Age and growth of the nototheniid fishTrematomus bernacchii Boulenger from Terra Nova Bay,Antarctica

Age and growth of the nototheniid fishTrematomus bernacchii Boulenger 1902 were estimated by reading the sagittal otoliths of 457 adult specimens caught off Terra Nova Bay (Ross Sea) in the austral summer 1990–1991. Annuli in ground and polished otoliths were examined using a dissecting microscope under reflected light. The Von Bertalanffy growth equation was L_t=273.5 [1 − e^{−0.109(t+2.10)}] for males (n=122) and L_t=422.2 [1 − e^{−0.055(t+1.92)}] for females (n=211) where L is total length in millimetres. Maximum estimated age was 21 years for females and 16 years for males. This is in agreement with the hypothesis that considers slow growth and old age as a typical feature of Antarctic fishes.     

Early life history of mebaru,sebastes inermis (scorpaenidae), in sendai bay, japan

The early life history of the viviparous scorpaenid,Sebastes inermis, in Sendai Bay, Japan, was studied and early development described. Newborn preflexion larvae ofS. inermis were about 5.2 mm BL. Notochord flexion occurred at 5.4–8.0 mm BL and transformation at 14–20 mm BL. Preflexion and flexion larvae ofS. inermis were distinguished from similar larvae by the pigmentation pattern along the dorsal and ventral midlines of the tail. Pigmentation inS. inermis was light throughout the larval and early juvenile periods. Planktonic larvae were particularly abundant in coastal waters of Sendai Bay but not offshore. Vertical and horizontal larval sampling indicated that early larvae occupied near surface waters and horizontal larval sampling indicated that early larvae shift to a benthic habitat occurred at about 12 mm BL, at the end of the postflexion larval period.Sebastes inermis do not have a distinct pelagic juvenile stage, unlike many North Pacific species ofSebastes.     

Evidence for high iron requirements of colonial Phaeocystis antarctica at low irradiance

We have carried out field and laboratory experiments to examine the iron requirements of colonial Phaeocystis antarctica in the Ross Sea. In December 2003, we performed an iron/light-manipulation bioassay experiment in the Ross Sea polynya, using an algal assemblage dominated by colonial Phaeocystis antarctica, collected from surface waters with an ambient dissolved Fe concentration of ∼0.4 nM. Results from this experiment suggest that P. antarctica growth rates were enhanced at high irradiance (∼50% of incident surface irradiance) but were unaffected by iron addition, and that elevated irradiance mediated a significant decrease in cellular chlorophyll a content. We also conducted a laboratory iron dose–response bioassay experiment using a unialgal, non-axenic strain of colonial P. antarctica and low-iron (<0.2 nM) filtered seawater, both collected from the Ross Sea polynya in December 2003. By using rigorous trace-metal clean techniques, we performed this dose–response iron-addition experiment at ∼0°C without using organic chelating reagents to control dissolved iron levels. At the relatively low irradiance of this experiment (∼20 μE m⁻² s⁻¹), estimated nitrate-specific growth rate as a function of dissolved iron concentration can be described by a Monod relationship, yielding a half-saturation constant with respect to growth of 0.45 nM dissolved iron. This value is relatively high compared to reported estimates for other Antarctic phytoplankton. Our results suggest that seasonal changes in the availability of both iron and light play critical roles in limiting the growth and biomass of colonial Phaeocystis antarctica in the Ross Sea polynya.     

Seasonality in fish larval assemblage structure within marine reef National Parks in coastal Kenya

