Effect of temperature on the respiration of an Antarctic freshwater anostracan, <Emphasis Type="Italic">Branchinecta gaini</Emphasis> Daday 1910, in field experiments

The Antarctic crustacean Branchinecta gaini (Branchiopoda, Anostraca) occurs in nine fresh water lakes near the Polish H. Arctowski Station. In one of the largest, Lake Wujka (Lake Uncle in English), we determined how temperatures affect its respiration and whether this is sex dependent. Experiments were carried out on males and females bearing eggs over a range of temperatures from 0.5 to 10°C. An ANOVA showed that while the amount of oxygen consumed increased with temperature (P < 0.001) males consumed more oxygen than similarly-sized females bearing eggs (P < 0.001).     

Distribution of microphytobenthic biomass in Martel Inlet,King George Island (Antarctica)

The spatial and temporal variation of microphytobenthic biomass in the nearshore zone of Martel Inlet (King George Island, Antarctica) was estimated at several sites and depths (10–60 m), during three summer periods (1996/1997, 1997/1998, 2004/2005). The mean values were inversely related to the bathymetric gradient: higher ones at 10–20 m depth (136.2 ± 112.5 mg Chl a m⁻², 261.7 ± 455.9 mg Phaeo m⁻²), intermediate at 20–30 m (55.6 ± 39.5 mg Chl a m⁻², 108.8 ± 73.0 mg Phaeo m⁻²) and lower ones at 40–60 m (22.7 ± 23.7 mg Chl a m⁻², 58.3 ± 38.9 mg Phaeo m⁻²). There was also a reduction in the Chl a/Phaeo ratio with depth, from 3.2 ± 3.2 (10–20 m) to 0.7 ± 1.0 (40–60 m), showing a higher contribution of senescent phytoplankton and/or macroalgae debris at the deeper sites and the limited light flux reaching the bottom. Horizontal differences found in the biomass throughout the inlet could not be clearly related to hydrodynamics or proximity to glaciers, but with sediment characteristics. An inter-summer variation was observed: the first summer presented the highest microphytobenthic biomass apparently related to more hydrodynamic conditions, which causes the deposition of allochthonous material.     

Redescription of Branchinecta granulosa Daday, 1902 from Argentina (Crustacea: Branchiopoda)

The species Branchinecta granulosa Daday 1902, is redescribed on the basis of adult material from near Facundo (Chubut Province, Argentina). Its relationship to its regional congeners is outlined.     

On the competitive balance of macroalgae at Potter Cove (King George Island,South Shetlands)

The sublittoral zonation of macroalgae and abundant animals in Potter Cove, King George Island, is described in relation to substrate, exposure to turbulence and impact of grounding icebergs. Implications on the ecological niches of the most prominent phaeophytes are discussed. It is concluded that Desmarestia anceps and D. menziesii exclude Himantothallus grandifolius under favourable conditions. However, Himantothallus, by its potential to inhabit unstable substrates, may be better adapted to withstand the ice impact. The replacement of Desmarestia by Himantothallus at greater depth can be explained only partially at present.     

A new freshwater oligochaete species (Clitellata: Enchytraeidae) from Livingston Island,Antarctica

The new enchytraeid species Lumbricillus healyae sp. n. is described from freshwater streams, with well-oxygenated and poorly mineralised waters, situated in Byers Peninsula (Livingston Island, South Shetland Islands, Antarctica). Lumbricillus healyae sp. n. is morphologically close to L. antarcticus and L. incisus, and it is mainly distinguished by the structure of the spermatheca with a short, distinct ectal duct, the oval penial bulb (greatest diameter in the transverse body axis) associated with strong dorso-ventral muscular fibres, and a protrusible pseudopenis. A second undetermined Lumbricillus species is described from a small stream. Study specimens are not fully mature; however, the highly irregular form and size of the testis-sac lobes and the absence of a penial bulb encapsulated under a muscular layer are remarkable. It is probably related to a small group of Lumbricillus species reported from the Antarctic maritime region (L. colpites, L. griseus and L. aestum), characterised by the structure of the male duct, which ends in a simple pore surrounded by glands.

