279 research outputs found

    The status of Otala punctata (Muller, 1774) : a recently established terrestrial gastropod in Malta

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    A population of the alien helicid Otala punctata (Müller, 1774) has recently been found on the island of Malta (Central Mediterranean), located around a single plant nursery at Mosta in the central part of the island. Extensive field collections indicate that this species was very probably introduced via the horticultural trade and is gradually extending its range from its point of introduction, occupying a variety of natural and anthropic habitats. Analysis of size-frequency data suggests that Otala punctata has successfully bred through at least three consecutive reproductive events until 2006. We hypothesise that Otala punctata was originally imported accidentally with plant material and established itself in the nursery, from where it then escaped into the surrounding land since 2003. This situation represents the introduction of yet another alien species on Malta with the potential of becoming an agricultural pest, and a threat to the islands’ biodiversity.peer-reviewe

    Biology and interspecific interactions of the alien crab Percnon gibbesi in the Maltese Islands

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    Spatial and bathymetric distribution, population density, habitat preferences, fecundity, breeding season and interspecific interactions of the alien grapsoid crab Percnon gibbesi (H. Milne-Edwards, 1853) from the Maltese Islands (Malta and Gozo) are compared among localities in the Mediterranean where established populations have been reported since 1999. In the Maltese Islands, habitat preferences and bathymetric distribution were similar to those in other Mediterranean localities. Spatial distribution was found to be limited by the availability of the boulder habitat in which this crab nearly always occurs. Fecundity was higher in the Maltese Islands than in Linosa and Lampedusa, the breeding season lasting from the end of May until September. On Maltese shores the habitat of the alien overlapped with that of the native grapsid Pachygrapsus marmoratus (Fabricius, 1787) (Crustacea: Brachyura: Grapsoidea) and, to a lesser extent, that of the native xanthid Eriphia verrucosa (Forska°l, 1775). Laboratory studies to assess the possible interactions of the alien species with P. marmoratus suggest that the latter shows a competitive advantage over P. gibbesi, since 80.8% of encounters between the two species were initiated by P. marmoratus, and in 80% of the encounters it prevailed. This suggests that P. marmoratus is unlikely to be excluded from its natural habitat by the alien species, and that significant spatial resource partitioning on the part of P. marmoratus is unlikely to occur.peer-reviewe

    Records of Cephalopods (Mollusca : Cephalopoda) from Maltese and surrounding waters (Central Mediterranean)

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    Based on an examination of several collections made in Maltese waters, 20 cephalopods are recorded of which three genera and seven species are reported for the first time from Maltese waters. The identity of some previously dubious records is clarified. Information is given on the material examined during the present study as well as on geographical distribution and habitat preferences of the species. Notes on the diagnostic charactcrs required for accurate identification and details of important diagnostic features arc included. All the species recorded are also known from the Strait of Sicily and other areas in the Central Mediterranean. There are very few Maltese records of pelagic species. This is partly a result of the fishing techniques used by local fishermen and partly because cephalopods are only a by-catch in Malta.peer-reviewe

    A synthesis of the echinoderm fauna of the Maltese Islands

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    A review of existing literature records of echinoderms from Malta and a study of a large collection of specimens was carried out between 2000 and 2004 so as to update and produce a validated checklist of echinoderms occurring in Maltese waters. Seventy different species of echinoderms are recorded, including a number of species for which only single records exist for the Maltese islands and five species that were not found in the present study. The Maltese echinoderm fauna includes 45% of the 153 recorded Mediterranean echinoderm species, and apart from two aliens, is typical of the central Mediterranean region.peer-reviewe

    On the occurrence of Crocidura Suaveolens Pallas (Mammalia, Insectivra) in the Maltese Islands with notes on other Maltese shrews

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    Crocidura suaveolens Pallas, 1811 is recorded definitely for the first time from the Maltese Islands. Previous records of this species are reviewed and are shown to refer to other species or else to be unconfirmed. Besides C. suaveolens, two other shrews inhabit the Maltese Islands. Sunclts e"ruscus (Savi) is distributed in both Malta and Gozo while both C. suaveolens Pallas and C. russula (Hermann) appear to be restricted to the island of Gozo. The latter species has not, however, been recorded in this study.peer-reviewe

    A note concerning the scorpions (Arachnida : Scorpiones) of the Maltese Islands (Central Mediterranean)

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    All scorpions collected from the islands of Malta, Gozo, Camino and St. Paul's belonged to Euscorpius (s.str.) carpathicus (linnaeus, 1773) ssp. candiota Birula, 1903 as used by Kinzelbach (1975) for populations showing a complex of morphological characters intermediate between E.carpathicus carpathicus and E.mesotrichus Hadzi. Similar intermediate populations are found in several eastern Mediterranean localities (Greece, some Greek islands and Crete)" however the Maltese populations are more heterogenous than any other so far studied. The literature contains records of other species of scorpion from the Maltese Islands whereas the collections of the British Museum (Natural History), London include specimens of Mesobuthus gibbosus (Brulle) reportedly collected from Malta. These records are discussed and it is postulated that they are either errors of identification or labelling, or else represent introduced exotics now locally extinct.peer-reviewe

