The Mediterranean Copepod <Emphasis Type="Italic">Calanipeda aquaedulcis</Emphasis> Kritschagin, 1873 (Crustacea,Calanoida) in the Volga River Reservoirs

The Mediterranean copepod Calanipeda aquaedulcis Kritschagin, 1873 was first recorded in the Kuibyshev Reservoir in August 2015. It has been detected at all surveyed stations from the Volga-Kama reach to the dam of the Zhiguli hydroelectric power plant; the most northern finding of the copepod has been recorded in the mouth of the Kama River (55°24′ N). C. aquaedulcis (0.3–7.3 thous. ind./m³) is in the group of dominant species and forms, on average, 13% of the total abundance and biomass of zooplankton. Comparatively large (1.0–1.4 mm) copepods reproduce intensively; females carry up to 18 eggs (on average 10 ± 0.6). The main part of the population (>90%) are represented by nauplii. The species has been found in smaller quantities (0.04–1.1 thous. ind./m³) throughout the Saratov Reservoir, which is located downstream the cascade. The ecology of the species and its potential importance in the zooplankton of the Volga reservoirs is discussed.     

The growth of four species of Azolla as affected by temperature

The growth of 22 strains of Azolla pinnata R. Br., 3 strains of A. filiculoides Lam. and one strain each of A. mexicana Presl and A. caroliniana Willd. was tested separately in liquid culture media kept in controlled, artificial light (30 klux) growth cabinets. Three temperature levels were used: 33°C (37/29°C day/night), 29°C (33/25°C) and 22°C (26/18°C)/ Photoperiod was 12 h a day.For most A. pinnata strains (except three) and an A. mexicana strain the maximum weekly relative growth rate was higher at 33°C than at 22°C, but not for A. filiculoides and A. caroliniana. The highest value of maximum relative growth rate corresponded to 1.9 doubling days and in most strains this occurred in the first week. As the plants grew, the growth rate slowed down more severely at higher temperatures. The maximum biomass was higher at 22°C than at 33°C in all strains. At 22°C, it took 30–50 days to attain maximum biomass and the highest value was 14 g N m^?2 or 320 g dry m^?2 by A. caroliniana, followed by 12 g N m^?2 or 290 g dry wt. m^?2 by one strain of A. filiculoides. At 29°C, the maximum biomass was attained in 20–35 days. The highest value was 6.3 g N m^?2 or 154 g dry wt. m^?2 by A. caroliniana. At 33°C, most A. pinnata strains gave a maximum biomass of less than 4 g N m^?2 after 13–23 days, while some strains grew up to 30 days, resulting in a higher maximum biomass. The highest maximum biomass at 33°C was 5.5 g N m^?2 or 140 g m^?2 dry wt. by A. pinnata from Cheng Mai while the maximum biomass of A. filiculoides and A. caroliniana was much less. Azolla filiculoides requires lower temperature than other species for its growth. Azolla pinnata has the best tolerance to high temperatures among the four species. Azolla mexicana could not be discriminated from A. pinnata in its response to temperature. Azolla caroliniana may keep an intermediate position between A. filiculoides and A. pinnata in temperature response.The formation of ammonia in the medium was examined and it occurred mostly under stationary growth conditions, but, at 33°C, some strains of A. pinnata and A. mexicana released or formed ammonia at 0.3–0.8 μg N ml^?1 per week during their initial exponential growth stage.     

Leptodora kindti and Flexible Foraging Behaviour of Fish – Factors behind the Delayed Biomass Peak of Cladocerans in Lake Hiidenvesi

In the eutrophic L. Hiidenvesi, the spring biomass maximum of cladoceran zooplankton is missing and the highest biomass takes place in July–August. The factors behind the delayed biomass peak were studied in four different basins of the lake with concomitant data on cladocerans assemblages, density of the predatory cladoceran Leptodora kindti and food composition of fish. In all the basins, the abundance of Leptodora peaked in June, being highest (up to 800 ind. m^–3) in the two most shallow basins (max depth < 4 m). The duration of the high population density was short and in July‐August Leptodora density stayed below 200 ind. m^–3, although the water temperature was still favourable. The collapse of the Leptodora population coincided with the change in the feeding habits of fish. In early summer, fish predation was targeted mainly on copepods and zoobenthos, while in high summer Leptodora was one of the main preys of perch, white bream and bleak. The biomass of herbivorous cladocerans was below 10 μg C l^–1 in June, and climbed to a maximum in August in the two most shallow basins (34 and 76 μg C l^–1), in July in the deepest basin (27 μg C l^–1), and in September in the intermediate basin (55 μg C l^–1). In the two most shallow basins, the death rate of the dominating cladoceran, Daphnia cristata, closely followed the food consumption rate by the Leptodora population. In the deeper basins, the agreement was not so close, smelts (Osmerus eperlanus) and chaoborids being important predators of herbivores. The duration of the period of high Leptodora density thus depended on the predation pressure by fish, while the increased fish predation on Leptodora in July–August allowed the elevation of the biomass of herbivorous cladocerans.     

