Wednesday, July 25, 2012

Frogs Alive!

Common Frog, Rana temporaria
I shouldn't have doubted. The tadpoles in the 'temporary pool' that I didn't think would survive..... have survived. Not only survived but metamorphosed into frogs. None were visible in the puddle that sheltered them as tadpoles, but I spotted a number of them in the undergrowth next to it. It seems that the wetter than usual summer has been a boon for them, maintaining water bodies that may otherwise have dried up. Individuals were not more than 2 cm in length, as can be seen from the picture below. The frogs are about 4 months old, based on average spawning dates for Rana temporaria in Ireland (1) and the size of the tadpoles when they were first spotted in May. However, I wouldn't try to put an exact age on them based on size.

Common Frog, Rana temporaria
Other than the obvious external changes, R. temporaria adults also have quite different stomachs to their tadpole stage. The gastric mucosa is removed and a new adult, definitive one develops, along with peripheral connective and muscular tissues (2).

References: 
  1. Sterry, 2004. Collins Complete Guide to Irish Wildlife p. 94
    Rovira et al., 1995. Tissue Cell 27 pp. 13-22

Thursday, July 19, 2012

The Bee Orchid

Bee Orchid, Ophrys apifera
Probably the most beautiful wildflower growing in Ireland is the Bee Orchid (Ophrys apifera). Its devastatingly ornate flowers are shaped, as the common name suggests, just like a bee. Such morphology is a form of mimicry used to facilitate pollination. No pollen nectar or pollen is offered by O. apifera to potential pollinators: instead male bees are attracted by odours that act on their sexual instincts (1). Patrolling males that are attracted to a flower become sexually excited and alight on the labellum. The male is then guided in a copulation attempt by a variety of tactile clues such as the firmness of the labellum. Movements during such copulation attempts brings about pollination. Other species of the Ophrys genus have similar chemical, visual and tactile stimuli which are sufficiently different from each other to act as pollination barriers between taxa. However, in Ireland (and Britain) there is an absence of a sufficent pollinator O. apifera are self-fertilised here (2).
Bee Orchid, Ophrys apifera
O. apifera is a perennial of grassy, calcareous ground, and is especially prevalent on recently disturbed ground (3, 4). Numbers in Ireland have been in decline since the beginning of the twentieth century due to a combination of altered agricultural practices and habitat loss (2). In County Cork, most sites for O. apifera are located on the west and east coasts and, according to Tony O'Mahony's Wildflowers of Cork City and County (2) no sites in Mid Cork are in existence. It was therefore with some excitement that I discovered c. 10 plants in a 2 m2 area of ground in an abandoned, flooded quarry just outside Shanbally some 19 km from Cork city. The disturbed nature of the quarry and the calcareous parent material provide the perfect habitat for this enigmatic flower.
Bee Orchid, Ophrys apifera
References:
  1. Karin and Karlson, 1990. Phytochemistry 29 pp. 1359-1387
  2. O'Mahony, 2009. Wildflowers of Cork City and County pp. 302-303
  3. Phillips, 1977. Wild Flowers of Britain p. 94
  4. Gardiner and Vaughan, 2009. Conservation Evidence 6 pp. 39-41

Thursday, July 12, 2012

Centaury Tackles Diabetes

Diabetes mellitus, commonly referred to as just diabetes, is a metabolic disease resulting from defects in insulin metabolism. This may be due to an inability of ones own pancreas to produce enough insulin or if a body cannot utilise insulin that is produced effectively. Since insulin controls blood sugar levels, this results in chronic hyperglycemia (heightened blood sugar levels) in individuals which leads to long-term damage of, but not limited to, the body's nervous and circulatory systems. With the WHO estimating that 3.4 million people died in 2004 alone of diabetes and that some 346 million people worldwide have the disease, it is recognised as a serious global health issue (1).
Common Centaury, Centaurium erythraea
One of the complications associated with diabetes is the increased production of free radicals, such as reactive oxygen species, due to hyperglycemia (2). These unstable radicals react with lipids, proteins and DNA in cells, producing cellular changes and abnormal function. It has been proposed that phytochemicals could be a valuable source of compounds that could be used to control free radical concentrations (3). One such source is from the pretty but unassuming annual flower Common Centaury (Centaurium erythraea). At this time of the year, its pink flowers are in bloom in dry grassy places, sand dunes and waste places (the plants pictured were seen in an abandoned quarry) (4). Though capable of growing to 50 cm, it rarely reaches more that 15 cm in height and is widespread throughout much of Europe, western Asia and North Africa with several chemotypes described (5). It is also present in North America and Australia as an introduced alien.
Common Centaury, Centaurium erythraea
C. erythraea is commonly used in traditional medicine as a purgative, sedative, to relieve indigestion and to relieve indigestion and to treat jaundice, wounds and sores (2). It has also been shown to have antioxidant properties, and with this in mind, rats that had diabetes induced experimentally were treated with extract of C. erythraea leaves by researchers in Tunisia and Morocco (2). It was shown that oxidative stress and pancreatic cell damage decreased in those animals treated with the leaf extract. Indeed, that pancreatic ╬▓ cells of diabetic animals treated with C. erythraea showed nearly normal morphology after treatment. While the exact molecular mechanism of action remains unclear, such results are promising in the global battle against diabetes.

