Late Miocene brackish Loxoconchidae (Crustacea, Ostracoda) from Italy

The Late Miocene Italian brackish Loxoconchidae are herein discussed and illustrated. Three genera and two subgenera have been recognized in the brackish Italian basins: Loxoconcha, Loxocorniculina, Loxoconchissa (Loxoconchissa) and Loxoconchissa (Loxocaspia). Taking into account the diagnostic characters of several Loxoconchidae genera, in this paper Loxocorniculina is raised at a generic rank, Loxocaspia is confirmed as a subgenus within genus Loxoconchissa and several new species are established: Loxoconchissa (Loxoconchissa) kinoi nov. sp., Loxoconchissa (Loxocaspia) cosentinoi nov. sp., Loxoconchissa (Loxocaspia) nuda nov. sp., Loxoconchissa (Loxocaspia) punctata nov. sp., Loxoconchissa (Loxocaspia) reticulata nov. sp., Loxoconchissa (Loxocaspia) tuberosa nov. sp. and Loxoconchissa (Loxocaspia) velonae nov. sp. Loxocorniculina is a typical Paratethyan genus which widespread into the Palaeo-Mediterranean during the late Messinian Lago-Mare event. Loxoconchissa was known to be widespread only in the Paratethyan realm and in this paper it is signalled for the first time in the Late Tortonian-early Messinian of Italy. The palaeobiogeography of these genera is discussed and the observed continuous distribution of Loxocorniculina against the disjunct distribution of Loxoconchissa leads to suggest that this latter genus underwent a passive dispersal via aquatic birds.     

Larval Konosirus punctatus(Clupeidae) in a brackish river mouth on the Pacific coast of central Japan

Eggs of Konosirus punctatus in early developmental stages were collected from the eastern part of the mouth of Sagami Bay on the Pacific coast of central Japan. Advanced‐stage eggs and early larvae with notochord length ( L _N) of <7·5 mm were collected from the inner bay near the mouth of the Sagami River. Feeding larvae of >8·4 mm L _N were distributed in the mouth of the river, and juveniles of 24–90 mm standard length ( L _S) were collected from the lower reaches of the river between the river mouth and c . 3 km upstream of the river mouth. Hatch dates of larvae and juveniles collected in 2001 ( n  = 158) and in 2002 ( n  = 109) extended from late March to late July. The relationship between the otolith radius ( R _O) and L _N or L _S changed during the metamorphosis stage as characterized by 320 μm R _O and 22 mm L _S. Otolith growth rate, as an index of somatic growth rates in larval and early juvenile stages, was higher in cohorts that hatched later in the spawning season, i.e . from March to July. Konosirus punctatus that were spawned in the bay mouth area survived with different growth histories in the bay and lower reaches of the river, and recruited to the young‐of‐year population in the Pacific coastal waters of central Japan.     

Variability of nutrients and phytoplankton biomass in a shallow brackish water ecosystem (Chilika Lagoon, India)

Seasonal and spatial variations in water quality parameters, such as nutrients [NH₄ ⁺–N, NO₂⁻–N, NO₃⁻–N, PO₄³⁻–P, total nitrogen (TN) and total phosphorus (TP)], Secchi disc depth, salinity, dissolved oxygen, chlorophyll a, primary productivity and phytoplankton standing stock, were studied in Chilika Lagoon (from 27 sampling locations) during 2001–2003 to assess the present ecological status. The study was undertaken after a major hydrological intervention in September 2000, which connected the lagoon body and the Bay of Bengal via a manmade opening (new mouth). Current and old data on water quality were also compared to establish the changes that had occurred after the hydrological intervention. Multivariate techniques and gridding methods were used to investigate the spatial and seasonal variability of the data and to characterize the trophic evolution of the basin. Results of principal component analysis (PCA) indicated that the 27 stations can be classified into five groups based on similarities in the temporal variation of nutrients, chlorophyll a concentration, salinity, and other physicochemical parameters. The tributaries and the exchange of lagoon water with the Bay of Bengal most probably determine the water quality and the dynamics of the ecosystem. Hydrodynamics of the lagoon, weed coverage, input of urban sewage through tributaries and agricultural runoff are probably the key factors controlling the trophic conditions of the lagoon. An increase in salinity and total phosphorus was noted after the new mouth was opened, while the total suspended sediment load, the water column depth, and nitrogenous nutrients decreased. The new mouth opening also brought changes in the phytoplankton species composition.     

