The Biology of Upogebia pusilla (PETAGNA) (Decapoda, Thalassinidea)

Abstract. The distribution of the thalassinidean shrimp Upogebia pusilla was studied at four sites in the North Adriatic Sea: 1) a tidal flat in the lagoon of Grado, 2) a tidal flat at Lido di Staranzano near the mouth of the Isonzo, 3) a mud flat seawards of a salt marsh in a protected bay north of Rovinj, and 4) a sublittoral station in 6m depth near Aurisina. Information on grain size distribution, organic content, amount of debris, redox profiles and pH of sediment as well as temperature and salinity is given. Density, as determined by hole counts and a hole: burrow relationship derived from resin casting, generally increased with increasing water depth in the intertidal. The upper limits ranged between +10cm (Rovinj) and -20cm (Grado); densities between mean water and low water level varied strongly due to microtopography and macrophyte cover. Maximum densities in the intertidal ranged from 189 (Grado) to 2420 (Rovinj, juveniles) animals m². Shrimp density at the sublittoral station ranged between 80 and 230 m"². The zonation of the Upogebiidae and Callianassidae with respect to environmental parameters is discussed.     

The Biology of Upogebia pusilla (Petagna) (Decapoda, Thalassinidea) I. The Burrows

Abstract. The biology of the thalassinidean shrimp Upogebia pusilla was studied on a tidal flat in the Lagoon of Grado (Northern Adriatic). Burrows were investigated using in situ resin casting and with additional in situ and laboratory observations. Burrows show a basic pattern consisting of a U or a double U with turning chambers and a vertical shaft. Mean burrow diameter depends on animal size, it is smaller than the rigid carapace of the animal. Dimensions, distance between openings, depth of U, total depth, volume and surface are size dependent. The burrow wall is smooth and oxidized. Burrows are always inhabited by a single shrimp. Although they overlap, they are never interconnected. They are mainly constructed by compression of the sediment and are relatively permanent structures. A comparison of the burrows of Thalassinidea with regard to shape, number and appearance of openings, dimensions, properties of the burrow wall and dynamics is given.     

Population Dynamics of Sergio mirim RODRIGUES 1971 Decapoda: Thalassinidea: Callianassidae in Cassino Beach, Southern Brazil

Abstract. Thalassinid shrimps have been extensively exploited for bait in many countries around the world. In order to prepare future management strategies for a little-exploited population of Sergio mirim in southern Brazil, growth, mortality and reproduction of this species were studied between June 1988 and November 1992. Size-frequency distributions were dominated by mature individuals, and recruitment occurred in austral spring, with widely variable abundances between years. Females attained larger mean and maximum sizes than males. The sex ratio was balanced for young individuals and female-biased for the mature segment of the population, as previously reported for other species of burrowing shrimps. Ovigerous females were found mostly between September and January, and egg numbers were a function of carapace length. From parameters of the VON BERTALANFFY growth curves, a maximum life span of approximately 4 years was estimated for both sexes. Among callianassids for which reproductive measures are known. S. mirim represents one of the highest reproductive potentials. The advantages of the thalassinidean female-biased sex ratio pattern is discussed.     

Studies on the population ecology of Upogebia deltaura (Leach) (Crustacea, Thalassinidea)

Upogebia deltaura was collected quantitatively and qualitatively between June 1980 and August 1982 from a level, sandy bottom at a 12 m depth in the archipelago of Lysekil (on Gullmarsfjorden) about 70 km north of Göteborg, in western Sweden. A total of 347 individuals were obtained. The deepest burrows reached a depth of more than 65 cm into the substrate. During the cold season, U. deltaura was situated much deeper in the substrate than it was during the summer, probably as a result of ‘hibernation’. The average density was 5·0 individuals 0·1 m⁻², and the maximum of 10 specimens was found in one 0·1 m² sample. Out of the 341 individuals identifiable as to sex, 186 (54·6%) were females and 155 (45·4%) were males. Berried females were found between May and August, and the average number of eggs carried was 4757. Ecdysis took place between May and August; most females moulted in the middle of June and most males about one month later, in mid July. The chelipeds of large males were proportionally bigger than were those of large females. Maximum total body length of the females was 65·7 mm, and that of the males was 65·3 mm.     

