Thursday, January 7, 2016

The First Irish Trees

The wettest winter on record has finally brought us a cold snap. Temperatures that were touching the mid-teens have finally reverted to the winter norm and started to approach zero, bringing with them the long missed pleasure of the crisp, dazzlingly bright morning. Blue skies frame naked trees, an architecture that is all too absent from the Irish landscape. Despite having a reputation for being a verdant land, Ireland has long had the lowest area of forestry in the EU. Only 10.5% of the country is covered in forest (1). And while this is estimated to be at its highest level in 350 years (in 1928 the percentage cover was a measly 1.2%), more than three quarters of this are non-native coniferous plantations. The methods of cultivation of these forests, namely close and intensive planting which discourages lateral branching to maintain the bulk of the timber in one solid piece, renders such forests as areas of monoculture (predominantly Sitka Spruce, Picea sitchensis (1)) with a very low level of biodiversity. What we would refer to as native woodlands account for only a small fraction of Irish forests, but even calling them native is rather misleading as many of these are also themselves deliberately planted, such as Powerscourt estate in Co. Wicklow which dates to the first half of the 18th century (2). In truth, even trees in Ireland unmolested by humankind can only date from the after the most recent global glaciation period, when the vast majority of the island of Ireland was covered in ice.

Yet the history of Irish trees does extend back beyond the ice age, back into the mists of the Devonian period, some 350 million years ago when Ireland, as we know it now, was to be found near the equator. The present Irish landmass which had been previously divided by an ocean, now began to develop small lakes (3). These were surrounded by what many people believed to be the first tree, Archaeopteris, specifically Archaeopteris hibernica. Paleobotanical evidence points to plant species prior to this as tending to be ground covering. This was also thought of A. hibernica when it was first discovered, as the leaf like fronds were described separate to its woody trunk (called Callixylon) (4). This Callixylon could grow to impressive sizes, with fossils one meter in diameter and ten meters in length often being unearthed. Yet it was incorrectly identified as a Late Devonian conifer in when described in 1911. It took nearly 50 years for the link between Callixylon and Archaeopteris to be made. A chance discovery of a section of Archeaopteris with parts of the woody stem attached by Charles Beck allowed both Archaeopteris to be given the title of tree and the establishment of the extinct group of plants the progymnosperms (4). He was able to section an immaculately preserved sample and show that the attached wood was indeed Callixylon.

Archaeopteris hibernica fossil

Archaeopteris plants were non-seed bearing, producing spores much like modern day ferns on fronds that were arranged on branches. These extruded horizontally and in a helical pattern from a single trunk (5). Branching patterns were quite complex and longer living in comparison to other plants at the time allowed Archaeopteris to occupy more space, more efficiently. Indeed, it shares many of these features phylogenetically with modern seed plants (5). Its success was such that it was the pre-eminent vegetation of forests in the Late Devonian period though to the Mississippian.

Recreation of Archaeopteris hibernica

In old Devonian Ireland, A. hibernica was dominant. Wonderfully preserved examples of the fronds have been recovered from the Devonian-Carboniferous Kiltorcan Formation in Co. Kilkenny. Study of this area reveals a swamp like environment, with meandering streams feeding into pools surrounded by dense growth of A. hibernica (6).

References:
  1. Teagasc.,2014. Irish Forests -  Annual Statistics. http://www.teagasc.ie/forestry/docs/stats/Ireland%20Forests%20-%20Annual%20Statistics%20Report%20-%20issue%202014.pdf
  2. Pilcher and Hall, 2004. Flora Hibernica. Collins Press, Cork.
  3. Clayton et al. 1979. Journal of Earth Sciences. Vol. 2, pp. 161-183.
  4. Bora, 2010. Principles of Paleobotany. Mittal Publications.
  5. Meyer-Berthaud et al. 1999. Nature 398 pp. 700-701.
  6. Jarvis, 2000. Geological Society, London, Special Publications 180 pp. 333-341.

