Distribution patterns of the Diaptomidae (Calanoida: Copepoda) in southern Africa

All freshwater calanoids in southern Africa belong to the family Diaptomidae of which there are two subfamilies, the Paradiaptominae (Lovenula, Paradiaptomus and Metadiaptomus) and Diaptominae (Tropodiaptomus and Thermodiaptomus). The Paradiaptominae are endemic to Africa, while the Diaptominae have one endemic African genus Thermodiaptomus, and the other genus Tropodiaptomus, occurs in other parts of the world as well as Africa. Knowledge of distribution of the Diaptomidae has been hampered by incomplete taxonomic knowledge and lack of co-ordination of available information. Distribution patterns of 19 described species and 11 new species confirm that the majority of species have a limited distribution, and that the Paradiaptominae are arid-adapted and belong to temporary pool communities. Six species are endemic to coastal pans and vleis of the western and southern Cape Province. Only those species with a wider distribution have been recorded as colonising man-made lakes. The four Lovenula species are predators and often co-exist with a Metadiaptomus species as prey. Synapomorphies of widely separated species of the Paradiaptominae, provide interesting insights into how their evolution may have been governed by vicariance, dispersal and palaeoenvironments of the African continent.     

Redescription and distribution of Mastigodiaptomus montezumae (Copepoda, Calanoida, Diaptomidae) in Mexico

Mastigodiaptomus montezumae is redescribed on the basis of material from several localities in Mexico. It is characterized by an asymmetrical fifth pediger in both sexes. It appears to be restricted to central Mexico, where it is quite common. It is associated with M. albuquerquensis and occasionally with L. siciloides and Leptodiaptomus novamexicanus.     

Importance of the genital operculum in the taxonomy of South American Diaptomidae (Copepoda,Calanoida)

For the first time, the structures of the female genital field are described and compared among ten species of Venezuelan diaptomids. A nomenclature for these structures is suggested, and there is a preliminary report on the interspecific differences observed in one of these structures, the genital operculum.     

The biogeography of three Boeckella species (Copepoda: Calanoida) in New Zealand

The New Zealand distributions of three species of Boeckella (Copepoda, Calanoida), B. triarticulata, B. dilatata and B. hamata are mapped. B. triarticulata is primarily a pond dweller but is also found in reservoirs and shallow lakes. B. dilatata is mainly found in the deeper glacial lakes and ponds in the central region of the South Island and B. hamata has a more widespread distribution in lakes and ponds in the South Island and lower half of the North Island. Differences in temperature optima, food requirements and dispersal ability among the three Boeckella species are related to vicariant events to explain their distribution in New Zealand.     

Deep genetic divergences among morphologically similar and parapatric Skistodiaptomus (Copepoda: Calanoida: Diaptomidae) challenge the hypothesis of Pleistocene speciation

We used mitochondrial [cytochrome c oxidase subunit I (CO I ), cytochrome b , and 16S] and nuclear [internal transcribed spacer (ITS) phylogenies of Skistodiaptomus copepods to test hypotheses of Pleistocene divergence and speciation within the genus. Mitochondrial (mt)DNA sequence divergences do not support hypotheses for Pleistocene speciation and instead suggest much more ancient speciation events in the genus. Skistodiaptomus oregonensis and Skistodiaptomus pygmaeus (i.e. two morphologically similar and parapatric species) exhibited uncorrected mtDNA sequence divergences exceeding 20%. Similarly, we identified three divergent clades of Skistodiaptomus pallidus that exhibited mtDNA sequence divergences exceeding 15%, suggesting that even intraspecific divergence within this morphospecies predates the Pleistocene. We found clear evidence of CO I pseudogenes in S. pygmaeus , but their presence did not lead to significant overestimates of sequence divergences for this gene. Substitution saturation and strong purifying selection have most likely led to underestimates of sequence divergences and divergence times among Skistodiaptomus . The widespread phenomenon of morphological stasis among genetically divergent copepod groups indicates that speciation often occurs with little or no morphological change. Instead, morphological evolution may occur idiosyncratically after speciation and create discordant patterns of morphological similarity, shared ancestry and divergence time. Cryptic species complexes are therefore common in copepods, and morphological species concepts underestimate their true species diversity.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 150–165.     

