Sipunculan Larvae and "Cosmopolitan" Species
*Department of Marine Biology, Texas A&M University at Galveston, P.O. Box 1675, Galveston, TX 77553, USA Integrative and Comparative Biology
(Impact Factor: 2.93).
05/2012; 52(4):497-510. DOI: 10.1093/icb/ics082
Sipuncula is a relatively small taxon with roughly 150 recognized species. Many species are geographically widespread or "cosmopolitan." The pelagosphera larvae of some species are estimated to spend several months in the plankton. However, recent molecular evidence suggests that many of the "cosmopolitan" species actually represent species-complexes, some not even monophyletic. Herein, we present data on three sipunculan species with different developmental modes that occur both in the Sea of Japan and in the Northeast Pacific. The development of the three species-Phascolosoma agassizii, Thysanocardia nigra, and Themiste pyroides-is exceptionally well studied in both regions of the Pacific. Significant differences have been observed between the two regions with respect to egg size, developmental mode, and developmental timing. In general, eggs are larger and development slower in the Northeast Pacific when compared with the Sea of Japan. These differences have been explained as a result of phenotypic plasticity exhibited under different environmental conditions, in particular temperature, but we show that the populations of all three species are also remarkably distinct genetically and that gene flow between the two regions is extremely unlikely. In Thysanocardia nigra, we even found two very distinct genetic lineages within the same location in the Northeast Pacific. The amount of genetic divergence between populations from the Sea of Japan and those from the Northeast Pacific is not correlated with developmental mode. Themiste pyroides, the species with the most abbreviated development, actually has the least degree of genetic divergence between the regions. Analyses of molecular variance show that the majority of the observed variation in all three species is between the regions. We conclude that all three "cosmopolitan" species actually represent complexes of cryptic or pseudo-cryptic species. These examples demonstrate that a solid taxonomic framework based on molecular and morphological evidence is a prerequisite for evaluating relationships between dispersal capabilities, species' ranges, and the connectivity of populations.
Available from: Sonia Andrade
- "They are also emerging as important non-model organisms for evolutionary and developmental biology, or evo-devo (Schulze and Rice, 2009b; Wanninger et al., 2005, 2009; Wanninger, 2008; Boyle and Seaver, 2010; Boyle and Rice, 2014). Fourth, due to an extended larval phase described for several species within multiple families (Scheltema and Hall, 1965, 1975; Rice, 1976, 1981; Scheltema and Rice, 1990), sipunculans constitute an interesting group for studying dispersal within and between widely separated oceanic regions, which is a topic addressed in several recent studies of cosmopolitanism in the marine realm (Staton and Rice, 1999; Kawauchi and Giribet, 2010; Kawauchi and Giribet, 2013; Schulze et al., 2012; Young et al., 2012; Lemer and Planes, 2014). These and similar studies rely upon robust phylogenetic hypotheses, from species to family-level relationships, to provide a stable evolutionary framework for critical re-interpretation of previous research, and to guide future investigations. "
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ABSTRACT: Sipunculans (also known as peanut worms) are an ancient group of exclusively marine worms with a global distribution and fossil record that dates back to the Early Cambrian. The systematics of sipunculans, now considered a distinct subclade of Annelida, has been studied for decades using morphological and molecular characters, and has reached the limits of Sanger-based approaches. Here, we reevaluate their family-level phylogeny by comparative transcriptomic analysis of eight species representing all known families within Sipuncula. Two data matrices with alternative gene occupancy levels (large matrix with 675 genes and 62% missing data; reduced matrix with 141 genes and 23% missing data) were analysed using concatenation and gene-tree methods, yielding congruent results and resolving each internal node with maximum support. We thus corroborate prior phylogenetic work based on molecular data, resolve outstanding issues with respect to the familial relationships of Aspidosiphonidae, Antillesomatidae and Phascolosomatidae, and highlight the next area of focus for sipunculan systematics.
Copyright © 2014. Published by Elsevier Inc.
Molecular Phylogenetics and Evolution 10/2014; 83. DOI:10.1016/j.ympev.2014.10.019 · 3.92 Impact Factor
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ABSTRACT: The present study analyses the distribution and diversity of sipunculan species inhabiting soft substrata in the Gulf of Va-lencia and Cape Nao (western Mediterranean) in relation to the characteristics of the sediment. Eighty-seven stations in 14 localities were sampled annually from 2004 to 2008. Nine species were reported, with Aspidosiphon (Aspidosiphon) muelleri being the dominant species in the area and Thysanocardia procera the most widely distributed. Pearson correla-tion coefficient and multivariate analysis showed how sipunculan abundances of certain species were related to the sedi-ment characteristics, especially grain size. The shell-dwelling species A. (A.) muelleri and Phascolion (Phascolion) caupo were dominant in stations with high amount of coarse sand and gravel, while Sipunculus (Sipunculus) nudus appeared in stations dominated by fine sand with low organic content. Pn. (Pn.) caupo and T. procera were reported for the first time in the study area. Moreover, it was the second record of Pn. (Pn.) caupo for the Mediterranean Sea.
Zootaxa 05/2012; 3646(3):235–250. DOI:10.11646/zootaxa.3646.3.3 · 0.91 Impact Factor
Available from: Anastassya S. Maiorova
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ABSTRACT: Sipunculan worms from the Russian waters of the Sea of Japan are still poorly investigated while they are much better known from the Japanese coast. The aim of this paper is to describe sipunculans from the Russian coast and from the deepest part of the Sea of Japan near the Primorye Province collected by SoJaBio expedition, and to provide keys for identification of sipunculan species from the Sea of Japan. At the Russian coast of the Sea of Japan only 8 valid species of sipunculans were found and identified: Golfingia margaritacea, G. vulgaris, Nephasoma capilleforme, N. wodjanizkii, Phascolion strombus, Thysanocardia nigra, Themiste hexadactyla (=T. pyroides), Phascolosoma agassizii. Taking into account 4 other valid species noted for this area, Nephasoma eremite, Thysanocardia catharinae, Themiste blanda and Phascolosoma scolops, which were not found, the sipunculan fauna of the Russian waters of the Sea of Japan now comprises 12 valid species. Nephasoma capilleforme and Nephasoma wodjanizkii are the first records for the North-West Pacific and the Sea of Japan. Species accounts include the most important taxonomic characters and specific biotope data. Accordingly, a key up to species level is provided. Totally, the fauna of the Sea of Japan is now estimated as having 31 valid species of sipunculans.
Deep Sea Research Part II Topical Studies in Oceanography 02/2013; s 86–87:140–147. DOI:10.1016/j.dsr2.2012.08.009 · 2.19 Impact Factor
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