Distribution and abundance of co-occurring chthamalid barnacles Chthamalus montagui and Chthamalus stellatus (Crustacea,Cirripedia) on the southwest coast of Portugal

Two co-occurring chthamalid barnacle species occur on the rocky shores of continental Portugal: Chthamalus stellatus (Poli) and Chthamalus montaguiSouthward. In the present study, patterns of distribution and abundance (density and percentage cover), both vertically (tidal level) and horizontally (wave action), were studied for each species on headlands (more wave action) and not on headlands (less wave action) and at two spatial scales (shore and site) and three tidal levels (low, mid and upper). Chthamalus montagui was significantly more abundant than C. stellatus in both degrees of wave action and at all tidal levels. Despite this great difference in abundance and considering each species individually, C. montagui was more abundant at mid tide-level, while C. stellatus was more abundant at the low tide-level, and C. montagui was less abundant on headlands, while C. stellatus was more abundant on headlands. Small-scale variability (between sites, tens of meters) of abundance of each species was detected, while differences on a larger scale (between shores, tens of kilometres) were not significant.     

Notes on the distribution and biology of the deep-sea crab Bathynectes maravigna (Brachyura: Portunidae) in the Mediterranean Sea

Data on the distribution and biology of the deep-sea portunid crab Bathynectes maravigna are reported for the Mediterranean Sea, based on several fisheries research surveys. Densities are low and, therefore, biological data are scarce. In the western Mediterranean, the species is much commoner in Alborán Sea than in the Catalano-Balearic Sea. Occurrences are also scarce in the southern Adriatic and northwestern Thyrrenian Sea, as well as in the Ionian Sea. The Alborán Sea and the seas surrounding the southern Italian peninsula are the areas where densities are the highest. The occurrence depth range was found to be 245–786 m, but most of the occurrences took place deeper than 500 m. Sizes ranged between 9 and 51 mm carapace length in males and between 12 and 51 mm in females. Ovigerous females have been only reported in October–December and March–May. Eighty three percent of both males and females are right-handed. Sexual dimorphism was present in cheliped length with males having longer chelae than females. The species appears to be much commoner in those areas where Atlantic influence is the highest.     

Epibiontic and endobiontic polychaetes of Geodia cydonium (Porifera,Demospongiae) from the Mediterranean Sea

Polychaete assemblages associated to the sponge Geodia cydonium were investigated at two sampling sites in the Mediterranean Sea: Porto Cesareo Basin (Apulia) and Marsala Lagoon (Sicily), both characterized by sheltered hydrodynamic conditions. Samples were seasonally performed during 1997, in order to compare the assemblages coming from the two localities studied, considering separately the internal and external tissues of the sponge, and with the aim of evaluating the influence of sponge size on polychaete colonization. The examined sponge is characterized by a peculiar stratification of its tissues: an external thick and hard layer, the cortex, and an internal softer one, the choanosome. Statistical analysis showed that this was the main factor controlling polychaete assemblage, with the internal tissue, less rich and diversified, appearing impoverished with respect to the external layer. A similarity in species composition was observed between sites, even though some differences were evidenced in the abundance of some species, mainly reflecting differences in local environmental conditions. Species richness and density increased with the increasing sponge size. Such a situation is particularly evident at Porto Cesareo, where sponges are covered by an algal layer which is particularly rich on the largest specimens, thus suggesting that most of the species of polychaetes were linked more to the neighbouring environment than to the sponge itself.     

The niche-width variation hypothesis reconfirmed: Validation by genetic diversity in the sessile intertidal cirripedes Chthamalus stellatus and Euraphia depressa (Crustacea,Chthamalidae)

Genetic diversity in a pair of cirripede species, based on electrophoretic analysis of 25 gene loci, is higher for Chthamalus stellatus, the species with a broader biogeographical distribution, and hence, with a broader ecological niche, than that of Euraphia depressa. Comparing the genetic diversity within E. depressa we again report a higher genetic diversity among the specimens exposed to solar radiation (living in the wider ecological niche) versus the specimens confined to the sheltered dark environments in caves or under boulders. The indices of genetic diversity used in this study are polymorphism, heterozygosity, mean number of alleles per locus and gene diversity. We conclude that the niche-width variation hypothesis has been confirmed in this pair of species: genetic diversity is positively correlated with niche breadth.     