Toxicity of Karlodinium micrum (Dinophyceae) associated with a fish kill in a South Carolina brackish retention pond

A dinoflagellate bloom was found associated with a fish kill event in a South Carolina brackish water retention pond. A multi-analytical approach was used to confirm the identity of the bloom dinoflagellate and evaluate its potential toxicity. Karlodinium micrum was confirmed through light microscopy, pigment profile comparisons, species-specific PCR, and gene sequence data. Necropsy findings on several fish were suggestive of an acute kill event. Toxicity of filtrate from bloom samples was tested by a hemolytic assay using rainbow trout (Oncorhynchus mykis) erythrocytes and an ichthyotoxicity assay using larval zebrafish (Danio rerio). Hemolytic activity was measurably high (>80% hemolysis) in both whole filtrate and fractionated filtrate (from the 80% MeOH C₁₈ column elution). This fraction also demonstrated high ichthyotoxic activity as exposed fish experienced rapid death. These results implicate toxic K. micrum as a causative factor in fish death in a non-aquaculture brackish pond associated with a housing development, and extend recent findings linking this species to fish kills in aquaculture ponds.     

Neomysis integer in a shallow hypertrophic brackish lake: distribution and predation by three-spined stickleback (Gasterosteus aculeatus)

The mysid shrimp Neomysis integer is a common invertebrate predator in brackish waters of Western Europe and is thought to play a central role in the food web owing to its predation on zooplankton. Neomysis distribution and abundance were investigated for 3 years in brackish, shallow and hypertrophic Lake Ferring (surface area: 3.2 km², mean depth: 1.4 m, salinity: 3–6, total P: 0.29–0.78 mg P l^-1, Secchi depth: 0.14–0.22 m). Mean summer abundance of Neomysis varied from 53 to 882 ind. m^-2. Neomysis density within the lake was relatively uniform and not related to sediment type, but increased with increasing depth. The high abundance of Neomysis is considered to reflect a fish stock almost completely dominated by small-sized fish species (mainly three-spined stickleback, Gasterosteus aculeatus). Three-spined stickleback density was high and catch per unit effort ranged between 30 and 80 per gill net. Stomach analyses showed that the sticklebacks preyed on Neomysis, but preferred specimens smaller than 3–4 mm, and only occasionally consumed those larger than 5–7 mm. In summer, between 33 and 67% of the Neomysis ingested by sticklebacks were smaller than 3 mm, while in the lake as a whole, only 5–14% were smaller than 3 mm. The periods when Neomysis is vulnerable to stickleback predation are restricted to a few weeks in late May and late July, when the new generations emerge. Sticklebacks therefore have a limited capacity for controlling large Neomysis, including gravid females.     

Apparent semi-lunar spawning rhythmicity in a brackish cardinalfish

The purpose of the present study was to examine the lunar-related spawning rhythmicity of the amboina cardinalfish Apogon amboinensis, which is a euryhaline species inhabiting mangrove creeks in the Indo-Pacific area. During the reproductive season, the gonado-somatic index increased towards and peaked within a week of the first and last quarter moon. Histological observations of the ovaries also showed development of yolk-laden oocytes towards the first and last quarter moon; postovulatory follicles, an indicator of spawning, appeared around these lunar phases. Fish with immature oocytes in the ovary were also collected in the same lunar phases, suggesting that at least two fish populations with different oocyte development stages exist at any given time. The levels of two steroid hormones secreted from the ovarian pieces into a culture medium with human chorionic gonadotropin were measured using enzyme-linked immunosorbent assay (ELISA). The level of oestradiol-17β increased around the new and full moon periods. On the other hand, 17α,20β-dihydroxy-4-pregnen-3-one levels increased around the first and last quarter moon, suggesting that the fish are actively undergoing vitellogenesis and final oocyte maturation around the respective lunar phase. These results suggest that with the 1 month ovarian development process, A . amboinensis exhibits a semi-lunar spawning pattern with peaks around the first and last quarter moon. When A . amboinensis were reared under laboratory conditions without the tidal stimuli, mouth-brooding was initiated in 13 of 20 males within a week of the first and last quarter moon. The possibility of a lunar-related endogenous rhythm in A . amboinensis is discussed.     

