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At least 181 records · Page 10Linked to original sources
PubMed1997

Repetitive DNA sequences as an insight into Aeglidae (Crustacea, Anomura) evolution.

The evolutionary relationships of five Atlantic Aeglidae species (Aegla neuquensis affinis, A. humahuaca, A. jujuyana, A. platensis, and A. uruguayana) were studied by (i) satellite DNA analysis using a restriction enzyme digestion and hybridization pattern approach and (ii) genome screening by using randomly amplified polymorphic DNA (RAPD) typing. The identical restriction patterns and intense interspecific hybridization patterns obtained in this study strongly suggest a recent cladogenetic event for the Aeglidae. The species-specific amplification products which were detected using RAPD markers allowed species characterization. A total of 49 amplification products were used to construct trees by cluster analysis. The new scheme agrees in part with previous proposals based on biogeography and morphology. We considered that the subdivision northwestern-platensis species was probably due to the rising of the Andes, which started in the Middle Miocene. Divergence due to altitude is suggested by the different altitudinal distribution of three northwestern species along the same river. The possible role of selection by ecological factor/s was observed at the population level in A. jujuyana, which has a wider altitudinal range distribution. RAPD markers revealed a high level of intraspecific diversity and important genetic flow among populations. However, a few markers showed significant differences in frequency or H between the lowermost population and the other populations, located in a different biogeographical region. The differences were not in relation to geographical distance, and we interpreted them as being due to selection. Repetitive sequences constitute an important reservoir of genetic variation, and these results show their usefulness in testing and proposing evolutionary hypothesis in crabs. These sequences seem to have played an important role in aeglid evolution. Ecological factors related to altitude have probably influenced macro- and microevolutionary processes, at least in northwestern species.

Animals↗
PubMed2005

Giant spermatozoon coiled in small egg: fertilization mechanisms and their implications for evolutionary studies on Ostracoda (Crustacea).

Ostracods of the superfamily Cypridoidea have giant spermatozoa. However, little data exist on the sperm-egg interaction in this group: only two publications have so far given the most ambiguous indication that the entire sperm enters the egg on fertilization. These assumptions have not yet been tested with modern techniques, nor has their putative value for developmental and evolutionary investigations been realized. The present paper gives the first, clear, light- and scanning electron microscopical evidence of the entire giant ostracod spermatozoon being incorporated into the egg. Coiling of the sperm underneath the egg shell is shown in the early zygotes of the species Mytilocypris praenuncia and Pseudocandona marchica. Additionally, data on the morphology of female and male reproductive tracts are given for M. praenuncia. Hypotheses on the evolution of giant filiform sperm in the Animal Kingdom are reviewed, and their applicability to ostracods is discussed. The demonstrated ingression of the entire sperm implies the entry of the two giant paternal mitochondrial derivates into the zygote in Cypridoidea and potentially casts doubt upon the dogma of strict maternal inheritance of mitochondrial DNA. Evidence of paternal inheritance of mtDNA in several organisms has recently given rise to a controversial debate on this issue; the possible significance of this phenomenon for molecular studies on ostracod phylogeny and evolution is discussed.

Animals↗
PubMed2005

Larval development of Lynceus brachyurus (Crustacea, Branchiopoda, Laevicaudata): redescription of unusual crustacean nauplii, with special attention to the molt between last nauplius and first juvenile.

