Nuclear Small Ribosomal RNA Research Articles

Peltaster cerophilus is a new species of the apple sooty blotch complex from Europe

Adopting the currently used concept for the genus Peltaster, the sooty blotch fungus Peltaster cerophilus is newly described from the cuticle of ripening or ripe apples. It forms a punctate phenotype consisting of superficially formed pycnothyria and a superficial mycelial mat consisting of a net of brown or brownish black hyphae. The pycnothyria are olivaceous brown to brown but have a spot in the center that is less strongly pigmented. Pycnothyria on the holotype of P. fructicola are homogeneously pigmented. On synthetic nutrient-poor agar, P. cerophilus is largely indistinguishable from P. fructicola. It forms delicate, spreading hyphae and intercalary conidiogenous cells with short, lateral, apically thick-walled conidiogenous necks forming blastic, unpigmented, one-celled conidia in basipetal succession. Conidia can swell and become one-septate. The species has microcyclical conidiation in proximate parts of colonies. DNA sequence analyses based on the ITS and the partial nuclear small and large subunit ribosomal RNA genes, the partial mitochondrial small subunit rRNA gene and the partial translation elongation factor 1-α gene support the distinction of the European P. cerophilus from P. fructicola, which is known from North America and Europe. The nuclear small ribosomal RNA subunit gene sequences of P. cerophilus contain two group I introns at locations known to accommodate introns in certain other, unrelated taxa. One of these, for which the code “SSU-1506 intron” was adopted, is 1459 base pairs long and located between the universal primer sites ITS5 and ITS1. Similar or positional-differing introns were encountered also in three currently undescribed Peltaster species. Representative strains of Peltaster fructicola did not accommodate introns in the nuclear small subunit ribosomal RNA gene.

Neverita delessertiana (Récluz in Chenu, 1843): a naticid species (Gastropoda: Caenogastropoda) distinct from Neverita duplicata (Say, 1822) based on molecular data, morphological characters, and geographical distribution

The members of the caenogastropod family Naticidae show highly conserved morphological characters, which in many cases complicate species separation. In such cases DNA sequence analysis may help to distinguish between species. In this work partial sequences from the small mitochondrial ribosomal RNA (16S rRNA) gene, the small nuclear ribosomal RNA (18S rRNA) gene, a short intron of the nuclear calmodulin (Cal) gene, and the mitochondrial cytochrome oxidase subunit I (COI) gene are shown to differ significantly between the genomes of what generally had been considered to be merely two morphological variants of the common Western Atlantic naticid Neverita duplicata (Say, 1822). Sequence differences between the two forms of Neverita duplicata are similar to differences between either of these two forms and the Eastern Pacific Neverita reclusiana (Deshayes, 1839), the Indopacific Neverita didyma (Röding, 1798), and the Mediterranean Neverita josephinia (Risso, 1826). The COI sequences divergence between the two forms of Neverita duplicata is in the range of the average COI sequences divergence reported for congeneric species of Mollusca (Hebert 2003). We conclude that in addition to Neverita duplicata a second shallow water species of Neverita exists along the US Atlantic and Gulf coasts for which the name Neverita delessertiana (Récluz, 1843) is available.

Neverita delessertiana (Récluz in Chenu, 1843): a naticid species (Gastropoda: Caenogastropoda) distinct from Neverita duplicata (Say, 1822) based on molecular data, morphological characters, and geographical distribution

The members of the caenogastropod family Naticidae show highly conserved morphological characters, which in many cases complicate species separation. In such cases DNA sequence analysis may help to distinguish between species. In this work partial sequences from the small mitochondrial ribosomal RNA (16S rRNA) gene, the small nuclear ribosomal RNA (18S rRNA) gene, a short intron of the nuclear calmodulin (Cal) gene, and the mitochondrial cytochrome oxidase subunit I (COI) gene are shown to differ significantly between the genomes of what generally had been considered to be merely two morphological variants of the common Western Atlantic naticid Neverita duplicata (Say, 1822). Sequence differences between the two forms of Neverita duplicata are similar to differences between either of these two forms and the Eastern Pacific Neverita reclusiana (Deshayes, 1839), the Indopacific Neverita didyma (Roding, 1798), and the Mediterranean Neverita josephinia (Risso, 1826). The COI sequences divergence between the two forms of Neverita duplicata is in the range of the average COI sequences divergence reported for congeneric species of Mollusca (Hebert 2003). We conclude that in addition to Neverita duplicata a second shallow water species of Neverita exists along the US Atlantic and Gulf coasts for which the name Neverita delessertiana (Recluz, 1843) is available.