Affinities among anostracan (Crustacea: Branchiopoda) families inferred from phylogenetic analyses of multiple gene sequences

To gain insights into the relationships among anostracan families, molecular phylogenetic analyses were performed on nuclear (28S D1-D3 ribosomal DNA) and mitochondrial (16S rDNA, COI) gene regions for representatives of seven families and an outgroup. Data matrices used in the analyses included 951 base pairs (bp) of aligned sequences for 28S, 465 bp for 16S, and 658 bp (219 amino acids) for COI. Maximum-parsimony and maximum-likelihood methods were used to construct phylogenetic trees, enabling the evaluation of both previous hypotheses of taxonomic relationships among families based on morphology, and of the relative merits of independent versus simultaneous analyses of multiple data sets for phylogeny construction. Data from various combinations of the gene regions produced relatively congruent patterns of phylogenetic affinity. In most analyses, two monophyletic groups were resolved: one cluster included the families Polyartemiidae, Chirocephalidae, Branchinectidae, Streptocephalidae, and Thamnocephalidae, while the other contained the Artemiidae and Branchipodidae. Comparative analyses showed that combining gene regions in a single matrix generally resulted in increased resolution and support for each cluster relative to those obtained from single-gene analyses. Statistical tests demonstrated that morphology-based hypotheses of relationships among families had poorer support than those determined from molecular data, reflecting the homoplasy in characters used to differentiate families.     

Morphological diversity of the resting eggs in the anostracan genus Chirocephalus (Crustacea, Branchiopoda)

Resting egg morphology of the species groups in Chirocephalus defined by Brtek (1995) on the basis of classical characters was examined by scanning electron microscopy (SEM) in order to verify this taxonomically useful character. The results are complex: some species groups show well delineated cyst morphology, but often not. Some species show rather constant morphologies, while in others, cyst ornamentation varies widely with and between populations.     

Branchipus cortesi n. sp.: a new anostracan from western Spain (Crustacea,Branchiopoda)

Branchipus cortesi, n. sp. (Anostraca, Branchipodidae) is characterized by the broadly enlarged distal segments of male antenna 2, and a combination of morphological features concerning thoracic limbs, abdominal segments and egg morphology. The species occurs in temporary fresh water bodies in flatlands with temperate Mediterranean climate; it is distributed in the south-western part of Spain. Our study includes a morphological analysis using optical and scanning electronic microscopes. Questions about ecology and distribution of the new species are also discussed.     

Assessing anostracan (Crustacea: Branchiopoda) cyst bank size: An attempt at a standardized method

Egg (cyst) banks play a fundamental role in the survival strategy of the hydrobionts of temporary pools. Therefore a quantitative estimate, as accurate as possible, of their size is the starting point for all the possible considerations concerning the life history of the inhabiting populations. We describe here, in some details, a sampling procedure to evaluate the number of cysts laid by the anostracan Chirocephalus ruffoi Cottarelli & Mura, 1984, in an experimental pool and we show that this procedure results in a good estimate of the cyst bank consistency. A pool 150 cm in diameter was divided into five concentrical rings, 13 cm apart from each other, and a central core (with a 10 cm radius). The number of samples needed to obtain an accurate estimate was calculated by taking into account that, to perform uniform sampling, the total volume of the samples must be proportional to the volume of the pool bed in each ring. The number of cysts in each of the rings was then estimated by considering the mean of the experimental results of a previous study (61 core samples along six transects across the pool itself), multiplied by the number of samples ideally performed in each sector. Evaluating the cyst bank size by the above method resulted in an estimate with an error of only 4% compared to the real cyst bank size. We also show that the number of samples needed can significantly be reduced, with an error on the total number of cysts that can be controlled. This result, that follows from statistical considerations on the confidence interval for the mean, allows us to obtain a general sampling procedure that can be applied to statistically comparable pools.     