The larval development of "conchostracans" has received only scattered attention. Here I present the results of a study on the larval (naupliar) development and the metamorphosis of Lynceus brachyurus, a member of the bivalved branchiopod order the Laevicaudata. Lynceus brachyurus is the only species of the "Conchostraca" in Denmark. The phylogenetic position of the Laevicaudata has traditionally been a source of controversy, and this study does not solve the question completely. This work focuses on features potentially important for phylogeny. The general appearance of the larvae of L. brachyurus has been known for more than a century and a half, and some of its unique features include a large, larval dorsal shield; a huge, plate-like labrum; and a pair of immovable, horn-like antennules. However, many details relating to limb morphology, potentially important for phylogeny, have not been studied previously. Based on size categories, five or six larval stages can be recognized. The larvae approximately double their length and width during development (length: 230-520 microm). Most morphological features stay largely unchanged during development, but the antennal coxal masticatory spines are significant exceptions: they become bifid after one of the first molts. In all larval stages only the antennae and the mandibles actively move. In late naupliar stages the trunk limbs become visible as rows of laterally placed, undeveloped, and still immovable lobes. Swimming is performed by the antennae, whereas the mandibles appear to be involved mainly in feeding, as in other branchiopod larvae. The last naupliar stage undergoes a small metamorphosis to the first juvenile stage, the details of which in part were studied by following the premolt juvenile condition through the cuticle of the last stage nauplius. Among other changes there is a characteristic change in the shape and morphology of the univalved dorsal naupliar shield to a bivalved juvenile carapace. The general morphologies of the antennae and the mandibles are very similar to those of other branchiopod larvae and fall well within the "branchiopod naupliar feeding apparatus" recognized as a branchiopod synapomorphy by Olesen (2003), but some specific features shared with the larvae of other "conchostracans" are also identified. These special "conchostracan" features include: 1) a similar antennular setation; 2) a similar comb-like setulation of the bifid antennal coxal processes; and 3) mandibular palpsetae with setules condensed. In light of recent suggestions concerning branchiopod phylogeny (Cyclestheria as a sister group to the Cladocera), these similarities probably do not support a monophyletic "Conchostraca" but rather are symplesiomorphies of this taxon. A final decision must await a phylogenetic analysis of a more complete set of characters.

Animals↗
PubMed2002

Gut-associated cells of Derocheilocaris remanei (Crustacea, Mystacocarida).

The gut-associated cells (GA-cells) of the mystacocarid Derocheilocaris remanei were investigated by transmission electron microscopy. These cells are characterized by a dense cytoplasm, the presence of clear vesicles adjacent to the gut epithelium, glycogen, and lipid droplets. GA-cells envelop the midgut and hindgut and send blunt cytoplasmic extensions to the gut epithelium through its basal lamina. The GA-cells also extend dorsolateral projections to the body wall by means of intermediate cells. In addition to a mechanical function of suspending and stabilizing the gut, these cells may affect the flow of the hemocoelic fluid and may be implicated in the processes of transport, assimilation, and storage of nutrients.

Animals↗
PubMed1990

Origin and early development of female germ cells in Eoleptestheria ticinensis Balsamo-Crivelli, 1859 (Crustacea, Branchiopoda, Conchostraca).

We have studied the early stages of the development of the female germ cells in the Conchostraca Eoleptestheria ticinensis Balsamo-Crivelli, 1859. The gametes originate in a scattered way throughout the tubular units of the gonad, with no development gradient recognizable. The female germ cells arise from successive karyokineses not followed by cytokinesis, within an unorganised area in which a sort of plasmodium is formed. Each primordial nucleus of this germarium develops and then forms an individual plasmic membrane. Subsequently, the usual organules differentiate in the cytoplasm. The presence of synaptinemal complexes and the beginning of the endogenous vitellogenesis by the rough endoplasmic reticulum and the Golgi apparatus qualify the previtellogenesis. The general characteristics of this early development phase of the gametes, as well as several substantial differences in the gametogenesis with respect to the other Phyllopoda studied, lead us to suggest the systematic positioning of the Leptestheriidae.

Animals↗
PubMed2001

Effects of Cu+2 and pH on the fitness of Ceriodaphnia dubia (Richard 1894) (Crustacea, Cladocera) in microcosm experiments.

