Biology and life cycle of Tmetonyx similis (G. O. Sars, 1891) (Amphipoda,Lysianassidae), a scavenging amphipod from the continental slope of the Mediterranean

The present study focused on the biology and life cycle of Tmetonyx similis, a scavenging amphipod inhabiting the continental slope of the north‐western Mediterranean. All the categories of individuals were observed in the samples. The emergence of offspring occurs in successive cohorts. The lifespan of the females is longer than that of the males, but the sex ratio is strongly in favour of the males. The fecundity was found to be lower than that of the other female crustaceans present in these samples. The growth pattern was modelled. A strong correlation was observed between the length and the weight of the animals collected. Several hypotheses are proposed to explain a sex ratio in favour of males. This result may be explained by a migratory process of the females of T. similis. A comparison of the reproduction strategy is given for the three main scavenger crustacean species (amphipods and isopod) collected in this area.     

Effects of temperature on the survival and growth of age-0 least chub ( Iotichthys phlegethontis )

Larval and juvenile stages of many fishes require nursery habitats that provide optimal conditions for growth. Loss or degradation of these habitats limits recruitment, causing population and species declines. Least chub ( Iotichthys phlegethontis ), an endemic cyprinid in the Bonneville Basin, is currently restricted to a few spring complexes in Utah. This species utilizes the warm shallow spring margins as spawning and rearing habitat throughout the summer. This study was conducted to determine effects of temperature on survival and growth of age-0 least chub to understand the importance of temperature in selection of spring margins as rearing habitat. Age-0 least chub were exposed to 5 temperatures (14°C, 17°C, 21°C, 24°C, and 27°C) for 112 days. Growth rates varied significantly with temperature except at 17°C and 27°C, and growth rates were highest at 21°C ( P < 0.001). Maximum growth rate for age-0 least chub, estimated from a 2nd-order polynomial regression, would occur at 22.3°C. These thermal requirements indicate the importance of warm rearing habitats in producing strong year classes and viable populations. However, warm spring margins also enable western mosquitofish, a nonnative competitor and predator of least chub, to thrive in these spring habitats. Broad thermal limits of the least chub suggest that it could persist at cooler temperatures, which would reduce the viability of western mosquitofish populations.     

Biology and life cycle of Scopelocheirus hopei (A. Costa, 1851), a scavenging amphipod from the continental slope of the Mediterranean

The biology of Scopelocheirus hopei, a deep-sea (500 m) scavenging amphipod that lives on the continental slope of Mediterranean canyons, was studied. Animals were collected using a baited trap. A new method was developed for reproducibly measuring the exact length of the animals. All the categories of individuals were always present in the samples. The emergence of offspring occurs in successive cohorts. Individuals of the two sexes do not grow at the same rate: the males grow more quickly than the females, but their lifespans are shorter. The males are always less numerous than the females. Two production cycles occur. The females produce offspring all year round. The mean fecundity was found to be 218 eggs per female. The growth pattern was modelled. A strong correlation was observed between the length and the weight of the animals collected. Several hypotheses are proposed to explain the results obtained.     

Oostegite development during the sexual maturation of females of Tmetonyx similis (G. O. Sars, 1891) (Amphipoda,Lysianassidae)

The development of the oostegites was studied in the females of Tmetonyx similis (Crustacea, Amphipoda) during the period of sexual maturation. The process is complex and involves a series of variably long sequences. These sequences may constitute a means of adjusting the animals' sexual maturation to environmental conditions in order to increase their reproductive efficiency. The age and lifespan given by most authors working on amphipod species have probably been underestimated and should be regarded as minimum data. The physiological significance of the development of the oostegites is probably more complex than has generally been thought to be the case up to now.     

The amphipod genus Alexandrella (Amphipoda,Stilipedidae): taxonomic status,allometric growth and description of two new species

Two new species of the genus Alexandrella are described: A. mandibulata and A. martae. One species, A. mixta, is considered a junior synonym of the type species A. dentata. The genus now comprises six species, all of which are restricted to either the Antarctic or sub‐Antarctic region or the South Pacific. Oostegites are observed to be present on pereopod 1 in two Alexandrella species. This is a novel morphological trait among the Amphipoda. Developmental information is presented for two other Alexandrella species, in which the mandibular incisor is seen to be modified from strongly toothed in marsupial young to totally smooth in mature specimens. Also the armature dorsally on their body and the morphology of the telson undergo conspicuous allometric changes. A key to all known Alexandrella species is provided.     