Anthesis effects on Posidonia oceanica (L.) Delile phenology in the Bay of Calvi (Corsica,Mediterranean Sea)

In Posidonia oceanica (L.) Delile, anthesis induces a decrease in the number of juvenile leaves resulting in a significant reduction in the number of leaves on the flowering shoots. All the leaves of the flowering shoots are narrower than the leaves of nonflowering shoots. A modification of the leaf growth also appears in flowering shoots: the oldest leaves are longer and the leaves induced during or after anthesis are shorter. At 10 m depth, in the Bay of Calvi, anthesis lasts roughly 3 months and the flowering is induced 7 months before anthesis.     

Fishery of the Deep-water Rose Shrimp Parapenaeus longirostris (Lucas, 1846) (Crustacea: Decapoda) in the Northern Tyrrhenian Sea (Western Mediterranean)

The aim of this study is to provide information on the fishing pattern of Parapenaeus longirostris in the northern Tyrrhenian Sea (western Mediterranean), in order to improve the management of the resource in the area. Data were obtained from commercial fishery, covering the period 1991–2002. Catch rates revealed notable inter-annual fluctuation of the P. longirostris landing, probably due to the life cycle of the species. The highest yields (kg per hour of trawl) of the commercial fishery were obtained at depths ranging between 180 and 300 m, the lower ones at depths between 100 and 180 m, where small specimens are more abundant. Commercial catches were characterised by a very low presence of specimens smaller than 20 mm carapace length (CL), mainly due to the deeper localisation of the fishing grounds when compared to the recruitment areas of the species. The size at which 50% of the specimens were discarded by the fishermen was 15 mm CL, while the estimated size at first capture of the individuals caught by the commercial net was 12.4 mm CL.     

Settlement behavior of Chthamalus anisopoma larvae largely determines the adult distribution

Summary In the northern Gulf of California the adult distribution of the intertidal barnacle species, Chthamalus anisopoma, on exposed shores is approximately between 0.0 and 2.0 m above mean low water (MLW). The species is typically absent in protected (from wave splash) areas. In this study, I examined a series of alternative hypotheses relating to the factors that could be responsible for limiting the distribution. Post-settlement factors appear to be unimportant because settlement was largely restricted to areas within the adult distribution. Two processes could account for the high correlation between settlement and adult distributions. First, hydrodynamic factors could restrict deposition of larvae to sites that coincidently were in areas in which individuals could survive to maturity. Second, larvae may choose to settle only on sites where they can survive to maturity. Of the two, the later was supported as settlement could be induced on surfaces outside the adult distribution using transplanted adult conspecifics as cues. Thus, competent larvae were present outside the adult distribution of Chthamalus zone but did not settle under normal conditions. Also, there was no evidence that pre-emption of space by other sessile species, by itself, restricted the distribution of Chthamalus. Settlement within the existing adult distribution may be an evolutionary response to increased mortality for individuals settling outside the adult distribution compared to those settling within it.     

Life history, aspects of reproductive biology and production of Corophium orientale (Crustacea: Amphipoda) in Monolimni lagoon (Evros Delta, North Aegean Sea)

Monthly samples of Corophium orientale were collected during February 1998–February 1999 in both parts of Monolimni lagoon (0.3 < Sal. < 6 psu, 2 < Temp. < 28.5 °C). Corophium orientaleshowed a semiannual life cycle. In the southern part, breeding occurred from early spring to mid autumn having three peaks, in early spring, early summer and early autumn, and three cohorts were produced, a spring cohort, a summer cohort and an overwintering one. In the shallower innermost northern part of Monolimni lagoon, breeding peaked in mid-spring and, also, in early autumn, and two discrete cohorts, a spring and an overwintering one, were produced. A lack of large individuals, attributed to a temporary size – selective predation by migrating shorebirds, was observed during summer. That lack possibly contributed to the hiatus in reproduction. Photoperiod seemed to be a more important cue than temperature in the initiation of the reproductive cycle, while extremely low salinities (<1 psu) did not deter breeding. Females attained maturity at a smaller size in late spring and, especially, in summer than in early spring at lower temperatures. Brood size was a function of females body size. Females, matured during summer at high temperatures, showed the lowest brood size, body length ratio. Mean brood size was small (12–13 early embryos) and embryo loss during development high (54%), possibly due to a negative effect of low salinities. A 1:1 sex ratio existed in the small body length classes, but females preponderated in the large ones. The spring cohort in the southern part, which developed at moderate temperatures, showed the highest growth rate (40 m day^–1). Secondary production of C. orientalecalculated by Hyness method gave a mean annual density of 4562.5 and 9327.6 ind. m^–2, a mean annual crop (B) of 1.03 and 2.67 g DW m^–2, an annual production (P) of 6.91 and 22.54 g DW m^–2 and a P/B ratio of 6.7 and 8.4 in the northern and southern part of the lagoon, respectively.     