Variability of larval assemblages within marine habitats has an effect on population structure of adults, and on patchiness of populations in space and time. However, despite this effect, few studies have examined this variability in the Western Indian Ocean (WIO) especially in relation to marine park boundaries. In this study, we tested the hypothesis that seasonality and biophysical variables influence fish larval assemblage structure within two of the oldest marine parks in Kenya of differing reef structure. Monthly samples were obtained from the parks using oblique plankton tows for 14–24 months. A total of 38 families and 52 genera of fish larvae were obtained from Malindi Marine Park, while 20 genera in 20 families were sampled from the more enclosed Watamu Marine Park but with a connection to an estuarine system. The preflexion larvae comprised over 80% of the total larvae in the parks with the dominant groups being; Gobiidae, Blenniidae, Engraulidae and Apogonidae. The availability of a wide size range of larvae for some groups like Blenniidae, Gobiidae, Engraulidae, Labridae and Scaridae indicated the possibility of some larvae completing their pelagic phase within the parks. Larval densities differed significantly between seasons and stations in both parks, with higher densities ranging between 95–311 larvae/100 m³ during the calm northeast monsoon (NEM) season, compared to 5–58 larvae/100 m³ during the stormy southeast monsoon (SEM) season. Stepwise multiple regression analysis indicated a significant positive influence of zooplankton density on fish larval abundance in Malindi Park, while a positive and significant influence of temperature was found in Watamu Park. Distinct assemblages of larvae occurred within the parks indicating within park patchiness in larval distribution and, perhaps existence of retention features. These results provide useful baseline data on larval distribution in the WIO, and will be useful in understanding population dynamics of adult populations when complimented with additional oceanographic data.     

Settlement behaviour of larvae of the Stripey Snapper, <Emphasis Type="Italic">Lutjanus carponotatus</Emphasis> (Teleostei: Lutjanidae)

Larval behaviour is important to dispersal and settlement, but is seldom quantified. Behavioural capabilities of larval Lutjanus carponotatus in both offshore pelagic and reef environments at Lizard Island, Great Barrier Reef were observed in situ to determine if they were sufficient to influence dispersal. Offshore, larvae swam with higher directional precision and faster on the windward side of the island (28 cm.s⁻¹) than on the leeward side (16 cm s⁻¹). Most larvae swam directionally. Mean swimming directions were southerly in the windward area and northerly in the leeward area. Larvae avoided the surface and remained mostly between 3–15 m. Larvae released near reefs were 2–3 times faster swimming away from reefs (19 cm s⁻¹) than swimming toward or over them (6–8 cm s⁻¹). Speed swimming away was similar to that offshore. Of 41 larvae released near reefs, 73% reached the reef, 59% settled, and 13% of those reaching the reef were eaten. Larvae settled onto hard and soft coral (58%), topographic reef features (29%) and sand and rubble (13%). Settlement depth averaged 5.5 m (2–8 m). Before settling larvae spent up to 800 s over the reef (mean 231 s) and swam up to 53 m (mean 14 m). About half of the larvae interacted with reef residents including predatory attacks and aggressive approaches by residents and aggressive approaches by settling larvae. Settlement behaviour of L. carponotatus was more similar to a serranid than to pomacentrids. Settlement-stage larvae of L. carponotatus are behaviourally capable, and have a complex settlement behaviour.     

Growth of larval and juvenile Diaphus theta (Pisces: Myctophidae) in the transitional waters of the western North Pacific

Diaphus theta is one of the most common myctophid fish species in the subarctic and transitional waters of the North Pacific. The growth of larval and juvenile D. theta was investigated using sagittal otolith increment analysis of specimens caught in transitional waters of the western North Pacific. Samples taken over a 24-h period demonstrated that otoliths exhibited daily growth cycles, allowing accurate determination of age. Calcification of the incremental zone of otoliths took place only at night, suggesting that the formation cycle of the increment of juvenile D. theta was different from that of shallow-water fishes and would be related to their diel vertical migration. The relationships between standard length (SL) and daily growth increment (D) were expressed as linear equations: SL = 2.65 + 0.141D (r ² = 0.942) for larvae of 5.1–9.6 mm SL and SL = 3.54 + 0.129D (r ² = 0.933) for juveniles of 13.7–27.6 mm SL. The growth rates were 0.14 mm d⁻¹ in larvae and 0.13 mm d⁻¹ in juveniles; this is slow compared with tropical or subtropical mycto-phid species, in which growth occurs at about twice these rates. The larval period, including the metamorphic stage, was long compared with species at lower latitudes and was estimated to be 71 days. The slow growth rate and long period of larval stage of D. theta would be the life history pattern of high-latitudinal species adapted to a low-temperature habitat. Received: March 23, 2001 / Revised: July 5, 2001 / Accepted: July 19, 2001     

