Henri J. Dumont

The dry weight estimate of biomass in a selection of Cladocera, Copepoda and Rotifera from the plankton, periphyton and benthos of continental waters

SummaryA procedure for determining dry weights has been standardized and applied to a number of Cladocera, Copepoda and Rotatoria. In most of the Cladocera, regression equations of the exponential type, relating dry weight to body length, were computed. In the Copepoda, one equation per suborder was computed, and suggestions for future refinements are made. In both groups, a fairly satisfactory agreement was found with literature data where these exist. In both groups, the egg and embryo weight proved to be considerable, relative to the weight of the adult female. In Rotatoria, 4 species could be dealt with in size-classes, and their weight increment per unit length was found to be lower than in the Cladocera and Copepoda. A large number of species were weighed as adults only. A conclusion applicable to the 3 groups is that, as a rule, limnetic species weigh relatively less than littoral, periphytic or benthic species. Even within a species, populations with a more pronounced limnetic way of life weigh less than populations of littoral nature.

Biogeography of rotifers

The biogeography of rotifers is discussed in light of general biogeographical concepts. It is argued that, in spite of considerable abilities for passive dispersal, vicariance can develop well in this group. Examples selected from the Branchionidae illustrate the high levels of endemicity found in Australia and South America, while the Indian subcontinent and Africa have a predominantly cosmopolitan fauna. An explanation for these patterns is found in drifting continents and Pleistocene climatic changes.

On the diversity of the Cladocera in the tropics

The mythical concept of an impoverished tropical cladoceran fauna is refuted. On a planetary scale, around half of the cladoceran species presently known occur exclusively in the tropics-subtropics, often with considerable restriction to particular geographical subzones. On a regional (political) scale, the situation is often unclear because of the continued fragmentary nature of studies, and because political units are not a good basis for biogeographical comparisons. At the finest level of resolution (lake-perlake comparisons), there appears to be an upper limit of c. 50 cladoceran species per individual lake. No significant difference between lakes in the temperate zone and in the tropics could be established here. Daphnia is largely absent from the tropics, but is replaced by more Sidids, Moinids, and Bosminids, such that the average cladoceran community in the limnetic zone of a tropical lake is not characterized by less species but rather by lower population densities. This, in turn, is considered a consequence of higher prevalent predation levels in the tropics.

Invasion of the Caspian Sea by the Comb Jellyfish Mnemiopsis Leidyi (Ctenophora)

Vladimir P. Ivanov1, Andrey M. Kamakin1, Vladimir B. Ushivtzev1, Tamara Shiganova5, Olga Zhukova1, Nikolay Aladin2, Susan I. Wilson3, G. Richard Harbison4 & Henri J. Dumont6,∗ 1CaspNIRH, Astrakhan, Russia; 2Brackish Water Laboratory, Russian Academy of Sciences, St.-Petersburg, Russia; 3School of Biology and Biochemistry, Queens University, Belfast, UK; 4Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, USA; 5P.P. Shirshov Institute of Oceanology, Russian Academy of Sciences, Moscow, Russia; 6Laboratory of Animal Ecology, Ghent University, Belgium; ∗Author for correspondence (e-mail: Henri.Dumont@rug.ac.be)

A molecular phylogeny of the Odonata (Insecta)

Abstract. We estimated the phylogeny of the order Odonata, based on sequences of the nuclear ribosomal genes 5.8 S, 18S, and ITS1 and 2. An 18S‐only analysis resolved deep relationships well: the order Odonata, as well as suborders Zygoptera and Epiprocta (Anisoptera + Epiophlebia), emerged as monophyletic. Some other deep clades resolved well, but support for more recently diverged clades was generally weak. A second, simultaneous, analysis of the 5.8S and 18S genes with the intergenic spacers ITS1 and 2 resolved some recent branches better, but appeared less reliable for deep clades with, for example, suborder Anisoptera emerging as paraphyletic and Epiophlebia superstes recovered as an Anisopteran, embedded within aeshnoid‐like anisopterans and sister to the cordulegastrids. Most existing family levels in the Anisoptera were confirmed as monophyletic clades in both analyses. However, within the corduliids that form a major monophyletic clade with the Libellulidae, several subclades were recovered, of which at least Macromiidae and Oxygastridae are accepted at the family level. In the Zygoptera, the situation is complex. The lestid‐like family groups (here called Lestomorpha) emerged as sister taxon to all other zygopterans, with Hemiphlebia sister to all other lestomorphs. Platystictidae formed a second monophylum, subordinated to lestomorphs. At the next level, some traditional clades were confirmed, but the tropical families Megapodagrionidae and Amphipterygidae were recovered as strongly polyphyletic, and tended to nest within the clade Caloptera, rendering it polyphyletic. Platycnemididae were also non‐monophyletic, with several representatives of uncertain placement. Coenagrionids were diphyletic. True Platycnemididae and non‐American Protoneurids are closely related, but their relationship to the other zygopterans remains obscure and needs more study. New World protoneurids appeared relatively unrelated to old world + Australian protoneurids. Several recent taxonomic changes at the genus level, based on morphology, were confirmed, but other morphology‐based taxonomies have misclassified taxa considered currently as Megapodagrionidae, Platycnemididae and Amphipterygidae and have underestimated the number of family‐level clades.