Size at first maturity in females of the spiny lobster jasus verreauxi (Crustacea: Decapoda: Palinuridae)

The carapace length and total length size at first maturity in females of Jasus verreauxi (H. Milne Edwards, 1851) has been investigated by a detailed study of (a) the detection of the smallest size class with external eggs, and (b) the incidence of egg‐carrying females per size‐class interval. For the study 834 females were measured and examined at Spirits Bay, New Zealand, during mid October and late December 1966. The specimens ranged in carapace length from 12.0 cm to 23.9 cm, and in total length from 29.0 cm to 56.9 cm.

The results of the study show clearly that the females reach first maturity at a carapace length or a total length larger than the present minimum legal size, i.e. a carapace length of 10.2 cm (4.02 in.), or a total length of 25.4 cm (10.0 in.). No mature females were found less than 13.5 cm carapace length, or 32.0 cm total length. First maturity was attained by the majority (50% or more) of the J verreauxi females at a carapace length of 15.3 cm or larger, or at a total length of 38.0 cm or larger.

No undersized (smaller than the minimum legal size) females were present in the collections—yet 10.3% of the specimens were found to be immature. Immature females ranged in carapace length from 12.0 cm to 16.9 cm, or in total length from 29.0 cm to 41.9 cm. Being larger than the minimum legal size, all of the immature specimens examined were “harvested"—without having reached first maturity. It appears therefore that the stocks of small, immature female J. verreauxi are not protected by the present New Zealand minimum size regulation.     

Study of a Crustacea Decapoda Taxocoenosis of Posidonia oceanica Beds from the Southeast of Spain

Abstract. During 1986 and 1987 a decapod crustacean taxocoenosis of Posidonia oceanica beds from the southeast of Spain has been studied.
Data on abundance-dominance of the 50 species found and other information such as reproduction and the selective use of gastropod shells by the dominant hermit crabs arc given.
Differences in richness and cquitability between shallow (3–4 m) and deeper (5–7 m) samples arc also shown.
The taxocoenosis presents a geometrical distribution in which only 9 species have a relative abundance higher than 1 % and in which the structure is basically controlled by the two dominant hermit crabs, Cestopagitius limidus and Calcium tubularis , and hydrodynamic conditions.     

First record of the Thalassinid Upogebia issaeffi (Balss, 1913) (Crustacea: Decapoda: Upogebiidae) in Korean waters

Several specimens of Upogebia issaeffi (Balss, 1913) found on Namhae Island off the southern coast of Korea, where they were collected in the intertidal boulder habitat, are described and illustrated. This species has been reported from Vladivostok, Russia to Kagoshima, Japan, but this is the first reported occurrence in Korean waters. The species, closely related to the common Upogebia major that have been reported to be in Korean waters by Kim (1973), are distinguished by the morphology of the dactylus of the first pereiopod. Specifically, in male U. issaeffi, the dactylus has a longitudinal crest bearing a row of fine transverse striae, two longitudinal rows of granules on the outer side, a row of 12–16 granules and another row of 10–13 oblique ridges on the inner side. However, in females, the dactylus lacks a row of transverse striae but bears a row of rounded granules instead on the upper margin on outer side. Oblique ridges are also present on the inner side, but they are much shorter and less conspicuous than in males.     

Isolation By Distance (IBD) signals in the deep-water rose shrimp Parapenaeus longirostris (Lucas, 1846) (Decapoda,Panaeidae) in the Mediterranean Sea

The identification of boundaries of genetic demes is one of the major goals for fishery management, and few Mediterranean commercial species have not been studied from a genetic point of view yet. The deep-water rose shrimp Parapenaeus longirostris (Lucas, 1846) is one of the most important components of commercial landings in Mediterranean, its fishery aspects have received much attention, regrettably without any concern for the genetic architecture of its populations. The population structure in the central and eastern Mediterranean Sea (captures from six Italian and two Greek landings) has been analysed on the basis of surveys carried out with mitochondrial and AFLP markers. Data revealed the presence of a gradual discrepancy along a west–east axis. This species, occurring mainly at a depth of between 100 and 400 m, is not strongly confined in isolated demes, but it demonstrates an ‘Isolation By Distance’ model, within the Mediterranean Sea, which includes geographical areas with a some degree of isolation. The role of hydrodynamic forces, such as currents, water fronts, is discussed; and a further evidence of the ‘Levantine isolation’ within Mediterranean basin is shown.     

