Lyda R. Castro

The phylogenetic position of Neritimorpha based on the mitochondrial genome of Nerita melanotragus (Mollusca: Gastropoda).

This is the first report of the mitochondrial gene order and almost-complete DNA sequence of a representative of the Neritimorpha, the highest-ranking gastropod clade lacking such data. Mitochondrial gene order in Nerita is largely plesiomorphic. Its only difference from the cephalopod Octopus vulgaris is a tRNA transposition shared by Vetigastropoda and Caenogastropoda. Genome arrangements were not informative enough to resolve the evolutionary relationships of Neritimorpha, Vetigastropoda and Caenogastropoda. The sister-group taxon of Neritimorpha varied in sequence-based analyses. Some suggested that Neritimorpha is the sister group of Caenogastropoda plus Heterobranchia and some that Neritimorpha and Caenogastropoda are sister groups. No analysis significantly supported the hypothesis that Vetigastroda is more closely related to Caenogastropoda than is Neritimorpha.

Sequence and comparison of mitochondrial genomes in the genus Nerita (Gastropoda: Neritimorpha: Neritidae) and phylogenetic considerations among gastropods.

In the present study, we determined the mitochondrial DNA (mtDNA) sequence of three Neritas, Nerita versicolor, Nerita tessellata, and Nerita fulgurans. We present an analysis of the features of their gene content and genome organization and compare these within the genus Nerita, and among the main gastropod groups. The new sequences were used in a phylogenetic analysis including all available gastropod mitochondrial genomes. Genomic lengths were quite conserved, being 15,866bp for N. versicolor, 15,741bp for N. tessellata and 15,343bp for N. fulgurans. Intergenic regions were generally short; genes are transcribed from both strands and have a nucleotide composition high in A and T. The high similarity in nucleotide content of the different sequences, gene composition, as well as an identical genomic organization among the Nerita species compared in this study, indicates a high degree of conservation within this diverse genus. Values ​​of Ka/Ks of the 13 protein coding genes (PCGs) of Nerita species ranged from 0 to 0.18, and suggested different selection pressures in gene sequences. Bayesian phylogenetic analyses using concatenated DNA sequences of the 13 PCGs and the two rRNAs, and of amino acid sequences strongly supported Neritimorpha and Vetigastropoda as sister groups.

Phylogenetic relationships among superfamilies of Neritimorpha (Mollusca: Gastropoda).

Despite the extraordinary morphological and ecological diversity of Neritimorpha, few studies have focused on the phylogenetic relationships of this lineage of gastropods, which includes four extant superfamilies: Neritopsoidea, Hydrocenoidea, Helicinoidea, and Neritoidea. Here, the nucleotide sequences of the complete mitochondrial genomes of Georissa bangueyensis (Hydrocenoidea), Neritina usnea (Neritoidea), and Pleuropoma jana (Helicinoidea) and the nearly complete mt genomes of Titiscania sp. (Neritopsoidea) and Theodoxus fluviatilis (Neritoidea) were determined. Phylogenetic reconstructions using probabilistic methods were based on mitochondrial (13 protein coding genes and two ribosomal rRNA genes), nuclear (partial 28S rRNA, 18S rRNA, actin, and histone H3 genes) and combined sequence data sets. All phylogenetic analyses except one converged on a single, highly supported tree in which Neritopsoidea was recovered as the sister group of a clade including Helicinoidea as the sister group of Hydrocenoidea and Neritoidea. This topology agrees with the fossil record and supports at least three independent invasions of land by neritimorph snails. The mitochondrial genomes of Titiscania sp., G. bangueyensis, N. usnea, and T. fluviatilis share the same gene organization previously described for Nerita mt genomes whereas that of P. jana has undergone major rearrangements. We sequenced about half of the mitochondrial genome of another species of Helicinoidea, Viana regina, and confirmed that this species shares the highly derived gene order of P. jana.

Rickettsial infection in ticks (Acari: Ixodidae) from reptiles in the Colombian Caribbean

Although more reptiles are illegally traded in Colombia than any other group of animals, for both local and international markets, little is known about ticks associated with reptiles or pathogens associated with these ticks. In this study, ticks were collected from reptiles in Magdalena, Cesar and La Guajira regions in northern Colombia, and identified morphologically using taxonomic keys and molecularly by sequencing of the COI gene. In addition, Rickettsia spp. were detected by PCR amplifying the gltA, 16S rRNA, and sca1 genes. Ticks were identified as Amblyomma dissimile, representing the first record for this species in 17 of the 26 species of reptiles sampled. Additionally, our data expand the distribution range for this tick in Colombia. Rickettsia spp. DNA was detected in 18 ticks (3.6%) from 16 reptiles. Sequence analyses indicated that most of the Rickettsia were members of the R. monacensis clade, most closely related to Rickettsia sp. strain Colombianensi. We detected one tick infected with a Rickettsia with 99% identity to R. bellii.

