Wednesday, October 31, 2012

A mollusc in the shape of a heart

Rough seas can deposit very interesting creatures on the shore.  

A walk on the beach after a storm can be very rewarding especially for those who do not dive or snorkel and have to rely on the waves to see some of the creatures that live below the surface.

Many creatures are too fragile to survive the pounding waves intact but many mollusc have very strong shells and remain intact even after a considerable amount of pounding.

Cockles have strong, compact heart-shaped shells that can be rolled over the sand and banged without damage to the living mollusc. 

About twenty species are found in the Mediterranean of which ten have been recorded in Maltese waters. 

The cockle shell, known in Maltese as xedaq, is common in sandy bottoms while the slightly smaller edible cockle, known in Maltese as arzella tal-Marsa prefers brackish water such as is found in estuaries.

Cockles are bivalves, that is, molluscs whose shell is made up of two opposing valves attached together by means of a flexible ligament.   

About 9,200 species, of which 8,000 live in the sea, are known to exist. These range in size from miniscule species to the giant clam which can grow up to 200 kilograms. About 230 species have been recorded in the seas around the Maltese islands with another two species live solely in fresh water.

Some species live attached to solid surfaces while others bury themselves in sediment. Scallops one of which is known in Maltese as pellegrina are free living and can escape from predators by clapping the valves together and creating a jet of water to swim away from danger.

Most bivalves are edible although relatively few species are collected for consumption. Nowadays large numbers are farmed in many parts of the world not only for sale in food markets but also for the cultivation of pearls. 

This article was published in The Times on 14.03.2012.

Fascinating organisms

200 lichens are found locally
Last Saturday I gave a lecture about nature photography to group of young people. I was surprised by their knowledge of plants and animals as they were able to easily identify most species of plants and animals that I showed them.

However what surprised me more was the fact that none of them could tell me what lichen is.

This was surprising because lichens are common everywhere being able to grow in the most unusual places including  bare rock and walls even in urban areas. About 200 lichens have been recorded in the Maltese islands but I am sure that with some effort more unrecorded species can be found.

Lichens are unusual because each species is made up of two organisms, a fungus and an alga, living intimately together. This gives lichens the ability to survive under harsh conditions where no other organism can survive.
In some cases the fungus and alga which make up a lichen can be found living separately in nature but in many cases the two organisms have become so dependent on each other that one can not survive without the other.

Lichens do not have leaves or roots and absorb nutrients directly through their surface. This leaves them susceptible to air pollutants which accumulate in their body without being eliminated. 

Lichens can tolerate different concentrations of pollutants with some species dying at lower levels than others. This makes lichens excellent biomonitors and many species are used to indicate levels of environmental pollutants.

Many species of lichen are eaten especially in times of famine despite of the fact that they can be difficult to digest. Many species also contain mildly toxic compounds although few species are poisonous. 

Some species are used to produce dyes including the pH indicator litmus.

This article was published in The Times on 07.03.2012

Wild orchids

Orchids are my favourite group of plants. They are fascinating mainly because they are beautiful and interesting and although there are many species none of them is common.

Orchids have been arousing passions for a long time. In the Victorian era adventurous individuals embarked on orchid hunting trips in central and south America and Asia mainly to collect specimens for gardeners and horticulturalists in Europe and the USA. They often went back home with large numbers of rare species and long tales about their dangerous expeditions. 

Today many orchids are legally protected and it is not allowed to collect or export them. Although illegal trade in orchids still exists modern orchid hunters collect images. They are equipped with cameras, identification books and notebooks and often publish their results in specialist websites. Some restrict their hunting to a particular country or area while others travel and wide.

In Malta orchids can be found from the end of December to early June most species are in flower in March and April. 

Thirty eight species of orchids have been recorded in the Maltese islands. Over the past two decades the number of recorded species has increased partly because new species have been found by plant enthusiasts but also because what was considered as one species, the brown orchid, is now considered to be five different species. 

These species belong to a group known as the insect orchids. Male insects, especially bees and wasps, are attracted to the flowers which look like female members of the species. They land on them and attempt to mate. While their attempts to mate are unsuccessful they unknowingly end up with pollen on their back which is then transferred to another orchid of the same species which manages to trick them into landing on it. 

Some species of orchids enhance their performance by producing chemicals known as pheromones similar to pheromones used by female insects to attract males.

Finding, photographing and identifying orchids is an interesting and challenging hobby that can give days, weeks and months of satisfaction.

This article was published in The Times on 29.02.2012

The things you didn’t know about wildlife and colour

The poppy

Carnival is over, bringing an end to five days of colour that added some cheer to life after weeks of dull cloudy weather. 

For this carnival as in previous years many designers were inspired by the most colourful species in nature particularly parrots, butterflies and fish. 

Colours are used as an effective means of communication giving such messages as “I am good to eat”, “I am dangerous” and “I am a good partner”. 

On the other hand colours are often used as camouflage to hide the animal from prey or predators.

Many fruits and berries change colour from green to red as they ripen. 

