Otala punctata

Otala punctata

Otala punctata is the scientific name of a snail indigenous in Spain but which a few years ago was discovered in the Maltese islands.

It does not seem to have an established name in English. In Spanish it is called la cabrilla which according to an online translator means the leopard. In a database it was referred to as the Spanish snail so for this article to avoid constantly using its scientific name I decided to call it the Spanish leopard. It has not yet been given a Maltese name.

This species can be found in eastern Spain, the Balearic Islands, Corsica, the south of France and northwestern Algeria. Nowadays it can also be found in the Americas including the United States, Argentina, Uruguay and Chile. In the United States it is being assumed that it could be a serious pest which could have negative effects on agriculture, and local biodiversity. In Europe it has been found also in Sardinia.

It appeared in Malta around 2003. It established itself in the areas surrounding a plant nursery in Mosta which indicates that it was probably imported accidentally with plants. Studies have shown that its range expanded slowly into the surrounding areas.

It was recently recorded in fields around Baħrija. No Spanish leopards were recorded between Baħrija and Mosta. This indicates that the snails in Baħrija were introduced there by humans. Although it is possible that this was an accidental introduction it could also have been introduced intentionally.

If this did happen it was a very irresponsible act as the introduction could have many negative consequences for the area.

Introduced species often do not have natural enemies and often increase in numbers to the detriment of local species. The Spanish leopard is very similar to the indigenous common garden snail, the species that is collected for cooking and could interact negatively with it.

It could also become a serious pest, creating more problems to the farmers of the area. This could lead to the use of even more snail poison with more negative consequences to the environment.

In Spain this species is cooked in a spicy tomato sauce and no harm would be done if it is also collected in Malta for consumption. 

 

Conserving Maltese molluscs

Goat snail (Cantareus apertus) Mogħża

Molluscs are soft-bodied animals that more often than not have an external shell made of calcium carbonate.

The best known molluscs are the gastropods, bivalves and cephalopods.  In layman’s terms gastropods are the snails and slugs, bivalves are the two-shelled creatures such as oysters, clams and mussels and the cephalopods are the octopuses and squids. Molluscs are often found in aquatic habitats especially marine habitats.

There are about 93,000 species of molluscs in the world and more will be identified as more research is carried out. In Malta hundreds of species can be found on land and in the surrounding waters. Between 63 and 69 species are found on land. These include those species which live in fresh or brackish water. Surprisingly enough these include one species of freshwater bivalve. Of the gastropods, nine live in fresh water, nine are found in brackish water while the rest are terrestrial. Three species are not indigenous as they were introduced in the Maltese islands in relatively recent times. These species are restricted to a small number of public gardens.

One aquatic species which lived in the mouth of a spring is now probably extinct in the wild as building in the vicinity of the spring destroyed the source of fresh water which is needed by this particular species. This is not the only mollusc that has become extinct in the Maltese islands. Three species which lived in fresh water have not been seen in recent years. Other species are considered as vulnerable or threatened with extinction. The most endangered species live in restricted areas or habitats such as brackish water.

Maltese molluscs are also interesting because several are endemic to the Maltese islands, that is, they are not found outside the Maltese islands. Many of these endemics are restricted to a small area and can easily become extinct as well but in this case their extinction is far more serious as since they are not found living anywhere else they would be lost to humanity forever. This is not a remote possibility as more of the Maltese countryside is destroyed every year as happened to half the habitat of a particular species which now lies underneath a carpark.

The Maltese are responsible for the conservation of all the endemic Maltese species. There is nothing wrong with supporting the conservation of popular species such as whales but more importantly we must ensure that the small less glamorous species are protected and not allowed to become extinct.

This article was published in The Times on 9 December 2009.

The snail coated with ‘chocolate’

The red banded snail, or as it is sometimes known the chocolate-banded snail, is a large land snail. 

It belongs to a group of land snails and slugs known as the pulmonates. These are characterised by having a ‘lung’. Other molluscs have gills which allow them to take exchange gasses with the surroundings from air or water that flows over them. 

Pulmonates, on the other hand, have lost their gills and ‘breath’ air or water through a hole known as a pneumostome, into a cavity which functions as a lung. In some species the pneumostome remains permanently open while in others, such as in the common slug, it can be seen opening and closing rhythmically.

This species is very common especially in open spaces such as garigue. In Maltese it is known as għakrux mara which means female għakrux. It belongs to the Helicidae family in which we also find other common species such as the edible snail which is known in Maltese as għakrux raġel (male għakrux). This shows that in former times these two species were believed to be the male and female of the same species.

The red banded snail is mainly a Mediterranean species but can be found as far east as Crimea. It has also been introduced in other parts of the world and is now found in south eastern Australia. 

In 2006 it was found in London. It has also been found in Germany, Hungary and in the United States of America although it is not yet known whether it has managed to establish itself permanently in these countries.

This species, like other members of its family, is edible and is in fact collected and sold for food in parts of the Mediterranean particularly in Italy and Greece. In Malta although it was believed to be the female of the edible snail, which is collected in large numbers, it is believed to be inedible and is not collected. 

This article was published in The Times on 24.10.2012

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.

The pomatias

Pomatias sulcatus

I recently took some pictures of an interesting species of snail but although I found its scientific name I could not find a common name for it so as its scientific name is Pomatias sulcatus, I used part of this name for the title of this article.

This species of land snail is found throughout the western Mediterranean. It is common on calcareous soils near the coast and inland. It can be found on soil, in crevices in rocky ground, under stones and among fallen leaves. Sometimes it buries itself in the soil while the specimens I photographed were living on a tree trunk. In the Maltese island it is common on Malta, Gozo and Comino as well as on some of the smaller islands.
There was and probably still is some controversy about this snail in the Maltese islands. Some biologists have listed it as a distinct species endemic to the Maltese island others as a subspecies while others believe that the snails found on Malta are not different enough from the snails found in other parts of the Mediterranean to be considered as a separate species or subspecies.

Pomatias sulcatus is not the only species of pomatias that can be found in the Maltese islands. Another species, Pomatias elegans which is known as the round mouthed snail, can be found at San Anton Gardens at Attard. It probably found its way there on imported plants. This species is common in southern Europe and lives in similar habitats as Pomatias sulcatus.

The pomatias are one of the few groups of land snails that have an operculum. This is a calcareous structure like a small lid that fits neatly in the opening of the shell sealing the soft body inside. The operculum is found in most species of marine and freshwater snails but very rarely in land snails. Its main function is to prevent desiccation especially in those species that live in the intertidal or splash zone of the coast. The presence of an operculum in the pomatias suggests that these snails evolved from marine snails. 

This article was published in The Times on 06.04.10