Phenology of cryptomonads and the CRY1 lineage in a coastal brackish lagoon (Vistula Lagoon,Baltic Sea)

Cryptomonadales have acquired their plastids by secondary endosymbiosis. A novel clade—CRY1—has been discovered at the base of the Cryptomonadales tree, but it remains unknown whether it contains plastids. Cryptomonadales are also an important component of phytoplankton assemblages. However, they cannot be readily identified in fixed samples, and knowledge on dynamics and distribution of specific taxa is scarce. We investigated the phenology of the CRY1 lineage, three cryptomonadales clades and a species Proteomonas sulcata in a brackish lagoon of the Baltic Sea (salinity 0.3–3.9) using fluorescence in situ hybridization. A newly design probe revealed that specimens of the CRY1 lineage were aplastidic. This adds evidence against the chromalveolate hypothesis, and suggests that the evolution of cryptomonadales’ plastids might have been shorter than is currently assumed. The CRY1 lineage was the most abundant cryptomonad clade in the lagoon. All of the studied cryptomonads peaked in spring at the most freshwater station, except for P. sulcata that peaked in summer and autumn. Salinity and concentration of dissolved inorganic nitrogen most significantly affected their distribution and dynamics. Our findings contribute to the ecology and evolution of cryptomonads, and may advance understanding of evolutionary relationships within the eukaryotic tree of life.     

Long-term stability of the seasonal succession of different zooplankton species in a brackish water lagoon (southern Baltic Sea)

While it has been widely suggested that freshwater fishes from East Asia invaded the western Palaearctic, details about this process are largely unknown. Here, using the cytochrome b gene, we evaluated the phylogenetic relationships of a small group of Eurasian primary freshwater fishes (Cobitidae), which are widely distributed and species rich in East Asia and Europe, with the purpose of inferring their invasion process of Europe from East Asia. Though phylogenetic relationships of cobitids were not well resolved, our analysis could identify three sister groups formed by the European and East Asian cobitids, which brought new insights into the biogeography of the genera Cobitis, Misgurnus, and Sabanejewia. The present results support the view that Asian cobitid fishes may have invaded Europe at least five times independently, and once reverse colonization of European cobitids to East Asia could also be found. Ancestral Sabanejewia might have been the first cobitids to cross Siberia and invade the EMZS (Euro-Mediterranean zoogeographic subregion) about 33.54 million years ago (MYA). One lineage of Cobitis and the ancestor of Misgurnus fossilis (Linnaeus) almost in the same time invaded the Europe, responding to 16.71 MYA and 16.59 MYA, respectively. Three different lineages of Cobitis were found to have invaded the EMZS from East Asia, and once reverse invasion to East Asia occurred to one subclade of European Cobitis. And our data also suggest that the diversity of East Asian cobitid fishes, especially of the genus Cobitis, is greatly underestimated. Handling editor: C. Sturmbauer     

The occurrence and ecological requirements of the horse-flies (Tabanidae) of brackish marshes in Belgium