Larval fish distribution,growth and feeding in Patagonian fjords: potential effects of freshwater discharge

In fjord systems, freshwater inputs occur by ice melting and river discharge, affecting seawater salinity along fjord and adjacent waters, and potentially the ecology of early life stages of marine fish occurring in the area. During austral spring 2008, a bio-oceanographic cruise was carried out in southern Chile between 47°00′ and 50°09′S, an area influenced by Baker River discharge and ice melting of Northern and Southern Ice Fields, the largest glaciers from Patagonia. Surface salinity and temperature ranged from 1.22 to 32.80, and from 8.11 to 10.68°C, respectively. Larval lightfish Maurolicus parvipinnis (Sternoptychidae) and Falkland sprat Sprattus fuegensis (Clupeidae) were the dominant species, with abundances of 2.2–39.9 larvae 10 m⁻² and 3.4–77.1 larvae 10 m⁻², respectively. Postflexion stages of both species were collected mainly in surface density fronts. Otolith-based growth analyses estimated linear growth rates of 0.136 mm day⁻¹ for M. parvipinnis of 4.1–15.1 mm, and 0.448 mm day⁻¹ for S. fuegensis of 5.4–20.5 mm. Recent Otolith Growth Index (ROGI), based on the residual analysis of the relationship between increment width of outermost five microincrements and otolith radius, indicates that larval M. parvipinnis collected in low salinity waters showed a reduction of its recent growth rate compared those collected in saltier waters. Also, ROGI was positively correlated with salinity of the water column for larval M. parvipinnis. Gut content analysis showed that large larvae collected near sources of freshwater had lower number of prey in its guts and preyed on different items than fish larvae collected in saltier waters. Therefore, freshwater inputs from rivers and glaciers from Patagonia affected horizontal distribution, recent growth and feeding of larval fish in fjords and channels of southern Chile.     

Composition and distribution of pelagic ostracods (Ostracoda: Myodocopa) in the Somov and Ross seas and adjacent waters of the Southern Ocean

The study of materials collected by Russian expeditions and literature data showed that the pelagic ostracod fauna of the Somov Sea, which lies south of the Antarctic Divergence (AD), is an impoverished complex of the fauna of the Australian-New Zealand Antarctic sector. While to the north of the AD the ostracod fauna includes species introduced from waters of the subantarctic and tropical-subtropical structures, ostracods of the Somov Sea are mainly typical Antarctic species. To the north and south of the AD, ostracod abundance and species richness are highest in the depth range of 200–500 m (especially at 300–400 m). Austrinoecia isocheira is the most common species in the Somov Sea and Alacia hettacra in the adjacent northern region. The more southerly Ross Sea has harsher environmental conditions than the Somov Sea and its ostracod fauna is a more impoverished complex of mainly Antarctic species. Alacia belgicae and A. isocheira are the dominant species in the Ross Sea, with their highest abundances at 200–300 m depths. The proportion of A. hettacra in the Ross Sea taxocene decreases southwards. The taxonomical composition and biogeographical structure of ostracod faunas change in the AD region at the northern boundaries of both seas.     

Embryonic and larval development of a cold adapted Antarctic ascidian

Ova of the Antarctic ascidian Cnemidocarpa verrucosa were mature at 240–245 μm. At 0 to −1.5°C, embryos hatched as swimming tadpoles at 8 days from fertilization, which is close to the ages at which some Antarctic echinoderm and nemertean embryos hatch as blastulae. Comparisons of Antarctic and temperate ascidian larvae suggest that the ascidian’s development rate is affected by low environmental temperatures to about the same extent as embryos and larvae of an echinoid, nemertean, and calanoid copepods. The ascidian’s tadpoles were bright orange and large, >2 mm in length including tunic and >1.5 mm in length without tunic. The large and brightly colored tadpoles were conspicuous when swimming, which supports the hypothesis that larvae of C. verrucosa are chemically defended against predators. Metamorphosed juveniles were found in cultures within 16 days from fertilization, when some unsettled tadpoles still moved but were less active. The potential pelagic period may therefore be 16 or more days with 8 days as an unhatched embryo and up to 8 or more days as a tadpole. The resting metabolic rate of tadpole larvae was 15 pmol O₂ h⁻¹ individual⁻¹ which is equivalent to larval respiration rates in Antarctic echinoderms. A low resting metabolic rate suggests a potential mechanism for the extended larval lifespan in C. verrucosa.     