First geo-marine survey of living cold-water Lophelia reefs in the Ionian Sea (Mediterranean basin)

Abstract Prosperous deep coral mounds including living colonies of Lophelia pertusa together with Madrepora oculata and Desmophyllum dianthus (= D. cristagalli) have been discovered in 2000, by fishery operations on the eastern side of the Ionian Sea. The living coral mounds are located between ca. 300 and 1,100 m on a gently dipping shelf off Apulia at Santa Maria di Leuca (SML), and characterized by a complex seabed topography. Side scan sonar, shallow high-resolution seismics and sampling indicate that these Lophelia-bearing coral mounds colonize quasi-indurate (firmground) Pleistocene sediment. At places live corals were found on Pleistocene coral-hardgrounds. The fauna associated with these Ionian modern coral mounds is less diversified than modern Eastern Atlantic counterparts. The core of living coral mounds colonies is at present located in 500–700 m and is tentatively suggested that their survival is mostly controlled by oceanographic factors. The SML coral banks represent so far a unique example of living Lophelia-bearing coral mounds in the Mediterranean basin.This revised version was published online in January 2005 with corrections to the author name and figure captions 4 and 5.     

Selectivity Parameters and Size at First Maturity in Deep-Water Shrimps, Aristaeomorpha foliacea (Risso, 1827) and Aristeus antennatus (Risso, 1816), from the North-Western Ionian Sea (Mediterranean Sea)

Selectivity experiments were carried out during trawling targeting deep-water shrimps Aristaeomorpha foliacea (Risso, 1827) and Aristeus antennatus (Risso, 1816) (Crustacea, Decapoda, Aristeidae) in the North-Western Ionian Sea (Eastern-Central Mediterranean). Different criteria were employed to analyse maturity; however, the proportion at 50% of retained, mated and mature specimens was always used to indicate the size, expressed as Carapace Length (CL, mm), at first capture (CL_c), mating (CL_sp) and at first maturity (CL_m), respectively. In order to estimate the size at 50% maturity (CL_m) for females of both species, three criteria were adopted. In particular, CL_m was computed for the mature females not considering the presence of spermatophores, for the mature females with spermatophores and for the mature females intersected by the decreasing proportion with size of females without spermatophores. Three diamond stretched mesh codends of 40, 50 and 60 mm were tested using a cover of 20 mm. The 40-mm stretched mesh size (European Union legal size in the Mediterranean) was not selective for the sampled population of each species. The size at first capture (CL_c), calculated in both species for the two sexes combined, increased significantly with mesh size. Even for the mesh size of 60 mm, the size at first capture was still smaller than the sizes at 50% maturity, whatever the criterion adopted. Since the differences between the size at first maturity and the sizes at first capture are greater in A. foliacea than A. antennatus, the former species appears in this respect to be more vulnerable to trawling than the latter.     

Thaliacean distribution and abundance in the northern part of the Levantine Sea (Crete and Cyprus) during the eastern Mediterranean climatic transient, and a comparison with the western Mediterranean basin

First results are presented on the composition, abundance and vertical distribution of the thaliacean fauna in the Levantine basin obtained from stratified tows at three deep-sea sites in 1993: SE off Crete, and SW and NE off Cyprus. Samples with a 10 m²-MOCNESS (mesh size 1.67 mm) were poor in species and specimens as compared to samples with a 1 m²-double-MOCNESS (0.333 mm). Of the 12 species identified, six species belonged to the most abundant Doliolida, predominated by the phorozooids of Doliolum nationalis, five species belonged to the Salpida and one to the Pyrosomatida. Thaliaceans, most abundant by species and numbers SE off Crete, comprised ≤0.2% of the local mesozooplankton standing stocks. Presumably, they did not contribute substantially to the vertical flux generating the locally increased biomass and activity of the microbial benthos at the 4,300 m deep Cretean site. Most doliolids and salps were collected from the epipelagic and upper mesopelagic layers, and appeared to be most abundant close to the deep maximum of chlorophyll-a. Samples below 150 m were rarely rich in specimens, although two species performed diel migrations from the mesopelagic zone into the surface layers where some vertical segregation was evidenced. The aspect of niche separation is discussed.     