A genetic determination of cryptic species (Copepoda: Calanoida) and their postglacial biogeography in North America

Allozyme electrophoresis of Hesperodiaptomus arcticus (Marsh) sensu lato at subarctic Churchill, Canada revealed significant deviations from random mating in several populations, as shown by the complete absence of certain heterozygous types. A broad geographic survey of 20 enzyme loci in 1077 individuals from 27 ponds at 11 arctic and alpine sites west of Hudson Bay demonstrated that there were three genetically distinct types. Morphological analysis of genetically classified populations uncovered consistent morphological differences that had been ignored previously. These morphological characteristics were used to reclassify preserved museum and private specimens from additional sites from the entire North American distribution of H. arcticus sensu lato. A detailed study of two of the distinct types co-occurring at Churchill showed reproduction timing and habitat differences consistent with reproductive isolation. I concluded that there are three species and each have different distributions. Most regions examined must have been repopulated by dispersal from glacial refugia after deglaciation. The nominal species is apparently restricted to western arctic localities in the vicinity of the Alaskan refugium while the other two putative taxa have dispersed widely into previously glaciated regions.     

A new Hesperodiaptomus Light (Copepoda, Calanoida, Diaptomidae) from Mexico with comments on the distribution of the genus

A new species of the freshwater planktonic copepod genus Hesperodiaptomusis described from material collected in several water bodiesin the state of Morelos, central Mexico. Hesperodiaptomus morelensisn. sp. differs from its congeners in having a very reduced endopodon the male fifth right leg, and a hook-shaped cuticular processon the inner margin of the first exopodal segment of the sameleg. Besides other characters of the female fifth legs, thenew species has a distinctive genital somite, with asymmetricallateral wing-like processes. This species seems to be closelyrelated to H. kiseri mainly because of similarities betweenthe male fifth legs and the structure of the female genitalsomite. This predominantly nearctic genus is known to be distributedmainly in north-western and central North America, althougha few species have been recorded in north-eastern Asia (Siberia).Hesperodiaptomus has not been recorded previously south of California.Apparently, this genus radiated in North America and spreadin different directions. The apparent disjunct distributionof at least two species (including the new one) could be explainedas resulting from a previous extensive radiation related toglaciation and consequent post-glacial repopulation that mighthave left these forms as stranded remnants, or by dispersalprocesses: central Mexico is connected with North America bytwo high-altitude potential passages. The new species seemsto be restricted to a high altitude area in Mexico. It seemsunlikely that species of Hesperodiaptomus will be recorded furthersouth on the American continent.     

Molecular phylogeny of the Calanoida (Crustacea: Copepoda)

The order Calanoida includes some of the most successful planktonic groups in both marine and freshwater environments. Due to the morphological complexity of the taxonomic characters in this group, subdivision and phylogenies have been complex and problematic. This study establishes a multi-gene molecular phylogeny of the calanoid copepods based upon small (18S) and large (28S) subunits of nuclear ribosomal RNA genes and mitochondrial encoded cytochrome b and cytochrome c oxidase subunit-I genes, including 29 families from 7 superfamilies of the order. This analysis is more comprehensive than earlier studies in terms of number of families, range of molecular markers, and breadth of taxonomic levels resolved. Patterns of divergence of ribosomal RNA genes are shown to be significantly heterogeneous among superfamilies, providing a likely explanation for disparate results of previous studies. The multi-gene phylogeny recovers a monophyletic Calanoida, as well as the superfamilies Augaptiloidea, Centropagoidea, Bathypontioidea, Eucalanoidea, Spinocalanoidea and Clausocalanoidea. The phylogeny largely agrees with previously-published morphological phylogenies, including e.g., enlargement of the Bathypontioidea to include the Fosshageniidae.     

Phylogeography of the African catfish,Chrysichthys maurus (Valenciennes, 1839)

Polymorphism at 19 allozyme loci was studied in 227 individuals of the catfish, Chrysichthys maurus (Valenciennes, 1839), collected from ten populations representing nine different river basins in west Africa. Eleven of the loci studied were polymorphic. Analysis showed that populations clustered according to their geographical origin: eastern populations close to the root represented by a population of a closely related species (C. auratus); then populations from the centre of the species' range, followed by the more western populations. Networks observed, regression of genetic distances versus geographical distances, results of the Mantel test as well as the apomorphic status of two alleles suggested that the genetic differentiation corresponds to an isolation by distance model. These results strongly suggest that the populations initially occurred in the lagoons and rivers of Ivory Coast and from here spread to the western part of the species' range by progressively colonising basins from east to west.     