Early life history of kitsune-mebaru,sebastes vulpes (scorpaenidae), in the sea of japan

The larval and juvenile stages of kitsune-mebaru,Sebastes vulpes, based on 50 wild specimens collected in, the Sea of Japan, are described and illustrated, and some ecological aspects of the early life history (feeding, horizonal distribution and habitat shift) included. Preflexion larvae became extruded between 3.9–4.6 mm body length (BL) and notochord flexion occurred between 4.7–7.1 mm BL. Transformation from postflexion larvae to pelagic juventiles occurred between 13–17 mm BL. Compared with other rockfish species,S. vulpes is deep-bodied, throughout both larval and, juvenile stages. Larval and juvenileS. vulpes inhabit mainly coastal water surface layer (usually on the continental shelf), but do not occur offshore region (northwest of Oki Islands). Although someS. vulpes juveniles are associated with drifting seaweed, such clumps are not indispensable habitats for any stages. Surface-to-benthie migration of juveniles occurs at about 25 mm BL. Preflexion and flexion larvae feed mainly on copepod nauplii, and postflexion, transforming larvae and pelagic juveniles mainly on calanoid copepodites (Parracalanus parvus).     

Occurrence of Ayu (<Emphasis Type="Italic">Plecoglossus altivelis</Emphasis>) larvae in northern Vietnam

The early life history of Ayu (Plecoglossus altivelis) was investigated in the Kalong and Tien Yen River systems, northern Vietnam, which is probably the most southern distribution locality for this species, during the period of November 2010 to February 2011. A total of 248 larvae were captured in the Kalong, and none were collected in the Tien Yen. There was little difference in development between the Kalong larvae and those of P. a. altivelis and P. a. ryukyuensis. Temperatures and salinities when the larvae were collected ranged from ca. 12 to 21°C and from ca. 3.5 to 30 psu. The preflexion to flexion larvae (primarily preflexion with yolk, 5.2–12.9 mm BL) occurred in the central current from December to February, with a peak abundance in early January. The flexion to postflexion (primarily postflexion, 14.1–23.8 mm BL) larvae occurred in the bank waters from early January to late February. The larval occurrence in the Kalong was 1–2 months later than for P. a. altivelis in Japan and P. a. ryukyuensis in the Ryukyu Islands, probably because of the delay until a reasonable photoperiod for the start of spawning in the lower latitudinal region. The larvae were never collected from the sea, where the temperatures were lower than in the river and estuary in January and February, unlike in Japan.     

Energy flow and subsidies associated with the complex life cycle of ambystomatid salamanders in ponds and adjacent forest in southern Illinois

Breeding adults and metamorphosing larval amphibians transfer energy between freshwater and terrestrial ecosystems during seasonal migrations and emergences, although rarely has this been quantified. We intensively sampled ambystomatid salamander assemblages (Ambystoma opacum,A. maculatum, and A. tigrinum) in five forested ponds in southern Illinois to quantify energy flow associated with egg deposition, larval production, and emergence of metamorphosed larvae. Oviposition by female salamanders added 7.0–761.4 g ash-free dry mass (AFDM) year⁻¹ to ponds (up to 5.5 g AFDM m⁻² year⁻¹). Larval production ranged from 0.4 to 7.4 g AFDM m⁻² year⁻¹ among populations in three ponds that did not dry during larval development, with as much as 7.9 g AFDM m⁻² year⁻¹ produced by an entire assemblage. Mean larval biomass during cohort production intervals in these three ponds ranged from 0.1 to 2.3 g AFDM m⁻² and annual P/B (production/biomass) ranged from 4 to 21 for individual taxa. Emergent biomass averaged 10% (range=2–35%) of larval production; larval mortality within ponds accounted for the difference. Hydroperiod and intraguild predation limited larval production in some ponds, but emerging metamorphs exported an average of 70.0±33.9 g AFDM year⁻¹ (range=21.0–135.2 g AFDM year⁻¹) from ponds to surrounding forest. For the three ponds where larvae survived to metamorphosis, salamander assemblages provided an average net flux of 349.5±140.8 g AFDM year⁻¹ into pond habitats. Among all ponds, net flux into ponds was highest for the largest pond and decreased for smaller ponds with higher perimeter to surface area ratios (r ² =0.94, P<0.05, n=5). These results are important in understanding the multiple functional roles of salamanders and the impact of amphibian population declines on ecosystems. Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.     

