Daphniopsis australis nov.sp. (Crustacea: Cladocera), a further daphniid in Australian salt lakes

Daphniopsis australis, a new species of cladoceran in Australian salt lakes, is described, and some brief comments on its distribution are given.     

A new species of Daphniopsis (Crustacea: Anomopoda: Daphniidae) from Australian salt lakes

A new species of the genus Daphniopsis found in Australian salt lakes is described and illustrated. A differential diagnosis and short taxonomic remarks are presented.     

The systematics of Australian Daphnia (Cladocera: Daphniidae). Multivariate morphometrics

Forty nine characters were measured in each of 76 male and 200 female Daphnia including specimens from all eleven taxa described from the genus in Australia, except D. jollyi. Separate multivariate analyses (cluster, principal components and discriminant) of males and females each revealed only five morphological groups in the genus corresponding to the species D. occidentalis, D. lumholtzi, D. cephalata, D. nivalis, and a conglomerate of all other taxa described from the D. carinata complex, D. carinata (sensu lato). Interpretation of the male results was straightforward, but that for females was not because of the occurrence of an environmentally induced seasonal change in morphology (cyclomorphosis) in females. Log transformations of the female data successfully isolated the effects of cyclomorphosis. The seasonal morphs formed two groups which were further differentiated into taxonomic groups.     

Daphniopsis studeri (Crustacea: Cladocera) in lakes of the Vestfold Hills,Antarctica

Summary The adult sizes and reproductive capabilities of populations of the cladoceran Daphniopsis studeri Rühe from freshwater and slightly saline lakes in the Vestfold Hills, Princess Elizabeth Land were monitored during December, 1990. The population of Crooked Lake was studied in detail from July 1990–March 1991. Limited samples were also obtained from Heard Island (sub Antarctic). Obligate parthenogenesis involving the production of subitaneous eggs appears to be the case. No males occurred. The overwintering populations of continental Antarctica consist mainly of adult females containing extensive fat reserves. The main reproductive effort occurs in spring. some females produce a smaller second brood during the summer. Reproductive output increases with adult size which is related to the nutrient status of the lake and its productivity. The Heard Island populations have a higher weight to length ratio than the Vestfold populations and have a much greater reproductive output.     

The systematics of Australian Daphnia (Cladocera: Daphniidae). Electrophoretic analyses of the Daphnia carinata complex

Genetic variation at eleven allozyme loci was scored in approximately 1600 individual Daphnia. The samples included representatives of all nine taxa described from the D. carinata complex in Australia. Principal coordinates and cluster analyses revealed only three groups of genotypes within the complex, corresponding to the taxa D. cephalata, D. nivalis, and a conglomerate of all other taxa described from the complex, D. carinata (sensu lato). These results are consistent with recent multivariate morphological analyses of the complex.     

On the ecology of Haloniscus searlei (Isopoda,Oniscoidea), an inhabitant of Australian salt lakes

The taxonomy, geographical distribution, salinity tolerance, bathymetric distribution, tolerance to desication and osmotic regulation of Haloniscus searlei Chilton (1920), an aquatic oniscoid isopod living in salt lakes in Australia, are considered.     

Daphnia curvirostris Eylmann in Japanese high mountain waters (Cladocera: Daphniidae)

A species of Daphnia, Daphnia curvirostris Eylmann, found in high mountain lakes and ponds in central Japan is described. Although there were some differences in the shape of the male rostrum and the chromosome number between European populations as described by Johnson (1952) and Trentini (1980), and Japanese ones collected from high mountain waters, Japanese specimens had many characteristics similar to the taxon D. curvirostris of Europe.     

A comparison of populations from the Daphnia similis group (Cladocera: Daphniidae)

European populations of Daphnia similis Claus have been compared with populations from tropical Asia. Daphnia similoides n. sp. from tropical Asia was described as the sibling species of D. similis. The female has characteristic neonate, postabdomen, head, and ephippium. The male has characteristic rostrum, antennules, and the distalmost part of the postabdomen. The D. similis group was compared with D. carinata s. str. Australian populations.     

Genome size evolution and polyploidy in the Daphnia pulex complex (Cladocera: Daphniidae)

Genome size was estimated in 49 clones of the Daphnia pulex complex from temperate and subarctic locations using flow cytometry and microsatellite DNA analyses. Significant genome size differences were found in diploid species belonging to the two genetically distinct groups (the pulicaria and the tenebrosa groups), with clones from the tenebrosa group having genome sizes 22% larger than those in the pulicaria group. Combined flow cytometry and microsatellite DNA analyses revealed that nearly all polyploid clones in the D. pulex complex are triploid and not tetraploid, as was previously suggested. Sequencing analyses of the ND5 gene to position clones in their respective clades within the D. pulex complex have uncovered three triploid clones of Daphnia middendorffiana with a D. pulex maternal parent. This result was unexpected because Daphnia pulicaria has always been identified as the maternal parent of these hybrid polyploid clones. Triploid clones likely owe their origins to interactions between sexual and asexual populations. Further interactions in the tenebrosa group have generated tetraploid clones but these events have been rare.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 97 , 68–79.     