The food and chick feeding of blackbellied stormpetrel (Fregetta tropica) at King George Island, South Shetlands

Food and chick feeding of the blackbellied stormpetrel were investigated at King George Island, South Shetland Islands, from December 1995 till March 1996. Seventy-five regurgitates and 174 samples from stomach flushing were analysed. Provisioning rate and meal size of the chicks were estimated by daily and three-hourly chick weighing. The mean weight of regurgitates of adult birds was 1.63 g. Fish (53.3% of occurrence) and crustaceans (50%) formed the main part of the diet. The frequencies of crustaceans in the diet were 8.3% amphipods, 21.7% euphausiids, 1.7% mysids and 18.3% unidentified crustaceans. Cephalopods represented only a small part in the diet (1.7%). Diet composition did not change throughout the season. The feeding frequencies of the chicks were 0.98 feedings per day on average. The mean meal size ranged from 9.2 to 11.0 g. Feeding and meal size data were calculated by different methods and compared with those of other petrel species. Received: 26 August 1997 / Accepted: 16 December 1997     

Uptake of lead,cadmium and zinc by the fairy shrimp,Branchinecta longiantenna (Crustacea: Anostraca)

Individuals of the fairy shrimp, Branchinecta longiantenna, were subjected to 5 concentrations (0.1 to 15 mg l^–1) of Pb in diluted habitat water at 13 °C. Lead concentrations (mg kg^–1 wet weight) in the animals were determined at 2-day intervals by digestion in nitric acid followed by atomic absorption analysis. The shrimp were also subjected to 0.1 mg l^–1 media of Cd and Zn, separately.Uptake rates by the fairy shrimp for the three metal ions at 0.1 mg l^–1 were: 0.111, 0.0885, and 0.0460 mg kg^–1 day^–1 for Zn, Pb, and Cd, respectively. After 2 days in 1.0 mg l^–1 Cd or Zn, the animals expired; but they surviced for 8 days in a 10 mg l^–1 Pb medium and for 2 days in 25 mg l^–1 Pb. Lead uptake demonstrated a linear dependence on the Pb concentration in the media.Shrimp survived at much higher tissue accumulations of Pb compared to Zn and Cd. Estimated lethal doses were 20, 1.2–2.4, and 0.4–1.4 mg kg^–1 wet weight for Pb, Zn, and Cd, respectively. Pb was found to be at much lower concentration than Cd or Zn in the natural pond water but between Cd and Zn levels in the sediment. Thus Cd and Zn probably present a greater threat to B. longiantenna than Pb, although Pb may be in higher concentration in the environment.Contribution 47, Laboratory of Ecology, The Claremont Colleges, Claremont, CA 91711, USA. Send reprint requests to Clyde Eriksen.     

Distribution patterns in the biomass of macrozoobenthic communities in Admiralty Bay (King George Island, South Shetlands, Antarctic)

The distribution patterns of macrozoobenthic communities as shown by the biomass of the higher taxa were investigated in Admiralty Bay. Material was collected at depths ranging from 4 to 500 m (102 quantitative samples), representing the full depth range of this basin and including areas characterized by the different levels of glacial influence. Five community groups were distinguished by multivariate analysis (clustering, MDS) based on the Bray--Curtis similarity index. In the Ezcurra Inlet, the area characterized by intensive glacial processes resulting in a high sedimentation rate, the distribution of biomass was not depth related, but was associated with the intensity of glacial disturbance along the axis of the fjord. The innermost part of this fjord, which receives strong outflows from glaciers, had a low biomass value (2.9 g/0.1 m²) and was dominated by polychaetes. The middle part of the fjord which is not so heavily disturbed had higher biomass values (46.1 g/0.1 m²) due to the dominance of bivalves. A clear depth gradient of biomass distribution was observed in bottom areas located far from glaciers, in the central basin of the bay, with three zones within the depth ranges 4–30, 40–380, and 400–500 m. The highest mean biomass values (92.5 g/0.1 m²) were found in the middle sublittoral (40–380 m) dominated by ascidians. In the shallow and deep assemblages, the biomass was lower (33.8 g/0.1 and 30.9 g/0.1 m² respectively), most probably associated with the ice disturbance in the shallows and lower food supply in the deepest part of the shelf.     

The life cycle of Laodicea indica (Laodiceidae,Leptomedusae, Cnidaria)

The life cycle of Laodicea indica is described. In the Bismarck Sea this species shows a normal alternation of generations in the wet season; but in the dry season the cycle is contracted, and planulae give rise to gonothecae without formation of a hydroid colony. Medusae are liberated about 3 d after planula settlement. This life cycle pattern is previously unreported in hydromedusae. The possible adaptive value of such a life cycle and the evolution of polyp reduction in hydromedusan life cycles are discussed.     

