Sticking with it: Footprints of the Starfish

The most common starfish found in Irish waters, and in the north-east Atlantic as a whole, Asterias rubens can be found in quite deep waters, but is usually found in the intertidal region where it feeds on a variety of molluscs (1). The quantity of prey to be found is quite high here, but so are the challenges posed to A. rubens. These chiefly come from the disruptive action of waves, which can easily wash individuals onto the shore line, which is just what happen to the starfish pictured.
 

Common Starfish, Asterias rubens

A. rubens overcomes this by the ingenious use of adhesives. The numerous tube feet located on the underside of the animal that are used for locomotion, secrete globular nanostructures forming a meshwork deposited on a thin homogeneous film (2). Two cell types have been identified in the production of this adhesive material:- type 1 cells, which produce the material forming the meshwork, and type 2 cells which are responsible for the release of the material constituting the homogeneous film. These will leave behind a footprint with a reticulate pattern on the substrate. This pattern is due to the arrangement of the adhesive cell secretory pores on the disc surface of the tube feet.

References:

1. Allen, 1983. Journal of Experimental Marine Biology and Ecology 70 pp. 79-90
2. Hennebert et al., Journal of Structural Biology 164 (2008) 108–118

Established: The Harlequin Ladybird

Harlequin Ladybird (Harmonia axyridis var. succinea) adult at site of establishment near Cork city

Our recent record of the Harlequin Ladybird (Harmonia axyridis) prompted me to reexamine some older pictures of Coccinellidae beetles, to see if any other of the morphs had inadvertently been seen. Lo and behold, buried among the pictures of moths, flowers and wading birds, there was an example of H. axyridis var. succinea. However, this was just one picture among about 25 taken. The rest showed no more adults, but, worryingly, did show many, many pupae as well as larvae. These pictures taken on the 19th of October, 2010 show the first evidence of establishment of H. axyridis in Ireland. 

Harlequin Ladybird (Harmonia axyridis) pupa at site of establishment near Cork city

The site of establishment is a collection of Griselinia littoralis bushes that border a footpath and that is backed by a small stream on a previously heavily industrialised area about 2 km from Cork city centre. The area is quite near the river Lee, Cork city's main river, and also near Tivoli Dock, a major container port that may be the site of entrance for H. axtridis. Examination of the site last week, just over a year after the first sighting, showed H. axyridis pupae still present on the same G. littoralis bushes, showing that it survived the unprecedently harsh weather last winter, something that has been observed in other countries such as Belgium (1). This is not the only site, with another being reported from Co. Carlow in July of this year. Establishment of H. axridis in Ireland is worrying, as they have had adverse effects on other Coccinellidae species where introduced in North America, reducing numbers by up to 20 times in some cases (2). They have also been seen to cause damage through feeding to soft fruits (grapes) and pears.

Harlequin Ladybird (Harmonia axyridis) larva at site of establishment near Cork city

References:

1. Berkvens et al., 2010. Journal of Insect Physiology 56 pp. 438-444
2. Kock, 2003. Journal of Insect Science, 3 pp. 1-16

King Harvest Has Surely Come

Leiobunum rotundum, feeding. Note the missing second leg on the animals left side. This is an example of autopasy, a defensive strategy involving losing an appendage along a preformed brake plane in response to stress such as a predator.

Everybody knows them, but few know much about them: Daddy Long Legs. Because of this lack of knowledge, much of what is known is superstition and folklore. Even the very name we give them, 'Daddy Long Legs', suggests a monstrous, lurking menace rather than the fascinating and ancient creatures that they are.
Daddy-Long-Legs (or Harvestmen) are arachnids of the order Opiliones and with over 5000 species described they are the third largest group of arachnids after the Acari (mites and ticks) and Aranae (spiders) (1). Their body has two basic regions; a prosoma (or cephalothorax) which carries all the appendages and eyes, and a limbless opisthosoma (or abdomen) which has the spiracels and genital opening. Although they resemble spiders, the two body regions are not clearly defined and they thus lack the constriction or waist that can be seen in spiders. Opiliones also lack spinning organs and so do not spin webs. They are in fact much more closely related to scorpions and pseudoscorpions (2) and are among the oldest of arachnids, with fossil records showing little morphological change in the group in 400 million years (1). They possess many characteristics that are unique to their group. These include the presence of paired trachae, the presence of a penis or spermatopositor organ in males and an ovipoistor in females and scent glands that are present on the prosoma (3). These glands release chemicals during defensive behaviour that can repel other arthropods (4). Other than these chemicals, opiliones do not produce venom and the commonly held belief that they are poisonous is untrue.
They are found on every continent, bar Antarctica, in moist to wet habitats and are excellent indicators of undisturbed environments where they feed on arthropods, snails and worms. These they ingest in particles, unlike many arachnids which need to liquify their food, and also may eat vegetable matter (2). Most species in the Northern Hemisphere overwinter as eggs, hatching in the spring. Maternal care is common in opiliones, as it is in many other arachnid groups, but uniquely so is paternal care. Adults reach maturity in the Autumn, which has lent them one of their common names, Harvestmen. Many species are very tolerant of other individuals, again unlike other arachnid groups, and often large aggregations of adults and subadults can be seen near water sources.
One of the most conspicuous of the 18 species of opiliones present in Ireland (15 native, 3 introduced and naturalised) (5) is the longlegged Leiobunum rotundum. Preferring open spaces, L. rotundum feeds on a variety of invertebrate prey as well as soft fruits (6). The individual pictured is mising one of its legs and thus shows an example of autopasy (also called autotomy). This is a situation where an outside agent is responsible for the severance of an appendage at a preformed breakage plane (e.g., the loss of limb to a predator who has seized it) (7). The limb will not grow back.