Extraction of DNA from anostracan cysts (Crustacea,Branchiopoda) for use in RAPD-PCR analyses

The total lipid content in Artemia franciscana (21–23% ofdry weight (DW)) when enriched with either Super Selco or DHA Selco wastwice as high as in the adult copepods Temora longicornis and Eurytemora sp.(9–11% of DW). In Brachionus plicatilis the total lipid contentwas 11 and 6.6% for cultures growing at high and low growth rate,0.12 d^–1 and 0.38 d^–1, respectively. In thecopepodid stages I, II and III of Calanus finmarchicus the total lipid levelwas 12–13%, increasing to 24% in copepodid stage IV, Vand the adults. In T. longicornis and Eurytemora sp. the predominant fattyacids were DHA (22:6n-3), EPA (20:5n-3) and the saturated fatty acid 16:0,which constituted 40–45%, 21–24% and8–12% of total fatty acids, respectively. C. finmarchicuscontained the same dominant fatty acids. In both the cultivated live feedorganisms DHA, EPA and 18:1 were the predominant fatty acids. In A.franciscana the content of these fatty acids varied according to theenrichment medium and in B. plicatilis according to the growth rate.     

A reclassification of the anomopod families Macrothricidae and Chydoridae,with the creation of a new suborder,the Radopoda (Crustacea: Branchiopoda)

An investigation, using optical microscopy and SEM, of the trunk limbs of the Anomopoda has revealed a large number of characters, previously underused or unused in taxonomy and comparative morphology. All these characters, which are nicely paralleled by some more conventional traits (head shield and pores, postabdomen, antennae ...), show one clear tendency across all groups studied: a state of complexity at one extreme, and a state of often incisive simplification at the other extreme, with a number of transitional stages in between. The complex character state, which itself is a simplification of the leg structure of the Ctenopoda and other, large Branchiopoda, is here considered to represent a primitive condition. The simplified state is considered advanced. Based on this assumption, we list a number of unifying characters (mainly structural aspects of P1 and P2, but also the gnathobase of P3 and P4) for all macrothricid and chydorid-like anomopods, which we unite in the new suborder Radopoda. Non-radopod Anomopoda are not reclassified. We then derive a cascade of (mainly trunk-limb based) characters to work out a hypothesis on the evolution of the Radopoda. The chydorid line (basically the former family Chydoridae) is classified as a superfamily (the Eurycercoidea), with three families; the macrothricid line is capped by the superfamily Macrothricoidea, with four families. Of these seven families, four are upgraded from subfamily status, the Chydoridae are left status quo, the Macrothricidae are redefined, and the Neothricidae are a new family. The Macrothricidae are further subdivided in two subfamilies, of which the Macrothricinae appear reasonably homogeneous (monophyletic), while the non-Macrothricinae require further study. Some of these (e.g. Guernella) have almost completely lost their P5, a situation parallel to that of the P6 in the Eurycercidae, Acantholeberidae, and Ophryoxidae.     

SEM morphological survey on the egg shell in the italian Anostracans (Crustacea,Branchiopoda)

The screening of the egg shell morphology of all italian species of Anostracans (14) by means of SEM, as well as the analysis of preliminary data on electrophoretical patterns of the adults, concerning the genus Chirocephalus (five species), suggest the need for a reconsideration, from a taxonomical point of view, especially as far as the species of the diaphanus group (Ch. diaphanus, Ch. ruffoi, Ch. salinus, Ch. sibyllae) are concerned.In this light, within the above mentioned group remarkable differences have been observed for Ch. ruffoi, whilst for other species like Ch. diaphanus and Ch. sibyllae, conspecificity is suspected. Electrophoretical and reproductive isolation studies, in progress, will provide a clearer understanding of the actual situation.Research carried out with M.P.I. (60%) and C.N.R. (chBr. 83.02549.04 Gruppo di Biologia Naturalistica) financial support.Research carried out with M.P.I. (60%) and C.N.R. (chBr. 83.02549.04 Gruppo di Biologia Naturalistica) financial support.     

