Species spotlight VI

Xerocrassa meda (Porro, 1840)
Santa Venera, Malta

One of the commonest snails in Maltese gardens is this medium-sized species that apparently does not mind living in human-influenced habitats, actually preferring cultivated patches to the Mediterranean garigue so beloved of its other relatives. It might have originally been a Maltese and South-Sicilian endemic, eventually spreading to other Mediterranean islands by human intervention.


X. meda is one of two species in the genus Xerocrassa in Malta, which is sometimes treated as a synonym of Trochoidea, but which actually presents anatomical differences from that genus and is herein treated separately following the AnimalBase entry.

Shell identification

• 6-8mm
• pale brown or cream colour with darker bracket-shaped stripes
• aperture with a slight pinkish colour
• umbilicus pin-point shaped

A walk around the Colosseum

The Amphitheatrum Flavium, better known as the Colosseum, is an iconic Roman era building in the centre of Rome. Ravaged by natural phenomena and looters throughout the centuries, it still stands towering above the city, and offers a wonderful opportunity to admire the architectural and engineering prowess of the ancient Romans.

In 1643, far before the advent of Linnaean taxonomy, a gent by the name of Domenico Panaroli decided to publish an inventory of the plants found inside the Colosseum after noticing several exotic (mainly North African) species inside and around it, resulting in the tome Plantarum Amphytheatralium Catalogus. Nowadays, the list of species from the Colosseum has grown to 684 species of plants (Caneva, 2003).

A humidity-loving moss, bearing sporangia (fruiting bodies) on stalks

Adiantum capillusveneris L., also found in Malta

Cymbalaria muralis G. Gaertn., B. Mey. & Scherb.

Of course, the ample vegetation offers much cover for my favourite invertebrates - snails. The most common ones present in soil were Eobania vermiculata (Müller, 1774) and a species of Cernuella (I have not yet decided which this is out of the confusing trio of C. virgata (Da Costa, 1778), C. cisalpina (Rossmässler, 1837) and C. neglecta (Draparnaud, 1805)). Later on, a few specimens of Papillifera bidens (Linnaeus, 1758) and Xerotricha apicina (Lamarck, 1822) were encountered amongst the ruins.

Cernuella sp.

Xerotricha apicina (Lamarck, 1822)

On a totally unrelated note, here's one of the modern day inhabitants of the Colosseum:

References:

Caneva, G., 2003. The Colosseum's use and state of abandonment as analysed through its flora. International Biodeterioration & Biodegradation, 51: 211-219.
Panaroli, D., 1643. Jatrologismi sive medicae observationes quibus additus est in fine Plantarum Amphytheatralium Catalogus. Typis Dominici Marciani, Rome.

New project uploaded

A small website required for a University assignment has been uploaded at the link pasted below:

Maltese Endemic Landsnails

Virtually all photographs included are appearing on the web for the first time.

The website expires this year, so I will upload the content here as soon as that occurs.

Ornithological escargot

Many bird species egest the hard indigestible parts included in their food intake (bones, cuticles, etc.) as pellets. These pellets are expelled from the mouth, and examination of the contents of course gives very interesting insight into the bird's diet and habits.

The following photograph shows such a pellet, measuring about 2cm in diameter, found at Mġarr harbour, Gozo, on the 7th of January 2010. The contents include chiefly exoskeletons of earwigs and large ants, together with one shell of the endemic snail Trochoidea spratti (Pfeiffer, 1846).

According to John J. Borg at Heritage Malta, the size and contents of the pellet may point towards production by a species of thrush or a starling. There are ten species of thrush-related birds and three starlings recorded for the Maltese Islands (BirdLife Malta, 2008).

References:

BirdLife Malta (2008). Birds of Malta checklist. [www document, url: http://www.birdlifemalta.org/bird_watchers/bird_watching/malta_birds/, accessed 8.I.2010]

Part II: The endemic species of the Maltese Islands

The Maltese Islands, though small, boast a considerable number of endemic species and infraspecific forms, consisting of 23 plants and 55 animals (Schembri, 1994).

Such species, apart from being unique, are biologically important because they show reproductive isolation and speciation at work. The lizard Podarcis filfolensis is perhaps the best known example of this, having evolved into different sub-species on most of the islands of the archipelago. It is the only endemic vertebrate in addition to the shrew Crocidura sicula calypso.

Terrestrial molluscs are a type of animal that evolves relatively quickly, in fact, 14% of the endemic animals are gastropods. Of these, the most interesting are the Hygromiidae and the Clausiliidae, which give clues as regards the isolation of the Maltese Archipelago from the surrounding land. The endemic snails Cernuella caruanae and Trochoidea spratti are relatively widespread, but the rarest gastropod is also an endemic – Lampedusa melitensis is a clausiliid whose population only consists of a few hundred individuals in a restricted ‘rdum’ area at Dingli. A sister species is Lampedusa imitatrix which is found further to the west along the southern coast of Malta. The last endemic clausiliid is Muticaria macrostoma, a taxon previously thought to consist of four different species, but these are anatomically indistinguishable (Giusti et al., 1995). The forms mamotica and scalaris are extremely restricted and therefore vulnerable. The forms macrostoma and oscitans, on the other hand, are frequent and one form prevails according to the geographical location. The southern coast of Malta (including Dingli) harbours the oscitans form.

81% of the endemic animal species are arthropods. These include the beautiful Maltese race of the butterfly Papilio machaon as well as the well-known freshwater crab Potamon fluviatile.
Endemic plants of the Maltese Islands are usually relicts from larger populations in a time when Malta was joined to Europe by a land bridge, for this reason they are called palaeoendemics. These are mostly restricted to rupestral habitats where they have competitively excluded other plants by tolerating harsh conditions such as high salinity. At Dingli, one can witness the species Darniella melitensis, Jasonia bocconei, and Palaeocyanus crassifolius, which is also Malta’s national plant. Cremnophyton lanfrancoi and Allium lojaconoi, a wild garlic that forms part of a cluster of similar species in central Mediterranean islands, are other palaeoendemics. Other endemic plants with more recent evolution are the orchid Anacamptis urvilleana and two species of Limonium, for this reason, they are referred to as neoendemics.

Figures:

Fig. 4. Muticaria macrostoma form macrostoma, from Floriana, Malta

Fig. 5. Muticaria macrostoma form oscitans, from Siġġiewi, Malta

References:

Giusti, F., Manganelli, G. & Schembri, P. J. (1995). The non-marine molluscs of the Maltese Islands. pp. 1-608, Torino.

Schembri, P. J. (1994). Natural heritage. In: Frendo, H. & Friggieri, O. (eds) Malta – Culture and Identity. pp. 105-124; Ministry of Youth and the Arts, Valletta, Malta