The evolution of euhermaphroditism in caridean shrimps: a molecular perspective of sexual systems and systematics

<p>Abstract</p> <p>Background</p> <p>The hippolytid genus <it>Lysmata </it>is characterized by simultaneous hermaphroditism, a very rare sexual system among Decapoda. Specialized cleaning behavior is reported in a few pair-living species; these life history traits vary within the genus. Unfortunately, the systematics of <it>Lysmata </it>and the Hippolytidae itself are in contention, making it difficult to examine these taxa for trends in life history traits. A phylogeny of <it>Lysmata </it>and related taxa is needed, to clarify their evolutionary relationships and the origin of their unique sexual pattern. In this study, we present a molecular phylogenetic analysis among species of <it>Lysmata</it>, related genera, and several putative hippolytids. The analysis is based upon DNA sequences of two genes, 16S mtDNA and nuclear 28S rRNA. Phylogenetic trees were estimated using Bayesian Inference, Maximum Likelihood, and Maximum Parsimony.</p> <p>Results</p> <p>Phylogenetic analysis of 29 species of <it>Lysmata</it>, eight genera of Hippolytidae and two genera of Barbouriidae based on a single (16S, 28S) and combined gene approach (16S+28S) indicates that three groups of <it>Lysmata </it>differentiate according to antennular morphology: (1) <it>Lysmata</it>, having a multi-segmented accessory branch, (2) <it>Hippolysmata </it>(prior to Chace 1972), with a one-segmented accessory branch, and (3) a third group of <it>Lysmata </it>outliers, with one-segmented unguiform accessory branch, and close affinity to the genera <it>Exhippolysmata </it>and <it>Lysmatella</it>. The monophyly of the clade bearing a multi-segmented accessory branch is robust. Within the short accessory branch clade, species with specialized cleaning behaviors form a monophyletic clade, however, the integrity of the clade was sensitive to alignment criteria. Other hippolytid and barbouriid genera used in the analysis are basal to these three groups, including one displaying simultaneous hermaphroditism (<it>Parhippolyte</it>). The two barbouriid species occur in a separate clade, but among hippolytid taxa.</p> <p>Conclusions</p> <p>The data support the historical morphological division of <it>Lysmata </it>into clades based on accessory branch morphology. The position of the "cleaner" shrimps, indicates that specialized cleaning behavior is a derived trait. The topologies of the cladograms support the monophyly of the barbouriids, but do not support their elevation to familial status. Taxa ancestral to the genus <it>Lysmata </it>display simultaneous hermaphroditism, suggesting that this life history trait evolved outside the genus <it>Lysmata</it>.</p

DNA Barcoding and Molecular Phylogeny of Drosophila lini and Its Sibling Species

Drosophila lini and its two sibling species, D. ohnishii and D. ogumai, are hardly distinguishable from one another in morphology. These species are more or less reproductively isolated. The mitochondrial ND2 and COI-COII and the nuclear ITS1-ITS2 regions were sequenced to seek for the possibility of DNA barcoding and to reconstruct the phylogeny of them. The character-based approach for DNA barcoding detected some diagnostic nucleotides only for monophyletic D. ogumai, but no informative sites for the other two very closely species, D. lini and D. ohnishii, of which strains intermingled in the molecular phylogenetic trees. Thus, this study provides another case of limited applicability of DNA barcoding in species delineation, as in other cases of related Drosophila species. The molecular phylogenetic tree inferred from the concatenated sequences strongly supported the monophyly of the cluster of the three species, that is, the lini clade. We propose some hypotheses of evolutionary events in this clade

Two new species of freshwater crab (Crustacea: Decapoda: Potamidae) from Tokashiki Island, central Ryukyu Islands, Japan

10.1017/S1477200007002551Systematics and Biodiversity54409-41

Seven Cysteine-Deficient Mutants Depict the Interplay between Thermal and Chemical Stabilities of Individual Cysteine Residues in Mitogen-Activated Protein Kinase c‑Jun N‑Terminal Kinase 1

Intracellular proteins can have free cysteines that may contribute to their structure, function, and stability; however, free cysteines can lead to chemical instabilities in solution because of oxidation-driven aggregation. The MAP kinase, c-Jun N-terminal kinase 1 (JNK1), possesses seven free cysteines and is an important drug target for autoimmune diseases, cancers, and apoptosis-related diseases. To characterize the role of cysteine residues in the structure, function, and stability of JNK1, we prepared and evaluated wild-type JNK1 and seven cysteine-deficient JNK1 proteins. The nonreduced sodium dodecyl sulfate–polyacrylamide gel electrophoresis experiments showed that the chemical stability of JNK1 increased as the number of cysteines decreased. The contribution of each cysteine residue to biological function and thermal stability was highly susceptible to the environment surrounding the particular cysteine mutation. The mutations of solvent-exposed cysteine to serine did not influence biological function and increased the thermal stability. The mutation of the accessible cysteine involved in the hydrophobic pocket did not affect biological function, although a moderate thermal destabilization was observed. Cysteines in the loosely assembled hydrophobic environment moderately contributed to thermal stability, and the mutations of these cysteines had a negligible effect on enzyme activity. The other cysteines are involved in the tightly filled hydrophobic core, and mutation of these residues was found to correlate with thermal stability and enzyme activity. These findings about the role of cysteine residues should allow us to obtain a stable JNK1 and thus promote the discovery of potent JNK1 inhibitors