The systematics of Australian Daphnia and Daphniopsis (Crustacea: Cladocera): a shared phylogenetic history transformed by habitat-specific rates of evolution

This study examines the molecular‐genetic divergence and evolution of Australian aquatic micro‐Crustacea Daphnia and Daphniopsis. The results indicate that species of Daphniopsis are accommodated within the genus Daphnia. Although their phyletic integrity is no longer supported, all Daphniopsis species (save one from North America) form a monophyletic group and may warrant subgeneric recognition pending further systematic investigations. A total of five lineages are shown to occupy Australian inland waters, including an endemic subgenus (Australodaphnia) and representatives of the subgenus Ctenodaphnia. The subgenera (Daphnia and Hyalodaphnia) that dominate the North American fauna are absent in Australia. The large extent of sequence divergence among major groups suggests that continental isolation has helped shape the early evolution of daphniids. More recent speciation is also evident, particularly by the Daphnia carinata species complex, whose numbers have grown to 13 members by the addition of a species previously assigned to the nominal subgenus and species yet to be formally described. The molecular data provide more evidence that the colonization of distinct habitats and ecological settings is a key factor in spurring diversification in the genus, while also modulating the pace of molecular evolution. This study attributes habitat‐specific molecular clocks to the intense ultraviolet (UV) exposure in both saline and transparent oligohaline waters. Adaptations to these harsh environments by at least four independent lineages include the convergent acquisition of a melanic carapace. Yet some lineages, clearly under mutational duress, lack this commonly acquired protective trait. There are numerous adaptive lines of defense against UV damage, including the complex regulatory mechanisms required to initiate a cellular response to guard and repair DNA. Functional molecular studies may soon challenge a notion built on morphology that convergence is the general directive to Daphnia’s ecological and evolutionary success. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society, 2006, 89 , 469–488.     

The feeding mechanisms of the Daphniidae (Crustacea: Cladocera): recent suggestions and neglected considerations

While the importance of grazing by anomopod cladocerans of thefamily Daphniidae on crops of planktonic algae and bacteria,and on detritus, is widely recognized, and although many calculationshave been made on the filtering rate of these crustaceans, thefeeding mechanisms involved in these processes have frequendybeen misinterpreted by ecologists. Recent accounts that purportto describe the feeding mechanism of Daphnia are based on misinterpretationsof morphology and are completely erroneous. The ancestors ofdaphniids were probably benthic, littoral animals, similar invarious respects to primitive represcritatives of extant chydoridsand macrothricids. The feeding mechanisms of the latter giveuseful indications of the kind of device from which that ofthe daphniids probably arose. The daphniid mechanism was derivedby restricting particle abstraction to trunk limbs 3 and 4.Contraiy to recent claims, mink limbs 1 and 2 are not involvedin this element of the feeding process. Comparative studieson many anomopods reveal invariable correlations. Species employingcurrents to cany food particles have filter plates bearing filtratorysetules. Species that, for whatever reason, do not employ currents,except sometimes for respiration, have homologous structuresthat lack filtratory setules, even when, as is often the case,they feed on particulate matter. Comparisons with other branchiopodsare also helpful.     

On the occurrence of males and production of ephippial eggs in populations of Daphniopsis studeri (Cladocera) in lakes of the Vestfold and Larsemann Hills, East Antarctica

Populations of the cladoceran Daphniopsis studeri Rühe in freshwater and brackish lakes of eastern Antarctica have been thought to consist solely of females that reproduce parthenogenetically by the production of ameiotic subitaneous eggs. This note reports the presence of male D. studeri and the production of ephippial (sexual) eggs in a number of lakes of the Vestfold and Larsemann Hills, which indicate the possibility of sexual reproduction within these populations. Received: 12 May 1997 / Accepted: 8 September 1997     

Garra tibanica ghorensis subsp.nov. (Pisces: Cyprinidae), an African element in the cyprinid fauna of the Levant

Garra tibanica ghorensis subsp. nov. is described from the southern Dead Sea Valley. In the Levant it represents the only cyprinid fish with African affinities known to date. It is suggested that G. t. ghorensis reached the area of its present distribution from the south and is not to be regarded as a relict of an earlier migration of the species to Africa via the Levant.Results of the travels of R. Kinzelbach to the countries of the Middle East, No. 18.Results of the travels of R. Kinzelbach to the countries of the Middle East, No. 18.     

