Dog Lichen Out Muscles the Grass

Dog Lichen, Peltigera canina

Lichens are excellent primary collonisers. All they need is sunlight, something to anchor to and, given enough moisture, they will grow. Most species are to seen on bare rock, on the bark of trees or the peaty soils of moors. Here their main competitors for light resources are bryophytes which rarely outgrow them. There are some exceptions, however, a notable one being the Dog Lichen, Peltigera canina. While it can be found on walls and rocks and other dry habitats, this marcolichen with Nostoc cyanobacteria as its photobiont (1), is most commonly seen in Ireland growing among grasses in woods and lawns (2). The large lobed thalli can form patches 10 cm across, which helps when competing with grasses for resources. Furthermore, the lichen has been shown to produce compounds with inhibitory effects on the germination of grass seeds and the subsequent growth of seedlings (3). The presence of cyanobacteria as the photobiont also gives P. canina the competitive advantage of being able to fix its own nitrogen (4).

Thalli of the Dog Lichen, Peltigera canina

The thalli of P. canina are thick and downy and when wet are dull brown, but pale grey when dry and produce distinctive reddish brown spore producing structures on the edge of the lobes (2) (the sample pictured was observed in January). The underside is covered with well developed rhizinae.

Fruiting Structures of the Dog Lichen, Peltigera canina

The ability of P. canina to survive in a number of habitats lies in the fact that its is not a single species but a species complex (5). Twenty five taxa are known in the complex, however only seventeen of these are recognised, the other eight being under-described.

Rhizinae of the Dog Lichen, Peltigera canina

References:

1. Miadlikowska and Lutzoni 2000, International Journal of Plant Science 161 pp. 925–958
2. Phillips 1980, Grasses, Ferns, Mosses and Lichens of Great Britain and Ireland p. 176
3. Pyatt 1967, The Bryologist 70 pp. 326-329
4. Lockhart et al. 1978, FEMS Microbiology Letters 3 pp. 127–130
5. Miadlikowska et al. 2003, Mycologia 95 pp. 1181–1203

Who Needs a Shell?

Nudibranch

Bar cephalopods, most marine molluscs move slowly, if at all. While this leaves them open to predation, tough calcium based shells provide excellent protection. The nudibranchs buck this trend. Over time, they have lost their protective armour, yet in spite of their apparent vulnerability they are rarely the victims of predators (1). The loss of shell in nudibranchs appears to be associated with the development of chemical defense mechanisms (2). In most cases these are derived from the diet of the nudibranch, however there are some species of synthesising their own chemical defenses (1).  Aeolid nudibranchs procure stinging cells from their cnidarian prey (3) and ascoglossan and aplysiid nudibranchs obtain toxic secondary metabolites as they graze on algae (4). Others obtain their chemical defenses from their diets of sponges, bryozoans and tunicates. Hypserlodoris webbi selects sponges with high levels of secondary metabolites for predation, which it then sequesters in dorsal glands for pretection (2). Similarly Hexabranchus sanguineus obtains its defense chemicals from Halichondria spp. sponges but also passes these compounds to its egg ribbons, which are otherwise defenseless (5).

Nudibranch

References:

1. Fontana et al. 1994, Cellular and Molecular Life Sciences 50 pp. 510-516
2. Pawlik et al. 1988, Journal of Experimental Marine Biology and Ecology 119 pp. 99-109
3. Thompson 1976, Biology of Opisthobranch Molluscs p. 207
4. Lewin 1970, Pacific Scientific 24 pp. 356-358
5. Avila and Paul 1997, Marine Ecology Progress Series 150 pp. 171-180

Beef or Salmon? Prawns please!!!

A guest post by Ken.