Phylogenetic relationships, divergence time estimation, and global biogeographic patterns of calopterygoid damselflies (odonata, zygoptera) inferred from ribosomal DNA sequences.

The calopterygoid superfamily (Calopterygidae + Hetaerinidae) is composed of more than twenty genera in two families: the Calopterygidae (at least 17) and the Hetaerinidae (at least 4). Here, 62 calopterygoid (ingroup) taxa representing 18 genera and 15 outgroup taxa are subjected to phylogenetic analysis using the ribosomal 18S and 5.8S genes and internal transcribed spacers (ITS1, ITS2). The five other families of calopterid affinity (Polythoridae, Dicteriadidae, Amphipterygidae, Euphaeidae, and Chlorocyphidae) are included in the outgroup. For phylogenetic inference, we applied maximum parsimony, maximum likelihood, and the Bayesian inference methods. A molecular phylogeny combined with a geographic analysis produced a well-supported phylogenetic hypothesis that partly confirms the traditional taxonomy and describes distributional patterns. A monophyletic origin of the calopterygoids emerges, revealing the Hetaerinid clade as sister group to the Calopterygidae sensu strictu. Within Calopterygidae, seven clades of subfamily rank are recognized. Phylogenetic dating was performed with semiparametric rate smoothing by penalized likelihood, using seven reference fossils for calibration. Divergence time based on the ribosomal genes and spacers and fossil constraints indicate that Calopteryginae (10 genera, approximately 50% of all Calopterygid taxa studied here), Vestalinae (1 genus), and Hetaerinidae (1 genus out of 4 studied here) started radiating around 65 Mya (K/T boundary). The South American Iridictyon (without distinctive morphology except for wing venation) and Southeast Asian Noguchiphaea (with distinctive morphology) are older (about 86 My) and may be survivors of old clades with a Gondwanian range that went extinct at the K/T boundary. The same reasoning (and an even older age, ca. 150 My) applies to the amphipterygids Rimanella and Pentaphlebia (South America-Africa). The extant Calopterygidae show particular species and genus richness between west China and Japan, with genera originating between the early Oligocene and Pleistocene. Much of that richness probably extended much wider in preglacial times. The Holarctic Calopteryx, of Miocene age, was deeply affected by the climatic cooling of the Pliocene and by the Pleistocene glaciations. Its North American and Japanese representatives are of Miocene and Pliocene age, respectively, but its impoverished Euro-Siberian taxa are late Pliocene-Pleistocene, showing reinvasion, speciation, and introgression events. The five other calopterid families combine with the Calopterygidae and Hetaerinidae to form the monophyletic cohort Caloptera, with Polythoridae, Dicteriadidae, and Amphipterygidae sister group to Calopterygoidea. The crown node age of the latter three families has an age of about 157 My, but the Dicteriadidae and Polythoridae themselves are of Eocene age, and the same is true for the Euphaeidae and Chlorocyphidae. The cohort Caloptera itself, with about 197 My of age, goes back to the early Jurassic.

Rotifera of some lakes in the floodplain of the River Niger (Imo State, Nigeria) II. Faunal composition and diversity

The rotifer fauna of thirteen freshwater habitats in the lower Niger delta is commented upon. A total of 207 species of monogonont rotifers is recorded. The most diverse genus is Lecane with 59 species. Ten species appear to be endemic to the lower Niger delta, another 3 are restricted to Central and/or West Africa. Eleven taxa had ranges encompassing the Oriental and African regions, and six occur both in America and the study region. Three of the latter may represent recent introductions to the African continent.Two lakes (Iyi-Efi and Oguta), with 136 and 124 species on record, rank among the richest rotifer environments ever studied. It is hypothesized that (sub)tropical floodplains are the worlds richest habitats for rotifers.