Composition and abundance of phytoplankton in the Baidarata Inlet of the Kara Sea in summer and autumn

The species composition and abundance of phytoplankton were determined in the Baidarata Inlet (Kara Sea) in August 2005 and July and September–October 2007. A total number of 220 species were found. In the surface layer, phytoplankton biomass ranged from 1.5 to 15.4 mg C/m³ (mean 5.7 ± 3.0 mg C/m³) in July, from 1.2 to 11.8 mg C/m3 (mean 5.2 ± 2.8 mg C/m³) in August, and from 4.4 to 22.6 mg C/m³ (mean 12.8 ± 5.6 mg C/m³) in September-October. In July at different sampling sites, the biomass was dominated by dinoflagellates, diatoms, and chrysophycean. Dinoflagellates dominated at almost all stations in August. Diatoms dominated in autumn with the most abundant species Paralia sulcata.     

Seasonal variations in abundance, development and vertical distribution of Calanus finmarchicus, C. hyperboreus and C. glacialis in the East Icelandic Current

The seasonal variation in abundance and development of Calanusfinmarchicus, Calanus hyperboreus and Calanus glacialis in relationto hydrography and chlorophyll (Chl) a was studied in the Arcticwaters of the East Icelandic Current to the north-east of Icelandfrom March 1995 to February 1996. The sampling was carried outat approximately monthly intervals on a transect of five stationsextending from 67°00'N, 13°55'W to 68°00'N, 12°40'W.In April, May and June, vertical distribution was also investigated.Spring warming of the surface waters began in May, with maximumtemperatures recorded in August (~5°C, mean for uppermost50 m). Below 75 m, temperature remained at <0°C throughoutthe year. The spring bloom of phytoplankton started in earlyMay and the highest Chl a concentrations were measured duringlate May to early June (~1 mg Chl a m^-3). Calanus finmarchicusdominated in terms of numbers (~75%), while C. hyperboreus dominatedbiomass (~76%). Calanus glacialis occurred only in low numbers(~1%) and was only a small portion of biomass (~0.7%). The abundanceof all species was low during the winter and peaked once duringsummer: C. finmarchicus in July (~16 000 ind. m^-2) and C. glacialisand C. hyperboreus in June (~370 and ~7700 ind. m^-2, respectively).The biomass of C. finmarchicus had two maxima, in April (~1.9g m^-2) and July (~1.5 g m^-2), while C. hyperboreus peaked inJune (~12.3 g m^-2). Calanus finmarchicus was estimated to spawnin early May at about the start of the spring bloom, while C.hyperboreus spawned prior to the spring bloom, in late Februaryto early March. On the basis of copepod stage distribution,C. finmarchicus was considered to have a 1-year life cycle andC. hyperboreus at least a 2-year life cycle.     

Interannual fluctuations in copepod abundance and contribution of small forms in the Drake Passage during austral summer

The relative importance of small forms of copepods has been historically underestimated by the traditional use of 200?C300-??m mesh nets. This work quantified the distribution and abundance of copepods, considering two size fractions (<300???m and >300???m), in superficial waters (9?m deep) of the Drake Passage and contributed to the knowledge of their interannual fluctuations among three summers. Four types of nauplii and eleven species of copepods at copepodite and adult stages were identified, with abundance values of up to 13 ind L^?1 and 28,300???g C m^?3. The <300-??m fraction, composed of Oithona similis, small cyclopoids and nauplii, dominated the copepod communities in the 3?years; it accounted for more than 77% of the total number and for between 40 and 63% of the total biomass. Changes in density and biomass values among the three cruises differed according to copepod size fraction and water mass; the >300-??m fraction showed no changes among the 3?years, both in Antarctic (density and biomass) and in Subantarctic waters (density), whereas the <300-??m fraction showed higher (density and biomass) values in 2001 both in Subantarctic and in Antarctic waters. Sea surface temperature and its anomaly accounted for the largest proportion of variability in copepod density and biomass, particularly for the <300-??m fraction.     