Life cycle and ultrastructure ofDucellieria chodati (Oomycetes)

Ducellieria chodati forms colourless, evidently plastid-lacking aggregates. For the first time, details of the reproduction cycle are reported: Biflagellate zoospores, released from the aggregates, infest coniferous pollen grains drifting on lake surfaces. The unicellular thallus growing inside the pollen grain develops into a sporangium. 10 to c. 60 spores are discharged, gather at the mouth of the discharge tube, and form new aggregates. After more than 30 cycles, the formation of aggregates ceases in favour of the direct production of zoospores which again infest pollen grains. If several zoospores infest the same grain, a resting spore can be produced, probably by a sexual process. It is evident from this complex life cycle thatDucellieria chodati is misplaced inChlorophyceae orXanthophyceae and needs to be grouped within theOomycetes. Dedicated to Prof. DrLothar Geitler on the occasion of his 90th birthday.     

Life cycle and host specificity of Amblyomma triste (Acari: Ixodidae) under laboratory conditions

We report biological data of two generations of Amblyomma triste in laboratory and compared the suitability of different host species. Infestations by larval and nymphal stages were performed on guinea pigs (Cavia porcellus), chickens (Gallus gallus), rats (Rattus norvegicus), rabbits (Oryctolagus cuniculus), wild mice (Calomys callosus), dogs (Canis familiaris) and capybaras (Hydrochaeris hydrochaeris). Infestations by adult ticks were performed on dogs, capybaras and rabbits. Tick developmental periods were observed in an incubator at 27 °C and RH 90%. Guinea pigs were the most suitable hosts for larvae and nymphs, followed by chickens. The remaining host species were less suitable for immature ticks as fewer engorged ticks were recovered from them. Mean larval feeding periods varied from 3.8 to 4.7 d between different host species. Mean larval premolt periods ranged from 8.9 to 10.4 d. Nymphal mean feeding periods varied from 4.2 to 6.2 d for ticks fed on different host species. Premolt period of male nymphs (mean: 15.4 d) was significantly longer than that of female nymphs (14.7 d). Female nymphs were significantly heavier than male nymphs. The overall sex ratio of the adult ticks emerged from nymphs was 0.9:1 (M:F). Capybaras were the most suitable host for the tick adult stage as significantly more engorged females were recovered from them and these females were significantly heavier than those recovered from dogs or rabbits. The life cycle of A. triste in laboratory could be completed in an average period of 155 d. The potential role of guinea pigs, birds and capybaras, as hosts for A. triste in nature, is discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Life Tables of Phytoseiulus Macropilis (Banks) (Gamasida: Phytoseiidae) at Different Temperatures

The biology of Phytoseiulus macropilis (Banks) fed on Tetranychus urticae Koch was studied at different temperatures. The total development times averaged 7.5, 5.7, 4.2, 4.2 and 5.6 days at 20, 25, 28, 30 and 32°C, respectively at 78 ± 2% RH and 16 h photoperiod daily. The intrinsic rate of natural increase (r_m) and the net reproduction (R_o) reached maximum values 0.47 and 88.9, respectively, at 28°C. The mean generation time decreased (20.0-8.8 days) with increasing temperature 20-28°C.     

Life cycle and adaptive strategies of three non-annual,ruderalCardueae: Onopordum nervosum,Carthamus arborescens,andCirsium scabrum

The life cycle and autoecology of three Mediterranean thorny species,Onopordum nervosum (Iberian endemic),Cirsium scabrum (Western Mediterranean) andCarthamus arborescens (Iberian-North African), of potential use in agriculture as bioenergetic, forage or oil producing plants were studied. These threeCardueae spp. are good examples of ways in which Mediterranean plants adapt their typical annual cycle to avoid summer droughts.O. nervosum is a perennial, monocarpic, heliophilous species which flowers in early summer and grows even under the extreme xeric conditions of the Mediterranean summers. It is a basiphilous plant usually found in sandy-loamy and sandy-clayey-loamy soils with a marked geographical variability in its seed germination.C. scabrum is a perennial, monocarpic species which has a long life cycle, flowering in summer and growing only during the wet months. It is not well-adapted to droughts and is usually restricted to acid soils.C. arborescens is a perennial, polycarpic species which flowers in spring and dries up in summer. It is usually found in basic loamy-sandy or sandy-loamy soils poor in organic matter.     