An important disturbance of anthropogenic origin frequently occurring in freshwater ecosystems is a rise in the concentration of heavy metals in solution, among which copper stands out due to its known toxicity. However, the study of the chemical behavior of copper in solution is highly dependent on pH. In this study, the effect of ionic copper on the fitness of Ceriodaphnia dubia was assessed in microcosm experiments under different conditions of Cu+2 and pH. Two groups of experiments were conducted: effects on survival and fecundity, and effects on population dynamics. In the former, both pH and copper concentrations were manipulated. On the other hand, only the concentration of biologically available ionic copper was manipulated whereas pH was maintained constant in the population dynamics experiments. There was an agreement between both sets of experiments in terms of their results, showing important toxic effects of copper as evidenced through significant differences between controls and treatments in survival and fecundity. Mean age of first reproduction was delayed, and both the number of neonates produced per female and number of broods decreased with the increase in the concentration of copper. R0 was always lower at pH 6 than at pH 8 and was negatively related to the increment in the concentration of copper under either pH. A significant effect on population dynamics at 5 micrograms l-1 of copper sulfate was found and the extinction of the population at 20 micrograms l-1 of copper sulfate. New values of toxicity from copper are proposed, and the potential effects that an increment in copper could have on the communities that occupy a central position in aquatic food webs are discussed.

Animals↗
PubMed1999

Short-term toxicological effects of cadmium on the woodlouse, Porcellio laevis (Crustacea, Isopoda).

Terrestrial isopods have been used in a number of studies as test organisms concerning the effects of chemicals in a (eco-)toxicological context. They are saprophages, which are in direct contact with polluted plant material. Cadmium is a metal with no known biological function and is toxic to life. There are a variety of anthropogenic sources of cadmium in the environment. The aims of this study were to determine the LC50 for cadmium sulfate for Porcellio laevis and the acute effect of this metal salt on the mass of this species and also to determine if P. laevis could distinguish and avoid cadmium sulfate-contaminated leaves. Acute toxicity tests and behavioral tests were conducted using concentrations ranging from 10,000 to 40,000mg/kg cadmium sulfate. The LC50 obtained of 26,700 mg/kg cadmium sulfate is an indication of P. laevis' tolerance to cadmium contamination. P. laevis also exhibited the ability to distinguish and avoid leaves contaminated with high cadmium sulfate levels.

Animals↗
PubMed2000

Optimization of culture conditions of Porcellio dilatatus (Crustacea: Isopoda) for laboratory test development.

This paper describes the experimental results for optimizing isopod culture conditions for terrestrial ecotoxicity testing. The influence of animal density and food quality on growth and reproduction of Porcellio dilatatus was investigated. Results indicate that density influences isopod performance in a significant way, with low-density cultures having a higher growth rate and better reproductive output than medium- or high-density cultures. Alder leaves, as a soft nitrogen-rich species, were found to be the best-quality diet; when compared with two other food mixtures, alder leaves induced the best results, particularly in terms of breeding success. Guidance regarding culture conditions of isopod species, especially in terms of culture density and diet, is given.

Animals↗
PubMed1996

Ovarian and hemolymph ecdysteroids in the terrestrial isopod Armadillidium vulgare (Malacostracan Crustacea).

Ovarian and hemolymph ecdysteroids in Armadillidium vulgare were analyzed at four stages of ovarian maturation through the reproductive molt cycle using high-performance liquid chromatography and radioimmunoassay. The major ecdysteroids in the ovaries and hemolymph of A. vulgare were 20-hydroxyecdysone and ecdysone in free and conjugated forms. The concentration of ovarian ecdysteroids reached a maximal level in maturing ovaries during stage D (premolt period) of the molt cycle. At the end of stage D, a high level of ecdysteroids was detected in fully matured ovaries. On the other hand, hemolymph ecdysteroid titers in reproductive females showed a peak during stage D and declined rapidly to a low level at the end of stage D. No appreciable differences in the amounts of hemolymph ecdysteroids and in molecular species of them were apparent in females in reproductive and nonreproductive molt cycles. The amounts of hemolymph ecdysteroids were about fivefold higher in females than those in males. These ecdysteroids may have a role in controlling ovarian development in female A. vulgare.

Animals↗
PubMed1997

Sexual bipotentiality of developing ovaries in the terrestrial isopod Armadillidium vulgare (Malacostraca, Crustacea).