Seasonal Dynamics of Mesozooplankton in Brazilian Coastal Waters

The composition, numerical abundance and seasonal distribution of mesozooplankton, in addition to copepod biomass, were studied in the São Sebastião Channel (SSC) during different seasonal periods and hydrographic regimes. Two stations were sampled every 3 months from January 1996 to July 1997 and also in July 1998 and January 1999. Temporal differences in oceanographic conditions in the SSC were observed; there was clear seasonal variation in the thermohaline structure. Phytoplankton composition, standing-stock and biomass also showed consistent seasonal variation, peaking during summer due to advection of cold and nutrient-rich South Atlantic Central Water (SACW). Sixty-nine mesozooplankton taxa were identified and counted. Mesozooplankton density also increased during summer, ranging from 93 to 12,774 ind  m^?3. In contrast, a unimodal peak of copepod biomass was recorded during winter and under the influence of the oligotrophic Coastal Water (CW), suggesting that copepod biomass at SSC is driven by resource control. There was no significant evidence of seasonal pattern in overall community composition or evidence of changes due to water mass advection. The mesozooplankton community was continuously dominated by coastal and warm-water species, particularly the copepods Acartia lilljeborgi, Paracalanus aculeatus, P. quasimodo, Parvocalanus crassirostris, Corycaeus giesbrechti and Oithona oswaldocruzi, the cladocerans Penilia avirostris and Evadne tergestina, in addition to the appendicularians Oikopleura longicauda and O. dioica, all of which are perennial species in the SSC. This taxonomic composition may represent an efficient biotic structure for rapid recycling of primary production during periods of SACW influence.     

Reproduction,population dynamics and production of <Emphasis Type="Italic">Nereis falsa</Emphasis> (Nereididae: Polychaeta) on the rocky coast of El Kala National Park,Algeria

The polychaete Nereis falsa Quatrefages, 1866 is present in the area of El Kala National Park on the East coast of Algeria. Field investigations were carried out from January to December 2007 to characterize the populations’ reproductive cycle, secondary production and dynamics. Reproduction followed the atokous type, and spawning occured from mid-June to the end of August/early September when sea temperature was highest (20–23°C). The diameter of mature oocytes was approximately 180 μm. Mean lifespan was estimated to about one year. In 2007, the mean density was 11.27 ind. m⁻² with a minimum of 7.83 ind. m⁻² in April and a maximum of 14.5 ind. m⁻² in February. The mean annual biomass was 1.36 g m⁻² (fresh weight) with a minimum of 0.86 g m⁻² in December and a maximum of 2.00 g m⁻² in June. The population consisted of two cohorts distinguishable from size frequency distributions. One cohort corresponded to the recruitment of 2006 and the other appeared during the study period in September 2007. The annual production of N. falsa was 1.45 g m⁻² year⁻¹, and the production/biomass ratio was 1.07 year⁻¹.     

Population dynamics and production of the small copepod Oithona spp. in a subarctic fjord of West Greenland

The small cyclopoid copepod Oithona is widely occurring in polar areas; however, knowledge of its biology and ecology is very limited. Here, we investigate the population dynamics, vertical distribution, and reproductive characteristics of Oithona spp. from late winter to summer, in a subarctic fjord of West Greenland. During winter–early spring, the abundance of Oithona spp. was low (1.8 × 10³ ind. m^?2) and the population was mainly composed of late copepodites and adults, whereas in summer, abundance peaked and younger stages dominated (1.1 × 10⁶ ind. m^?2). In general, all stages of Oithona spp. remained in the upper 100 m, with nauplii exhibiting a shallower distribution. Although no general seasonal migration was found, a deeper distribution of the adult females in winter was observed. The mean clutch size of Oithona spp. varied from 16 to 30 eggs per female, peaking in summer. Egg production rates (EPR) were low in winter–early spring (0.13 ± 0.03 eggs female^?1 day^?1) and reached maximum values in summer (1.6 ± 0.45 eggs female^?1 day^?1). EPR of Oithona spp. showed a significantly positive relationship with both temperature and protozooplankton biomass, and the development of the population seemed to be appreciably affected by temperature. Oithona spp. remained active throughout the study, stressing the key importance of these small copepods in high-latitude ecosystems, especially in periods when larger copepods are not present in the surface layer.     