Bathymetric distribution and growth patterns of Bathypterois mediterraneus from the north-western Mediterranean Sea

Bathypterois mediterraneus was collected on 148 bottom trawls between 147 and 2251 m depth in the north-western Mediterranean. The species appeared below 700 m, its relative abundance and biomass increased progressively and reached its maximum at 2100-2300 m. A total of 1913 specimens were measured, ranging from 4 to 20 cm standard length ( L _s). The size composition with depth did not show any specific trend, and no modal progression could be distinguished in the length frequency distribution by cruise, with dominance of large fish (13-15 cm L _s) and a unimodal size pattern. The otoliths of 173 specimens were examined and showed the ring pattern common to teleost fishes. The age ranged between 0 and 15 years, although specimens of 4-12 years old were the most abundant. The growth parameters and the growth curve obtained from the interpretation of the growth rings in otoliths showed a low growth rate.     

A comparative study on recurrent blooms of Alexandrium minutum in two Mediterranean coastal areas

Alexandrium minutum is a toxic dinoflagellate widespread along the Mediterranean coasts. This species is frequently detected year-round at low concentrations within the Mediterranean basin. However, it only proliferates recurrently in some localities. Two affected areas are the Catalan and Sicilian coasts. In order to identify the factors determining the A. minutum blooms in the Mediterranean Sea, we compare the bloom conditions in two harbours: Arenys de Mar (Catalan coast, Spain) and Syracuse (Sicily, Italy), during 2002–2003. Arenys de Mar harbour is a fishing and leisure harbour and receives an input of freshwater rich in nutrients. Likewise, the Syracuse harbour – located on the Ionian coast of Sicily – is subject to freshwater inputs. Some points of this site are used for productive activities such as shellfish farming. A. minutum from the two areas studied were morphologically and genetically identical. In both sites, recurrent blooms take place from winter to spring. Surface water temperatures and salinities during A. minutum bloom events were 12–14.5 °C and 32–38, and 16–24 °C and 32–37.7 for Arenys and Syracuse, respectively. During the blooms, the spatial distribution of A. minutum in the two harbours, the physicochemical characteristics and the phytoplankton community were studied. Similarities in composition of the phytoplankton community were evidenced, with a clear dominance of dinoflagellates over the other taxa. In Arenys, the second dominant species was Prorocentrum micans followed by Scrippsiella spp. and Dinophysis sacculus. The same species were found in Syracuse although P. triestinum, and alternatively Lingulodinium polyedrum, reached cell densities much higher than the other dinoflagellates giving marked water discolourations.     

Sex-related variability of rostrum morphometry of Aristeus antennatus (Decapoda: Aristeidae) from the Ionian Sea (Eastern Mediterranean, Greece)

Sex-related rostral variability was studied in the aristeid shrimp Aristeus antennatusfrom the Eastern Ionian Sea (Mediterranean). Shrimps were collected on a monthly basis from December 1996 to November 1997 using a commercial bottom trawl in a depth range of 446–728 m. Female relative growth of rostrum proved to be negative allometric both seasonally and in the pooled annual data set. Males on the other hand, showed no or negative correlation of rostrum length with size. Mature males with short rostra dominated in the male population all year around. The appearance of males with long and intermediate rostra during winter, which disappear thereafter in favour of those with short rostra, indicates that rostrum shortening takes place during the end of winter. The increase of mated females during spring supports the hypothesis already addressed by other authors on the function of the male short rostrum in this species mating behaviour. Nevertheless, the paucity, in comparison to other Mediterranean populations, of males with long or intermediate rostra could indicate that for the bulk of the male population, the process of rostrum shortening in the Eastern Ionian Sea occurs outside the geographical locality or depth range sampled.     