Use of morphological characters for species separation within the genus Artemia (Crustacea, Branchiopoda)

Doubts have been raised about the use of morphological characters as criteria for species separation within the genus Artemia because of their relative validity. The characters considered to date, i.e. morphology of the frontal knobs of the male and the presence/absence of a spine-like projection on the basal part of the penis, are only partly efficacious, since they allow us to reliably distinguish only the Mediterranean species, Artemia salina, from the other bisexual species. While A. salina is characterized by subconical frontal knobs and the absence of the spine-like projection, the other species present subspherical frontal knobs and the spine-like projections. There is no information about the aspect of the frontal knobs in the Asian bisexual species. The aim of the present study is to clarify the situation by means of SEM observations of characters not considered in detail (ornamentation of the apical part of the spine-like projections) and by examination of the frontal knobs in the Asian species, which were not described at the time of the first studies.     

The anostracan genus Branchinella (Crustacea: Branchiopoda), in need of a taxonomic revision; evidence from penile morphology

Three morphologically different penile types discovered in branchinellids from Botswana are compared with literature information on congeners. The striking differences among penile structures in Branchinella ondonguae, B. ornata and the halobiontic B. spinosa raise doubts about their congeneric status. Penis morphology in B. ondonguae corresponds with the most common configuration in branchinellids, but it is largely deviant in the other two. Branchinella ornata shares penile structures with Dendrocephalus , while basal parts in B. spinosa reflect affinity with chirocephalids. A considerable general morphological variability in Branchinella , not met in any other anostracan genus, may reflect the antiquity of the group, or else poor taxonomy. Large intra-branchinellid variability and vague generic boundaries, even when considering the usually conservative penile structures, stress the need of a thorough revision of the entire family of the Thamnocephalidae.     

Phylogeny of Branchiopoda (Crustacea) based on a combined analysis of morphological data and six molecular loci

The phylogenetic relationships of branchiopod crustaceans have been in the focus of a number of recent morphological and molecular systematic studies. Although agreeing in some respects, major differences remain. We analyzed molecular sequences and morphological characters for 43 branchiopods and two outgroups. The branchiopod terminals comprise all eight “orders”. The molecular data include six loci: two nuclear ribosomal genes (18S rRNA, 28S rRNA), two mitochondrial ribosomal genes (12S rRNA, 16S rRNA), one nuclear protein coding gene (elongation factor 1α), and one mitochondrial protein coding gene (cytochrome c oxidase subunit I). A total of 65 morphological characters were analyzed dealing with different aspects of branchiopod morphology, including internal anatomy and larval characters. The morphological analysis resulted in a monophyletic Phyllopoda, with Notostraca as the sister group to the remaining taxa supporting the Diplostraca concept (“Conchostraca” + Cladocera). “Conchostraca” is not supported but Cyclestheria hislopi is the sister group to Cladocera (constituting together Cladoceromorpha) and Spinicaudata is closer to Cladoceromorpha than to Laevicaudata. Cladocera is supported as monophyletic. The combined analysis under equal weighting gave results in some respects similar to the morphological analysis. Within Phyllopoda, Cladocera, Cladoceromorpha and Spinicaudata + Cladoceromorpha are monophyletic. The combined analysis is different from the morphological analysis with respect to the position of Notostraca and Laevicaudata. Here, Laevicaudata is the sister group to the remaining Phyllopoda and Notostraca is sister group to Spinicaudata and Cladoceromorpha. A sensitivity analysis using 20 different parameter sets (different insertion–deletion [indel]/substitution and transversion/transition ratios) show the monophyly of Anostraca, Notostraca, Laevicaudata, Spinicaudata, Cladoceromorpha, Cladocera, and within Cladocera, of Onychopoda and Gymnomera under all or almost all (i.e., 19 of 20) parameter sets. Analyses with an indel‐to‐transversion ratio up to 2 result in monophyletic Phyllopoda, with Laevicaudata as sister group to the remaining Phyllopoda and with Spinicaudata and Cladoceromorpha as sister groups. Almost all analyses (including those with higher indel weights) result in the same topology when only ingroup taxa are considered. © The Willi Hennig Society 2007.     

