Redescription of Diaphanosoma celebensis Stingelin, 1900 (Crustacea,Cladocera)

A rare species, Diaphanosoma celebensis (Stingelin, 1900) is redescribed from type material and material from the South of Vietnam. In comparative morphological aspect it is close to D. volzi, but it is relatively less specialized. D. celebensis is known from single locations in Indonesia, Sri Lanka, Vietnam. It probably also occurs in Malaysia. The size frequency and sex structure of a population from Vietnam is described.     

Toward a phylogeny and biogeography of Diaphanosoma (Crustacea: Cladocera)

Aquatic Ecology - Diaphanosoma s.l., with 40+? described species, is the largest genus of the Sididae and the Ctenopoda, similar in many ways to the anomopod genus Daphnia. Here, we offer a c...     

Tolerance of Ceriodaphnia quadrangula and Diaphanosoma brachyurum(Crustacea: Cladocera) to experimental soft water acidification

We analysed in how far the decrease of pH, that is part of the ongoing restoration of the softwater Lake Windsborn (conductivity below 30 S cm^–1), may in future influence the occurrence of the two cladoceran species Ceriodaphnia quadrangula and Diaphanosoma brachyurum. In the field, the abundance of Ceriodaphnia was positively correlated with lake water pH, whereas there was no correlation between abundance and pH for D. brachyurum. Experiments on the tolerance against acidification included dynamic (24 h) and static tests (24, 48 h, 30 d), and were conducted with acidified lake water. C. quadrangula tolerated a slight acidification to pH 5.2, but not pH 4.8, whereas the NOEC value seems to be between pH 4.2 and 4.5 for D. brachyurum. Differences between the experimental NOEC values and field data may be explained by diurnal pH fluctuations and the low ion content of Lake Windsborn which puts an additional physiological challenge to its inhabitants.     

Peculiarities of the biology of two Diaphanosoma species (Crustacea,Cladocera) in Rybinsk Reservoir

The spatial distribution, long-term dynamics of occurrence and abundance, and the peculiarities of the seasonal cycle of two cladocerans, an alien species Diaphanosoma orghidani Negrea and a native species D. brachyurum (Liévin), were studied in Rybinsk Reservoir in 2005–2011. The successful coexistence of the species for over a 7-year period was favored by the differences in their seasonal cycles, the distributional pattern in the reservoir, the predator press, and the preference of the alien species to inhabit areas of running water where the native species was not numerous. Competitive advantages of the invader under conditions of global warming are discussed.     

A new species of the genus Diaphanosoma Fischer, 1850 (Crustacea: Cladocera: Sididae) from Japan

Diaphanosoma kizakiensis sp. nov. is described from material from Lake Kizaki (Honshu, Japan). It can be regarded as a member of the D. brachyurum species group, and is characterized by some specific but not readily visible features, such as the presence of a relatively small head, a small and sharp (not large and lanceolate) spine on the outer side of the distal end of the antennal basipodite, and particular features of the armament of the posteroventral valve margins. This species along with some other recently investigated Japanese cladocerans form a group of taxa which highlight that this country is one of the regional centers of cladoceran endemicity in Eastern Asia.     

Two new species of Diaphanosoma Fischer, 1850(Crustacea: Branchiopoda: Cladocera) from the United States

Two new species of the genus Diaphanosoma, D. oligosetum and D. dorotheae, from Louisiana and North Carolina respectively, are described. The former species has large head with protruding dorsal part, large lanceolate spine on the basipodite's distal outer end, an extremely reduced number of antennal setae, up to six in adult specimens, and unique armament of valve margin. On the whole, it shows the pronounced combination of primitive and specialized morphological traits. D. dorotheae is a member of D. brachyurum species group differing from its other known representatives in presence of a small but very conspicuous spine on the end of proximal segment of antennal exopodite and a variable number of setae (seven or eight) on the distal segment of the branch. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Development and characterization of eight polymorphic microsatellite markers for Daphnia atkinsoni (Crustacea: Ctenodaphnia)

A microsatellite‐enriched genomic library was developed for the water flea Daphnia atkinsoni Baird, 1859, a dominant species of intermittent wetlands in Europe. Eight polymorphic microsatellite markers were successfully optimized. Characterization of 77 individuals from Belgium and Spain showed moderate (in the former) to high (in the latter) levels of polymorphism with two to 11 alleles per locus and an observed heterozygosity ranging from 0 to 0.87. Some of these microsatellite markers were successfully amplified in three other Daphnia species (D. magna n = 4, D. similis n = 6; D. obtusa n = 6).     

Population dynamics and production of Daphnia galeata (Crustacea, Cladocera) in Lake Esrom

The population dynamics and production of D. galeata Sars were investigated from April 1974 to April 1975. The population density and biomass was maximum in June. Population dynamics indicated that food supply was better in spring and early summer than mid-summer. Net production was calculated by method of daily addition of biomass for eight size groups. The total net production of biomass for the year of investigation was 26.5 g dw m⁻². The P/B yr⁻¹ was 35 8.     