Aspects of the biology of the icefish Dacodraco hunteri (Notothenioidei, Channichthyidae) in the Ross Sea, Antarctica

On the basis of five specimens, the icefish Dacodraco hunteri (Notothenioidei, Channichthyidae) is documented for the first time in the Ross Sea, Antarctica. Meristic counts and morphometric measurements are provided for this small, streamlined, laterally compressed species. D. hunteri has a weakly ossified skeleton with considerable cartilage in the skull. It has a partially persistent notochord and reduced amounts of bone in the vertebral column since the centra are incompletely constricted. Its weight in seawater averages only 1.28% of its weight in air and, as one of the lightest notothenioids, D. hunteri is probably a permanent inhabitant of the water column. The diet consists of relatively large specimens of the pelagic nototheniid fish Pleuragramma antarcticum. Accepted: 27 September 1998     

Impact of Microzooplankton and Copepods on the Growth of Phytoplankton in the Yellow Sea and East China Sea

Dilution and copepod addition incubations were conducted in the Yellow Sea (June) and the East China Sea (September) in 2003. Microzooplankton grazing rates were in the range of 0.37–0.83 d⁻¹ in most of the experiments (except at Station A3). Correspondingly, 31–50% of the chlorophyll a (Chl a) stock and 81–179% of the Chl a production was grazed by microzooplankton. At the end of 24 h copepod addition incubations, Chl a concentrations were higher in the copepod-added bottles than in the control bottles. The Chl a growth rate in the bottles showed good linear relationship with added copepod abundance. The presence of copepods could enhance the Chl a growth at a rate (Z) of 0.03–0.25 (on average 0.0691) d⁻¹ ind⁻¹ l. This study, therefore parallels many others, which show that microzooplankton are the main grazers of primary production in the sea, whereas copepods appear to have little direct role in controlling phytoplankton.     

The role of platelet ice microalgae in seeding phytoplankton blooms in Terra Nova Bay (Ross Sea,Antarctica): a mesocosm experiment

The aim of this study was to assess the role of platelet ice microalgal communities in seeding pelagic blooms. Nutrient dynamics, microalgal biomass, photosynthetic parameters, cell densities and species succession were studied in two mesocosm experiments, designed to simulate the transition of microalgal communities from platelet ice habitat to pelagic conditions. The microalgal assemblages were dominated by diatoms, 70% of which were benthic species such as Amphiprora kufferathii, Nitzschia stellata, and Berkeleya adeliensis. Photoacclimation of benthic species was inadequate also at relatively low irradiances. Exceptional growth capacity at different light levels was observed for pelagic species such as Fragilariopsis cylindrus and Chaetoceros spp. which may be important in seeding blooms at ice breakup. Fragilariopsis cylindrus showed high growth rates both at 65 and 10% of incident light and in nutrient replete as well as in nutrient depleted conditions. Five days after inoculation, phytoplankton biomass increased and nutrient concentrations decreased in both light conditions. Nutrient uptake rates were up to 9.10 μmol L⁻¹ d⁻¹ of TIN in the high light tank and 6.18 μmol L⁻¹ d⁻¹ in the low light tank and nutrient depletion in the high light tank occurred 3 days prior to depletion in the low light tank. At nutrient depletion, biomass concentrations were similar in both tanks, 30 and 34 μg Chla L⁻¹. This article belongs to a special topic: Five articles on Sea-ice communities in Terra Nova Bay (Ross Sea), coordinated by L. Guglielmo and V. Saggiomo, appear in this issue of Polar Biology. The studies were conducted in the frame of the National Program of Research in Antarctica (PNRA) of Italy.     

