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Abstract
The serrulatus-group (genus Eucyclops, Eucyclopinae, Cyclopidae), which includes species having a 12-segmented antennule possessing a smooth hyaline membrane on its distal three segments, caudal rami of moderate length (l/w ratio 3.5-7), and a strong inner spine on P5, is here defined and described. The species of this group also share a particular set of microcharacters on the coxopodite of P4 and on the basipodite of the antenna, which in particular includes one or two groups of fine setae (= hair-like setae) on the distal part of the caudal side. A simple numerical mapping of these microcharacters is proposed. Examination of Eucyclops populations collected from many locations all over the world that were identified as Eucyclops cf. serrulatus provided a set of morphological variations that allowed us to define the morphological characteristics within the serrulatus-group. Based on this definition of the species group, we give the composition of the E. serrulatus group, currently represented by 17 species and subspecies. The description of some taxa of this group is completed in particular with the microcharacters of the antennary basipodite and the P4 coxopodite. The taxonomic status of some other taxa, until now related to E. serrulatus, is changed as: E. agiloides roseus Ishida, 1997 (n. comb.); E. macrurus baikalocorrepus Mazepova, 1955 (n. comb.); and a key to the species of the Eucyclops serrulatus group is provided.
From our observations, we were able to establish that the distribution of Eucyclops serrulatus (Fischer, 1851) sensu stricto is restricted to the Palaearctic region. Previous data on geographical distribution of the species outside this area are critically analysed. It is hypothesized that records of E. serrulatus from Japan, Australia, North America, and other zoogeographical zones, could be a result of recent invasions, possibly via human activities in relation to ship transport.
Abstract
Several independent methods: molecular-genetic, biogeographical, and morphological analyses — were applied to explain the origin of the continental calanoid fauna and the distribution of their recent genera. The theory of Continental Drift and the evolution of the Tethys Sea were also used for that purpose. The molecular-genetic-based phylogenetic tree that we constructed, as well as the largest number of genera and species in Diaptomidae, allow us to support the idea that this family of fresh- and brackishwater Copepoda arose earlier than the Temoridae and Centropagidae. The ancestors of the Diaptomidae likely invaded, and were distributed across, the supercontinent Pangaea before its division into two continental plates in the Mesozoic Era, i.e., not later than 180-200 Ma. Therefore, various genera of this family can be found almost everywhere on all continents, except Antarctica. The family Temoridae is known only from Europe, Asia and North America. These three continental plates stayed together long after separation of Pangaea into two parts: Laurasia and Gondwana (until circa 50 Ma). At approximately the same time (50 Ma), the genus Eurytemora should have been created, as its representatives are known from North America and Eurasia. The family Centropagidae seems to have invaded inland waters somewhere between Temoridae and Diaptomidae, as its representatives can be found on all continents except Africa. Also, as a possibly alternative option, this centropagid invasion could have happened independently in the northern and southern Pangaea blocks, by different marine ancestors, at the same time as Temoridae, as is shown herein in the molecular-genetic-based phylogenetic tree. Using the evolution model of the Tethys Sea proved to be very productive for explaining the modern ranges of continental calanoids, both within families and in individual genera, including the genus Eurytemora.
In:
Crustaceana
Proceedings of the Eurytemora Conference, St. Petersburg, 2019
This monograph is a summary of the conference on Eurytemora, gathering renowned researchers from all over the world to discuss new advances in Phylogeny, Biogeography, Taxonomy, and Ecology of this important group of estuarine crustaceans, held the 13-17 May 2019 in St. Petersburg, Russia. The present volume includes 17 selected papers, in which you will discover new aspects of the modern theory on the history and recent geographical distribution (biogeography) of an important group of estuarine crustaceans, revealing coincidences with a modern model of continental drift. The researchers suggest a new hypothesis on time and place of origin of continental calanoid copepods. The specialists show that studying external morphology in detail helps to increase identification and differentiation between closely related sibling species within the Eurytemora group. Several ecological questions on invasive and pseudocryptic copepod species are debated. Finally, the last chapter of this monography is devoted to taxa related to the Eurytemora group, Epischura, Temora, Temoropia, and Pseudodiaptomus.
First published as a Special Issue of Crustaceana 93(3-5): 241-547.
First published as a Special Issue of Crustaceana 93(3-5): 241-547.
