Nemertean nervous system : a comparative analysis

Most described nemerteans are marine benthic hunters. Thus, they possess a well developed nervous system. Basically, the nervous system comprises a four lobed brain, two main lateral medullary cords, some minor nerves, various nerve plexus and sensory structures. The brain and lateral nerve cords are composed of a central neuropil and a layer of neuronal cell somata, which are homogeneously distributed around the neuropil. Formerly, nemerteans fell into three major taxa, the Palaeo- Hetero- and Hoplonemertea. But this classification has been controversially discussed in recent years. Especially the monophyly of palaeonemerteans is matter of debate. But there is a consensus that Hetero- and Hoplonemertea are monophyletic and form an evolutionary lineage called Neonemertea. In recent years, neuroanatomical studies by immunohistochemistry have yielded promising data to contribute to unraveling the phylogeny of the invertebrate metazoans. For Nemertea, however, only one species has been investigated, which most likely shows derived characters states. Therefore the nervous system of 16 species of different evolutionary lineages of nemerteans was reinvestigated using different techniques. Azan staining was chosen to reveal the overall anatomy of the nervous system, additionally immunohistochemical methods were applied to reveal the details. A careful analysis of the nervous system showed considerable differences in the structure of the peripheral nervous system of even closely related species. A number of 61 characters concerning the morphological elements of the nervous system resulted from this investigation. The analysis yielded one most parsimonious tree. According to this result hoplonemerteans and heteronemerteans are monophyletic and form a monophyletic taxon called Neonemertea. Whether Palaeonemertea are mono- or paraphyletic remains uncertain due to the unknown outgroup conditions. Compared to other recently published results, the nervous system, although being just one organ system, turned out to be a valuable morphological system to infer nemertean phylogeny

Nemertinos bentónicos asociados al litoral rocoso en la región de Santa Marta. un enfoque morfológico y molecular

Los nemertinos son animales bilaterales, no segmentados, cuya característica principal es poseer una probóscide retráctil, alojada en una cavidad celómica independiente del sistema digestivo, conocida como rincocele. De las 1275 especies descritas, 36 han sido reportadas para el Mar Caribe, y de estas, tres para Colombia: Ototyphlonemertes erneba, Ototyphlonemertes lactea y Baseodiscus mexicanus. Aunque en estudios realizados sobre ecosistemas bentónicos de Colombia los nemertinos son abundantes, estos son reportados simplemente como “Nemertea”. En esta investigación, 61 ejemplares fueron colectados en litorales rocosos de Santa Marta (Inca-Inca, Bahía Concha y Taganga), estos fueron identificados basados en caracteres morfológicos como: color y forma, presencia de surcos, cirros, ocelos y disposición de la musculatura, vasos sanguíneos y cordones nerviosos. Se encontraron 19 especies: Amphiporus cruentatus, Amphiporus cf. chraceus, Amphiporus texanus, Baseodiscus delineatus, Cratenemertidae sp.,Dushia cf. atra, Lineus stigmatus, Micrura ignea, Micrura chlorapardalis, Nemertopsis bivittata, Ototyphlonemertes erneba, Ototyphlonemertes lactea, Punnettia cf. natans, Tetrastemma sp.1, Tetrastemma sp.2, Tetrastemma sp.3, Tubulanus rhabdotus, Zygonemertes fragariae y Zygonemertes virescens, las cuales pertenecen a a nueve familias: Amphiporidae, Cratenemertidae, Drepanophoridae, Emplectonematidae, Lineidae, Ototyphlonemertidae, Tetrastemmatidae, Tubulanidae y Valencinidae. A seis de estas especies (A. texanus, Cratenemertidae sp., M. ignea, N. bivittata, O. lactea, Z. virescens) se les realizó un análisis molecular de código de barras genético con base en la secuenciación de un fragmento del gen que codifica para la subunidad uno de la enzima Citocromo C Oxidasa. 17 especies representan nuevo registros para Colombia: Amphiporus cruentatus, Amphiporus cf. ochraceus, Amphiporus texanus, Baseodiscus delineatus, Cratenemertidae sp., Dushia cf. atra, Lineus stigmatus, Micrura ignea, Micrura chlorapardalis, Nemertopsis bivittata, Punnettia cf. natans, Tetrastemma sp.1, Tetrastemma sp.2, Tetrastemma sp.3, Tubulanus rhabdotus, Zygonemertes fragariae y Zygonemertes virescens. Dushia cf. atra fue la especie más común y abundante. La nemertifauna encontrada en la región de Santa Marta parece ser un sobre lapamiento de las especies presentes en la Florida, Golfo de México y Centroamérica, con las que se encuentran en Brasil; esto puede ser explicado por la convergencia de corrientes como: Guyana, Caribe, Norte de Brasil y la contracorriente de Panamá Colombia en el área de estudio. Este trabajo representa el primer aporte a la taxonomía de los nemertinos en Colombia; las imágenes de alta calidad contenidas en el documento, la clave taxonómica, las descripciones cortas y los códigos de barras genéticos, constituyen información útil para las investigaciones que se realicen sobre los ecosistemas bentónicos en el país y el desarrollo de futuras investigaciones sobre distintos aspectos de la biología de estos organismos

