The World's Largest Bony Fish

Reaching a weight of 1500 kg, the pelagic Ocean Sunfish (Mola mola) is a spectacular animal. Its distinctive laterally compressed shape and “chopped off” appearance make it one of the most distinctive of fish (1). Its truncated shape lends it its common name, as well as its tendency to bask on its side, close to the surface. One of only five members of the Molidae family, it has some unique features including the largest number of eggs produced by a vertebrate (300,000,000 eggs at one time) and larval metamorphosis that passes through two distinct stages (1). M. mola is distributed throughout the worlds oceans, with reports from the North and South Atlantic, the Pacific, the Mediterranean and the Gulf of Mexico (2). It feeds mainly on jellyfish and comb jellies, making it one of the few animals to do so. The increase in jellyfish numbers worldwide as commented on in this blog (here and here) means that there has been a marked increase in research into M. mola and the other sunfish species world wide. Satellite tracking of individuals has shown that they move up and down in the water column during the day and night, most probably in synchrony with their prey (2). They are also shown to migrate north in spring/summer and south in winter, again in response to prey movements but possibly also due to its preferred temperature range of 10-19°C (2). M. mola is preyed upon by relatively few other animals with reports of sharks, orcas and sea lions reported as feeding on them (3). They are, however, prone to high levels of parasitism, possibly due to their large surface area.

Ocean Sunfish, Mola mola

Unfortunately the picture used to illustrate this post is of a dead M. mola, caught off the south coast of Ireland and photographed in a fishmongers*. And while a live example would have been much more preferable, this picture does point to the fact that sunfish are being caught in huge numbers as a result of commercial fishing of swordfish and tuna species. These bycatch numbers are alarming: in South African swordfish and tuna fishing, 170 sunfish are caught for every 1000 hooks deployed (2). In Californian drift gillnet fishing for swordfish M. mola comprised 29% of total catch – much more than the target species (4). The enigmatic nature of this sunfish means that the effect of fishing practices on populations remains unknown.

*Note: The sale of all Molidae species is banned in the EU as they are classed as poisonous under Chapter II part G of Regulation (EC) no 854/2004 of the European Parliament and of the Council. I can only assume that the fish was for display purposes only.

References:

1. Bass et al., 2005. Marine Biology 148 pp. 405–414
2. Sims et al., 2009. Journal of Experimental Marine Biology and Ecology 307 pp. 127-133
3. Pope et al., 2010. Reviews in Fish Biology and Fisheries 20 pp. 471-487
4. Cartamil and Lowe, 2004. Marine Ecology Progress Series 266 pp. 245-253

The Caring Leech

Glossiphonia complanata

Mention leeches and immediately images of large, swamp dwelling beasts, stuck to the bodies of fever racked unfortunates, to be removed with a lighted cigarette, are conjured up. Yet Ireland has its fair share of the animals, some thirty two species from two orders and five families (1). Eighteen of these are marine. And they are not all out for your blood either. Many feed exclusively on other invertebrates. Take the fresh water Glossiphonia complanata, a snail leech. As its common name implies, it feeds on aquatic gastropods that it encounters in fast flowing, rock streams, although it will also feed on Oligochaeta, Chironomidae, and Amphipoda in decreasing magnitude (2). It achieves this by inserting its probiscus into the soft parts of its prey and sucking out their body fluids. G. complanata is a relatively short leech, with a broad body that is flattened dorso-ventrally. It is often encountered attached to the underside of stones, waiting for prey (3).

G. complanata shows a degree of parental care that is surprising for an invertebrate. As hermaphrodites, each individual produces a cocoon with a soft transparent covering containing the developing embryos. This is attached a stone and brooded over by the parent for about 20 days. Upon hatching, the young cling to the ventral surface of the parent (4).