Diversity and Distributional Patterns of Neotropical Freshwater Copepods (Calanoida: Diaptomidae)

The distributional patterns and diversity of the diaptomid calanoid copepods were analysed to assess the faunistic affinity of North and South America with respect to Mexico and Central America. In the Neotropical region, the most speciose genera of Diaptomidae are Leptodiaptomus and Mastigodiaptomus. The former genus is a Nearctic form, and Mastigodiaptomus is Neotropical. Based on the current distribution of their diversity, it is probable that these genera radiated into Mexico and Central America from North America and the insular Caribbean, respectively. Arctodiaptomus dorsalis is a primarily Palaearctic taxon, it is widely distributed between North and Central America. This species probably radiated in the Americas as a Tethyan derivate. Prionodiaptomus is the only member of the highly diverse South American diaptomid fauna that has expanded beyond the subcontinent. Despite the high diversity present in South America, its influence in Mexico and Central America appears to be weak; this is probably a consequence of the geologically recent union of the two main subcontinental landmasses. Mexico shares 33% of its species with NA, and no species are shared between NA and SA. For the Diaptomidae, the Nearctic influence is strongest in Mexico. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Overlooked cryptic endemism in copepods: Systematics and natural history of the calanoid subgenus Occidodiaptomus Borutzky 1991 (Copepoda,Calanoida, Diaptomidae)

Our comprehension of the phylogeny and diversity of most inland–water crustaceans is currently hampered by their pronounced morphological bradytely, which contributed to the affirmation of the “Cosmopolitanism Paradigm” of freshwater taxa. However, growing evidence of the existence of cryptic diversity and molecular regionalism is available for calanoid copepods, thus stressing the need for careful morphological and molecular studies in order to soundly investigate the systematics, diversity and distribution patterns of the group.Diaptomid copepods were here chosen as model taxa, and the morphological and molecular diversity of the species belonging to the west-Mediterranean diaptomid subgenus Occidodiaptomus were investigated with the aim of comparing the patterns of morphological and molecular evolution in freshwater copepods. Three species currently lumped under the binomen Hemidiaptomus (Occidodiaptomus) ingens and two highly divergent clades within H. (O.) roubaui were distinguished, thus showing an apparent discordance between the molecular distances recorded and Occidodiaptomus morphological homogeneity, and highlighting a noteworthy decoupling between the morphological and molecular diversity in the subgenus.Current Occidodiaptomus diversity pattern is ascribed to a combined effect of ancient vicariance and recent dispersal events. It is stressed that the lack of sound calibration points for the molecular clock makes it difficult to soundly temporally frame the diversification events of interest in the taxon studied, and thus to asses the role of morphological bradytely and of accelerated molecular evolutionary rates in shaping the current diversity of the group.     

Using 18S rDNA to resolve diaptomid copepod (Copepoda: Calanoida: Diaptomidae) phylogeny: an example with the North American genera

The phylogenetic relationships among the numerous genera of diaptomid copepods remain elusive due to difficulties in obtaining sufficient numbers of phylogenetically informative morphological characters for cladistic analysis. Molecular phylogenetic techniques offer high potential to resolve phylogenetic relationships in the absence of sufficient morphological characters because of the ease in which many characters can be unambiguously coded. I present the first molecular phylogeny for diaptomid copepod genera using 18S rDNA. Specifically, I test Light’s (1939) hypothesis regarding the interrelationships among the North American diaptomid genera. The 18S phylogeny is remarkably consistent with Light’s hypothesis. The endemic North American genera represent a monophyletic group exclusive of the non-endemic genera. Moreover, his hypothesized basal genus for the North America genera, Hesperodiaptomus, is the basal genus in this analysis. However, his Leptodiaptomus group is not reciprocally monophyletic with his Hesperodiaptomus group, but is rather a derived member of the latter group. Finally, the genus Mastigodiaptomus is found to be more closely allied with the non-endemic genera, as Light suggested. This phylogeny contributes heavily to the understanding of phylogenetic relationships among North American diaptomids and has large implications for the systematics of diaptomids in general. The use of 18S rDNA sequences in phylogenetic analyses of diaptomid copepods can be used to confirm the monophyly of recognized genera, the interrelationships among genera, and subsequent biogeographic interpretation of the family’s diversification. The use of molecular data, such as 18S rDNA sequences, to test phylogenetic hypotheses based on a very limited number of morphological characters will be a particularly useful approach to phylogenetic analysis in this system.     