Section Abstracts: Natural History and Biodiversity

Abstracts of the Natural History and Biodiversity Section for the 89th Annual Meeting of the Virginia Academy of Science, May 25-27, 2011, University of Richmond, Richmond VA

Disturbance and community structure: An experimental study of bioturbation in marine soft-bottom environments

Bioturbators alter the sediment surface in the following ways: by depositing sediment on the surface in the form of feces or in the process of tunnelling, and by transporting sediment about the surface while feeding or while burrowing…

New invasive Nemertean species (Cephalothrix Simula) in England with high levels of tetrodotoxin and a microbiome linked to toxin metabolism

The marine nemertean Cephalothrix simula originates from the Pacific Ocean but in recent years has been discovered in northern Europe. The species has been associated with high levels of the marine neurotoxin Tetrodotoxin, traditionally associated with Pufferfish Poisoning. This study reports the first discovery of two organisms of C. simula in the UK, showing the geographical extent of this species is wider than originally described. Species identification was initially conducted morphologically, with confirmation by Cox 1 DNA sequencing. 16S gene sequencing enabled the taxonomic assignment of the microbiome, showing the prevalence of a large number of bacterial genera previously associated with TTX production including Alteromonas, Vibrio and Pseudomonas. LC-MS/MS analysis of the nemertean tissue revealed the presence of multiple analogues of TTX, dominated by the parent TTX, with a total toxin concentration quantified at 54 µg TTX per g of tissue. Pseudomonas luteola isolated from C. simula, together with Vibrio alginolyticus from the native nemertean Tubulanus annulatus, were cultured at low temperature and both found to contain TTX. Overall, this paper confirms the high toxicity of a newly discovered invasive nemertean species with links to toxin-producing marine bacteria and the potential risk to human safety. Further work is required to assess the geographical extent and toxicity range of C. simula along the UK coast in order to properly gauge the potential impacts on the environment and human safety

Avanços na compreensão dos padrões evolutivos em Myrtaceae : estudo de caso do complexo de espécies Eugenia involucrata através de uma abordagem integrativa