The distribution and molecular diversity of the Eastern Atlantic and Mediterranean chthamalids (Crustacea, Cirripedia)

The three chthamalids Chthamalus stellatus , C. montagui and Euraphia depressa are common inhabitants of the intertidal zone in the Eastern Atlantic, Mediterranean Sea and Black Sea. In this study, we investigated the occurrence of these barnacles in a wide range of their distribution. Population divergences of these two species have been inferred using three molecular markers — internal transcribed spacer (ITS), elongation factor 1α (EF-1α) and cytochrome oxidase subunit I (COI). ITS sequences of C. stellatus were identical throughout the species range, whereas ITS sequences of C. montagui indicated that the Black Sea and Mediterranean populations are isolated from the Atlantic population. The COI and EF-1α sequences were the most variable and informative. They indicated a high genetic divergence between Atlantic, Mediterranean and Black Sea populations for C. montagui . In addition significant genetic structure was found among the populations of C. stellatus based on EF-1α but not COI. Interestingly, our molecular dating analysis correlated the pattern of diversification in C. montagui to major geological changes that occurred in the Mediterranean during the end of the Messinian and Pleiocene periods. We suggest that palaeohistory shaped the divergences between Chthamalus populations that have probably been maintained by current hydrographic conditions. Finally, COI phylogenetic analysis placed the genus Euraphia within the Chthamalus clade, suggesting the need for a taxonomic revision of Euraphia . This study represents the most detailed phylogeographical analysis of intertidal Mediterranean species to date, and shows that geological events have strongly shaped the current diversity pattern of this fauna.     

Aspects of the reproductive biology ofPollicipes pollicipes (Cirripedia; Lepadomorpha) from the southwest coast of Portugal

The pedunculated cirripedePollicipes pollicipes is of considerable economic importance in Portugal, particularly along the southwest coast. Current knowledge of its biology is poor, as evidenced by the paucity of available literature. This paper reports on the reproduction of twoP. pollicipes populations, Castelejo and Zavial, on the southwest coast of the Algarve. Differences in reproductive patterns between the two sites were minor and not statistically significant, despite differences in environmental conditions between the two sites. Adult animals carried fertilised eggs from April throughout September, and the percentage of individuals with egg masses correlated positively with air but not with sea water temperature. Brooding success was greater with average air temperature in excess of 14°C during months of strong upwelling and presumed food availability. Functional ovaries and testes are available in the population all year round but fertilisation does not appear to occur during the winter months. Reproduction ofP. pollicipes on the southwest coast of the Algarve appears closely linked to the upwelling phenomenon with the rate of deposition of gonadal tissue probably being determined by environmental temperature. The cues which determine the cessation of fertilisation remain to be investigated.     

Larval development of the rhizocephalanSacculina polygenea (Crustacea: Cirripedia)

Larval development of the rhizocephalanSacculina polygenea (Crustacea: Cirripedia: Rhizocephala) parasitizing the coastal crabHemigrapsus sanguineus was studied in Vostok Bay, the Sea of Japan. At 22–23°C, the entire cycle of larval development takes 2.5 days and includes five naupliar stages and one cypris stage. Like other rhizocephalans, the larvae ofS. polygenea are lecithotrophic and only grow slightly in size in the course of development, and like all sacculinids, they have no flotation collar. The naupliar stages IV and V have a tubercle between the furcal rami; this tubercle is absent in the larvae of the genusPeltogasterella, but it has been described inS. carcini. The first seta of the antennule only disappears completely at the fourth stage, although it is markedly reduced at the third stage. No morphological differences, except differences in size, are found between male and female nauplii.     

The Sperm Whale,Physeter macrocephalus,in the Eastern Mediterranean Sea

Abstract

After the successful establishment of free–living populations of Rose–ringed Parakeets (Psittacula krameri) and Common Mynas (Acridotheres tristis) in Jeddah, an overview of all exotic birds imported into Jeddah in the first three months of 1990 is given.     

Spatial patterns of abundance and growth of Mytilus edulis on boulders in the Northern Baltic Sea proper

Small scale spatial patterns of abundance, growth and condition of the mussel Mytilus edulis on sub-littoral boulders (approx. 1–2 m high) were investigated at the island of Askö in the northern Baltic proper. The effect of side (exposed/sheltered with respect to wave action and sunlight) of boulder and position (up/down) on boulder was investigated. A large spatial variability in abundance of M. edulis between boulders and between various sites within boulders were found. The highest numbers of mussels were found on the wave exposed side, near the top of boulders. Shell growth was favoured by a sheltered side and a down position. The body condition (meat weight/shell weight) of mussels was, on the other hand, affected only by position, the condition of mussels being better at the up position. Consequently, there seems to be temporal differences in the condition for growth within a spatial position. The body condition of the mussels was best near the top of boulders in the spring, but long-term shell growth was favoured by a sheltered side and a down position. This may reflect changes in the composition and availability of food during the year with phytoplankton as the major food source during the spring bloom and resuspension of benthic production and detritus as relatively more important during the rest of the year.