Soil microarthropods and macrofauna in monsoon tropical forests of Cat Tien and Bi Dup-Nui Ba National Parks,southern Vietnam

The abundance, biomass, vertical distribution, and taxonomic composition of soil invertebrates (springtails, macrofauna, and termites) were studied in forest formations differing in edaphic and climatic conditions: lowland forests dominated by Lagerstroemia spp. or Dipterocarpus spp. in the Cat Tien National Park and in a mountain pine (Pinus kesiya) forest on the Da Lat Plateau, southern Vietnam. In the lowland forests, springtails had a relatively low density (10000–12000 ind./m²), but their diversity was high (41–43 species in each forest). The density of large soil invertebrates (without ants and termites) reached 500–700 ind./m² at a biomass of approximately 30 g/m² (with earthworms accounting for up to 230 ind./m² and 19–28 g/m²). Among termites, species of the genera Macrotermes and Odontotermes were dominant. Their total biomass in some areas exceeded 15–20 g/m². In the mountain pine forest, the total biomass of soil macrofauna was approximately 11 g/m², the abundance and diversity of springtails were low (7500 ind./m², 28 species), and wood-destroying species of the genera Schedorhinotermes sp. and Coptotermes sp. dominated among termites.     

Earthworm Communities in the Pineapple (Ananus comosus) and Mixed Fruit Plantations of West Tripura, India

Present studies on the community characteristics of earthworms revealed the occurrence of 11 species of earthworms in the pineapple (Ananus comosus) and 14 species in the mixed fruit plantations of west Tripura (India). While 9 species of earthworms namely Drawida assamensis, Drawida papillifer papillifer, Drawida nepalensis, Kanchuria sp., Metaphire houlleti, Eutyphoeus gigas, Eutyphoeus scutarius, Eutyphoeus comillahnus and Pontoscolex corethrurus are of common occurrence to both the pineapple and the mixed fruit plantations, two and five earthworm species namely Kanchuria sumerianus, Eutyphoeus sp. and Metaphire posthuma, Perionyx excavatus, Lampito mauritii, Amynthus alexandri, Eutyphoeus gammiei are restricted to the pineapple and the mixed fruit plantations respectively. Earthworms were found mostly within 15 cm depth of soils having temperature 25–25.8 °C, moisture 18.8–22.4 %, water holding capacity 26–31.7 % and organic matter content 2.4–4.0 %. Mean earthworm densities (158 ind. m^?2) was significantly higher (p < 0.01, t = 9.67) and biomass (36.67 g m^?2) significantly lower (p < 0.01, t = ?5.98) in the pineapple plantation than the mixed fruit plantation (density 93 ind. m^?2, biomass 56 g m^?2). High density value of earthworms in pineapple plantation is linked with dominance of D. assamensis and high biomass value in mixed fruit plantation was due to the higher relative abundance of larger species like E. gigas, E. scutarius, E. comillahnus and E. gammiei. Compared to the mixed fruit plantation, significantly (p < 0.05) higher index of dominance, lower index of diversity, species richness index and species evenness were recorded in the pineapple plantation.     

Biogeochemical processes in the algal-bacterial mats of the Urinskii alkaline hot spring