Plants want birds and mammals to eat their fruit only when the seeds are fully developed and until this happens the fruit is not fit to eat.

Flowers use colour to attract pollinators, especially insects. 

Bright colours are easily seen against a green background but what we see is not necessarily what insects see because although insects, like humans can distinguish colours, their range of vision is different from ours. 

Insects are able to see ultraviolet light which we are not. Thus some flowers that are plain to us have lines and patterns that guide the insects to the nectar.

Many orchids are shaped and coloured like particular insects to mislead males into thinking that they are females and thus land on them and unwittingly carry pollen from one flower to the other.

This article was published in The Times on 26.02.12)

Surviving the bitter cold

Last Sunday’s sunshine and the relatively warm temperature was welcome especially after the cold wet days that we had been experiencing throughout most of this month. 

As I do on most Sundays I spent the morning photographing nature. I was not expecting any insects but was surprised to see a solitary asphodel bug (seffud tal-berwieq). 

This species which is usually seen from March to May is found mostly on asphodels. It was standing motionless on a leaf trying to warm up its body. It did not move away when I moved very close to it with my camera. 

This was not surprising as even though the low winter temperatures made it lethargic it normally does not bother to conceal itself or run away from danger as like other brightly coloured insects it felt secure in the knowledge that predators, especially birds are unlikely to harm it. Predators learn that animals with warning colours are inedible because they are either foul-tasting or poisonous.  

The presence of this insect made me think about how insects and other animals survive the winter. Many birds avoid cold weather by migrating to warmer parts of the world but in Europe very few insects migrate and their journeys are not as long and regular as those of birds. 

Some adult insects find a sheltered place usually underneath a stone or bark or in a crack in which to spend the winter. Others die as soon as the weather starts to cool but leave behind them eggs or pupae which will continue their lifecycle with the onset of warmer weather.

Malta’s only amphibian, the painted frog remains active throughout the winter as this is also the time when water, which is essential for this animal to survive, is present but the reptiles including the lizard, geckos and chameleon are inactive throughout most of the winter and venture out only on warmer days.

This article was published in The Times on 15.02.2012.

A kingdom of... fungi!

Fungi are very common everywhere and play an important role in the decomposition of organic matter. An uneaten piece of fruit or any other food within a short time becomes covered with a layer of mold which is nothing but the reproductive bodies of fungi. 

In nature these fungi recycle the nutrients which end up in the soil thus becoming available again for other plants.

Mushrooms are the fruiting bodies of a variety of fungi that generally have a stem on which the familiar gilled structure grows. The best known species are the cultivated edible species. 

Until a few decades ago, fungi were considered as part of the plant kingdom but now they form part of a kingdom. This is because although they have characteristics in common with plants, animals and bacteria they evolved separately from them. They have their own characteristics but are more closely related to animals than to plants.

About 100,00 species of fungi have been described although it is believed that hundreds of thousands if not millions more are still to be discovered. In Malta about 300 species have been recorded although this number does not include the microscopic species.

While fungi can cause serious diseases in humans they play an important role in the pharmacological and food industries. Perhaps the best known antibiotic is penicillin which was discovered by Alexander Fleming in 1928 when he noticed that a fungus which was contaminating his bacteria specimens was actually killing the bacteria. 

Another closely related species is used to inoculate cheese such as the Stilton and Roquefort to give them a unique taste and texture.

Baker’s yeast, a single-celled fungus, is used in the production of bread while another species of yeast is used in fermentation which leads to the production of alcoholic drinks. Other species are used in the fermentation of Soya beans in the production of soy sauce.

This article was published in The Times on 08.02.2012

Crocuses from sands of time

Next time you go for a walk in the countryside especially in areas with rocky garigue, look out for the brightly coloured sand crocuses which are starting to flower at this time of the year. 

Sand crocuses are scientifically known as the romulea a name derived from Romulus, one of the legendary founders of Rome, because whoever gave them their name found large numbers of these plants growing around the Italian city.

The romuleas, of which there are about 80 species, are found in Europe, North Africa and South Africa. 

They form part of the iris family which is characterised by having linear or sword-like leaves. 

The leaves of the sand crocuses are in fact look like green threads.

Until a few decades ago two species of romuleas were recorded in the Maltese islands with one species being divided into four varieties. 

These varieties have now been designated as species and we now have five romuleas present in the Maltese islands although to the untrained eye the five species are so alike that it seems next to impossible to tell apart.

Some species of romulea are cultivated as garden plants although they are not as popular as the larger crocuses.

The violet romulea (żagħfran tal-blat biċ-ċentru roża) is very rare and one is unlikely to meet it unless looking specifically for it. Another species, the Maltese romulea, (żagħfran tal-blat ta’ Malta) is endemic to the Maltese islands, although it is very rare and might already be extinct.

Some romuleas are very similar to crocuses with which they share the same habitat. Although they are both members of the iris family they belong to separate groups and have evolved separately. 

Their similarity is a result of the fact they the two groups of plants share the same ecological niche have evolved in the same way to deal with the same environmental conditions a process known as convergent evolution. 

This article was published in The Times on 01/02/2012