The deteriorated state and shrunken area of brackish marshes in Western-Europe has taken a toll of its typical inhabitants. Careful management of the remaining area is required to conserve the vulnerable biodiversity, yet with respect to the large group of invertebrates we have very poor knowledge on how to achieve this. In this study we investigated the occurrence of horse-flies (Diptera: Tabanidae) in Belgian brackish marshes in relation to habitat properties. We found three strictly halophile tabanid species occurring in Belgium: Atylotus latistriatus, Haematopota bigoti and Hybomitra expollicata. These halophile tabanids are rare insects as their habitat is now rare. Our data indicated that a prime critical condition may be a stable, high groundwater table. In addition, soil salinity probably needs to exceed some threshold, but more data are needed to substantiate this claim. Soil salinity measurements in brackish marshes indicated that soil salinity was significantly higher throughout the year in open, sparsely vegetated patches, compared to fully vegetated marshland. Such conditions could be beneficial to horse-flies or consorts, but have become rare because there is little impetus for maintaining a spectrum of brackish marshland types and associated species. However, maintaining this spectrum is required in order to conserve existing biodiversity in Western-European brackish marshlands.     

Microbial sulfate reduction in a brackish meromictic steppe lake

Patterns of sulfate reduction were studied in water and sediments of Lake Shira, South Siberia, Russia. The lake was characterized by a high level of sulfate (91-116 mM). The concentration of hydrogen sulfide in the anoxic waters of the lake reached 0.6 mM. In summer the sulfate reduction rate in the water column, measured by radiometric technique, varied from 0.25 to 9.81 mol sulfate l^-1 d^-1. There were two peaks of sulfate reduction activity: just below the chemocline and near the sediment surface. Sulfate reduction rate in the profundal silts ranged from 4.1 to 90.6 mol l^-1 d^-1. The zone of the most active sulfate reduction was restricted to the surface sediment layers. The acceleration of sulfate reduction rate (up to 236 mol l^-1 d^-1) and the increase of density of viable sulfate reducers (up to 2 x 10⁵ cells ml^-1) were recorded in the littoral sediments adjacent to the mouth of the Son River and sewage discharge. It was apparently caused by the input of allochthonous organic substrates and also by a high environmental temperature. On an areal basis, sulfate reduction rate in the water was approximately 8 times higher than that in the profundal sediments. Sulfate reduction was the most important process of anaerobic oxidation of organic carbon in Lake Shira. In summer in the profundal zone of the lake, sulfate reducers were able to mineralize about 67% of the daily integrated primary production of phototrophic and chemotrophic organisms.     

The distribution of brackish water Calanoida (Copepoda) along the coasts of Brazil

The distribution of 18 species of Calanoida Copepoda found in the estuaries of the Brazilian coast is analyzed. A slight tendency of a latitudinal decrease in diversity, from North to South is found. Salinity ranges from the different species are discussed and in some cases interspecific vicariance patterns are found. Two basic types of estuaries of the Brazilian coast are characterized on the basis of environmental parameters and population dynamics.     

Vegetation controls methane emissions in a coastal brackish fen

Climate change and associated sea level rise will likely affect coastal ecosystems and lead to more frequent inundations. Plants are an important control for methane (CH₄) emissions in peatlands because the metabolism of the living plant can either enhance or attenuate CH₄ emissions and plant litter supplies an easily available carbon source for methanogenesis. Here we compare the contribution of various dominant plant species to methane emissions in a degraded, rewetted coastal brackish fen at the southern Baltic Sea coast in Northeast Germany. We analyse one year of bi-weekly static closed chamber data gathered at measurement spots that were located in different mono-dominant vegetation stands (Bolboschoenus maritimus (L.) Palla, Schoenoplectus tabernaemontani (C.C.Gmel.) Palla, Carex acutiformis Ehrh.). Furthermore, data on water level, water temperature, conductivity (sulphate), and several peat characteristics were recorded. Generally, the annual methane emissions were low with an average across vegetation stands of 14 kg CH₄ ha^?1 a^?1, which we related to high decomposition of peat after drainage and to relatively low water levels in summer. Nevertheless, methane emissions varied between different vegetation types with significantly higher methane fluxes (31.8 ± 5.7 kg CH₄ ha^?1 a^?1) from Bolboschoenus maritimus stands compared to Carex acutiformis and Schoenoplectus tabernaemontani stands (4.3 ± 1.2 and 5.7 ± 2.4 kg CH₄ ha^?1 a^?1, respectively). None of the environmental variables that have been recorded can explain this difference. Thus, vegetation composition seems to be an important driver for methane emissions in coastal brackish fens and may therefore be crucial with regard to recreation measures.     

