Variations on a theme, Part I

The sea snail Columbella rustica (Linné, 1758) is a very common inhabitant of Maltese rock pools and shallow platforms. It has a large range, extending from the Mediterranean down to the coasts of Angola and the eastern Atlantic islands.

The shell is highly variable, even within relatively short distances in this range, since it relies directly on the habitat. Specimens from the northwest of Malta tend to be mostly small and dark, while others from the sandy beaches of eastern Malta are light coloured and much larger (photograph below). This can be explained by natural selection - yellow specimens are better camouflaged against the sand, while mechanical damage to the shells by waves is not a pressing problem in a soft substrate such as sand. The small compact individuals from rocky shores, on the other hand, are exposed to very rough currents, which may dislodge and batter the shells onto rocks, therefore a smaller surface area works better in this regard. The darker colour also conceals shells in the algae better than light ones.

In addition to population-scale differences, there is also some variability on the individual level. The above photograph, on the extreme left, shows a 'freak' elongated specimen with convex whorls. A 'turriculated' variety from the same area is figured below (photo by Constantine Mifsud).

Amphibious native

Discoglossus pictus pictus Otth, 1837. The only native amphibian of Malta, fairly frequent in occurrence but also quite vulnerable to loss of habitat. December 2009, Buskett.

Of a Swedish gentleman and his Maltese fish

It was yesterday reported in the online version of the Times of Malta that the notorious blooms of the jellyfish Pelagia noctiluca (Forsskål, 1775), which are reported once every few years around the Mediterranean and elsewhere, are still making appearances around the Maltese Islands well into winter. The summer months of 2009 were definitely not lacking in these swarms, several hundreds of specimens were in fact observed by the author in several places along the Maltese coast, including Ta' Xbiex, Birzebbuġa and Għar Lapsi. The following picture was taken in September at Baħar iċ-Ċagħaq, and shows one unfortunate individual in its death-throes after being washed by waves onto the sand.

In related news, the comparatively harmless (to humans) but larger jellyfish Cassiopea andromeda (Forsskål, 1775) has been reported for the first time in Malta, more accurately the Marsamxett harbour. The habitat needed by this tropical species is only provided in sheltered muddy areas, so it is unlikely that any substantially problematic populations will be established anytime soon.

Quite coincidentally, both these jellyfish were described by the same Swedish gentleman and contemporary of Linnaeus, namely Pehr Forsskål (below), who lived a tragically short life from 1732 to 1763 before succumbing to malaria. So how do these jellyfish bear the '1775' suffix, one might ask?

Carsten Niebuhr, another naturalist of the period, was entrusted with the posthumous editing of Forsskål's manuscripts, culminating in the 1775 publication 'Descriptiones Animalium - Avium, amphiborum, insectorum, vermium quæ in itinere orientali observavit Petrus Forskål'. This contained the descriptions according to the then-new Linnaean system of these two coelenterates (then Medusa noctiluca and Medusa andromeda) and of several other organisms including fish.

The most interesting thing pertaining to Malta in Forsskål's book is the inclusion of the Maltese names of fish accompanying the Latin descriptions in the part entitled 'Catalogus Piscium Melitensium' - Catalogue of Maltese Fish. Thus Squalus spinax is also Chelp il Bahar, Sparus dentex is i Dentici and Sparus auratus is l'Aurada. The man was known to give specific names based on ethnic languages with which he came into contact with, so these scientific names could constitute the oldest appearances of the Maltese language in the science of taxonomy.

References:

Forsskål, P. & Niebuhr, C., 1775. Descriptiones Animalium - Avium, amphiborum, insectorum, vermium quæ in itinere orientali observavit Petrus Forskål. Hafniae: Ex officina Mölleri, 164 pp.

Schembri, P. J., Deidun, A. & Vella, P. J., 2010. First record of Cassiopea andromeda (Scyphozoa: Rhizostomeae: Cassiopeidae) from the central Mediterranean Sea. Marine Biodiversity Records, 3 (6): 1-2.

Times of Malta, 2010. 'Thousands' of jellyfish seen in various bays. Times of Malta, 25.I.2010, [www document, url=http://www.timesofmalta.com/articles/view/20100125/local/thousands-of-jellyfish-seen-in-various-bays, last accessed 26.I.2010]

Zammit Maempel, G., 1992. The Arabian voyage of 1761-67 and Malta: Forsskål and his contribution to the study of local natural history. Melita Historica: Reprints from proceedings of history week 1992: 35-76.

Fossil geometry

Fossil Isocrinus sp., phosphatized fragments of stem and calyx (centre). Miocene (Langhian), Upper Globigerina Limestone Formation, Gozo.

Sluggish cousins

The slug Lehmannia valentiana (Férussac, 1822) is an Iberian peninsular species which has been spread inadvertently as far as Australia, and fairly recently it has also been recorded from Malta (Beckmann, 2003; Mifsud et al., 2003). These animals are imported mostly through plant nurseries, and are so far restricted to damp anthropogenic habitats like flowerbeds and potted plants. The following example is one of a few dozen individuals found beneath humid compost at a garden in Santa Venera. As can be seen, distinguishing features include a symmetrical pair of very dark bands on the dorsal side with a fainter one in the middle, over a light-brown or yellow body colour. It seems that fully adult specimens are highly unusual, probably because of pesticidal and meteorological interference. The population from which this individual came contained slugs of about 20-35mm length (in full extension).

Its close relative Lehmannia melitensis (Lessona & Pollonera, 1882) is, on the other hand, native to Malta and Italian islands. In Malta*, this can be distinguished from L. valentiana by an ash-grey colour, considerably clearer bands and a larger size (up to 55mm). In addition to this, it also seems to prefer more open spaces and minimal human presence. The typical specimen below originates from the countryside surrounding Mdina, where it seems to be relatively commoner than in other areas.

*Sicilian forms of this same species have a yellowish colour.

References:

Beckmann K.H. (2003). Kurze Mitteilungen - Neunachweis von Lehmannia valentiana für die Maltesischen Inseln. Heldia, 5 (1/2): 37-40.

Giusti F., Manganelli G. & Schembri P.J. (1995). The non-marine molluscs of the Maltese Islands. Monografie Museo Regionale di Scienze Naturali, Torino, 15: 1-608.

Mifsud C., Sammut P. & Cachia C. (2003). On some alien terrestrial and freshwater gastropods (Mollusca) from Malta. The Central Mediterranean Naturalist, 4 (1): 35-40.

Welter-Schultes F. (2009). Species summary for Lehmannia melitensis. In AnimalBase Project Team, 2005-2009. AnimalBase - Early zoological literature online, University of Göttingen. Retrieved 14th January 2010 from http://www.animalbase.uni-goettingen.de/zooweb/servlet/AnimalBase/home/species?id=2634

Welter-Schultes F. (2009). Species summary for Lehmannia valentiana. In AnimalBase Project Team, 2005-2009. AnimalBase - Early zoological literature online, University of Göttingen. Retrieved 14th January 2010 from http://www.animalbase.uni-goettingen.de/zooweb/servlet/AnimalBase/home/species?id=2637

Stamp-sized elephants

The Siculo-Maltese endemic Pleistocene elephant Elephas (Palaeoloxodon) falconeri Busk, 1867 is featured on the new set of definitive stamps from Maltapost Plc. Perhaps purely coincidentally, the miniature size of the animal is reflected in the stamp's denomination.

For philatelists, more information on this set can be found here. Skeletal remains of the animal can be seen at the Għar Dalam Museum.

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]