Can Simple Empirical Equations Describe the Seasonal Dynamics of Bacterioplankton in Lakes: An Eight-Year Study in Shallow Hypertrophic and Biologically Highly Dynamic Lake Søbygård,Denmark

Abstract Seasonal variation in bacterioplankton abundance, biomass, and bacterioplankton production was studied over eight years in hypertrophic Lake S?byg?rd. Biologically, the lake is highly variable; this is due mainly to large interannual variation in fish recruitment. Bacterioplankton production was low during winter, typically 1–3 × 10⁷ cells l⁻¹ h⁻¹, and high during summer, albeit greatly fluctuating with maximum rates typically ranging from 60 to 90 × 10⁷ cells l⁻¹ h⁻¹ (or 0.4 to 0.6 mg C l⁻¹ day⁻¹). Less pronounced variations were found in bacterioplankton abundance, which typically ranged from 3–8 × 10⁹ cells l⁻¹ in winter to 15–30 × 10⁹ cells l⁻¹ during summer. The specific growth rate of bacterioplankton varied from 0.02–0.2 d⁻¹ in winter to 0.5–2.3 day⁻¹ during summer. Interpolated mean bacterioplankton production, in terms of carbon, ranged from 0.08 to 0.16 mg C l⁻¹ day⁻¹, corresponding to 1.6–5.5% of the phytoplankton production, while biomass ranged from 0.28 to 0.36 mg C l⁻¹, corresponding to 1.9–4.6% of the phytoplankton biomass. We conducted regression analysis, relating the bacterioplankton variables to a number of environmental variables, and evaluated the interannual parameter variability. Chlorophyll a and phytoplankton production contributed less to the variation in the bacterioplankton variables than in most previous analyses using data from less eutrophic systems. We suggest that the proportion of phytoplankton production that is channelized through bacterioplankton in lakes decreases with increasing trophic state and decreasing mean depth. This probably reflects a concurrent increase in fish predation on macrozooplankton and loss by sedimentation. An important part of the residual variation in the equations hitherto proposed in the literature could be explained by variation in macrozooplankton biomass and pH > 10.2. A negative effect of high pH on bacterioplankton production was confirmed by laboratory experiments. The impact of different zooplankton varies considerably, with Daphnia seeming to have a negative impact on bacterioplankton abundance and, thereby, indirectly on bacterioplankton production, while Bosmina, rotifers, and cyclopoid copepods seem to stimulate both abundance and production. Bosmina apparently also stimulate the bacterioplankton specific growth rate. Received: 8 February 1996; Accepted: 16 July 1996     

Distribution of polar cod and age-0 fish in the U.S. Beaufort Sea

Little is known about species composition, distribution, and abundance of pelagic fish in the U.S. portion of the Beaufort Sea continental shelf and slope. To inventory the community and describe pelagic fish distributions relative to water characteristics, a systematic survey was conducted in August 2008. Acoustics (38 kHz), midwater trawling, and CTD casts were used to sample water depths from 20 to 500 m. Age-1+ polar cod (Boreogadus saida) was the dominant fish species, with peak densities of 155,000 # ha⁻¹ at bottom depths of 100–350 m. Age-0 fish (polar cod, sculpin (Cottidae family), and eelblenny (Lumpenus sp.)), dominated the pelagic biomass at bottom depths between 20 and 75 m, with peak densities of 160,000 # ha⁻¹, but were also found in surface waters at bottom depths >75 m. Age-1+ polar cod were associated with cold, saline waters likely of Chukchi Sea origin and mirrored published foraging distributions for beluga whales (Delphinapterus leucas). Conversely, age-0 fish were found in warm, fresher water, likely of ice melt and/or riverine origin, throughout the study area. This study provides a necessary baseline for the development of Arctic assessment surveys and management plans for polar cod.     