The resting eggs of the Ctenopoda (Crustacea: Branchiopoda): a review

The resting eggs of the Ctenopoda have been studied since the second half of the 19th century. By now they are known in 21 species of the group but only in 4 species (Sida crystallina, Diaphanosoma brachyurum, Penilia avistoris and Holopedium gibberum) have they been investigated thoroughly. Gross and internal structure of eggs are characterized by considerable diversity. In general their structure has much in common with resting eggs of the Anostraca, Notostraca, Conchostraca and Onychopoda as well as with that of some other remotely related groups of freshwater invertebrates (Rotifera, Hydra). The taxonomic value of resting eggs is discussed. Probably they play a significant role in determining geographical distribution. Waterfowl are the main agent of their dispersal.     

A redescription of Periclimenaeus fimbriatus Borradaile, 1915, with the designation of a new genus (Crustacea: Decapoda: Palaemonidae)

Specimens of Periclimenaeus fimbriatus Borradaile, 1915, a palaemonid shrimp reported from only three localities in the Western Indian Ocean, are described and illustrated. The species is removed from the genus Periclimenaeus Borradaile and a new genus Paraclimenaeus is designated for its accommodation. The characteristic features of the genus and its relationships are discussed. The palaemonid shrimp genera associated with sponge hosts are reviewed and a key provided for their identification     

Distribution,diversity and conservation of Anostraca (Crustacea: Branchiopoda) in southern Africa

Southern Africa is defined here as Africa south of the Zambezi and Kunene Rivers. Here, annual average rainfall, rainfall season, and effective temperature are climatic factors which influence anostracan distribution. The type of temporary pool also appears to have some effect on distribution. Areas of high species richness are not confined to any particular climatic region and such areas occur in arid, montane and subtropical regions of southern Africa. Forty-six anostracan species have been recorded from the subcontinent and 80% of these are endemic. IUCN Red Data assessment of species revealed that two species can be considered 'Critically Endangered', while a further four are 'Endangered', and three are 'Vulnerable'. Many parts of southern Africa have been inadequately sampled but in South Africa, where the anostracans are relatively well known, temporary pool inhabitants are threatened mainly by agriculture, urbanization, pollution and pesticides. This revised version was published online in August 2006 with corrections to the Cover Date.     

Redescription of Branchinecta granulosa Daday, 1902 from Argentina (Crustacea: Branchiopoda)

The species Branchinecta granulosa Daday 1902, is redescribed on the basis of adult material from near Facundo (Chubut Province, Argentina). Its relationship to its regional congeners is outlined.     

The status of Anostraca,Notostraca and Conchostraca (Crustacea: Branchiopoda) in Yugoslavia

The investigations of Anostraca, Notostraca and Conchostraca in Yugoslavia began after a great delay compared with other European countries. Intensive systematic investigations date back only to the 1970s.To date, 19 species have been recorded. All species, with the exception of Artemia salina, are faunal elements of the Pannonian region. Seven species, including Artemia salina, Branchinecta orientalis, Branchipus serbicus, Leptestheria dahalacensis, Limnadia lenticularis, Imnadia cristata and Imnadia panonica are known from single localities. Six species including Branchinecta ferox, Chirocephalus brevipalpis, Chirocephalus carnuntanus, Lepidurus apus, Eoleptestheria spinosa and Imnadia banatica have restricted distributions. Streptocephalus torvicornis and Cyzicus tetracerus are known from several localities, while Branchipus schaefferi, Chirocephalus diaphanus, Triops cancriformis and Leptestheria saetosaare common. Large branchiopods are mainly confined to anthropogenic landscapes, especially in the northern part of the country. Rare species inhabiting a single pond, or those with rather restricted distributions, are the most endangered and such species account for about 70% of the fauna. Limnadia lenticularis, Imnadia cristata and I. panonica have not been found for more than 20 years and they are probably extinct in Yugoslavia. Branchipus serbicus, Imnadia cristata and panonica have not been documented since being originally described. Eoleptestheria spinosa is currently the most endangered species since it only appears irregularly in small populations. At present, Branchinecta ferox, Chirocephalus carnuntanus and Imnadia banatica are the safest of the rare species as they regularly appear in large numbers. There are no large branchiopods on the List of protected animals in Yugoslavia. This revised version was published online in August 2006 with corrections to the Cover Date.     