Effects of the halocline on water quality and phytoplankton composition in a shallow brackish lake (Lake Obuchi, Japan)

The relationships of the halocline to both water quality and phytoplankton composition in Lake Obuchi, a shallow brackish lake in northern Japan, were investigated from April 2001 to December 2004. The halocline in this lake became stronger in summer (July–September, mean maximum density gradient 4.3–5.8 ρ_tm⁻¹) but weaker in spring, fall, and winter (1.9–3.3 ρ_tm⁻¹). Although the difference in water quality between the upper and lower layers separated by the halocline was high in summer, nutrients (PO₄³⁻-P and NH₄⁺-N) were eluted from the bottom sediment as levels of dissolved oxygen decreased in the bottom layer because of the strong stratification caused by the halocline formed over the long term. Moreover, phytoplankton taxa composition also differed between the upper and lower layers in summer, but was similar in other seasons. The dominant phytoplankton taxa in the upper layer in summer were Skeletonema costatum and Cyclotella spp., whereas in the lower layer, Gymnodinium spp. (Dinophyceae) and Chlorophyceae, which prefer eutrophic and low dissolved oxygen conditions, dominated. This suggests that the halocline was related to differentiations in both water quality and ecosystem components between the upper and lower layers in the brackish lake water.     

Spawning induced by injection of progesterone into the teleost crenimugil labrosus (risso, 1826) in a brackish milieu (author's transl)]

10 In the euryhaline fish Crenimugil labrosus, complete oocyte maturation does not occur in a brackish milieu. 20 The injection of progesterone induces complete maturation in 30% and 14% salinities, allowing larvae to be formed after artificial fertilization of the eggs. 30 The same result is obtained with hypophysectomized animals: thus the pituitary is not involved in this maturation.     

Identification of Stictodora lari (Heterophyidae) metacercariae encysted in the brackish water fish, Acanthogobius flavimanus

Metacercariae of the genus Stictodora encysted in the head tissue of Acanthogobius flavimanus (the gobies) caught at Sachun-gun, Kyongnam Province, were identified to be Stictodora lari Yamaguti, 1939 (Trematoda: Heterophyidae), a new parasite fauna in Korea. The metacercariae were 0.39-0.43 mm by 0.32-0.35 mm in size, long elliptical, and with a thin and transparent cyst wall. Total 200 metacercariae were collected from 50 gobies. In order to obtain adult worms two kittens and a puppy were infected each with 34-100 metacercariae, and total 33 adults were recovered between the day 4 and day 8 post-infection. The S. lari adults measured 0.95-1.18 mm long and 0.26-0.32 mm wide and the eggs in uteri 0.028-0.033 mm by 0.017-0.020 mm. The most characteristic morphological feature of these flukes was the presence of a gonotyl and gonotyl spines arranged in two groups; densely crowded group of 30-40 spines and linearly-arranged one of 30-40 spines, together of which made a comma (or reversed comma) shape along the lateral margin of the gonotyl. It has been proved by this study that S. lari is distributed in southern coasts of Korea.     

Trace metals in marine,brackish and freshwater prawns (Crustacea,Decapoda) from northeast Algeria

The concentrations of the trace metals Zn, Cu, Fe, Cd and Pb were measured in four caridean decapods; Atyaephyra desmaresti, Palaemonetes varians, Parapenaeus longirostris and Aristeus antennatus, from freshwater , estuarine and marine habitats in northeast Algeria variably affected by anthropogenic metal contamination. The two coastal species (P. longirostris and A. antennatus) are a food source for the local population. Accumulated metal concentrations varied interspecifically, and intraspecifically between sites and between seasons, except in the case of Aristeus antennatus. The fresh and brackish water species (Atyaephyra desmaresti and Palaemonetes varians) accumulated more Cd and Pb than their marine counterparts. Results are discussed with respect to anthropogenic inputs and the environmental conditions of the regions studied.