Biogeography of amphipods (Crustacea: Amphipoda: Gammaridae) from the central Zagros Mountains,Iran, with descriptions of two new species

Seven species of gammarid amphipods were studied in the relatively small province of Charmahal-Va-Bakhteyari in the central Zagros Mountains, Iran. Of these, four are previously known (Gammarus proiectus, G. komareki, G. syriacus and G. balutchi), one is a new record for the region (G. pseudosyriacus) and two are new species (G. lordeganensis and G. bakhteyaricus). From the taxonomic point of view, head microsculpturing characters were found to be reliable as discriminating sets of characters useful in species identification. Habitat diversification and climatic fluctuations appear to be the main factors for species diversity of the area, and the Zagros Mountains act as a geographical barrier to species distribution.     

Juvenile development and growth patterns in the mud crab Eurytium limosum (Say, 1818) (Decapoda,Brachyura, Xanthidae) under laboratory conditions

The post‐larval development of the mud crab Eurytium limosum was studied under laboratory conditions by using the offspring of ovigerous females collected at the Comprido River mangrove, SP, Brazil. The first crab stage is fully described and the juvenile development, until crab stage 10, is examined with emphasis on morphological change, sexual differentiation and growth patterns. The carapace of the first crab stage is nearly square as observed in other xanthids, becoming similar to adults only at stage 15. The sexes can be distinguished from stage four, based on the number of pleopods and their morphology. While the intermoult period increases, the moult percentage decreases at each stage. The abdominal allometric growth is sex‐dependent, with males showing a negative (b?=?0.71) and females an isometric (b?=?0.95) relative growth pattern. Male gonopods undergo a positive allometric growth, and their shape changes remarkably until sexual maturity. The cheliped dentition can be observed after stage 4. Regardless of sex, most crabs have a molariform right cheliped, which is thought to aid the handling of asymmetric prey such as gastropods.     

Effects of metals and organic compounds on survival and bioaccumulation in two species of marine gammaridean amphipod,together with a summary of toxicological research on this group

The toxicity and bioaccumulation of arsenic, cadmium, copper, lead, mercury, zinc, DDT, PCB and the water-soluble fraction of diesel fuel to the gammaridean amphipods Corophium insidiosum and Elasmopus bampo were measured. At 96 h exposure C. insidiosum was more sensitive to arsenic, zinc, DDT, PCB and the water-soluble fraction of diesel fuel than E. bampo, whereas E. bampo was more sensitive to cadmium, chromium and copper than C. insidiosum. Over a 20-day period C. insidiosum accumulated greater amounts of chromium, copper, lead and zinc than E. bampo, whereas E. bampo accumulated more cadmium, DDT and PCB than C. insidiosum. The toxicity and bioaccumulation of toxicants to other species of marine gammaridean amphipods are tabulated.     

A new species of amphipod of the genus Neomegamphopus (Crustacea,Amphipoda, Neomegamphopidae) from Rodrigues,Indian Ocean

A new species of Neomegamphopus Shoemaker is described from Rodrigues, Indian Ocean. The systematics of the Neomegamphopidae from the Indian Ocean is discussed and a key to the species from that ocean is provided.     

Morphology and growth variation of Agropyron Smithii RYDB. (western wheatgrass) at different salinity levels

The purpose of this study was to determine the morphology and growth responses of Agropyron smithii Rydb. To various saline environments as evaluated in the laboratory. Agropyron smithii Rydb. (Rosana) seeds were germinated, transplanted into nutrient solutions with NaCl concentrations of 0, 50, 100, 150, and 200 m M , and grown for 80 days. Plant height, length of culm, and number of culms per plant were significantly reduced by the presence of NaCl in the nutrient solutions. As the external NaCl concentrations increased, values of root and plant ratio and leaf dry/fresh mass ratio increased significantly; biomass decreased significantly. However, the stomatal index, number of leaves per culm, and ratio of leaf length to leaf width were not significantly affected by the presence of NaCl.     