Tuesday, February 10, 2015

A Barrel of Pain

A common jellyfish found off the Irish coast, the Barrel Jellyfish, Rhizostoma pulmo, has quite an extensive range. It is distributed in the Irish Sea, the Bay of Biscay, the North Sea, the Black Sea and is found extensively throughout the Mediterranean, so much so that it commercially fished (albeit on a small scale) off the coast of Turkey (1). It has even been found off the coast of Pakistan, where a record again associated with commercial fishing of the jellyfish was reported in 2007 (2). It is quite a striking animal, with a robust appearance and an ethereal, blushed mauve coloration. Despite their their relatively large size (up to 60 cm in diameter), and possibly due to an underreporting of cases, it was assumed for many years that this species was harmless to humans (3). However, this is no longer the case (4).
 
Barrel Jellyfish, Rhizostoma pulmo
 
R. pulmo, like all jellyfish, is contradictory animal being as it is a relatively simple organism with quite a complex life cycle. This begins with the production of pelagic planulae by sexually mature adult that settle as polyps on hard substrates on the sea bed. These then metamorphose into strobilae, which reproduce asexually to form 8-rayed ephyrae. Up to eight of these may be produced per strobila. These detach to roam the pelagic zone where they mature into the adult medusae (5).
 
Barrel Jellyfish, Rhizostoma pulmo
 
Adults produce Rhizolysin, a cytolysin, from their nematocysts for subduing prey. This has cytotoxic, hemolytic and clastogenic activity against human cells, which leads to irritation and the production of lesions upon contact with the skin (4, 6). Such lesions last for a few hours, but the subsequent pain can last for a period of days, causing considerable discomfort.


References:
  1. Omori & Nakano, 2001. Hydrobiologia 451 pp. 19–26.
  2. Muhammed & Sultana, 2007. JMBA2 Biodiversity Records (Published on-line) pp. 1–3.
  3. Addad et al, 2011. Marine Drugs 9 pp. 967-983.
  4. Kokelj & Plozzer, 2002. Contact Dermatitis 46 pp. 179-180.
  5. Fuentes et al, 2011. Marine Biology 158 pp. 2247-2266.
  6. Allavenaa et al, 1998. Toxicon 36 pp. 933–936.

Wednesday, February 13, 2013

A Personable Little Bug

Firebug, Pyrrhocoris apterus
As I progress through life, my opinions and outlook has changed, in a way that I would like to think is more mature. One thing that has not changed about me though is how I tend to be led by my stomach. When I'm hungry I need to eat. Otherwise I get irritable and withdrawn. People often mistake it for some deep troubles within me, but its just a primal need to fill my belly. However I have learned to deal with it though in the simple possible way: regular eating. And sometimes the joys are not only culinary. Recently hunger grabbed me in Cork city and I made my way into the nearest cafe, a wonderful vegan eaterie (I'm an omnivarian, I'll eat anything at all, and don't mind if there is no meat with my meal as many carnivores often do). While tucking into my felafel and salad (which was smashing, if you were wondering), my eye was caught by something small and red on the Crassula plant that was in front of me. I was a Firebug (Pyrrhocoris apterus), a species that if not native to Ireland and a species that, as far as I can ascertain, has not been reported here before. The mature adult had been there at least one week, according to the staff, and may have arrived in one of the many deliveries of vegetables that they receive every week from continental Europe where P. apterus has its base. A flightless bug, it feeds on Lime trees and tree-mallows, and is most associated with its swarming behaviour whereby numerous individuals clamour together. Its common name, Firebug comes from its wonderful crimson colour that contrast wonderfully with the black markings on its abdomen creating an almost face-like effect.