Concentration of particulate organic nitrogen in the marlborough sounds,New Zealand (note)

Samples of particulate matter were analysed for nitrogen by the micro‐Kjeldahl technique in an attempt to obtain an indication of the food available for mussels. The small amounts of nitrogen available in the samples prevented the detection of seasonal variation by this method. The mean concentration of 11.8 μg‐at of nitrogen per litre obtained from this study compares favourably with data from mussel farming areas in Spain.     

Biology of three Malacostraca (Decapoda) in a Mediterranean lagoon with particular emphasis on the effect of rapid environmental changes on the activity (catchability) of the species

The activity of three Malacostraca (Decapoda), Crangon crangon, Carcinus aestuarii and Paleamon squilla, was studied following rapid environmental changes in a Mediterranean lagoon linked temporarily with the sea. Nekton was sampled every 2–3 days using fixed fyke nets. A canonical analysis and a stepwise multiple regression were computed to determine which factor(s) can predict or account for the catch of these three decapods. In spite of rapid environmental changes no exceptional mortality was observed in each of the three species. Temperature is the environmental factor with major impact on the activity of C. crangon. Activity of P. squilla is controlled by water depth. At a depth of less than 20 cm two factors, salinity and phase of the moon, have a significant influence on the activity of this species. At depths deeper than 20 cm the activity is inhibited. There is only a weak relationship between the catch of C. aestuarii and salinity. Additional data on the life cycle of these species are given. The limitations of a monthly sampling period are discussed and the need for more short-term, consecutive sampling periods is stressed in order to understand the dynamics of systems with rapid environmental fluctuations.     

The Benthic Phase of the Life Cycle of Penaeus semisulcatus De Haan (Crustacea Decapoda) along the Southeastern Coast of the Mediterranean

Abstract. Recruitment, migration, growth and longevity of populations of Penaeus semisulcatus along the southeastern coast of the Mediterranean were investigated. The general pattern of the life cycle of P. semisulcatus and the parameters affecting it were identified.
Relative population density, measured by catch per unit effort, as well as relative age estimated by age group body length were used to study the pattern of the benthic phase of the life cycle.     

Notobathynella longipes sp. n. and new records of other Bathynellacea (Crustacea,Syncarida) from New Zealand

This paper deals with Bathynellacea collected by Entomology Division, DSIR, in 1972–73 by pumping water from wells and bores in different parts of New Zealand. Notobathynella longipes sp. n. is described from wells in Motueka (South Island). The distribution of the New Zealand Parabathynellidae is discussed briefly.     

Population dynamics of Callichirus major (Say, 1818) (Crustacea, Thalassinidea) on a beach in northeastern Brazil

We describe the structure, reproductive cycle, fecundity, growth, and mortality of a harvested population of the ghost shrimp Callichirus major. Samples were collected at monthly intervals from September 1999 to October 2000 on an urban sandy beach (08°11′S 34°55′W) in northeastern Brazil. During this period the sex ratio did not differ significantly from 1:1 (0.98 M: 1 F). Minimum and maximum sizes of the Dorsal Oval were 2.59 and 12.19 mm for males and 4.46 and 12.62 mm for females, respectively. Ovigerous females were found throughout the period, except between August and September 2000. Maximum lifespan was estimated as 3.3 and 3.4 years for females and males, respectively. This northeastern population differed from others previously studied in southern and southeastern Brazil, in regard to sex ratio, maximum attained size, maturation size, period and duration of the reproductive cycle, and fecundity. We interpret these regional differences as evidence for over-fishing at the study site, and suggest that large-scale management plans for callianassid populations should use regional population parameters.     