The structure and production characteristics of microbial communities from the Urinskii alkaline hot spring (Buryat Republic, Russia) have been investigated. A distinctive characteristic of this hot spring is the lack of sulfide in the issuing water. The water temperature near the spring vents ranged from 69 to 38.5°C and pH values ranged from 8.8 to 9.2. The total mineralization of water was less than 0.1 g/liter. Temperature has a profound effect on the species composition and biogeochemical processes occurring in the algal-bacterial mats of the Urinskii hot spring. The maximum diversity of the phototrophic community was observed at the temperatures 40 and 46°C. A total of 12 species of cyanobacteria, 4 species of diatoms, and one species of thermophilic anoxygenic phototrophic bacteria, Chloroflexus aurantiacus, have been isolated from mat samples. At temperatures above 40°C, the filamentous cyanobacterium Phormidium laminosum was predominant; its cell number and biomass concentration comprised 95.1 and 63.9%, respectively. At lower temperatures, the biomass concentrations of the cyanobacterium Oscillatoria limosa and diatoms increased (50.2 and 36.4%, respectively). The cyanobacterium Mastigocladus laminosus, which is normally found in neutral or slightly acidic hydrothermal systems, was detected in microbial communities. As the diatom concentration increases, so does the dry matter concentration in mats, while the content of organic matter decreases. The concentrations of proteins and carbohydrates reached their maximum levels at 45–50°C. The maximum average rate of oxygenic photosynthesis [2.1 g C/(m² day)], chlorophyll a content (343.4 mg/m²), and cell number of phototrophic microorganisms were observed at temperatures from 45 to 50°C. The peak mass of bacterial mats (56.75 g/m²) occurred at a temperature of 65–60°C. The maximum biomass concentration of phototrophs (414.63 × 10^?6 g/ml) and the peak rate of anoxygenic photosynthesis [0.42 g C/(m² day)] were observed at a temperature of 35–40°C.     

Growth performance of juvenile Russian sturgeon (Acipenser gueldenstaedtii Brandt & Ratzenburg, 1833) at two stocking densities in net cages

The growth performance of juvenile sturgeon (Acipenser gueldenstaedtii Brandt & Ratzenburg, 1833) was studied in experimental net cages (2 m × 2 m × 2 m) in freshwater Sapanca Lake. Fertilized eggs were imported from Krasnodar, Russia in January 2001. Two experimental stocking densities were employed (12 and 8 ind. m⁻³). Sturgeon were hand‐fed a pelleted commercial trout feed twice daily throughout the 203‐day experiment period. Fish were grown at ambient temperature (12.7–28.5°C) and natural photoperiod. Initial and final mean body weights were 279.5 g (±31.27) and 1112.8 g (±234.77) in the first group, and 271.1 g (±28.21) and 1140.5 g (±213.31) in the second group, respectively. Results were a fourfold biomass density increase in both trials from an initial 3.48 to 12.4 kg m⁻³ (high density) and 2.2 to 8.8 kg m⁻³ (low density). Mean specific growth rate (SGR) was determined as 2.69% day⁻¹ in both groups. Mean condition factor (CF) at the end of the experiment was 0.36 ± 0.05 in the high‐density group and 0.41 ± 0.05 in the low‐density group. Mean feed conversion ratio (FCR) was calculated to be 5.7 and 5.8, respectively. Survival was 92.7% in the first group (high density) and 96.1% in the second group (low density). The results demonstrated that sturgeon juveniles can be raised in cages and that growth performance (CF, SGR and FCR) and mortality of sturgeon were not significantly different at the two stocking densities (P > 0.05) tested.     

Zooplankton of Lake Kandrykul (Republic of Bashkortostan,Russia) under Conditions of Anthropogenic Eutrophication

The species diversity, abundance, and biomass of zooplankton in the pelagic and coastal zones of Lake Kandrykul were studied in 2007–2012. The community was dominated by large Cladocera. The maximum abundance of zooplankton was observed in the anomalously warm 2010. In July, the highest abundance of zooplankton (1300 thousand ind./m³) was recorded near the southern coast in stands of mare′s-tail Hippurus vulgaris; that of biomass (9 g/m³) was found near the northern shore in stands of narrow-leaved cattail Typha angustifolia. The lowest values of the number and biomass of aquatic invertebrates were observed in the pelagial (32 thousand ind./m³ and 0.1 g/m³) and along the M5 motorway stretching aside the northeastern coast (188 thousand ind./m³ and 0.5 g/m³). The Shannon index value (1.3–2.1) corresponded to the meso-eutrophic type of water bodies. In 2007, according to the Mjaemets trophicity index (E), the lake ecosystem was oligotrophic (E 0.11); in 2010–2012 it was mesotrophic (in the pelagial, E value was 0.54; in the open littoral it was 0.76) or weakly eutrophic (E values of protected littoral were 1.52). The estimates of water trophy as assessed by zooplankton are close to those assessed by the number and biomass of phytoplankton (meso-eutrophic type). The rapid eutrophication of the lake ecosystem was revealed. In 6 years the trophic status of the lake changed from oligo-mesotrophic to meso-eutrophic.     