The androgenic glands (AG) of crustaceans are responsible for differentiation of male sexual characters. The process of gonadal differentiation in females was studied morphologically in Armadillidium vulgare given a masculinizing AG implant. Gonadal masculinization was induced by implantation of an AG into females at various stages of postembryonic development. Functional sex reversal always occurred when an AG was implanted into females that were in stages 5 and 6 of development. Partial formation of testes was induced after implantation of an AG into stage 7 and 8 females. When an AG was implanted into a stage 9 female, development of a functional testis was not observed, but the ovaries were partially masculinized. These results show that after the onset of sex differentiation female gonads retain sexual bipotentiality through several stages of postembryonic development. Implantation of one AG into a female is enough to induce gonadal masculinization and sex reversal in this species. The AG implant up to stage 6 (3.4 mm in body length) is an experimental procedure certain to transform a genetic female into a functional male. The process of gonadal development in female A. vulgare is discussed.

Androgens↗
PubMed1998

Sex reversal by implantations of ethanol-treated androgenic glands of female isopods, Armadillidium vulgare (Malacostraca, crustacea).

The androgenic glands (AGs) of malacostracan crustaceans are responsible for differentiation of male sexual characteristics, and sex reversal is readily obtained by implantation of AGs in female crustaceans. In order to induce sex reversal, we implanted inactive AGs (dead cells) into young females of Armadillidium vulgare. Before implantation fresh AGs (living cells) were treated twice with 80% ethanol for 3 min and kept in crustacean physiological saline for 30 s. We refer to these AGs as ethanol-treated AGs (t-AGs). Stage 6 females were used as recipients of t-AG implantation. They received an implant of three t-AGs (3 t-AGs) three times, once each week. Testis formation in recipients was used as an indicator of the masculinized levels of female gonads. Female sexual characteristics were masculinized in proportion to the number of 3 t-AG implantations. Three implantations (total number of t-AGs, nine glands) induced development of testes, penes, and male copulatory organs in the recipient females. Furthermore, they could produce progeny. These results show that t-AG implantations are capable of inducing masculinization of female sexual characteristics. The procedure of three implantations with 3 t-AGs at stage 6 is enough to transform the sex from a genetic female into a functional male. If t-AGs are used to implant instead of fresh AGs, we can detect the effects induced by newly formed AGs of recipient females, not by implanted donor's AGs. The present method may be useful for examining the regulatory mechanism of sex differentiation of female A. vulgare.

Androgens↗
PubMed1999

Isolation and amino acid sequence of a peptide with vitellogenesis inhibiting activity from the terrestrial isopod Armadillidium vulgare (Crustacea).

The complete amino acid sequence of a neuropeptide was established using gas-phase microsequencing, mass spectrometry, and reverse transcription-polymerase chain reaction. This peptide, stored in the sinus gland of the terrestrial isopod Armadillidium vulgare, inhibited vitellogenin synthesis by the fat tissue and inhibited the onset of secondary vitellogenesis when tested in homologous bioassays. This peptide, named Arv-VIH, has 83 amino acid residues and a molecular mass of 9485 Da. Relationships with other related peptides are presented.

Amino Acid Sequence↗
PubMed1999

Membrane particle distribution in the sternal epithelia of the terrestrial isopod Porcellio scaber latr. (Crustacea, oniscidea) during CaCO(3) deposit formation and resorption, a freeze-etch analysis.

The anterior sternal epithelium of terrestrial isopods transports cuticular Ca(2+) to and from large sternal CaCO(3) deposits. We analyzed the anterior and posterior sternal epithelium by the means of the freeze-etch technique and measured the size distribution and density of intramembrane particles (IMPs) during three different molting stages. At least three IMP size classes around 4.5, 7.7, and 9.4 nm can be distinguished on the P-face of the apical and basolateral plasma membrane. An additional size class of around 12.8 nm is restricted to the apical compartment. In the anterior sternal epithelium, the density of these large particles changes by a factor of 1.9 during the molt cycle, suggesting a role in CaCO(3) formation and/or resorption. The density of the smaller IMPs rises transiently by a factor of 1.3 in the posterior sternal epithelium only. The IMP density of the basolateral plasma membrane increases significantly by a factor of 1.4 and 1.3 in the anterior and posterior sternal epithelia, respectively. The results indicate that increases in the IMP density contribute to the differentiation to an increased transport activity during the cyclic enlargements of the plasma membrane surface area in the anterior sternal epithelium.