The population dynamics of Chydoridae and Macrothricidae (Cladocera: Crustacea) from the River Thames, U.K.

SUMMARY.

• 1 A study was made of the population dynamics of benthic cladocerans in the River Thames, U.K. These included three species of Chydoridae (Alona affinis Leydig, Disparalona rostrata (Koch 1841) and Leydigia leydigi Schodler) and one species of Macrothricidae Iliocryptus sordidus (Lievan).
• 2 The pattern of chydorid abundance was similar to that found in many lakes: a midsummer peak followed by a sharp decrease in numbers and subsequent low abundance. This was caused by a temporary decrease in natality, possibly due to food limitation, and a more permanent increase in mortality, thought to be due to predation.
• 3 Iliocryptus sordidus differed considerably from the chydorids, the major population peak occurring in the autumn. The lifestyle and adult size of Iliocryptus sordidus (Lievan) must render adults less vulnerable to invertebrate and fish fry predation.
• 4 A literature survey showed that the assemblage of species found in the unvegetated littoral of lakes and rivers included a taxocene of cladocerans.

     

Population dynamics of Bosmina longirostris (Crustacea: Cladocera) in Lake Kariba,Zimbabwe

The population dynamics of Bosmina longirostris in a large tropical reservoir, Lake Kariba, Zimbabwe, are described. Population density showed two peaks associated with periods of high nutrient fluxes. Fecundity was always low. Two eggs per female was the maximum ever recorded. Instantaneous rates of birth, death and population growth calculated from field data using the egg ratio method are discussed. The rate of biomass change fluctuated in a regular pattern, probably linked to food availability or predation by a clupeid, Limnothrissa miodon.     

Der Ankerapparat vonSida crystallina (Crustacea,Cladocera)

Zusammenfassung Die in eine Grundsubstanz eingebetteten Klebanker und Ankerfäden, mit deren Hilfe sichSida crystallina am Substrat befestigt, liegen auf der Epicuticula. Die Fäden sind mit der Epicuticula über Trennvorrichtungen verbunden. Die Sekretion der Ankerstrukturen durch die Epidermiszellen erfolgt zunächst in oberflächenparallelen Schichten. Später wird das Sekretionsfeld mit den Fadenenden nach hinten verschoben. Es folgt die Bildung der Trennstellen und schließlich die Sekretion der Cuticula. Nach der Häutung klappt die Ankerleiste in ihre funktionelle Stellung und die Procuticula skierotisiert.

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The anchor apparatus ofSida crystallina (Crustacea, Cladocera)II. Ultrastructure and formation

Summary Sida crystallina attaches itself to the substratum by adhesive anchors. Anchors and anchor threads are embedded in a matrix and situated on the epicuticle. The anchor threads are connected to the epicuticle by special junctions at which they can be separated. The new structures of the anchor organs, which are secreted by epidermal cells, are firstly laid down in layers parallel to the surface. Later the area of secretion becomes shifted backward. Then the junctions are formed and finely the secretion of the cuticle follows. After molting the anchor ledge turns out in its functional position and sclerotisation of the procuticle takes place.

     

A Study of Diaphanosoma Species (Crustacea: Cladocera) of the “Mongolianum” Group

Material from 49 localities in Europe, Asia and Africa is used to study two similar Diaphanosoma species, viz. D. mongolianum UENO, 1938, and D. lacustris KORINEK, 1981, both of which were described earlier under other names, the most common of which were “D. brachyurum”, “D. leuchtenbergianum” and “D. birgei lacustris”. These species are redescribed in detail, consideration being given to interpopulational and individual morphological variability, the type material, and material from type localities. The morphology of the setae of the swimming antennae is studied in detail, and the author concludes that some of them are not only used for swimming but also perform a sensory function. Some aspects of the biology of the species are described. They inhabit water bodies of different types, are often so abundant that they constitute the main component of zooplankton communities, and are an important link in the trophic chain. Little known cases of the co-occurrence of Diaphanosoma species in a water body are described. Localities known for D. mongolianum and D. lacustris are situated mainly in the temperate and subtropical zones, the former species penetrating farther north than the latter. However, they are also found in the White Nile (Sudan) and Ethiopian lakes. This southward penetration may be connected with the azonal distribution of fluviatile fauna and with the altitude of Ethiopian lakes.     