Proceedings of the Eurytemora Conference, St. Petersburg, 2019
This monograph is a summary of the conference on Eurytemora, gathering renowned researchers from all over the world to discuss new advances in Phylogeny, Biogeography, Taxonomy, and Ecology of this important group of estuarine crustaceans, held the 13-17 May 2019 in St. Petersburg, Russia. The present volume includes 17 selected papers, in which you will discover new aspects of the modern theory on the history and recent geographical distribution (biogeography) of an important group of estuarine crustaceans, revealing coincidences with a modern model of continental drift. The researchers suggest a new hypothesis on time and place of origin of continental calanoid copepods. The specialists show that studying external morphology in detail helps to increase identification and differentiation between closely related sibling species within the Eurytemora group. Several ecological questions on invasive and pseudocryptic copepod species are debated. Finally, the last chapter of this monography is devoted to taxa related to the Eurytemora group, Epischura, Temora, Temoropia, and Pseudodiaptomus.
First published as a Special Issue of Crustaceana 93(3-5): 241-547.
First published as a Special Issue of Crustaceana 93(3-5): 241-547.
Abstract
Epischura baikalensis Sars is a dominant pelagic species of the Lake Baikal zooplankton. We empirically determined the duration of the development of Epischura from field data, as it is not possible to determine this experimentally. Based on our data, we conclude that the central pelagic food web of metazoan species in Lake Baikal has not two, as was previously accepted, but three generations during a year and each lasts not 6 but instead 3 to 4 months. The life cycle of the species also possibly includes a 3-months long winter embryonic diapause, starting in November and ending in late February with the start of the under-ice algae bloom. The high nauplii density in spring is not the result of high adult density, suggesting the presence of resting eggs in the E. baikalensis life cycle. We also found a large morphological difference between the pelagic eggs of the species in the winter and in the summertime. The possible participation of diatom algal toxins in the regulation of the seasonal dynamics of their main consumer in Lake Baikal, similar to those known in marine ecosystems, is discussed. The population dynamics in a year with relatively low diatom algae density show four peaks of reproduction, i.e., in February, June, September, and December. In years with significant (more than 15 000 cells/l) diatom blooming we found mass mortality of E. baikalensis juveniles in the plankton, with only two clear peaks of nauplii density. A negative correlation was found between the number of population density peaks for E. baikalensis and the spring-blooming of diatom algae.
Abstract
Several independent methods: molecular-genetic, biogeographical, and morphological analyses — were applied to explain the origin of the continental calanoid fauna and the distribution of their recent genera. The theory of Continental Drift and the evolution of the Tethys Sea were also used for that purpose. The molecular-genetic-based phylogenetic tree that we constructed, as well as the largest number of genera and species in Diaptomidae, allow us to support the idea that this family of fresh- and brackishwater Copepoda arose earlier than the Temoridae and Centropagidae. The ancestors of the Diaptomidae likely invaded, and were distributed across, the supercontinent Pangaea before its division into two continental plates in the Mesozoic Era, i.e., not later than 180-200 Ma. Therefore, various genera of this family can be found almost everywhere on all continents, except Antarctica. The family Temoridae is known only from Europe, Asia and North America. These three continental plates stayed together long after separation of Pangaea into two parts: Laurasia and Gondwana (until circa 50 Ma). At approximately the same time (50 Ma), the genus Eurytemora should have been created, as its representatives are known from North America and Eurasia. The family Centropagidae seems to have invaded inland waters somewhere between Temoridae and Diaptomidae, as its representatives can be found on all continents except Africa. Also, as a possibly alternative option, this centropagid invasion could have happened independently in the northern and southern Pangaea blocks, by different marine ancestors, at the same time as Temoridae, as is shown herein in the molecular-genetic-based phylogenetic tree. Using the evolution model of the Tethys Sea proved to be very productive for explaining the modern ranges of continental calanoids, both within families and in individual genera, including the genus Eurytemora.
Abstract
Epischura baikalensis Sars is a dominant pelagic species of the Lake Baikal zooplankton. We empirically determined the duration of the development of Epischura from field data, as it is not possible to determine this experimentally. Based on our data, we conclude that the central pelagic food web of metazoan species in Lake Baikal has not two, as was previously accepted, but three generations during a year and each lasts not 6 but instead 3 to 4 months. The life cycle of the species also possibly includes a 3-months long winter embryonic diapause, starting in November and ending in late February with the start of the under-ice algae bloom. The high nauplii density in spring is not the result of high adult density, suggesting the presence of resting eggs in the E. baikalensis life cycle. We also found a large morphological difference between the pelagic eggs of the species in the winter and in the summertime. The possible participation of diatom algal toxins in the regulation of the seasonal dynamics of their main consumer in Lake Baikal, similar to those known in marine ecosystems, is discussed. The population dynamics in a year with relatively low diatom algae density show four peaks of reproduction, i.e., in February, June, September, and December. In years with significant (more than 15 000 cells/l) diatom blooming we found mass mortality of E. baikalensis juveniles in the plankton, with only two clear peaks of nauplii density. A negative correlation was found between the number of population density peaks for E. baikalensis and the spring-blooming of diatom algae.
In:
Crustaceana