Naupliar development of Acanthodiaptomus denticornis (wierzejski, 1887) and Arctodiaptomus alpinus (Imhof, 1885) (Copepoda: Calanoida) and a comparison with other Diaptomidae

The six naupliar instars of the two alpine species Aconthodiaptornusdenticornis and Arctodiaptomus alpinus are described and illustrated.Their external morphology is compared with that of all presentlyknown diaptomid nauplii in an attempt to provide usehl taxonomiccharacteristics to identify larval diaptomids. The larval stagesof the two species are remarkably similar in size and overallappearance, and show an identical pattern of limb setation throughoutthe whole development. Diagnostic characters are mainly relatedto the differentiation of antennules and caudal armature.     

Amended delimitation of Mongolodiaptomus against Neodiaptomus and Allodiaptomus and redescription of the little known Mongolodiaptomus uenoi (Kikuchi, 1936) from Thailand (Copepoda: Calanoida: Diaptomidae)

Mongolodiaptomus uenoi (Kikuchi, 1936), a little known diaptomid copepod from Taiwan and Indonesia, is re-described based on specimens from Thailand, and its relationship with its congeners is discussed. To clear up the generic confusion between the closely allied genera Mongolodiaptomus Kiefer, Neodiaptomus Kiefer and Allodiaptomus Kiefer, a new criterion relating to the armature of the second exopodite-segment of the male right P5 is introduced. Accordingly, some dubious species of Neodiaptomus and Allodiaptomus are transferred to Mongolodiaptomus.     

The freshwater Calanoida (Crustacea: Copepoda) of Thailand

14 Species of freshwater Calanoida in Thailand are reported in this study. The most common species is Neodiaptomus botulifer. Most of these belong to the Southeast Asian species, the remainder are either Indian or East Asian copepods. The zoogeographical demarcation of copepods in Thailand is not very distinct due to its interconnecting riverine and reservoir systems as well as frequent flood. The peculiarity of the Thai Calanoida and their distribution is discussed in a Southeast Asia context. A taxonomic key to the Thai Calanoida is formulated.     

The Malaysian Tropodiaptomus (Copepoda : Calanoida) and its distribution

In Peninsular Malaysia there are three species of Tropodiaptomus namely: T. hebereri Kiefer, T. ruttneri Brehm, and T. vicinus Kiefer. The last species is most common in swampy habitats along the west coast whereas T. ruttneri occurs only in the north and T. hebereri is present in the south. The affinity of the Malaysian tropodiaptomids and their Sunda counterparts is discussed.     

Oogenesis in Centropages typicus (Copepoda, Calanoida)

We carried out a complete study of oogenesis in Centropages typicus using structural, ultrastructural and cytochemical data. The usual stages of oogenesis, i.e. germinative phase, premeiosis, primary and secondary vitellogenesis, were found. The latter two stages were the most typical. Primary vitellogenesis consisted of endogenous yolk accumulations; these substances, probably of lipoprotein or lipoglycoprotein nature, were produced at the granular endoplasmic reticulum level and then stocked in the reticulum cavities. During secondary vitellogenesis, endogenous yolk production continued, but we mainly observed the development of exogenous yolk accumulation (lipid droplets and protein globules) in the ooplasm. These accumulations resulted from the fusion of very numerous pinocytotic vesicles arising from the oolemma and containing substances probably brought to the oocytes by the hemolymph. The effect of various proteases on the vitellus globules caused a more or less marked digestion of their contents, tending to prove their protein nature. The end of vitellogenesis was marked by the appearance of vacuolar formations with dense lamellae which could correspond to cortical granules.     

The distribution of the Euchaetidae (Copepoda: Calanoida) around South Georgia

Summary Fourteen species of the genus Euchaeta (Copepoda: Calanoida) were encountered during two cruises undertaken around South Georgia during November–December 1981 (Summer) and July–August 1983 (Winter). All 14 species were present in summer but only nine in winter. The distribution of the majority of species centered on the mesopelagic (500–1000 m) and bathypelagic (1000–2000 m) depth horizons. During both cruises, four species, Euchaeta Antarctica, E. biloba, E. rasa and E. farrani were numerically dominant. Although all four species had a wide depth distribution, E. Antarctica and E. biloba had distributions centered around the 250–500 m (epi-mesopelagic) and mesopelagic depth horizons. E. rasa was most abundant in the mesopelagic whereas E. farrani, the largest species encountered, was centered on the mesopelagic and bathypelagic depth horizons. Two species, E. Antarctica and E. biloba commonly occurred in the surface 250 m, the former being far more abundant especially over the shelf and shelf break areas, with a high abundance of copepodite stages IV and V being present in summer and adults in winter.