Culture of a new medicinal leech: growth,survival and reproduction of Hirudo orientalis Utevsky and Trontelj, 2005 under laboratory conditions

The increasing demands for medicinal leeches around the world has increased the need for new sources of leeches. To assess the feasibility of culturing a new medicinal leech species, growth, survival and reproduction of Hirudo orientalis was investigated under laboratory conditions (28°C; 9.5D:14.5L light regime; monthly feeding by sheep blood) from hatching until sexual maturity. Several interesting results emerged from this study. (1) The first copulation was observed in 5.5-month-old leeches and cocoon deposition started by six months. (2) Cocoon length and diameter did not differ significantly between six- and nine-month-old leeches, but the percentage of leeches depositing cocoons was significantly higher in the nine-month old group. (3) The growth curve was saltatory, similar to other sanguivorous species. The mean (±SE) wet weight of 6-month-old individuals was 4.70 (±0.86) g. (4) Weight gain rate decreased with increasing age. (5) Mortality only occurred in the one-, seven- and eight-month age groups at the rate of 5.7%, 23.1% and 14.3%, respectively.     

Microhabitat selection in the sand recluse spider (Sicarius thomisoides): the effect of rock size and temperature

In spiders, temperature is considered an important environmental variable for microhabitat selection. In this study, we evaluated the effect of temperature and rock size on the presence of the sand recluse spider Sicarius thomisoides and the degree of selectivity in different locations. This species is a large spider that lives under rocks in desert and semi-desert climates and is particularly active during the summer. In Chile, these spiders can be found at both coastal and inland locations under different thermal conditions, where usually the temperatures are lower near the coast. If large-scale climatic conditions are important for this species, they may be expected to select lower rock temperatures on the coast than at inland locations. In addition, we would expect that the spiders would choose larger rocks in inland compared to coast locations, which reduce the effect of high temperatures. We found that the probability of finding individuals of this species increased according to rock temperature and rock size in the field. Our results suggest that S. thomisoides prefers larger and warmer rocks to shelter under during the day, this selectivity being similar at both coastal and inland locations. Thus, this species tends to select rocks with the same thermal and structural conditions, independent of the climatic conditions.     

North Pacific species of the amphipod (Crustacea) family Stegocephalidae,with description of one new species and redescription of another

The genera and species of the family Stegocephalidae Dana, 1852 (Crustacea: Amphipoda) of the North Pacific, including the Bering Sea, are surveyed, and a key to the species is presented. One new species, Stegocephalus beringi n. sp., is described, and Stegocephalopsis ampulla (Phipps, 1774) is redescribed; S. vegae Oldevig, 1959 is synonymized with S. ampulla. Comments are given on the morphology of three additional species.     

Apodidymochelia,a new genus of gammaridean amphipod from the tropical Atlantic Ocean (Crustacea: Amphipoda: Didymochellidae)

Apodidymochelia castellata, new genus, new species is the second genus and fourth species in the rare and poorly known family Didymocheliidae. Apodidymochelia is separated from Didymochelia primarily on mandible structure. This record extends the known range of the family into the Atlantic Ocean.     

Developmental stages and growth of Pseudocaligus fugu Yamaguti, 1936 (Copepoda: Siphonostomatoida: Caligidae) host-specific to Puffer

The post-embryonic development of the copepod Pseudocaligus fugu is described. This sea louse only parasitizes toxic pufferfish, and causes commercial loss of cultured Takifugu rubripes in Japan. Two naupliar, one copepodid and four chalimus stages preceding the adult are recognized in the species. The development pattern is similar to that of Caligus except for the suppression of leg 4 in the early chalimus phase. Pseudocaligus fugu lacks any preadult stage, as in Caligus, but contrasts with Lepeophtheirus species in which two preadult stages are reported. The nature of the metamorphic changes in size and even in degree of expression of articulations can occur without moulting. The validity of some chalimus stages recognized in Lepeophtheirus species is questioned. Growth and egg production in P. fugu were obtained in the laboratory. Pseudocaligus fugu attained adulthood 9 days after the infective copepodid attached to the host.     

Age,body size and growth pattern of Argenteohyla siemersi pederseni (Anura: Hylidae) in northeastern Argentina

In this study we analysed the body size, age structure, age at maturity, longevity and growth pattern of Argenteohyla siemersi pederseni in north-eastern Argentina using skeletochronological methods. Body size was sexually dimorphic; females were significantly larger and heavier than males, regardless of age. As A. s. pederseni is an explosive breeder with only one reproductive episode per year, we assumed that each Line of Arrested Growth (LAG) observed was equivalent to one period of decreasing growth, LAGs reflecting a direct estimation of individual age. The minimum number of LAGs counted was two for males and three for females, but there was no sexual difference in longevity. The von Bertalanffy's growth coefficients (K) were higher in males than in females for both size and body mass. Females had a lower growth rate than males, took longer to reach the minimum maturation size, and were older and larger at reproduction.