    On the occurrence of Agama agama (L.) (Reptilia : Agamidae) in the Maltese Islands

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    A live female specimen of Agama agama (L.) was found amongst crates of imported beer at Marsa, Malta in October 1979. This lizard was probably transported to Malta from North Africa with cargo.peer-reviewe

    A laboratory study of spatial organization in the crab Ebalia tuberosa (Pennant) (Crustacea : Decapoda : Leucosiidae)

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    In the laboratory, the spatial distribution of Ebalia tuberosa on a homogeneous substratum over a 20 day period was mainly random and was not affected by the initial distribution pattern. Population density and population sex-structure similarly had no effect. At low population densities no sexual difference in home range area was found but at high density male home range area was significantly larger than female home range area. There was little overlap in home range between individuals at low population densities but as density increased so did male-male overlap. Female-female and male-female overlap first increased and then decreased. Crowding suppressed female activity. At high population densities, females, and to a lesser extent, males, appeared to restrict their movements to a small area from which they probably excluded other individuals. At all population densities tested, the majority of individuals tended to move for short distances only and very infrequently. The crabs tended to remain in one spot for long periods especially in the case of females which, at high population densities, became very sedentary.peer-reviewe

    Malta : food, agriculture, fisheries and the environment

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    The Maltese archipelago, occupying an area of c.316 km 2 and situated in the central Mediterranean, consists of the inhabited islands of Malta and Gozo and a number of uninhabited islets and rocks. The islands are composed mainly of limestone of Oligo-Miocene age. Soils are young, show little horizon development, and are very similar to the parent rocks. There are no mountains, streams or lakes, but only minor springs. The main geomorphological features are karstic limestone plateaux, hillsides covered with clay taluses, and gently rolling limestone plains. The southwest coast is mainly steep sea-cliffs and the land tilts gently seawards to the northeast. The islands are riven by valleys which drain runoff during the wet season. The average annual rainfall is c . 530 mm of which some 85% falls during the period October to March. The mean monthly temperature range is 12-26°C. The islands are very windy and sunny. Natural water resources depend on percolating rainwater which collects in limestone aquifers. The flora and fauna are rich with c. 2,000 species of plants and more than 3,000 species of animals recorded to date; a relatively large number of species are endemic. The main ecosystems are maquis, garrigue and steppe. Minor ones include patches of woodland, coastal wetlands, sand dunes, freshwater and rupestral communities and those of caves. Human impact is significant. The resident population density is 1,140 per km2. Some 38% of the land area is cultivated and c.16% is built up. Environmental problems include accelerated soil erosion, quarrying, disposal of waste, high levels of chlorides and nitrates in the water supply, and loss of habitats and wildlife. The most important environmental issue at present is the rational use of land, a problem which is only now being tackled by the Maltese Government.peer-reviewe

    Feeding behaviour of fifteen species of hermit crabs (Crustacea : Decapoda : Anomura) from the Otago region, southeastern New Zealand

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    Hermit crabs are common and conspicuous; members of intertidal and subtidal habitats. Although there exists an extensive literature on their behaviour, in the main this deals with :shell related behaviour :such as shell selection and shell fighting, and with behaviour patterns associated with the various symbiotic relationships of which hermit crabs form part (see the extensive bibliography in the recent review of hermit crab behavioural ecoloKv by Hazlett 1981). Other aspects of their behaviour have received much less attention . A number of studies on hermit. crab tee(ling behaviour have been made. However, relative to the number of living species (estimated at '" 700, Alcock 1905, Gordan 1956) very few have been investigated. Moreover, those species which have been studied to date all belong to genera of only two out of six families of marine hermit crabs (the Diogenidae and the Paguridae), and are intertidal or shallow water species. The feeding behadour of hermit crabs belonging to less well known families or genera or from less accessible habitats has not been studied. Nonetheless the available'data are sufficient to show that these animals have a wide range of feeding mechanisms including deposit-feeding, suspension-feeding, predation and scavenging. Often a species is able to feed in different ways depending on what food is available at the time (Kunze and Anderwn 1979, Schembri, 1982). Given such complexity of behaviour: (1 larger cross-section of species from a wider taxonomic range and from more diverse habitats needs to be investigated before evolutionary trends and adaptive radiation within the group can be studied. Sixteen species of hermit crabs belonging to four families are known to occur in the Otago region (table I; the late E. J. Batham unpublished data, C. L. ;McLay), personal communication) in habitats ranging from rocky intertidal through relatively coarse sediments of various sorts on the continental shelf to finer sediment:; on the continental shelf edge and slope. This rich fauna presented an ideal opportunity to study feeding in hermit crabs from a variety of taxonomic grouping and habitat types. Here the feeding behaviour and feeding mechanisms of 15 species of Otago hermit crabs are described and discussed in relation to their morphology habitat and previous work on feeding in hermit crabs.peer-reviewe
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