References:

1. Pinto-da-Rocha et al., 2007. Harvestmen: the biology of Opiliones
2. Giribet et al., 2002. Cladistics 18 pp. 5-70
3. Giribet, 2009. Encyclopedia of Insects pp. 247-248
4. Hara et al., 2005. Biochemical Systematics and Ecology 33 1210-1225
5. Ferriss et al., Irish Biodiversity: a taxonomic inventory of fauna pp. 83-84
6. Höfer et al., 2002. Arthropod Structure and Development 29 pp. 13-21
7. Maginnis, 2006. Behavioral Ecology 17 pp. 857-872

Irish Spurge Is English Too

Irish Spurge, Euphorbia hyberna

Ireland scored a little bit of a coup when Irish Spurge was given the scientific name Euphorbia hyberna. A spurge from Ireland, is the (very) rough translation, even though it is also found extensively in the south-western Mediterranean region and northern Portugal (1). Indeed its distribution in Ireland is limited to the south-west of the country, in Co. Kerry and west Co. Cork. It is to be found in damp, shaded areas, particularly wooded slopes where its upright stems bear striking yellow flowers that lack sepals or petals (2) and that were unfortunately gone from the plant pictured here. Due to its distribution in Iberia and the west of Ireland, it is frequently quoted as one of the 'Lusitana Flora' common to both areas, but lacking in the flora of Ireland's nearest neighbour, Britain. However this assertion is not true: E. hybernia is present in the flora of West Cornwall, North Devon and South Somerset, being extremely local in all three areas (3).

Irish Spurge, Euphorbia hyberna

References:

1. Appendino et al., 2002. Fitoterapia 73 pp. 576-582
2. Sterry, 2004. Collins Guide to Irish Wildlife p. 218
3. Stace, 1997. New flora of the British Isles p. 459

The Size of the Emerald Damselfly

Female Emerald Damselfly, Lestes sponsa

In the race to be the top of the heap in biological terms, organisms can follow two paths. They can take their time about it all, growing nice and big and strong, but missing out every time a potential mate comes by and they are not developed enough to take advantage of the situation. Or they can rush into things, becoming sexually mature quickly but growing to be small in size, and possibly unattractive to potential mates. What makes this choice all the more difficult is the prevalent environmental conditions that can, and often do, hinder the organsisms development. Availability of resources, threats from predators and the vagaries of the seasons mean that the chosen path is soon skewed. This has been elegantly demonstrated in a series of studies on the Emerald Damselfly, Lestes sponsa (1). This attractive, bottle-green odonate overwinters in the egg stage, has a brief larval period in spring, then emerges and reproduces in late June, the latest Irish damselfly to do so. It is common and widespread through out Ireland, commonly found near small lakes and acid ponds. L. sponsa individuals were measured for foraging activity, development rate and mass at emergence when exposed to the presence/absence of predators and the perceived onset of winter, and the abundance/scarcity of food and, again, the perceived onset of winter. In the presence of predators, all three perameters measured were reduced, while individuals under time constraints showed increased foraging and development, but decreased mass at emergence. Larvae that had an abundance of food showed high levels of all three parameters, while those that had time constraints in high levels of food showed lower mass at emergence, as was to be expected. What was not expected, however, was larvae at low food levels under time constraints showed very slow development and that largest mass at emergence. This is thought to be a result of this last group delaying emergence until the following season. Such life history plasticity is a feature of the life of L. sponsa.