Myrtaceae inclui espécies vegetais com ampla distribuição mundial, sendo a Oceania e as regiões Neotropicais seus centros de diversidade. Na região Neotropical, a família é mais representada pela tribo Myrteae, com 29 gêneros e 2164 espécies de plantas frutíferas com significativa importância ecológica e econômica. A problemática na sistemática dentro de Myrteae limitou os estudos dentro deste grupo. A tribo inclui grandes gêneros com complexos crípticos de espécies, como Eugenia involucrata DC., uma espécie amplamente difundida e com alta variabilidade morfológica. Assim, a compreensão dos padrões evolutivos de Myrteae é de interesse. O principal objetivo deste estudo é fornecer uma visão geral da evolução das Myrtaceae Neotropicais e desvendar a história evolutiva de um complexo de espécies de Myrteae (Eugenia involucrata) através de uma abordagem integrativa baseada em genética de populações, filogeografia e morfometria. No capítulo II desta tese produzimos um artigo de revisão que contempla estudos de Filogenia, Biogeografia, Genética de Populações, Filogeografia, Citogenética e Genômica de Myrtaceae Neotropicais. A partir da análise desses artigos, evidenciamos avanços significativos na pesquisa e algumas áreas de pesquisa negligenciadas. Também detectamos que algumas espécies apresentam dificuldade de manutenção da diversidade intraespecífica devido a atividades antrópicas. Por um lado, identificamos um aumento no número de estudos filogenéticos baseados em marcadores moleculares nos últimos anos, contribuindo para a compreensão dos padrões macroevolutivos. Por outro lado, encontramos uma carência de estudos abrangendo aspectos microevolutivos, como estudos filogeográficos, os quais foram realizados apenas para duas espécies. No capítulo III, realizamos um estudo de diversidade genética e estrutura populacional de E. involucrata no sul da Floresta Atlântica. Também realizamos uma análise da morfometria geométrica foliar dessa espécie a partir de imagens de exsicatas. As análises populacionais com marcadores moleculares nucleares (ITS) e plastidiais (matK, trnC-ycf6, psbA-trnH, trnS-trnG) revelaram que as populações de E. involucrata no sul da distribuição apresentam uma alta diversidade genética e não estão geneticamente estruturadas. A análise das imagens de exsicatas de E. involucrata mostraram que alguns grupos de plantas apresentaram diferenças no formato das folhas. Em conjunto, esses resultados contribuirão para a compreensão dos processos micro e macroevolutivos na tribo Myrteae, e desvendarão a história evolutiva de E. involucrata. Particularmente para mostrar se a variabilidade fenotípica deste complexo está associada a algum fator ambiental ou genético.Myrtaceae includes plant species with worldwide distribution, with Oceania and Neotropical regions being its centers of diversity. In the Neotropical region, the family is more represented by the Myrteae tribe, with 29 genera and 2164 species of fruit plants with significant ecological and economic importance. The systematic problem within Myrteae limited the studies within this group. The tribe includes large genera with cryptic species complexes, such as Eugenia involucrata DC., a widespread species with high morphological variability. Thus, understanding the evolutionary patterns of Myrteae is of interest. The main objective of this study is to provide an overview of the evolution of Neotropical Myrtaceae and to unravel the evolutionary history of a Myrteae species complex (Eugenia involucrata) through an integrative approach based on population genetics, phylogeography and morphometry. In chapter II of this thesis we produced a review article that includes studies of Phylogeny, Biogeography, Population Genetics, Phylogeography, Cytogenetics and Genomics of Neotropical Myrtaceae. From the analysis of these articles, we evidenced significant advances in research and some neglected research areas. We also detected that some species have difficulties in maintaining intraspecific diversity due to anthropic activities. On the one hand, we have identified an increase in the number of phylogenetic studies based on molecular markers in recent years, contributing to the understanding of macroevolutionary patterns. On the other hand, we found a lack of studies covering microevolutionary aspects, such as phylogeographic studies, which were carried out only for two species. In chapter III, we carried out a study of genetic diversity and population structure of E. involucrata in the southern Atlantic Forest. We also performed an analysis of the leaf morphometry of this species from images of exsiccates. Population analyzes with nuclear (ITS) and plastid (matK, trnC-ycf6, psbA-trnH, trnS-trnG) molecular markers revealed that E. involucrata populations in the southern range have a high genetic diversity and are not genetically structured. The analysis of exsiccates images of E. involucrata, showed that some groups of plants showed differences in leaf shape. Together, these results will contribute to the understanding of micro and macroevolutionary processes in the Myrteae tribe, and will reveal the evolutionary history of E. involucrata. Particularly to show if the phenotypic variability of this complex is associated with some environmental or genetic factor

The world is their oyster : differences in epibiota on sympatric populations of native Ostrea edulis and non-native Crassostrea gigas (Magallana gigas) oysters

This research was funded by the Department of Learning (DEL) and the Department of Agriculture and Rural Development for Northern Ireland (DARDNI).In this study we aimed to assess the relative effects of native Ostrea edulis and non-native Crassostrea gigas and their associated epibiotic biodiversity. We recorded epibiont location on the shell as well as the upper or lower valve. Epibiont species richness was significantly lower on C. gigas. The epibiota communities differed significantly between the two oyster species. The continued spread of C. gigas may potentially impact the epibiont biodiversity associated with oyster species in Strangford Lough. Management strategies should prevent sustained population expansion and associated changes in colonisation habitat.PostprintPeer reviewe