The Origin of Cladocera (Crustacea,Branchiopoda): A New Understanding of an Old Hypothesis

Comparative analysis of the ontogeny of representatives of two sister taxa (Cladocera and Cyclestherida) showed that the paedomorphic morphology of cladocerans (the small number of thoracic segments and segments of branches of antennae II, and the reduction of the carapace) was caused by the cessation of development of the somatic structures at early larval stages of ontogeny. It is demonstrated that this stop is not associated with the accelerated development of the reproductive system (progenesis), since it takes place long prior to the beginning of reproduction. In accordance with this fact, the past hypotheses that cladocerans evolved from the reproducing larvae of the ancestral form or that they are early maturing metanauplii should be recognized as erroneous. Cyclestheria. The origin of Cladocera from a Cyclestheria-like ancestor should be regarded as neotenic, taking into consideration the extended interpretation of this term.     

A histological and histochemical study of the male reproductive system of artemia (Crustacea,Branchiopoda)

The male reproductive system of Artemia was studied by routine histological and histochemical techniques to demonstrate the general histology and distribution of proteins, carbohydrates, lipids, and alkaline and acid phosphatases. The System Consists Of Paired Testes, Vasa Deferentia, Accessory Glands, And Penes. The Testes Contain Germ Cells And Supporting Cells Throughout Their Entire Length. The Former Cells Are Located In Clusters And Undergo A Spermatogenic Maturation Which Is Similar To That Described For OtherAnimals. The Supporting Cells Seem Implicated In The Nourishment Of The Germ Cells. The Vas Deferens, Which Consists Of Secretory Epithelium Surrounded By Circular And Longitudinal Muscles, Secretes The Seminal Fluid, Containing A Neutral Mucopolysaccharide Or Mucoprotein, And Stores The Mature Sperm. The Accessory Gland Consists Of Approximately 20 Pairs Of Gland Cells, Each Pair Drained By A Neck Cell And Duct Cell Into The Collecting Duct. The Glandular Secretion, Mainly A Neutral Mucopolysaccharide Or Mucoprotein, Might Function As A Lubricant, A Copulatory Plug, Or An “Activator Substance” For The Sperm Or For Fertilization. Each Penis Consists Of A Non-Eversible Part And An Eversible Part Which Is A Tortuous Muscular Tube That Connects The Vas Deferens To The Outside.     

Cyclestheria hislopi (Crustacea: Branchiopoda): A group of morphologically cryptic species with origins in the Cretaceous

Cyclestheria hislopi is thought to be the only extant species of Cyclestherida. It is the sister taxon of all Cladocera and displays morphological characteristics intermediate of Spinicaudata and Cladocera. Using one mitochondrial (COI) and two nuclear (EF1α and 28S rRNA) markers, we tested the hypothesis that C. hislopi represents a single circumtropic species. South American (French Guiana), Asian (India, Indonesia, Singapore) and several Australian populations were included in our investigation. Phylogenetic and genetic distance analyses revealed remarkable intercontinental genetic differentiation (uncorrected p-distances COI > 13%, EF1α > 3% and 28S > 4%). Each continent was found to have at least one distinct Cyclestheria species, with Australia boasting four distinct main lineages which may be attributed to two to three species. The divergence of these species (constituting crown group Cyclestherida) was, on the basis of phylogenetic analyses of COI and EF1α combined with molecular clock estimates using several fossil branchiopod calibration points or a COI substitution rate of 1.4% per million years, dated to the Cretaceous. This was when the South American lineage split from the Asian–Australian lineage, with the latter diverging further in the Paleogene. Today’s circumtropic distribution of Cyclestheria may be best explained by a combination of Gondwana vicariance and later dispersal across Asia and Australia when the tectonic plates of the two continents drew closer in the early Miocene. The lack of morphological differentiation that has taken place in this taxon over such a long evolutionary period contrasts with the high level of differentiation and diversification observed in its sister taxon the Cladocera. Further insights into the evolution of Cyclestheria may help us to understand the evolutionary success of the Cladocera.