Present population and habitat status of potentially threatened Asian horseshoe crabs <Emphasis Type="Italic">Tachypleus tridentatus</Emphasis> and <Emphasis Type="Italic">Carcinoscorpius rotundicauda</Emphasis> in Hong Kong: a proposal for marine protected areas

While there are persistent calls for developing more marine protected areas (MPAs) for Asian horseshoe crab conservation in response to population declines in Asia–Pacific region, most existing horseshoe crab MPAs were designated without prior comprehensive population assessment and habitat characterization. This study collected biological and habitat information in Hong Kong, in order to identify priority sites for conservation and management of Asian horseshoe crab populations. The territory-wide surveys at 18 spawning/nursery beaches displayed a persistently low mean juvenile density from 0.16 to 2.19 ind/100 m² in 2012 and 0.08 to 1.41 ind/100 m² in 2014. These density data were within the same range of that in 2002 and 2007 (0.10–1.97 ind/100 m²), apart from a low survey return of 0.08–0.31 ind/100 m² in 2004. The current population of juvenile T. tridentatus and C. rotundicauda in Hong Kong is estimated about 2100–4300 and 2400–3000 individuals, respectively. From the 2012–2014 data, no new recruitments of 1st–3rd instar juveniles were found, as the shores were occupied mostly by 6th–9th instar juveniles of prosomal width between 23 and 45 mm, in which considerably high mortality rates were noted. The present findings of existing small and discrete juvenile populations, coupled with relatively few recruits, suggest that the status of juvenile horseshoe crabs in Hong Kong is fragile and vulnerable to local extirpation, especially if no urgent protection measures are implemented. Based on available population data and habitat characteristics, three MPAs, ranging from 5 to 7 km², are proposed, so as to conserve over 60 and 70 % of the existing juvenile populations of T. tridentatus and C. rotundicauda, respectively. The approach adopted in this study may serve as a case study for proposing other horseshoe crab MPAs in Asia, where increasing human disturbances and over-harvest are imminent.     

Some features of the biology of the mud shrimp Upogebia issaeffi (Balls, 1913) (Decapoda: Upogebiidae) from the subtidal zone of Vostok Bay,Sea of Japan

The study of the biology of the mud shrimp Upogebia issaeffi (Balss, 1913) from the subtidal zone of the Vostok Bay (Peter the Great Bay, Sea of Japan) revealed that this species occurs at depth of 1–6 m on mixed grounds of boulders, gravel, pebbles, shells of dead clams, and silty sand. The average population density of U. issaeffi in the local aggregation on a bottom transect of 300 m length ranged from 0.2 ± 0.4 to 8.0 ± 3.0 ind./m², the biomass varied from 0.5 ± 1.1 to 78.7 ± 28.3 g/m², or about 2.7% of the total biomass of macrozoobenthos and 51.2% of the biomass of decapod crustaceans, which is characteristic of the habitats of the mud shrimp. The maximum depth of burrowing of U. issaeffi was 65 cm. The aggregation consisted of animals with body lengths of 44–88 mm. The lifespan of U. issaeffi was 2–3 years. An equilibrium ratio of males and females (1: 1.06) was observed in the population. There were egg clutches on pleopods of 81.7% of the females. The body size of the smallest females with eggs was 67 mm. The larger the females were, the more of them were ovigerous individuals. About 4% of individuals of U. issaeffi were infected with the parasitic isopod Orthione griffenis.     

Population dynamics, growth and reproduction of Corophium insidiosum (Crustacea: Amphipoda) at low salinities in Monolimni lagoon (Evros Delta, North Aegean Sea)

Distribution, population dynamics, growth and aspects of reproductive biology of Corophium insidiosum were investigated in Monolimni lagoon. Samples were collected in July 1997 (at 30 psu S) and during February 1998–May 1999 (at 0.1–5.7 psu S). Corophium insidiosumwas almost exclusively found in the outer part of the lagoon, which showed a higher water renewal rate. Population density gradually decreased during winter and spring, when salinity was lower than 1 psu and the amphipod finally vanished from the lagoon. Salinity increase during summer (1.2–5.7 psu) was followed by the re-occurrence of C. insidiosum with a time lag of 2–3 months. Population density increased in autumn and peaked in early winter at salinities 1.6–4.2 psu. Three cohorts appeared in the population during September 1998–March 1999. Breeding activity peaked in early autumn (14–21?°C, 4 psu S) and ceased after December (2–6.5?°C, ¡1.5 psu S). The preponderance of females in the large size classes resulted in a female- biased sex ratio in the whole population. The population showed a growth rate of 7.5–11.2 μm d^?1 being faster in autumn (9–21?°C, 3–4 psu S) than in winter (2–12?°C, 0.2–3 psu). An exponential relation existed between body length and cephalic length or dry body weight, while brood size was directly related to body length. Mean brood size was small (4.96 early embryos) and egg loss during development high (53%), possibly as a consequence of low salinities.     