As with all insects, P. apterus goes through a series of ecdyses through out its life, five in all from hatching to adulthood. Interestingly it has been shown that at different stages of moult, individuals show distinctly different personalities. Larvae differed from adults in general in that they were bolder, explored their environment more thoroughly and seemed to be more active before final ecdysis (1). This raises the intriguing concept of personality differences between individual organisms as inherited traits. In an environment, it is argued, if fitness payoffs are dependent on an organisms behavioural history and the frequencies of competing strategies then personality differences can be selected for (2). It certainly is an interesting idea and is supported by evidence from diverse sources as lab rats, where heavier newborns are braver and more explorative (3), field crickets, where personality changes at maturity (4), and squid, where size determines personality. How exactly the behavioural changes take place in P. apterus is not know, but it may be due to hormonal reorganisation.
 
So perhaps my apparent grouchiness due to lack of food is just my inheritance...

References:
  1. Gyuris et al., 2012. Animal Behaviour 84 pp. 103-109
  2. Dall et al., 2004. Ecology letters 7 pp. 734-739
  3. Rödel and Meyer 2011. Developmental Psychobiology 53 pp. 601-613
  4. Niemelä at al., 2011. Functional Ecology 26 pp. 450-456
  5. Sinn and Moltschaniwskyj, 2005. Journal of Comparative Psychology 119 pp. 99-110


Thursday, December 27, 2012

A Mayfly in December

Mayfly
It has been a a mild winter here in Ireland, especially considering the arctic conditions of two and three years ago. It is therefore not unusual to see a few strange phenological events occurring, such as plants in full flower and moths on the wing. One of the oddest, yet most delightful that I have seen recently is most certainly an adult mayfly, on the wing, not eleven days ago some 17 km from Cork city. It was odd because, as the name suggests, mayflies tend to emerge around May. Yet the emergence period for some species can from March to October. Still, seeing one a little over a week from Christmas was a little peculiar.

This sighting is also of interest as it brings to mind the recently published Red List of Irish Ephemoptera (1), detailing a check-list of the Irish species and their conservation status. Ireland is home to 33 species of mayfly, quite a low number in comparison to that of mainland Europe (350 species, (2)). However, even this relatively low number of species contributes greatly to their associated aquatic habitats. Mayflies spend the majority of their life in nymphal form (in some cases up to three years), and the feeding of these nymphs contributes greatly to the cycling and availability of nutrients in aquatic habitats (3). Such feeding can also greatly contribute to the cleansing of water systems and help maintain their integrity. On emergence from the nymphal stage the mayfly, uniquely in the insect world, passes through two terrestrail adult stages: the winged subimago and the winged and sexually mature imago. The life of these two stages is quite short in comparison to the nymphs (little more than a couple of hours in some stages), but large scale, synchronous emergence of adults results in significant movement of nitrogen and phosphorus from aquatic to terrestrial environments (3).

Check-list of Irish Mayflies. Key: CR = Critically Endangered, EN = Endangered, VU = Vulnerable, NT = Near Threatened, lc = least concern dd = deficient data.
SpeciesConservation Status
Siphlonurus armatusCR
Baetis atrebatinusEN
Ephemerella notataEN
Rhithrogena germanicaVU
Procloeon bifidumVU
Leptophlebia marginataVU
Kageronia fuscogriseaNT
Ameletus inopinatusNT
Baetis fuscatusdd
Alainites (Baetis) muticuslc
Baetis rhodanilc
Baetis scambuslc
Baetis vernuslc
Caenis horarialc
Caenis luctuosalc
Caenis macruralc
Caenis rivulorumlc
Centroptilum luteolumlc
Cloeon dipterumlc
Cloeon similelc
Ecdyonurus disparlc
Ecdyonurus insignislc
Ecdyonurus torrentislc
Ecdyonurus venosuslc
Electrogena lateralislc
Ephemera danicalc
Heptagenia sulphurealc
Leptophlebia vespertinalc
Paraleptophlebia cinctalc
Rhithrogena semicoloratalc
Serratella ignitalc
Siphlonurus alternatuslc
Siphlonurus lacustrislc

In Ireland, six species of mayfly are listed as critically endangered, with two more near threatened (1). All of these species have restricted distributions and it is unfortunately unsurprising that they are classed as such. The are species found in streams and rivers, which points to the increased pressures of pollution that these habitats have had, and unfortunately continue to have (1).