The complete mitochondrial genome of Micrura ignea Schwartz & Norenburg 2005 (Nemertea: Heteronemertea) and comparative analysis with other nemertean mitogenomes

We sequenced the complete mitochondrial genome of the Heteronemertea species, Micrura ignea. The genome was amplified with a combination of short and long PCRs that were subjected to 454 sequencing. The mitogenome of M. ignea is a circular molecule of 15,333bp in size and encodes the 37 genes typically found in metazoans, and one non-coding region. The order of the genes is the same as for all the other Heteronemerteans. All genes are encoded on the heavy strand except trnT and trnP. The phylogenetic analyses recovered M. ignea as a basal taxon in the Lineidae family, no differences were found in the topology of the phylogenetic trees in comparison with previous studies.

Hemogregarine and Rickettsial infection in ticks of toads from northeastern Colombia

The toads Rhinella spp. are in constant contact with humans and domestic animals and are commonly parasitized by ticks, which are also potential vectors of pathogenic microorganisms, such as apicomplexans and rickettsia. However, little is known about microorganisms associated with toad ticks. In this work, we molecularly evaluated the presence of Rickettsia spp. and hemogregarines in ticks of Rhinella horribilis and R. humboldti in the Colombian Caribbean, finding two different species of Rickettsia: the colombianensi strain and one close to R. bellii. In the case of hemogregarines, since only 18S gene sequences are available, it is difficult to define species and place them correctly in a phylogeny, but most of our samples show a 99% identity with Hemolivia stellata, while others identical to each other seem to form another clade within this genre. All collected ticks were identified as Amblyomma dissimile, representing the first time that H. stellata was recorded in this tick. The prevalence of both microorganisms was very high, which makes it necessary to generate robust phylogenies to clarify their taxonomic diversity and to correctly define their ecological role and pathogenicity, which should be taken into account in amphibian conservation plans and veterinary medicine.

Nipponnemertes incainca sp. n. Adoption of the new taxonomic proposal for nemerteans (Nemertea, Cratenemertidae)

Abstract A new species Nipponemertes incainca is described from the intertidal zone of Santa Marta, Colombia. A new recent approach based on both morphological and molecular characters is applied for the description. The main characteristics of the species are: red color, head shield-shaped with a mid-dorsal cephalic ridge, furrows pre-cerebral inconspicuous with few faint ridges orthogonal to furrow axis, two irregular groups of eyespots situated at lateral margins in precerebral cephalic region, proboscis provided with papillae and 12 nerves, stylet smooth supported on an oval basis, and two pouches containing 3–4 accessory stylets each. The sequence of the COI gene was analyzed as an additional support for the new species.

Códigos de barras genéticos en una especie de Paramacrobiotus (Tardigrada: Parachela) en Santa Marta, Colombia

espanolDebido a la gran cantidad de especies y a las dificultades en su identificacion morfologica, muchos estudios taxonomicos actuales de tardigrados se basan en el uso de tecnicas geneticas y moleculares. En Colombia son necesarios estudios enfocados en esta disciplina que permitan complementar la informacion morfologica; por consiguiente se analizaron siete secuencias del gen COI en el genero de tardigrado Paramacrobiotus de la cuenca baja del rio Manzanares, en Santa Marta, y se compararon con las secuencias del mismo genero presentes en la base de datos de GenBank a traves de un analisis de divergencia especifica y analisis de vecino mas cercano (NJ). Las secuencias obtenidas en el estudio mostraron una clara diferenciacion de las secuencias de GenBank y una baja distancia intraespecifica, obteniendose el codigo de barras genetico correspondiente a una sola especie. Las diferencias de los resultados con el analisis morfologico reflejan la eficacia de tecnicas moleculares como los codigos de barras y evidencian la importancia de la integracion de tecnicas moleculares a los estudios taxonomicos de los tardigrados. EnglishBecause of the great number of species and troubles with their morphological identification, many current taxonomic studies in tardigrades are based on the use of genetic and molecular techniques. In Colombia, studies focused in this discipline are needed to be able to complement the morphological information; consequently, seven COI gene sequences were analyzed in the genus of tardigrade Paramacrobiotus at the lower basin of the Manzanares River, in Santa Marta, and were compared with the sequences of the same genus present in the GenBank database through an analysis of specific divergence and neighbor-joining (NJ). The sequences obtained in the study showed a clear differentiation of the GenBank sequences, while at the same time showed a low intraspecific distance, obtaining a DNA barcoding for a single species. The differences obtained in comparison with the morphological analyses reflect the effectiveness of molecular techniques such as barcoding, emphasizing the importance of integration of molecular techniques to taxonomic studies on tardigrades.