Female Emerald Damselfly, Lestes sponsa

 References:

1. Johansson et al., 2001. Ecology 82 pp. 1857-1869

A Record of the Harlequin Ladybird in Cork City

Harlequin Ladybird, Harmonia axyridis f. spectabilis

One of the most imminent threats to native Irish species by invasives is the one the Harlequin Ladybird (Harmonia axyridis) poses to Irish native ladybirds. H. axyridis is larger and more aggressive than native Irish ladybird species and is thus able to out-compete them in hunting their preferred food of aphids. They also can have up to four generations per year, compared to the just one for native ladybird species and display less susceptibility to common diseases and parasites (1). Allied to this, H. axyridis also targets many non-aphid insect species, such as lepidopteran larvae and, most worryingly, ladybird larvae (2).

Harlequin Ladybird, Harmonia axyridis f. spectabilis

H. axyridis is native to Asia, specifically China, Japan, Korea, Mongolia and Siberia (1). Its voracious appetite for aphids marked it out as a seemingly effective biolocontrol agent and was introduced as such into the US in 1916. Establishment took some time but H. axyridis was recorded as such in 1988 and is now considered a pest there. Other than its effect on native ladybird populations, its tendency to overwinter in nooks and crannies in houses in quite large numbers make it a nuisance and may cause allergic reactions in inhabitants. Despite such problems, H. axyridis was inexplicably marketed as a biocontrol agent in mainland Europe in the 1990s. Commercial field releases first occurred in 1995 in France and was subsequently introduced as such in Belgium, Germany, Greece, Italy, the Netherlands, Spain, Portugal and Switzerland. H. axyridis has since spread to Austria, Luxembourg, Demark, Norway, Sweden and Great Britain, where it was first recorded in 2004 (3). The first Irish record for H. axyridis was in 2007 in Co. Down, with the first record for the Republic being in 2010 in Co. Wicklow (4). Another individual was recorded in 2010 in Cork City in November entering a house where individuals are wont to overwinter.
The individual pictured here was sighted entering a dwelling in the suburbs of Cork City on the 12th of October. Specifically, it was H. axyridis f. spectabilis that was sighted. This is the same variety that was seen in both records in 2010. Two other varieties are present throughout Europe, f. succinea and f. conspicua. H. axyridis is distinguished from other ladybird species by being noticibly larger, having red legs, being more domed than other species and may have a distinctive 'M' or 'W' mark on its pronotum (4).

References:

1. Brown et al., 2008. Biocontrol 53 pp. 5-21
2. Rhule et al., 2010. Biological Control 53 pp. 243-247
3. Roy et al., 2005. British Wildlife 16 pp. 403–407
4. http://invasives.biodiversityireland.ie/speciesalert-harlequin/

Common or Soprano: Which Bat Is It?

Pipistrelle in Flight

I recently saw a Pipistrelle bat fly past my window, its erratic flying pattern indicating it was feeding. Now I don't claim to have excellent eyesight, butI knew it a Pipistrelle as I know there is a roost nearby. Beyond this however, I could not say what species it was. Ireland has three species of Pipistrelle: Nathusius’ Pipistrelle (Pipistrellus nathusii), the Common Pipistrelle (P. pipistrellus) and the Soprano Pipistrelle (P. pygmaeus). The only confirmed breeding colony for P. nathusii in Ireland was recorded in 1997 near Lough Neagh and while there has been recordings in other counties, no records exist for the bat as far south as where I live (1). Its therefore extremely unlikely that is was P. nathusii that I saw. So that leaves P. pipistrellus or P. pygmaeus. However if I had spotted this bat pre-1999, I would have been sure that it was P. pipistrellus. Prior to this, P. pygmaeus was not recognised as a species in its own right. The two species are morphologically identical, measuring about 4 cm long with a 20 cm wingspan. Their difference lies in the frequency used by both bats during echo location (2). P. pipistrellus uses a call of 45 kHz, with P. pygmaeus using one of 55kHz. While differences were noted within the P. pipistrellus species as early as 1865 (2), it wasn't until the 1980s that the use of bat detectors revealed differences in the echo locating frequency of the two species. Further investigation showed that the two species occurred in close association however they did not share roosts. Conclusive support for the two-species theory was provided in differences in the cytochrome b genes.

References:

1. Russ et al., 1998. Journal of Zoology, London 245 pp. 345-349
2. Hulva et al., 2004. Molecular Phylogenetics and Evolution 32 pp. 1023-1035
3. Barrat et al., 1997. Nature 387pp. 138-139