Dietary composition of juvenile Dissostichus eleginoides (Pisces, Nototheniidae) around Shag Rocks and South Georgia, Antarctica

A diet analysis of the Patagonian toothfish Dissostichus eleginoides, trawled in the South Georgia Islands area in March–April 1996, was carried out by frequency of occurrence (F%) and coefficient Q (%) methods. The samples consisted chiefly of immature specimens, with predominant length ranges of 30–70 cm (TL). Fish was by far the main food on the shelves of Shag Rocks and South Georgia, accounting for about 70% of prey. Krill appeared as secondary food, although its importance was overestimated by the frequency of occurrence method. Cephalopods and mysids were infrequent in the stomachs, and only at Shag Rocks and South Georgia, respectively. Lepidonotothen kempi, Champsocephalus gunnari and Chaenocephalus aceratus constituted the main fish prey and their variability between Shag Rocks and South Georgia depended on their local abundance. The large proportion of fish exhibiting stomachs full or close to fullness (together 62%) suggests that feeding intensity of the species was high.     

A new species of Mysella Angas, 1877 (Bivalvia: Galeommatoidea) from Admiralty Bay, King George Island, South Shetlands, Antarctica, with data on its biology and functional anatomy

Mysella narchii sp. nov. is described from the material collected in shallow-waters of Admiralty Bay at King George Island, South Shetlands, Antarctica. The species is characterized by shell features, biology and functional anatomy. The main shell features distinguishing M. narchii sp. nov. from all other Antarctic, Subantarctic and Magellanic Mysella spp. are provided, as are anatomical characteristics that separate this new species from M. charcoti (Lamy, 1906), its most similar congener and the first Antarctic species studied in its morpho-functional aspects. M. narchii sp. nov. is an infaunal, free-living, predominantly deposit-feeding bivalve; its creeping sole and the secretion of byssal threads allow it to crawl vertically and live sporadically on firm substrata.     

On the presence of the genus Branchinecta Verrill, 1869 (Crustacea,Anostraca) in Yugoslavia

The genus Branchinecta Verrill, 1869 is represented in Yugoslavia by two species: Branchinecta ferox (Milne-Edwards, 1840) and Branchinecta orientalis G.O. Sars, 1901. The first species was collected in the steppe-like province of Banat, Pannonian Lowland, and in the lowland around the Skadar Lake, Montenegro, the second only in the province of Banat.On the basis of rich material of both species, a detailed study of the most essential morphological characters has been carried out and comparisons have been made with data in the literature. In B. ferox, significant morphological deviations are not found, whereas, in B. orientalis, essential features are clearly ascertained which were previously unknown or were not stated with sufficient precision. B. ferox is known to appear in small, temporary, natronsoda water rainpools, while B. orientalis has been found in a large temporary inundation pool with a high content of natronsoda and salt in the water.     

Life cycle,behavior and morphology of a new tide pool dinoflagellate,Gymnodinium pyrenoidosum sp. nov. (Gymnodiniales,Pyrrhophyta)

A new tide pool dinoflagellate,Gymnodinium pyrenoidosum Horiguchi et Chihara sp. nov. is described from central Japan. It was found to form dense blooms with a characteristic greenish color from April to November. The species exhibits a characteristic diurnal vertical migration and an alternation of a motile with a nonmotile phase, which are dependent on light intensity and tidal movement. Cells of the motile phase are unarmored and relatively small. They have a single, reticulate chloroplast, orange stigma situated near the sulcus and conspicuous pyrenoid in epicone. The alga reproduces itself by means of zoospores which are produced by the bipartition of protoplasm within the parent cell wall during the nonmotile stage which occurs at night. The occurrence of another type of motile cell, termed a macroswarmer, which differs from normal zoospore in size and shape has also been demonstrated.     

The life cycle ofAcetabularia (Dasycladales,Chlorophyceae): A compilation of evidence for meiosis in the primary nucleus

Summary The life cycle ofAcetabularia is described with special reference to nuclear divisions. Recent arguments, derived from the fields of cytology, genetics and systematics are in favour of the hypothesis, that meiosis occurs during the division of the primary nucleus. This hypothesis is summarized in a schematical representation of the whole life cycle.