Population ecology of fiddler crab, Uca lactea annulipes (Decapoda: Ocypodidae) in Sirik mangrove estuary,Iran

Fiddler crabs are known as the most conspicuous bioturbating animals in mangrove forest, which by their burrowing activities promote nutrient cycling in ecosystems. Mangroves, crabs and bacteria are connected in the form of positive feedback loop, whereby an increase in the activity of any participant will tend to increase the activity of all others as well. Population structure, growth, mortality, recruitment, biomass and production of fiddler crabs as dominant species of deposit-feeder crabs have been investigated from May 2005 to March 2006 in the Sirik mangrove estuary in the eastern part of Strait of Hormuz. Ten 1 m² squares of the substrate were randomly sampled during low tide. There was a significant change in organic content in the sampling area during study period. The sex ratio was significantly deviated from 1:1 ratio in large sizes, where males were dominated year around. Fiddler crabs showed seasonal growth pattern during a year, which the maximum growth was observed during autumn and early summer and ceased during winter by low temperature. Growth parameters were estimated by Appeldoorn's method and fitted with seasonalized von Bertalanffy growth models. The Kimura likelihood ratio test revealed significant differences in the overall growth curves between males and females, originated from the differences in k$k$ and L_∞$L_{\mathrm{\infty }}$ between sexes. Males were found to exhibit higher growth rate and larger size than females, this could be attributed to the higher investment of energy for reproduction in females. Reproduction was restricted to spring and early summer, while recruitment occurs at the end of summer. Total annual production of males and females was 37.90 and 10.05 g dry weight/10 m² respectively and major production took place during early summer. Because of impact of temperature on the activity of fiddler crabs in subtropical regions, density of crabs has significant positive correlation with temperature (P < 0.01), while growth rate shows significant negative correlation with organic matter of sediment (P < 0.05). In conclusion these crabs showed lower mortality and production rate with the seasonal growth and recruitment in comparison with tropical species.     

Morphology of a Pre-collisional, Salt-bearing, Accretionary Complex: The Mediterranean Ridge (Eastern Mediterranean)

The Eastern Mediterranean Sea is a remnant of a deep Mesozoic oceanic basin, now almost totally consumed as a result of long-term plate convergence between Eurasia and Africa. The present-day surface morphology of the Eastern Mediterranean relates both to the early history of formation of the deep basins and the recent geodynamic interactions between interfering microplates. Among the most conspicuous morphologic features of the basin is an arc-shape, elongated and wide, bathymetric swell bisecting the entire basin from the Ionian to Levantine areas, known as the Mediterranean Ridge. During the last decade this tectono-sedimentary accretionary prism, which results from the Hellenic subduction, has been intensively surveyed by swath mapping, multichannel seismic profiling and deep dives. We present here, and briefly discuss, the main morphological characteristics of this feature as derived from swath bathymetric data that considerably help to better assess the lateral and north–south morphostructural variability of the Mediterranean Ridge. This study reveals that the characteristics and morphostructural variability of the Mediterranean Ridge are related to: (1) a specific incipient collision geodynamic setting south of Crete, where the African and Aegean continental margins are nearly in contact, (2) a unique regional kinematics, controlled by frontal convergence south of Crete (central Mediterranean Ridge) and oblique subduction with opposite sense of shear for the western (Ionian) and eastern (Levantine) domains of the Mediterranean Ridge, that explain the lateral variations of deformation and (3) particularities of its sedimentary cover, which includes massive salt layers within the outer Mediterranean Ridge and local salt deposits within the inner domains, that control the north–south morphostructural variability of the sedimentary wedge.     