References:

1. Ferriss et al., 2009. Irish Biodiversity: a Taxonomic Inventory of Fauna pp. 74-75
2. Wrona et al., 1979. Canadian Journal of Zoology 57 pp. 2136-2142
3. Mann, 1956. Journal of Animal Ecology 26
4. Kutschera, 1986. Animal Behaviour 34 pp. 941-942

It's Back

Borago officinalis

A guest post by Ken.

Three years ago, while out for a run, I spotted a most beautiful of blue flowers. I later identified it as Borago officinalis. It is a rare wild plant in Ireland. However every year I looked for it again but to my dismay was not to be found. So today you can imagine my delight in alighting again upon the same rare plant.

B. officinalis is a hairy annual herb known as 'Borage' and in Pakistan is called 'Lisan al-Thawr'. It is known for its mood elevating properties as early as the 1st century and is reputed as antispasmodic, antipyretic, demulcent, diuretic, antihypertensive, aphrodisiac and is also purported useful to treat asthma, bronchitis, cramps, diarrhea, kidney ailments and palpitations. Gilani et al. suggest the spasmolytic effects of crude extract of B. officinalis leaves are mediated through Ca++ antagonist mechanism which could explain its traditional use in hyperactive gastrointestinal, respiratory and cardiovascular disorders. (1)



Beautiful



The last time we met I took only one photograph of the plant with my Motorola V3 RAZR phone. It was never a clear picture but I used it as my phone's screen saver. Today I used a slightly more up to date phone and took more than one picture. I have a feeling that it might be a while before we meet again.

Later,

Ken.

1. Anwarul Hassan Gilani, Samra Bashir, Arif-ullah Khan, Pharmacological basis for the use of Borago officinalis in gastrointestinal, respiratory and cardiovascular disorders, Journal of Ethnopharmacology, Volume 114, Issue 3,  Dec 2007.

How to Click Like a Beetle

A click beetle, Athous haemorrhoidalis

One of the most common of the 25 species of click beetles (Elateridae) (1), Athous haemorrhoidalis is easily identifiable from its relatively narrow body, reddish-brown eltyra, darker head and thorax and the hairs coating its body that give it a downy appearance (2). The larvae, known as wireworms, feed on the roots of grasses and other plants and they, along with some Agriotes spp. are considered serious agricultural pests of cereal crops and potatoes (3).

A click beetle, Athous haemorrhoidalis

One of the most surprising features of A. haemorrhoidalis (and for the Elateridae as a whole) for someone encountering the beetle for the first time is its tendency to jump into the air, making a loud 'click' in the process, when alarmed. This action is achieved by the rapid sliding of a peg or spine located on the underside of the prosternum down a smooth track on the mesosternum (4). The beetle is propelled vertically up to 0.3 m high, turning head over tail several times during a jump. While an impressive (and entertaining) sight, this actual jumping action has been shown to be quite inefficient, with only 50-60% of energy expended in a jump is energy of translation, which actually raises the beetle (5).

References:

1. Ferriss et al., 2009. Irish Biodiversity: a Taxonomic Inventory of Fauna p. 98
2. Sterry, 2004. Collins Complete Guide to Irish Wildlife p. 148
3. Gibbons, 1999. Insects of Britain and Europe p. 207
4. Evans, 1972. Journal of Zoology 167 pp. 319-336
5. Evans, 1973. Journal of Zoology 169 pp. 181-194

Aphids Give Birth to Live Clones

Aphid female giving parthenogenetic birth

Why are there always seemingly innumerable aphids on plants? How come roses in a garden never have just one or two, but are covered in these little bugs, especially near the growing tips where the young tissue is easily pierced by the aphids' mouthparts to feed? The answer lies in the very plants they feed on: the aphid life-cycle and morphology is tailored to take direct advantage of available food sources. This is evident is in an impressive array of adaptations, on of the most startling being that species can reproduce asexually through parthenogenesis.
While female morphs predominate, male are produced in the autumn (1). Mating occurs to produce eggs that overwinter, hatching to produce females that give parthenogenetic birth to live young, which in turn reproduce parthenogenetically. This can result in huge numbers, which explains their ability to seemingly overwhelm plants if left uncontrolled. The young that are produced may be winged or wingless, with the winged individuals dispersing while the wingless are more optimised for reproduction. Such adaptations have been described by John Sorensen as nutrition driven evolution. Aphid life strategy means the individual is expendable but guarantees the survival of their genes.