Animals↗
PubMed1998

Cryptic species in a "living fossil" lineage: taxonomic and phylogenetic relationships within the genus Lepidurus (Crustacea: Notostraca) in North America.

Lineages which exhibit little morphological change over geologic time are evolutionarily and ecologically interesting, but often taxonomically difficult. For some morphologically conservative groups, not only is it almost impossible to identify significant changes in fossil forms over time, but the relationships among extant populations are often poorly understood due to lack of known characters which clearly delimit species. Notostracan crustaceans are a classic example of such "living fossils." The paradoxical characteristics of long-term stasis in gross morphology and hypervariability of many individual morphological characters make notostracans an especially taxonomically challenging group. We used molecular and biochemical techniques to investigate the taxonomic and phylogenetic relationships of four nominal species within the genus Lepidurus in North America, three of which had been alternately abandoned, resurrected, or synonymized under a single, globally distributed morphospecies since their original descriptions in the 1800s. Data from a 330-bp sequence of the mitochondrial 12S rDNA gene and from nine allozyme loci consistently indicate five highly genetically divergent clades among the populations we used to represent the four nominal species. Diagnostic molecular characters, magnitudes of genetic divergence among clades, and the fact that these genetically distinct clades have broadly overlapping geographical ranges strongly suggest that the five clades are reproductively isolated species. One of the nominal species (L. couesii) is not monophyletic, but rather consists of two species which are not sister taxa. The other three nominal species (L. lemmoni, L. packardi, and L. bilobatus) are supported as valid phylogenetic species. The best current hypothesis for phylogenetic relationships among the five species is provided by a simultaneous analysis of both 12S rDNA and allozyme data, which places L. bilobatus and L. "couesii"-1 as sister taxa and L. "couesii"-2 as the most basal of all the Lepidurus species included in this study. These results point to the existence of cryptic species within the current classification scheme for Lepidurus, the need for further taxonomic work within the Notostraca in general, and the role that genetic techniques can play in clarifying the systematics of morphologically conservative groups.

Animals↗
PubMed1998

Molecules and the body plan: the Hox genes of Cirripedes (Crustacea).

Among arthropods, Cirripedia (barnacles) are remarkable in that they completely lack abdominal segments. This feature prompted us to study the Hox genes of three cirripede species, representing a wide array of the diversity of these organisms, a segmented sessile barnacle, Elminius modestus (Thoracica), the parasite of a crab, Sacculina carcini (Rhizocephala), and the burrowing barnacle Trypetesa lampas (Acrothoracica). Using PCR amplification of genomic DNA and cDNA and library probing, we have found seven clear cirripedian homologues of the eight homeotic Hox genes known in insects, including labial and proboscipedia homologues, that were not previously reported in crustaceans. In addition we have isolated a divergent Antp-like gene, named Diva, that we homologize to the ftz gene of insects. The homeotic gene abdominalA (abdA) was not retrieved from any of these three cirripede species. By contrast, we have found all eight homeotic homologue genes, including abdA, in Ulophysema oeresundense, a crustacean possessing a well-developed abdomen, belonging to the Ascothoracica, generally thought to be the sister group of Cirripedia. Since we have found in barnacles homeobox-containing genes that are more divergent from the Antennapedia type than the typical abdA, we believe that a bona fide abdA gene would not have escaped our search. Hence, the abdA gene has been lost or is profoundly derived in sequence during the evolution leading to the cirripedian lineage. If confirmed, the lack of abdA would represent the first case in which the loss of a homeotic gene is correlated with a change in body plan during the evolution of metazoans.

Amino Acid Sequence↗
PubMed2000

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.

Animals↗