Reproductive Biology of Liocarcinus puber and L holsatus (Decapoda, Brachyura, Portunidae) from the Gower Peninsula, South Wales

Abstract. Routine monthly samples of the commercially important portunid crab Liocarcimtx puber and the sympatric but ecologically separated L. holsatus were collected from the waters and shores around the Gowcr Peninsula, South Wales, between November 1983 and September 1985.
The pubertal moult in L. puber occurred at 38 mm CW (carapace width) (females) and 42 mm CW (males). In L. holsatus this occurred at 17 mm (females) and 18.5 mm CW (males). The median size of ovigcrous females was 49.2 ± 6.7 mm CW in L. puber and 26.5 ± 2.0 mm CW in L. holsatus.
Moulting and copulation occurred between spring and autumn, the moulting period of males being earlier than that of the females. Ovigcrous L. holsatus were recorded throughout the year, with highest proportions between February and April. L. puber were ovigcrous mainly between January and March; none was recorded between September and November. The number of eggs of the wild brood (range: 39,000–280,000 for L. holsatus and 40.000–262.000 for L. puber ) was related to female body size as y = 3.099.51 c^0.1126x, r = 0.90, n = 21 and y = 6,335.98 c^0.051x, r = 0.88, n = 23, respectively, where y = number of eggs and x = carapace width (mm).
Following successful copulation, females of both species were able to spawn more than once during an intcrmoult period.     

High environmental salinity reduces the reproductive potential of the spider crab Maja brachydactyla (Decapoda,Majidae)

The spider crab Maja brachydactyla is an important fisheries species in Europe. Adults were sampled in Ría de A Coruña (NW Spain) and transported to IRTA rearing facilities. Salinity and photoperiod changes and their effect on reproduction were tested in the laboratory. The number of newly hatched larvae per batch (presence of actively swimming newly hatched larvae in a broodstock tank) was counted and sampled to estimate dry weight and proximal composition. Keeping spider crab broodstock in a high salinity environment (38 ppt) significantly reduced the number of newly hatched larvae, reaching up to fivefold difference in winter. The number of newly hatched larvae produced under a natural photoperiod was 10‐fold higher than those produced using a fixed photoperiod at 34 ppt salinity during winter. No clear pattern of changes in larval dry weight, protein, lipid or carbohydrate composition was observed under the environmental conditions tested. The results show that the salinity used for broodstock maintenance, especially during the embryonic development, is an important factor causing changes in larval production of M. brachydactyla and with potential implications for recruitment success.     

The annual cycle of Synechococcus (cyanobacteria) in the northern Levantine Basin shelf waters (Eastern Mediterranean)

Abundance of picoplanktonic chroococcoid marine cyanobacteria Synechococcus was monitored weekly over the year 1998 in shallow coastal waters of the northern Levantine Basin. The ambient physical, chemical and biological variables (temperature, salinity, Secchi disk depth, total suspended sediment, nitrate, phosphate, Chl a and phytoplankton) were also measured. Synechococcus was found to be more abundant during summer and early autumn and less during winter and early spring. At the surface and 15 m depth, cell concentrations were in the range 6.4 × 10³–1.5 × 10⁵ and 3.2 × 10³–1.6 × 10⁵ cells·ml⁻¹, respectively. Based on the Pearson product–moment correlation analysis, a highly significant correlation between Synechococcus abundance and ambient temperature was observed (n = 40, r = 0.558, P < 0.01). As Synechococcus forms blooms that usually do not last more than a week, the short time‐scale survey achieved in this study was appropriate to reveal its abundance dynamics. Several factors such as rapid changes in nutrient concentration (especially nitrate), phytoplankton, light availability, temperature, salinity, freshwater input and vertical mixing played a relevant role on the abundance of Synechococcus over the year in the highly dynamic shallow coastal waters of the Levantine Basin.     

Ficopomatus'Reefs' in the Po River Delta (Northern Adriatic): Their Constructional Dynamics, Biology, and Influences on the Brackish-water Biota

Abstract. The serpulid polychaete Ficopomatus enigmaticus (F auvel , 1923) builds huge aggregates in the "Sacca del Canarin", a brackish inlet of the Po River Delta (Italy). Distribution, structure and development of these 'reefs'. together with their associated biota, were studied by field observations and settlement panels from 1977 to 1979. Some aspects of the serpulid biology (settlement periods, tube growth, life strategy) were also taken into account. Ficopomatus reefs influence in many ways the brackish-water ecosystem: they form the main hard substrate; are major sediment source; help in regulating the trophic status of the lagoon; and act as refuge for many invertebrate species.