References:

1. Sorensen, 2009. In Encyclopedia of Insects pp. 27-31

Spiral Tubeworm

Sinistral Spiral Tubeworm, Spirorbis borealis

Even though it rarely grows larger than 3mm in diameter, the Sinistral Spiral Tubeworm, Spirorbis borealis is quite conspicuous on the seashore doe to the whiteness of the calcareous tube it forms around itself and the fact that it tends to occur in large numbers (1). Emerging from the tube when submerged, S. borealis filter feeds using feathery appendages in a manner similar to other marine annelids. It is most commonly found on the surfaces of algae such as Fucus and Laminaria species. While it can also be seen on other algae, rocks and mollusc shells, S. borealis larvae when settling tend to favour Fucus and Laminaria surfaces (2). Indeed, this substrate preference is one way of differenciating them from similar species such as S. corallinae and S. tridentatus.

References:

1. Sterry, 2004. Collins Complete Guide to Irish Wildlife p. 174
2. De Silva, 1962. Journal of Experimental Biology 39 pp. 483-490

Eyes on a Parasite

Eyebright, Euphrasia spp.

A pretty, summer to autumn flowering plant of calcareous grasslands and sand dunes, Eyebright has long confused taxonomists (1). The similarity of the species and their tendancy to hybridise with each other means that the 20+ species present in Ireland and Britain as grouped together as Euphrasia officinalis agg.. Considered scarce around Ireland (2), the flowers are basically white but may have purple veins, yellow patches or may even be pink (3). Eyebrights are hemiparasites of grasses and other plants. They produce haustoria at their root tips that burrow into the roots of the host and extract nutrients (4). Plants are capable of surviving without a host, however growth is reduced in such individuals (5).

References:

1. Silverside, 1991. Watsonia 18 pp. 343-350
2. Sterry, 2004. Collins Complete Guide to Irish Wildlife p. 242
3. Phillips, 1977. Wildflowers of Britain p. 92
4. Yeo, 1961. Watsonia 5 pp. 11-22
5. Yeo, 1964. Watsonia 6 pp. 1-24

Update on the Red Lily Beetle: Larval Camouflage

The presence of the Red Lily Beetle (Liloceris lilii) that was previously noted in this blog (here and again here) in a garden in Cork in Ireland has continued despite control attempts. Gardens within a 50 meter radius of the original recorded site have seen extensive damage to lily plants and scores of beetles have been reported from beds. Larvae at various instar stages are now visible on plants (see below).

Red Lily Beetle Larva. Note the covering of faeces that acts as camouflage.

Red Lily Beetle Larva

Red Lily Beetle Larvae with damage to lily

The Emperor in Ireland

Female Emperor Dragonfly, Anax imperator

One of the largest species of dragonflies in Europe, the Emperor Dragonfly (Anax imperator) is an impressive beast. Reaching an average length of c. 8 cm in flight they are unmistakable. Their markings too make it unlikely to be confused with other species. The males have an electric blue abdomen with a black stripe down it and a green thorax. The female pictured here differs in having a green abdomen. It was sighted on a meadowed area by a river glen near Cork city.

In Ireland, A. imperator was only recognised as being present on the island in 2000 (1). Previous records are not considered substantial enough to be accepted. A. imperator is widespread in southern parts of England and Wales with movement northwards noted in the 1980s. It is now established in Ireland as of 2000-01 with successful breeding being proved. This movement northwards of A. imperator follows the pattern of other dragonfly species that is taken by some authors as further evidence for global warming (2).

References:

1. Nelson et al., 2003. Irish Naturalists' Journal 27 pp. 266-272
2. Ott, 2010. in Atlas of Biodiversity Risk pp. 78-79