The common prawn (Palaemon serratus) is found on rocky shores around Ireland. They are often trapped in rock pools at low tide but can be difficult to spot due to the transparent body but become visible when moving. A closer look reveals purplish-brown dots and lines on its body. Their antennae are very long and a toothed rostrum extends forward between the eyes. It uses its fan like tail to swim backwards if alarmed. Has a diet mainly of scavenging. (1)

Common Prawn (Palaemon serratus)

Lovell et al. performed a study on P. serratus using a combination of anatomical, electron microscopic and electrophysiological approaches involving the statocyst. In crustaceans, the statocyst is found either at the anterior end of the animal in the basal segment of each antennule, or posteriorly within the uropods, abdomen or telson. It has been known that the statocyst is used as an equilibrium organ to orientate the animal within the water column. This study used an ABR (Auditory Brainstem Response) type investigation to determine the prawns hearing abilities. To acquire an ABR waveform conglomerate responses of peak potentials are averaged, which arise from nuclei in the auditory pathway during acoustic stimulation. This work provided conclusive evidence of low-frequency sound detection of frequencies ranging from 100 to 3000 Hz (a hearing acuity similar to that of a generalist fish) by a member of the sub-phylum crustacea. For hearing ability to be attributed to an organism, the physiological response sound should be initiated by a specialised receptor mechanism and here it was shown to be generated in the statocyst. In addition, recorded neural waveforms were shown to be similar in both amplitude and shape to those from fish and higher vertebrates, when stimulated with low-frequency sound, and complete ablation of the electrophysiological response was achieved by removal of the statocyst. (2)

References:

1. Sterry 1997, Collins Complete Guide to British Wildlife p. 216
2. Lovell et al. 2005, Comparative Biochemistry and Physiology, Part A 140 pp.89-100

Sniping About the Weather

Snipe, Gallinago gallinago, feeding

The Snipe (Gallinago gallinago) is an unmistakable bird, most commonly seen in Ireland in winter when resident numbers are swelled by migrant populations from northern Europe (1). Its is similar in shape to the Woodcock and the Jack Snipe, but its size and the yellow bars on its head and down its buff-brown plumage make it easily recognisable (2). It inhabits wetlands and moors where it uses its almost disproportionally long bill to probe the mud for invertebrates. This it tends to do alone, although small groups are sometimes seen foraging together.
While there has been a decline in numbers of Snipe over the past 30 years (3), the species is so numerous that the International Union for Conservation of Nature sees it as of least concern (4). The situation may become critical however due to continued destruction of wetland habitats by draining and further intensification of grassland management (5). Most grassland systems in Ireland lack botanical diversity, being composed typically of just a handful of ryegrass species (6). This results in a lack of invertebrate numbers and development of impenetrable rhizosphere areas, making feeding for the Snipe almost impossible (7).
Habitats where feeding is easy due to wet or waterlogged soil lead to longer nesting times for Snipe (5), and while wet weather does provide this increase in feeding ability, it also brings the problem of flooding. Flooding has been shown to delay Snipe nesting by up to 70 days, suggesting they are quite weather dependent breeders.

References:

1. Sterry 2004, Collins Complete Guide to Irish Wildlife p. 60
2. Hayman and Hume 2002, The New Birdwatcher's Pocket Guide to Britain and Europe p. 117
3. Henderson et al. 2002, Bird Study 49 pp. 17-25
4. www.iucnredlist.org/apps/redlist/details/150697/0
5. Green 1988, Journal of Applied Ecology25 pp. 79-93
6. Byrne 2009, Euphytica 166 pp. 61 – 70.
7. McCracken and Tallowin 2004, The International Journal of Avian Science 146 pp. 108-114

Putting the Moss in its Box

Moss classification is tough. To the casual observer there is very little to differentiate one patch of green in the undergrowth from another. Closer inspection reveals that, while there are certainly distinct groups, identification to the species level is an arduous task in some cases. Mosses' fruiting bodies provide something of an answer. The eminent Finnish bryologist Viktor Ferdinand Brotherus (1849 - 1929) was most influential in introducing classification based on moss peristomes, the structures in the fruiting bodies that regulate spore release (1). This poses problems however as these structures, by their very nature, are exposed to the vagaries of the elements and may lead to incorrect classification. Molecular characters are becoming more and more popular for moss taxonomy, however single-gene classification systems are just as likely to be faulty as any other type of single character classification, and therefore caution is needed (1). A combination of techniques is often needed.