References:
  1. Kelly-Quinn and Regan, 2012. Ireland Red List No. 7: Mayflies (Ephemeroptera). National Parks and Wildlife Service, Department of Arts, Heritage and the Gaeltacht, Dublin, Ireland
  2. Brittain, Michel Sartori, 2009. Encyclopedia of Insects pp. 328-334
  3. Burian, 2009. Encyclopedia of Inland Waters pp. 299-314

Wednesday, December 26, 2012

A Winter-time Orange

Yellow Brain Fungus, Tremella mesenterica
Trees denuned of their leaves can make for many a forlorn vista at this time of the year, but they do provide the opportunity to spot some strange fruit indeed. Arboreal fungi that would otherwise remain obscured are quite visible among the bare branches. One of the most obvious is the shocking-orange coloured Yellow Brain Fungus (Tremella mesenterica). For all the world looking like somebodies discarded worryingly luminous bubblegum, T. mesenterica is (like all members of the Tremella genus) an obligate parasite of other fungi. In Ireland it is most commonly encountered on Gorse (Ulex spp.), where its host is most commonly found growing, fungi of the genus Peniophora. Indeed, T. mesenterica is often found growing on the upper part of a Gorse branch with the Peniophora species producing fruiting bodies on the underneath of the branch (1).
Yellow Brain Fungus, Tremella mesenterica
T. mensenterica's almost cartoonish colour belies an organism that has shown itself to have a number of surprising and useful applications. For example, fruiting bodies of the fungus fed to rats with diabetes have been shown to have a significant effect on the disorder (2). It also posses extracellular polysaccharides that have been shown to have immunomodulatory properties and thus may have potential in anti-tumor and anti-inflammatory treatments (3). Specifically, it has been shown to surpress the production of hormones (human chorionic gonadotropin) associated with tumor cells and therefore may have a role in the chemotherapeutic treatment of certain forms of cancer in the future (4).
References:
  1. Roberts, 1995. Mycologist 9 pp. 110-114
  2. Hui-Chen et al., 2006. Life Sciences 78 pp. 1957-1966
  3. Nan-Yin et al., 2006. Food Chemistry 99 pp. 92-97
  4. Yen-Wen et al., 2006. Life Sciences 79 pp. 584-590

Tuesday, December 25, 2012

The Holly and the Ivy... and the Ivy

The two leaf forms of ivy (Hedera helix), cordate (left) and palmate (right)
Its Christmas time, and all around the house... people have placed a variety of plants to add to create a festive spirit about. Poinsettias have become quite popular in this part of the world (and make a convenient, low risk present for neighbours), but the traditional Christmas trees and garlands of holly and ivy are still the most popular. All three of these now Christian traditions arose from older traditions (1): ivy (Hedera helix) in particular was considered a sybol of female fertility because of its late flowering period (September to November) and production of berries (around this time of the year) (2). Although it can be quite an invasive pest in some parts of the world, these two facts make it an important source of nectar and pollen for insects in late autumn/early winter and an equally important source of food for birds later in the year in its native range.

However, one of the most striking features of holly is that two distinct, different leaf shapes will be seen on the one plant - a five lobed, palmate form and a cordate form that shows little to no lobing. The lobed leaf is found on the climbing, juvenile stems of the plant, with the cordate form on the flowering stems. This is known as heteroblasty, a phenomenon that is found in many plant species, but that is most famously illustrated in ivy. It was first described by Karl Goebel in 1898, who noted that as plants grow they add new modules (stem with attached leaf) which show gradual changes of form in most cases (3). However in some species, such as ivy, the changes are more dramatic. The reasons for this are still unclear but defence against herbivory and nutrient and water supply differences have been suggested as causes (3). Indeed, Ivy has been shown to produce palmate leaves in low light conditions and cordate leaves in high light (4).
 