Meiofauna distribution and mesoscale variability in two sites of the Ross Sea (Antarctica) with contrasting food supply

Meiofauna abundance, biomass and community structure were investigated in two comparable deep sites of the Ross Sea (Antarctica) characterized by different trophic and sediment characteristics. Site B (567 m depth, dominated by muddy sediments) and site C (439 m depth, characterized by the presence of calcareous debris and coarse sand) were located at increasing distance from the polynyas and were subject to different inputs of organic material to the seabed. Total meiofauna abundance ranged from 192.0 to 1191.2 ind. 10 cm⁻², and total biomass varied between 9.5 and 50.3 μgC 10 cm⁻². Meiofauna densities from the Ross Sea are, on average, 2–7 times lower than those reported from other similar deep polar regions and displayed significant differences between the sites. Nematodes dominated the samples at both sites, but their relative significance changed between the sites (80% at site B and 56% at site C), followed by copepods (1.6% and 35% at sites B and C, respectively). Meiofauna composition at site B appeared similar to that reported for deep-sea antarctic or temperate sediments, whereas the composition at site C was similar to that of coastal areas. On a macroscale, the different inputs of utilizable organic material at the two sites were reflected in meiofaunal distribution patterns, indicating that meiofaunal communities from the Ross Sea are dependent on particulate organic matter fluxes from the photic layer and are coupled to pelagic phenomena. Very low microscale variations (i.e. between replicates) in meiofauna density contrasted with large mesoscale variability, which was related to the concentration of the main food indicators (phytopigments, proteins, carbohydrates and lipids). Accepted: 18 February 1999     

Developmental morphology of the Indian cyprinid fish Barilius canarensis

Embryonic and larval development of an Indian cyprinid fish, Barilius canarensis, is described from laboratory-reared specimens. The eggs, measuring 2.1–2.4 mm in diameter, were demersal, almost spherical in shape, transparent and unpigmented, with a pale yellow yolk without oil globules. Hatching occurred 39–45 h after fertilization at 26.8°–27.4°C. The newly hatched larvae, measuring 4.8–5.1 mm in body length (BL) with 22 + 17 = 39 myomeres, were characterized by melanophores already deposited on the eyes. The eggs of B. canarensis resembled those of the related danionin species Candidia barbatus, Opsariichthys uncirostris uncirostris, Zacco platypus, Z. sieboldii, and Z. temminckii. Although the larvae of B. canarensis were also similar to those of the foregoing species in general morphology, they differed in having a straight notochord tip and pigmentation on the eyes at hatching and the almost entire absence of melanophores on the ventral body surface from the yolk sac to postflexion larval stages. Conversely, melanophores occurred on the anterior abdominal and pericardial cavities from the preflexion to postflexion larval stages.     

Cloning and expression of the Bacillus sphaericus 2362 mosquitocidal genes in a non-toxic unicellular cyanobacterium, Synechococcus PCC6301

Genes encoding the mosquitocidal binary toxin of Bacillus sphaericus 2362 were introduced into Synechococcus PCC6301, a cyanobacterium that can tolerate a number of potential variations in the mosquito breeding environment, and can serve as a food source for mosquito larvae. The toxin genes, preceded by a Synechococcus rbcL promoter, were located on a mobilizable Escherichia coli Synechococcus shuttle vector, which was introduced into Synechococcus PCC6301 at frequencies of 10⁻⁵–10⁻⁷ exconjugants/recipient, depending on the selective conditions used. Recombinant Synechococcus exhibited significant toxicity against 2-day-old and 6-day-old Culex quinquefasciatus larvae, the concentration required to kill 50 % of larvae (LC₅₀) being 2.1 × 10⁵ and 1.3 × 10⁵ cells/ml respectively. Mosquitocidal activity decreased tenfold after 20 generations of non-selective growth. Received: 23 July 1996 / Received revision: 11 November 1996 / Accepted: 15 November 1996