The distribution,growth, and reproduction of the Antarctic limpet Nacella (Patinigera) concinna (Strebel, 1908)

Twenty-one monthly collections of the Antarctic limpet Nacella (Patinigera) concinna (Strebel, 1908) were obtained by divers at Signy Island, South Orkney Islands. A mean monthly population density of 123.7 ± 21.2 · m^?2, mean biomass of 13.7 ± 2.7 g dry tissue wt · m^?2, and annual production of 2.9 g · m^?2 were recorded in the depth range 2–12 m below mean low water.Shell growth was slow with a maximum growth rate, in the first 3–5 yr of life, of 3 4 mm per year. Maturity was attained at 7–8 yr (21 mm length), and maximum size (41 mm length) at about 21 yr. Unique spawning behaviour was observed in two Austral springs, and data relating spawning to the spring increase in sea temperature were obtained.     

The effect of irradiance and temperature responses and the phenology of a native alga,Undaria pinnatifida (Laminariales), at the southern limit of its natural distribution in Japan

Phenology, irradiance, and temperature characteristics of an edible brown alga, Undaria pinnatifida (Laminariales), were examined from the southernmost natural population in Japan, both by culturing gametophytes and examining the photosynthetic activity of sporophytes using dissolved oxygen sensors and pulse amplitude-modulated chlorophyll fluorometer (IMAGING-PAM). Our surveys confirmed that sporophytes were present between winter and early summer, but absent by July. IMAGING-PAM experiments were used to measure maximum effective quantum yield (ΦII at 0 μmol photons m^?2 s^?1) for each of 14 temperatures (8–36 °C). Oxygen production was also determined over a coarser temperature gradient. Net photosynthesis and ΦII (at 0 μmol photons m^?2 s^?1) were observed to be temperature-dependent; the maximum ΦII was estimated to be 0.67, occurred at 21.2 °C, and was nearly identical to the optimal temperature of the net photosynthetic rate (21.7 °C). A net photosynthesis–irradiance (P–E) model revealed that saturation irradiance (E _k) was 119.5 μmol photons m^?1 s^?1, and the compensation irradiance (E _c) was 17.4 μmol photons m^?1 s^?1. Culture experiments on the gametophytes revealed that most individuals could not survive temperatures over 28 °C and that growth rates were severely inhibited. Based on our observations, temperatures greater than 20 °C are likely to influence photosynthetic activity and gametophyte survival, and therefore, it is possible that this species might become locally extinct if seawater temperatures in this region continue to rise.     

Purification of endo- and exolaminarinase and partial characterization of the exoacting form from the copepod acartia clausi (Giesbrecht, 1889)

• 1.1. The copepod Acartia clausi exhibited two laminarinases (exo- and endo-acting forms) purified by gel chromatography followed by affinity chromatography. Specific antibodies have been raised against the purified exolaminarinase antigen.
• 2.2. A single band of protein appeared on a polyacrylamide disc gel electrophoresis; its mol. wt is 21,000.
• 3.3. Biochemical properties of the purified enzyme showed a maximum activity at pH 5.2 and a temperature of 40°C with laminarin as substrate. The thermal stability of the enzyme and the effect of various cations on its activity were examined. The enzyme hydrolyses specifically the β(1–3) linked polysaccharides and had no activity against the α(1–4) or β(1–4) disaccharides or polysaccharides.
• 4.4. The kinetic parameters V_m and K_m vary with the temperature; the affinity constant (K_a) was maximum between 25–30°C. The Arrhenius plot defined two values of energy of activation: 7980 cal/mole and 17,506 cal/mole.
• 5.5. From the purification scheme the exoacting form appears to be largely dominant over the endoacting form.