Arnold Sciberras

Current Distribution of Two Species of Tylos (Isopoda: Oniscidea) in the Central Mediterranean and the Influence of Beach Sand Grain-Size Parameters

The psammophilic genus Tylos Audouin, 1826 is represented within the Mediterranean basin as two species: T. ponticus Grebnicki, 1874, and T. europaeus Arcangeli, 1938, according to Taiti and Ferrara (1996). It is impossible to define precisely the current distribution of the two species, mainly because, in literature, both taxa have been described as subspecies of T. latreillii or even, in some cases, as T. latreillii sensu lato. The current study surveyed populations of Tylos spp. on sandy beaches along the coastline of Sicily, circum-Sicilian islands and the Maltese archipelago. The aims of this study are to fully and correctly identify all the sampled populations, pursuant to characterizing the current distribution of the two species, which occupy similar ecological niches, and to investigate any possible granulometric preferences by the two species. Data acquisition proceeded along three tiers: in situ sampling, manually and through the deployment of pitfall trap constellations, literature review and by analyzing preserved specimens of Tylos held within the ‘Caruso’ collection (University of Catania, Catania, Italy). Generally, T. europaeus showed a preference for fine sand, whilst T. ponticus showed a preference for fine-medium sand, although, statistically, differences in the distribution of the two species could not be explained in terms of median grain size. The two species were never recorded on the same beach. The degree of inter-specific morphological differentiation was also evaluated through a detailed morphological study of sampled Tylos spp.

Comparative median grain size assessment through three different techniques for sandy beach deposits on the Maltese Islands (Central Mediterranean)

ABSTRACT Deidun, A., Gauci, R., Schembri, J.A., Šegina, E., Gauci, A., Gianni, J., Gutierrez, J.A., Sciberras, A. and Sciberras, J., 2013. Comparative median grain size assessment through three different techniques for sandy beach deposits on the Maltese Islands (Central Mediterranean) It is estimated that sandy beaches cover only 2.2 per cent of the Maltese coastline. Although small in size, Maltese pocket beaches exhibit complex geomorphological interactions. A granulometric analysis of Maltese beach deposits may thus shed further light on the understanding of these interactive processes and provide baseline information on how beach sediment size may relate geo-spatially and morphometrically. Surface (0-10cm) sand samples were collected from ninety sandy beaches in Sicily, circum-Sicilian islands and the Maltese Islands. The median grain size of these sediment samples was assessed through three different techniques: the conventional sieving technique, observation through stereo microscopy and through image processing. The two primary objectives of such work were firstly, to construct a repository of median grain size values for the entire stretch of Maltese sedimentary coastline (the first study ever to be done on such a comprehensive spatial scale), and secondly, to evaluate the degree of concordance between the three techniques. The highest Pearson correlation value (0.90) was recorded for the sieving-scanning match, although in many cases differences were large enough to result in a different sediment type classification. The highest level of agreement between the scanning and sieving technique was registered for the medium-fine (1.5–2.5phi) and very coarse categories (−0.5–0.0 phi). Median particle diameters measured through microscopy were those which diverged most from those of other techniques. This maybe due to the relatively small number of sediment grains which were analysed within such a technique.

The protected taxon Ocypode cursor (Linnaeus, 1758) (Crustacea: Decapoda: Ocypodidae) – documenting its well-established presence in the central Mediterranean

Abstract Ocypode cursor (Linnaeus, 1758) is the only Ocypode species present in the Mediterranean Sea, and one of the nine marine crustacean species protected in the basin. It is widely distributed in the eastern Mediterranean, but knowledge about its presence in the central Mediterranean is very limited so far. We hereby first document the established presence of O. cursor in the central Mediterranean (Sicily and Malta), backdate the known presence of this taxon in Italy, and offer preliminary observations on the main known Maltese population. In Sicily, O. cursor is distributed along most of the south-western coast of the island of Sicily, whilst at least three beaches in the Maltese Islands are known to support populations of this species. The main Maltese population exhibits numerous similarities (e.g. burrow width, zonation along the beach) to another Mediterranean population studied in northern Cyprus, although occurring at lower densities. We conclude that the species has been probably present within the study area for a long period, but went undetected in view of the low population densities at which it previously occurred, the lack of a comprehensive census for the species within the same study area, and its nocturnal habits. The presence of this species in the central Mediterranean seems to be attributable to secondary natural spreading.

Contributions to the fauna of reptilian chiggers (Acari: Trombiculidae) from the Central Mediterranean, with a description of one new species

A new species of chigger mite, Lacertacarus sardiniensis sp. nov., is described from a lizard Podarcis tiliguerta (Gmelin) collected in Sardinia. One species, Ericotrombidium caucasicum (Schluger, 1967), previously known from Southern Russia and Southern Ukraine, is recorded for the first time on the lizards Podarcis filfolensis (Bedriaga) and Podarcis siculus (Rafinesque-Schmaltz), and on Malta, Lipari Island and Alicudi Island (Aeolian Islands, Sicily, Italy). http://zoobank.org/urn:lsid:zoobank.org:pub:CD41E85B-1801-4FA3-BC42-28F5F1AC14C1