Significance of head and carapace pores inCeriodaphnia (Crustacea,Cladocera)

Twelve species ofCeriodaphnia were examined by light and scanning electron microscopy for the presence of head and carapace pores. Rostral pores, similar to those in the Scapholeberinae (Dumont & Pensaert, 1983) were found in all species, situated just anterior to or between insertions of the antennules. With two exceptions, the pattern of reticulations around the pores was distinctive for each species. Oval ‘head pores’ or fenestrae occur consistently on the anterior surface of the cervical notch of juvenile and adultC. dubia, cf.dubia (from Australia),lacustris, andreticulata. The patterns of reticulations around a fenestra are unique to each species. It appears thatC. cornuta (s.l.) in the Americas has a fenestra, whereas AustralianC. cornuta (s.s.) has none. Minute pores often occur bilaterally anterior and posterior to the cervical notch in heavily reticulated individuals of several species but are not constant enough to be taxonomically useful. Well-defined small pores are situated within narrow reticulations just medial to the ventral and posterior valve margins ofC. dubia, lacustris, andreticulata. These open into carapace glands of unknown, perhaps secretory, nature. Similar glands have been observed in related taxa. Such glands and marginal pores occur only occasionally or not at all in otherCeriodaphnia. Other small pores sometimes occur among reticulations of the head, fornix, and lateral and antero-ventral surfaces of the valves. They are found more often in juvenile or heavily reticulated individuals. As yet no consistent pattern to their occurrence among species has emerged. Head and carapace pores inCeriodaphnia may be most useful in identifying species rather than in determining species groups or evolutionary patterns within the genus.     

First record of fossil Mesozoic Ctenopoda (Crustacea, Cladocera)

Pre-Pleistocene representatives of the crustacean order Ctenopoda Sars, 1865 are unknown. Here we describe Mesozoic fossil specimens of ctenopods from two localities in Mongolia: Khotont (Jurassic/Cretaceous boundary, about 145 Mya) and Khutel Khara (Lower Cretaceous, about 129 Mya). All specimens apparently belonged to the tribe Latonini Korovchinsky, 1986 of the subfamily Sidinae Baird, 1850. At the Khotont site, ctenopods were the most numerous microscopic animal fossils. We assigned these cladocerans to a new genus and species Archelatona zherikhini gen. nov., sp. nov. Our findings support a pre-Cretaceous origin for cladocerans.  © 2006 The Linnean Society of London, Zoological Journal of the Linnean Society , 2006, 146 , 269–274.     

Biology and population dynamics of Porcellionides sexfasciatus (Crustacea,Isopoda, Oniscidea)

The biology and the population dynamics of Porcellionides sexfasciatus Budde-Lund (1879) were studied on a field and carried out at Garat Naam (Kasserine, Tunisia) from July 1996 to June 1998. The reproduction exhibited a seasonal pattern extending from February/March to October/November. The juveniles appeared in the population from April to November. Size frequency distributions were analysed and 14 cohorts were recognised during the sampling period. Six cohorts were identified at the first sampling and eight new ones on the other samplings. Among these latter cohorts, three were tracked till they disappeared. Minimum average length of new cohorts ranged from 3.07 +/- 0.35 mm to 3.47 +/- 0.2 mm. Maximum average length of cohorts was 10.42 mm. P. sexfasciatus is a semi-annual species (females producing two or three broods per year), with iteroparous and amphogenes females (females reproducing twice or more in their life and producing both males and females), and bivoltine life cycle (two generations per year). The females are able to produce two broods, in the laboratory, without new mating. Fecundity and fertility, corresponding to the number of eggs or embryos per brood, appeared positively correlated with females' size. Although oscillating throughout the year, the sex ratio was often in equilibrium.     

Gene Conversion and Evolution of Daphniid Hemoglobins (Crustacea, Cladocera)

The extracellular hemoglobins of cladocerans derive from the aggregation of 12 two-domain globin subunits that are apparently encoded by four genes. This study establishes that at least some of these genes occur as a tandem array in both Daphnia magna and Daphnia exilis. The genes share a uniform structure; a bridge intron separates two globin domains which each include three exons and two introns. Introns are small, averaging just 77 bp, but a longer sequence (2.2–3.2 kb) separates adjacent globin genes. A survey of structural diversity in globin genes from other daphniids revealed three independent cases of intron loss, but exon lengths were identical, excepting a 3-bp insertion in exon 5 of Simocephalus. Heterogeneity in the extent of nucleotide divergence was marked among exons, largely as a result of the pronounced diversification of the terminal exon. This variation reflected, in part, varying exposure to concerted evolution. Conversion events were frequent in exons 1–4 but were absent from exons 5 and 6. Because of this difference, the results of phylogenetic analyses were strongly affected by the sequences employed in this construction. Phylogenies based on total nucleotide divergence in exons 1–4 revealed affinities among all genes isolated from a single species, reflecting the impact of gene conversion events. In contrast, phylogenies based on total nucleotide divergence in exons 5 and 6 revealed affinities among orthologous genes from different taxa. Received: 8 March 1999 / Accepted: 14 July 1999     

Redescription of Scapholeberis echinulata Sars 1903 (Crustacea,Cladocera)

Scapholeberis echinulata Sars is rediscribed, based on type material of Sars (S. echinulata), Daday (s. erinaceus) and the author's own samples. A differential diagnosis with Scapholeberis spinifera Nicolet and S. mucronata O. F. Müller, S. microcephala Sars, S. kingi Sars and S. aurita Fischer is given.