Morphology and age variability of Daphnia galeata Sars (Cladocera: Daphniidae) in two adjacent water bodies of the Kola Peninsula

The morphology and age variability of Daphnia galeata Sars (Cladocera: Daphniidae) in two adjacent water bodies of the Kola Peninsula are studied. The reliability of characters usually used for diagnosis of adult individuals of the given species was verified, and their formation in the postembryonic period was traced. If the identification of D. galeata from Lake Bolshoi Vudvyar caused no doubts, the population from Lake Malyi Vudvyar was atypical with respect to several morphological characters. We concluded that plastic characters, such as body shape, as well as the shape of the dorsal crest and helmet on the head are unreliable for distinguishing closely related species of water fleas. At the same time, some small-size characters, for instance, the relative depth of the medial crest on the posterior side of the head, allow us to diagnose this species with confidence.     

Other environmental factors affect the size of crests developed by Daphnia carinata (Cladocera: Daphniidae) in response to notonectid predators

SUMMARY. 1. Crest size and body size was measured in Daphnia carinata King sampled from field enclosures in which environmental conditions and notonectid predator ( Anisops Hyperion Kirkaldy) levels had been manipulated, and from control treatments which had predator levels and other environmental factors equivalent to those in the natural environment.
2. Individuals of D. carinata developed larger crests in treatments with predators than in treatments without predators.
3. The environmentally manipulated treatment was considered to have lower levels of food but was also likely to have undergone other changes in physicochemistry and resource variability that may have affected crest size. The effect of the manipulation cannot be confirmed, therefore, as the result of variation in food levels. Animals in the treatments considered to have lower amounts of food had smaller crests than in the control treatment irrespective of whether predators were present. The effects of environmental manipulation and predators were additive.
4. Enclosures without predators, but in which water from the natural, predator-rich, environment was exchanged through the enclosure walls, showed no evidence of a chemical induction effect. Chemical induction effects may have been countered by a reduced food supply resulting from the higher D. carinata population densities that developed in these enclosures.
5. This work provides a second example of an alteration of the morphological response of daphnid prey to predators by environmental factors, probably food, and suggests this phenomenon may be general in cladoceran species displaying predator-induced changes in morphology.     

Photoperiod and temperature as inducers of gamogenesis in a dicyclic population of Scapholeberis armata Herrick (Crustacea: Cladocera: Daphniidae)

The induction of gamogenesis in a dicyclic population of Scapholeberis armata from a small pond at 40° N in Pennsylvania, USA, was studied. Animals were collected at the time of gamogenesis in mid-October (fall) 1988 and early June (spring) 1989). 10 clones were established from isolated females for each season and maintained at low density under standard conditions of 20 °C and 13.5L/10.5D, with Chlamydomonas reinhardtii diluted with pond water to 3 · 105 cells ml^–1 as a food source. For each clone, mothers of pairs of test animals were acclimated to 4 sets of conditions: 20 °C/15.5L (spring), 15 °C/11.5L (fall), 20 °C/11.5L (control), and 15 °C/15.5L. Test animals were observed bidaily or daily for up to 37 days. Occurrence of molts and of parthenogenetic broods or ephippia was recorded. At short photoperiod, ephippial females developed, usually after one or more parthenogenetic broods, among both spring and fall animals. The response was stronger (higher % sexual females) among fall clones, and was enhanced in both groups by 15 °C water. No animals responded to long photoperiod in warm or cool water. It is likely that additional factors, such as prior photoinduction, rapid depletion of food supply, and increased inter-animal contact due to high population density are required for the induction of spring gamogenesis. Differences in the responsiveness of spring and fall clones to inducing conditions suggest some differences in genotypes of spring and fall subpopulations in this pond. It is proposed that variable responses among genotypes to factors inducing gamogenesis may be the basis for the differences and clines in the timing of gamogenesis found among ecologically and latitudinally separated populations.     

The biogeographical affinities of the fauna in episodically filled salt lakes: A study of Lake Eyre South,Australia

Lake Eyre South, a large and normally dry playa in central Australia, filled with water in January 1984. Water persisted until January 1985. Salinity rose between these dates from 25 to > 270. Monthly observations on the fauna were made to determine if it consisted of widely dispersed species, and thus to test the assumption that episodically filled salt lakes are unimportant as evolutionary loci for the fauna of salt lakes. It was concluded that most species in the lake were indeed widely dispersed. Particularly common components of the fauna were: Craterocephalus eyresii (Steindachner) (fish), an undescribed species of Diacypris (ostracod), Moina baylyi Forró (cladoceran), Tanytarsus barbitarsis Freeman (chironomid), Parartemia minuta Geddes (anostracan), and Microcyclops platypus (Kiefer) (copepod).