The distribution and ecology of the fresh- and brackish-water medusae of the world

Limnocnida and Craspedacusta are the two main genera of Cnidaria from continental waters which have a free-swimming medusa in their life cycle. Both originated in tropical-subtropical Asia, but Limnocnida is also found in Africa, with one species (L. tanganjicae) perhaps endemic to lake Tanganyika. Halmomises from Trinidad, and two genera (Mansariella, Keralica) from India have limited ranges. No freshwater medusae evolved in Europe and the Americas (aside from Trinidad), but Craspedacusta sowerbii, by virtue of its drought resistant stages, has managed to colonise all continents, except Antarctica, in the course of the twentieth century. In all, there are about 10–14 freshwater species of medusae. An additional 4–5 species of Moerisia, Australomedusa, and Craspedacusta are sequestered in continental salt-lakes, while a few genera occur in brackish-water seas and estuaries (e.g. Moerisia, Odessia, Ostroumovia). This reduced diversity is probably due to (1) a rarity of drought resistant stages, adjusted to upstream dispersal, in the life cycle, and (2) difficulties to adapt the osmoregulatory system to a hypotonic environment.The feeding ecology of the freshwater medusae is also examined. Like all Cnidaria, they are opportunistic predators. However, fish egg predation might be their major means of subsistence, other types of food being taken only occasionally, or when fish eggs and larvae are scarce. Their impact on the true zooplankton might therefore be limited to short pulses of planktivory. Whether they are themselves limited by predation remains to be studied; many fish in the invasive part of their range avoid them, but some macrocrustaceans readily consume them. It is hypothesized that this might explain their success in Lake Tanganyika, and their absence from lake Baical. Finally, the absence of endemic species from South America could relate to the great diversity bf small-sized predatory aquatic reptiles on this subcontinent.

Aquatic Invasions in the Black, Caspian, and Mediterranean Seas

Preface H.J. Dumont, T.A. Shiganova, U. Niermann. 1: Mnemiopsis leidyi, Beroe cf ovata, and their interaction. 1. Mnemiopsis leidyi: distribution and effect on the Black Sea ecosystem during the first years of invasion in comparison with other gelatinous blooms U. Niermann. 2. Interactions between the invading Ctenophores Mnemiopsis leidyi (A. Agassiz) and Beroe cf ovata Mayer 1912, and their influence on the Pelagic Ecosystem of the Northeastern Black Sea T.A. Shiganova, et al. 3. Population dynamics of Mnemiopsis leidyi in the Caspian Sea, and effects on the Caspian ecosystem T.A. Shiganova, et al. 4. Distribution and biology of Mnemiopsis leidyi in the northern Aegean Sea, and comparison with the indigenous Bolinopsis vitrea T.A. Shiganova, et al. 5. Effects of Beroe cf ovata on gelatinous and other zooplankton along the Bulgarian Black Sea coast L. Kamburska. 6. Decreased levels of the invasive ctenophore Mnemiopsis in the Marmara Sea in 2001 M. Isinibilir, et al. 7. Preliminary investigation on the molecular systematics of the invasive ctenophore Beroe ovata K.M. Bayha, et al. 8. Support for the position that a deliberate introduction of Beroe cf ovata to the Caspian Sea will control the local population of Mnemiopsis leidyi S.P. Volovik, I.G. Korpakova. 9. Feeding, respiration and growth of the Ctenophore Beroe cf ovata in the conditions of low salinity of the Caspian Sea A.E. Kideys, et al. 10. A brief resume of the status of the Mnemiopsis population in the Turkmen sector ofthe Caspian Sea according to observations during the first half of 2002 F.M. Shakirova. 11. Dynamics of Mnemiopsis distribution in the Azerbaijan sector of the Caspian Sea in 2001 - 2002 Z.M. Kulijev. 12. Investigation on distribution and biomass of Mnemiopsis in the Kazakhstan sector of the Caspian Sea in May 2002 Y.A. Kim, et al. 2: Ponto-Caspian species invading Europe: information networking. 13. Range extensions of Ponto-Caspian aquatic invertebrates in Continental Europe H.A.M. Kentelaars. 14. Living in a sea of exotics - the Baltic case E. Leppakoski. 15. Internet-based information resources of aquatic alien species relevant to the Ponto-Caspian region V.E. Panov. 3: Other Mediterranean Invaders. 16. Invasion of the jellyfish Pelagia noctiluca in the Northern Adriatic: a non-success story A. Malej, A. Malej Jr. 17. Caulerpa taxifolia: 18 years of infestation in the Mediterranean Sea T. Thibaut, A. Meinesz. 4: Conclusions from the Meeting. 18. Henri J. Dumont, Tamara A. Shiganova & Ulrich Niermann. Index.

Crustacean species richness in temporary pools: relationships with habitat traits

We examined species richness separately for cladocerans and ostracods in 52 temporary pools in a small geographical area, relating species richness with habitat traits using multiple regressions. Habitat traits considered included surface area, water depth, permanence and sediment depth. Permanence was an important predictor of species richness of both cladocerans and ostracods. Additionally, variation in ostracod species richness was significantly explained by water depth (negative relationship) and sediment depth (positive relationship). Surface area was not a statistically significant factor in any of our analyses. The importance of permanence supports the hypothesis that extinction due to pool drying is a major driving force behind the structuring of microcrustacean communities in temporary pools.