moss species. As I've mentioned previously I'm an amatuer with no formal training in botany or biology. All my "identifications" (a.k.a. best guesses) come with this caveat!
Photo 1 shows a patch of moss I found growing on my lawn at (1.1,0.3) (see the Lie of the Land posting). I'm mildly curious to know how fast moss grows and spreads so I've measured the size of this patch - 9cm x 9cm at the widest point - with the aim of returning to look at it again in a years time (watch this space!). Photo 2 shows a microscope photo of one of the leaves.
Armed with my trusty copy of British Mosses and Liverworts (Watson, Cambridge Uni. Press 1955) I think I've identified it as Brachythecium rutabulum (Rough stalked feather moss). Watson describes it as 'almost ubiquitous in lowland districts' 'often found on lawns' and 'amongst the first mosses which the beginner will come to know'; So it seems a useful one to have identified!
Meanwhile, growing on the trunk of my apple tree (1.5,1.1) (of which, more in a future posting) is the moss in photo 3. The leaves of this one (shown in photo 4) are distinctly narrow, 'creased' with folds, and have tiny 'teeth' along the edges being most pronounced at the base of the leaf. My identification for this one is Camptothecium sericeum (Silky wall feather moss) which seems to have be renamed since Watson's book was published in the 1950's as Homalothecium sericeum.
I have frequently read that mosses are 'non vascular' plants i.e. that they lack a dedicated 'plumbing' system for transporting water and nutrients around. Given this explanation, what puzzles me (comments please!) is how in that case they do manage to transport nutrients around. Are moss leaves constrained to be as small as they are by this lack of a vascular system?
In the past I have hardly ever seen goldfinches in my garden, but recently, on a whim, I hung up a feeder of thistle seeds (a favourite food of the goldfinch, carduelis being Latin for thistle) and within 24hours I was able to take the photo left. (I do not have a fancy camera with telescopic lens. The shot was taken from as near as I could get!). You can see the tube of black thistle seeds at the top of the picture.
In an attempt to learn something about goldfinches I have been reading Finches by Ian Newton (part of the Collins ‘New Naturalist’ series). It seems I’m fairly lucky to have seen a goldfinch at this time of year since, according to the book, “4/5ths leave Oxford in winter” for southern Europe, especially Iberia where they are amongst the most common birds in winter. Goldfinches leave Britain around mid-September and return around mid-April.
Other points I found interesting include:
The goldfinch is the only finch that can reach the seeds of teasels, and apparently it is only the cocks that can do this easily (which seems a little unfair on the hens!). The beak of the cock is slightly longer (by ~1mm, 9%) a fact mentioned by Darwin: “I am assured…that the bird catchers can distinguish males by their slightly longers beaks”.
Further to the mention of ‘bird catchers’ the goldfinch was apparently a particular target of this profession in the last century with a record of 132,000 being caught in one year (1860). Combating this trade was one of the first targets for the then newly formed Society for the Protection of Birds (which I take to be the same organisation as today’s RSPB).
Goldfinches, unlike chaffinches, do not invest significant effort in defending territories. I am sure the experts out there will correct me, but I understand the argument is something like this: Trees harbour insects. If, like chaffinches, you sometimes eat insects it is worthwhile to defend a territory that contains trees (which are after all, “permanent fixtures” in the landscape). Goldfinches only eat seeds however. The timing and location of e.g. thistles in-seed is highly variable and therefore, as a goldfinch, you cannot afford to restrict the territory from which you are prepared to gather food.
I have said before that I do not envy the life expectancy of a robin. I do not envy the diet of a young goldfinch either : “While collecting food for the young, adult carduelines husk seeds…When their crops are full, they take a few sips of water and a few particles of grit, then fly to the nest and regurgitate the whole mass into the open mouths of the young”. Yummy!
The goldfinch was introduced into New Zealand, Tasmania and Australia in the 1860’s (I don't know by who or why) where it is now apparently extremely common.
Finally, I learnt from Narena Oliver’s website that the goldfinch’s fondness for thistle heads led to it being used to symbolise the Passion of Christ in sixteenth century art and that it gets a mention by Chaucer : “Gaillard he was as a goldfynch in the shawe” (which apparently ‘translates’ as: he was as merry as a goldfinch in the wood). Hooray for the gaillard goldfynch!