References:
  1. Miles, 2008. Christmas in Ritual and Tradition, Christian and Pagan p. 275
  2. Phillips, 1977. Wild Flowers of Britain p. 172
  3. Zotz et al., 2011. Botannical Reviews 77 pp. 109–151
  4. Rogler and Hackett, 1975. Physiologia Plantarum 34 pp. 141–147

Tuesday, December 11, 2012

Hiding Out With The Cuttlefish

Common Cuttlefish (Sepia officinalis)
The ability of cephalopods to vary their colour has been known since antiquity and while most species can achieve impressive colour changes, few can match the common cuttlefish (Sepia officinalis) for sheer dramatic quality. This is in part due to the size (1.5 mm in diameter) and density (50 per square mm) of the chromatophores (1), the neurally controlled colour bearing organs that can change the pigmentation and hence appearance of the animal with incredible detail. However in part it is, as the chromatophores are just one movement in the symphony that makes each animals body pattern.

Body pattern change is used in feeding feeding, avoiding predators and communication, and is therefore an integral part of S. officinalis life history. Its most striking aspect are the chromatophores, organs that are unique in the animal kingdom to cephalopods. Body pattern is controlled in a hierarchical fashion in S. officinalis: behaviour will dictate body pattern and hence organ response. Body pattern is constructed using four components, such as coloration of which chromatophores play a part. However, they are aided by organs such as leucophores which scatter light of all waveslengths and iridiphores, which produce interference colours when viewed from certain angles, often giving pink and iridescent greens and blues (1). The other three components are textural (the smoothness or papillation of the skin), postural (the orientation of the body parts) and locomotor (the action of the animal, e.g. resting, burying, scuttling, etc.). These components are themselves divided into units which are in turn divided into elements, such as the previously mentioned chromatophores. This complex hierarchy of organisation allows for the wide variety of body shapes observed in S. officinalis.
 
Such an intricate response mechanism is under tight control of the central nervous system and is driven by visual stimuli. Environmental cues taken in by the eye and transferred to the optic lobe where information is processed and transferred to the lateral basal lobe which will control motor response (1). Amazingly, these neural areas are already well developed upon hatching in S. officinalis and newly emerged cuttlefish are immediately able to conceal themselves from predators (2). They use strategies such as colour resemblence, disruptive coloration, obliterative shading, shadow elimination, disguise and adaptive behaviour to avoid becoming a meal from fish such as the Comber (Serranus cabrilla).
 
Human ability to distinguish symmetrical objects easily and quickly lead to the assumption that the use of these behaviours would be greatly enhanced by the use of asymmetrical patterns. However, it has been demonstrated that in cryptic behaviour, S. officinalis will exhibit a high degree of bilateral symmetry (3). This seems counter-intuitive: symmetrical objects would stick out much more obviously in a random, asymmetrical environment. Yet S. officinalis is notoriously difficult to spot in its native environment. This may be due to a number of factors (3). Predators of S. officinalis may not use symmetry as a visual clue. Also the orientation of the axis of symmetry is important, as unless the axis is horizontal or vertical, symmetry becomes less apparent to the viewer. Alternatively, symmetry may play a vital role in concealment. By highlighting a symmetrical pattern on its body, S. officinalis may be taking the emphasis off its own body shape, making it seem just an interesting but inedible artifact to its predators.
References:
  1. Hanlon and Messenger, 1998. Cephalod Behaviour pp. 31-46
  2. Langridge, 2006. Proceedings of the Royal Society Series B 273 pp. 959-967
  3. Hanlon and J. B. Messenger, 1988. Philosophical Transactions of the Royal Society of London, Series B, Biological Sciences 320 pp. 437-487
Cuttlefish picture taken at Galway Atlantiquaria, Salthill, Co. Galway.