Hart's Tongue Thyme Moss, Plagiomnium undulatum

One of these is the use of the karyotype (number and appearance of chromosomes in the cell) of the moss species. Bowers (2) used this cytological approach to re-classify some members of the family Mniacea. Species of one genus in this family, Plagiomnium, are especially difficult to separate morphologically. In once species, P. undulatum (Hart's Tongue Thyme Moss), cytology revealed variability in karyotype formula and chromosome set length, but a high uniformity of chromosome number (3). P. undulatum is common in damp, shaded places and is notable for its long stems, which may grow to 10 cm in length (4). Male and female structures are borne on different plants with the male forming rosette like structures as seen in the example pictured.

References:

1. Buck and Goffinet 2000, Bryphyte Biology (eds. Shaw and Goffinet) pp. 71-123
2. Bowers 1980, Lindbergia 6 pp. 22-31
3. Przywara et al. 2003, Acta Biologia Cracoviensia, Series Botanica 45 pp. 105-110
4. Phillips 1980, Grasses, Ferns, Mosses and Lichens of Great Britain and Ireland p. 133

Don't Eat the Jelly

Commonly called Jelly Fungi, the Heterobasidiomycetes are a comparitvely small group of fungi that differ from other Basidiomycetes in the structure of the basidium (1). The origin of their common name is self evident, their jelly-like appearance coming from the gelatinous structure of the fruiting bodies. These have a considerible capacity to withstand dessication.

White Brain Fungus, Exidia thuretiana

A common Jelly Fungus, often seen in large groups on dead and rotting branches of broadleaf trees (especially beech) is the White Brain Fungus, Exidia thuretiana. When wet, E. thuretiana appears cushion-like. It becomes contorted into brain-like folds, fusing with adjacent fruiting bodies that are smooth, shiny and white (1). Upon drying, it shrinks and becomes quite hard with smaller specimens becoming almost invisible. Odorless and tasteless it is inedible, appearing in autumn and winter.

Dacrymyces stillatus

Similarly inedible, Dacrymyces stillatus is yellowish orange when wet, becoming a deeper orange when dry. It is most common in the late summer to early autumn when the sub-spherical to saucer shaped frutiing bodies appear smooth and glistening (1). It can caused considerable decay of both broadleaf and coniferous wood (2).


References:

1. Jordan 1995, The Encyclopedia of Fungi of Britain and Ireland pp. 367, 369, 371
2. Seifert 1983, Mucologia 75 pp. 1011-1018

Ammonite's Feast

Ammonoid Fossil

Ammonites dominate marine fossils from the Late Silurian to the end of the Cretaceous, a period of 300 million years (1). Their abundance over this period of time has made them immensely important index fossils for dating Late Palaeozoic and Mesozoic rocks and for characterising various kinds of marine communities (2). The subgroup Ammonoidea, to which the ammonites (order Ammonitida) belong (along with Anarcestida, Ceratitida, Clymeniida, Goniatitida and Prolecanitida) appeared in the Early Devonian period and are classed as cephalopods, with extant members such as squid, octopuses and the nautiloids (3).

Despite their abundance in the fossil record, little is known about the paleobiology of ammonites due to the lack of a direct living counterpart and a lack of preserved soft tissue (4). However some light has been shed on their feeding habits in an intriguing study of the mouth of the Mesozoic ammonite Baculites using synchrotron x-ray microtomography (5). This method nondestructively generates three dimensional maps of the fossil using x-rays by building up cross sectional images(6). The images generated showed a tiny snail and three tiny crustaceans in one of the ammonite's mouth and jaws and a radula that were adapted for eating prey floating in the water suggesting that these ammonites fed on plankton. The research also suggests a reason for the decline and subsequent extinction of the ammonites around the Cretaceous-Tertiary extinction event as plankton were severely hit at this time.

References:

1. Parker 2007, The Complete Guide to Fossils and Fossil Collecting p. 168
2. Summesberger 1985, Annalen des Naturhistorischen Museums in Wien 87 pp. 145-166
3. Kennedy 1977, Patterns of Evolution as Illustrated by the Fossil Record (ed. Hallam) pp. 251-304
4. Tanabe 2011, Science 331 pp. 37-38
5. Kruta et al. 2011, Science 331 pp. 70-72
6. Flannery 1987, Science 237 pp. 1439-1444