References:
  1. http://www.who.int/mediacentre/factsheets/fs312/en/index.html
  2. Sefi et al., 2011. Journal of Ethnopharmacology 135 pp. 243-250
  3. Eddouks et al., 2005. Journal of Ethnopharmacology 102 pp. 228-232
  4. Phillips, 1977. Wild Flowers of Britain p. 116
  5. Šiler et al., 2012. Industrial Crops and Products 40 pp. 336-344

Tuesday, July 10, 2012

Mating Success and Larval Aggression

Male Large Red Damselfly, Pyrrhosoma nymphula
The Large Red Damselfly (Pyrrhosoma nymphula) is the only red bodied damselfly to be found in Ireland, something that makes identification of the adults quite easy. They also seem to be the most friendly: the individual pictured landed on my shoulder just after I had taken its photograph. However, like all other damsel- and dragonflies, the Large Red Damselfly spends the majority of its life as an aquatic nymph. This means that this stage of its life is the most important for mating success as an adult. Larval P. nymphula are territorial predators (1), generally found in acid water such as shallow bog pools and small oligotrophic and mesotrophic lakes. Due to the frequency of such habitats in Ireland, P. nymphula is one of the most widespread and frequently recorded damselflies in the country (2). During the nymphs four instar stages, it is feeding during the first three that determines the size in the last stage, and ultimately the size of the adult. Larger males have been shown to win more territorial disputes and thus obtain more mating events near water (1). So therefore the territorial aggressiveness of larval P. nymphula enhances short-term mating success in the adult stage.

References:
  1. Harvey and Corbet, 1985. Animal Behaviour 33 pp. 561-565
  2. Nelson and Thompson, 2004. The Natural History of Ireland's Dragonflies pp. 154-160

Wednesday, July 4, 2012

Climbing Up the Walls

Volucella pellucans
One of the larger hoverflies on the wing at this time of year is Volucella pellucans, a shiny syrphid with a strikingly distinctive half-black, half-white abdomen. Adults are common visitors to flowers such as bramble, various umbelliferous species and, as is the case in the individual pictured, other garden flowers such as privet. Females will lay eggs in wasps's nests with the resultant larvae living inside as scavengers (1).
"Foot" of Volucella pellucans
For its size (up to 15 mm), V. pellucans is quite agile upon lighting on a flower. This is due to a system of setose attachment pads on the pulvillus (located between the claws at the base of the tarsus). The setae create friction between the fly's leg and the surface. Due to its relatively large size, V. pellucans creates a greater frictional force than smaller hoverflies, but needs less acceleration to detach itself from the surface (2).

References:
  1. Chinery, 2004. Collins Gem Insects p. 199
  2. Gorb et al., 2001. The Journal of Experimental Biology 204 pp. 1421-1431

Rag-Robin-Rag

Ragged Robin, Lychnis flos-cuculi
A beautiful flower with a wonderful name, the Ragged Robin (Lychnis flos-cuculi) is perennial native to Ireland that begins flowering in May and continues to do so until August. For me, its charm lies in its ragged flowers, which are borne on stems up to 70 cm high. They consist of five petals, but each of these has four lobes making it seem like there are more. While it can be seen sometimes brightening up some roadside verges, it is most common in fens, marshes and damp grasslands (1). Unfortunately these habitats are becoming all to scarce in this country and the plant is now less common than it once was. Such habitat loss and fragmentation will lead to increased instances of inbreeding and associated inbreeding depression in populations of L. flos-cuculi. This has been shown to have a significant effect on the fitness of subsequent generations (2).
Ragged Robin, Lychnis flos-cuculi
References:
  1. Phillips, 1977. Wild Flowers of Britain p. 90
  2. Hauser and Loeschcke, 1996. Evolution 50 pp. 1119-1126

Tuesday, July 3, 2012

Why So Blue?

Male Common Blue Damselfly, Enallagma cyathigerium
The iridescent turquoise colour of the male Common Blue Damselfly (Enallagma cyathigerium) is a most enchanting thing to behold. It is common throughout Europe and in Ireland is the most frequently encountered damselfly. This is especially the case at this time of year, when individuals are at their most active (and will continue to be so until early August) around open and still waters. E. cyathigerium is especially characteristic of ponds and lakes with large areas of open water and beds of submerged vegetation. Its abundance in Ireland can in part be attributed to its greater tolerance of exposed, open shores as well as highly eutrophic lakes in comparison to other odonate species (1).
E. cyathigerium males' radiant blue comes from the interference and coherent reflection of light from photonic crystals in its cuticular epidermis (2). The colour is at its most conspicuous against surrounding aquatic vegetation during midday and it is at this time that E. cyathigerium is most active (3). Other Enallagma spp. with different colurs (red, yellow) are similarly most active in the evening when low sun angles provided the most contrast. It has been proposed that this The role of such an ability to stand allows males to distinguish both sexually and specifically between individuals (3).

References:
  1. Nelson and Thompson, 2004. The Natural History of Ireland's Dragonflies pp. 128-135
  2. Prum et al., 2004. Journal of Experimental Biology 207 pp. 3999-4009
  3. Schultz et al., 2008. Animal Behaviour 76 pp. 1357-1364