A stable phylogenetic hypothesis for families within jellyfish class Scyphozoa has been elusive. Reasons for the lack of resolution of scyphozoan familial relationships include a dearth of morphological characters that reliably distinguish taxa and incomplete taxonomic sampling in molecular studies. Here, we address the latter issue by using maximum likelihood and Bayesian methods to reconstruct the phylogenetic relationships among all 19 currently valid scyphozoan families, using sequence data from two nuclear genes: 18S and 28S rDNA. Consistent with prior morphological hypotheses, we find strong evidence for monophyly of subclass Discomedusae, order Coronatae, rhizostome suborder Kolpophorae and superfamilies Actinomyariae, Kampylomyariae, Krikomyariae, and Scapulatae. Eleven of the 19 currently recognized scyphozoan families are robustly monophyletic, and we suggest recognition of two new families pending further analyses. In contrast to long-standing morphological hypotheses, the phylogeny shows coronate family Nausithoidae, semaeostome family Cyaneidae, and rhizostome suborder Daktyliophorae to be nonmonophyletic. Our analyses neither strongly support nor strongly refute monophyly of order Rhizostomeae, superfamily Inscapulatae, and families Ulmaridae, Catostylidae, Lychnorhizidae, and Rhizostomatidae. These taxa, as well as familial relationships within Coronatae and within rhizostome superfamily Inscapulatae, remain unclear and may be resolved by additional genomic and taxonomic sampling. In addition to clarifying some historically difficult taxonomic questions and highlighting nodes in particular need of further attention, the molecular phylogeny presented here will facilitate more robust study of phenotypic evolution in the Scyphozoa, including the evolution characters associated with mass occurrences of jellyfish.

Exposure to oiled sediments can negatively impact the health of fish species. Here, we examine the effects of chronic exposure of juvenile southern flounder, Paralichthys lethostigma, to a sediment-oil mixture. Oil:sediment mixtures are persistent over time and can become bioavailable following sediment perturbation or resuspension. Juvenile flounder were exposed for 32 days under controlled laboratory conditions to five concentrations of naturally weathered Macondo MC252 oil mixed into uncontaminated, field-collected sediments. The percent composition of individual polycyclic aromatic hydrocarbons (PAHs) of the weathered oil did not change after mixing with the sediment. Spiked exposure sediments contained 0.04-395mg/kg tPAH50 (sum of 50 individual PAH concentration measurements). Mortality increased with both exposure duration and concentration of sediment-associated PAHs, and flounder exposed to concentrations above 8mg/kg tPAH50 showed significantly reduced growth over the course of the experiment. Evident histopathologic changes were observed in liver and gill tissues of fish exposed to more than 8mg/kg tPAH50. All fish at these concentrations showed hepatic intravascular congestion, macrovesicular hepatic vacoulation, telangiectasia of secondary lamellae, and lamellar epithelial proliferation in gill tissues. Dose-dependent upregulation of Cyp1a expression in liver tissues was observed. Taxonomic analysis of gill and intestinal commensal bacterial assemblages showed that exposure to oiled sediments led to distinct shifts in commensal bacterial population structures. These data show that chronic exposure to environmentally-relevant concentrations of oiled sediments produces adverse effects in flounder at multiple biological levels.

[1] Among the various factors affecting recruitment of marine invertebrates and fish, larval transport may produce spatial and temporal patterns of abundance that are important determinants of management strategies. Here we conducted a field and modeling study to investigate the larval transport of eastern oyster, Crassostrea virginica, in Mobile Bay and eastern Mississippi Sound, Alabama. A three-dimensional larval transport model accounting for physical transport, biological movement of larvae, and site-and larvalspecific conditions was developed. A hydrodynamic model was used to simulate physical transport, and biological movement was parameterized as a function of swimming and sinking velocity of oyster larvae. Site-and larval-specific conditions, including spawning location, spawning stock size, spawning time, and larval period, were determined based on the previous studies. The model reasonably reproduced the observed gradient in oyster spat settlement and bivalve larval concentration, although the model results were less dynamic than the data, probably owing to the simplified biological conditions employed in the model. A persistent gradient decreasing from west to east in the model results at time scales of overall average, season, and each survey in 2006 suggests that the larval supply may be responsible for the corresponding gradient in oyster spat settlement observed over the past 40 years. Biological movement increased larval retention near the spawning area, thus providing a favorable condition for local recruitment of oysters. Inclusion of biological movement, however, caused little change in the overall patterns of larval transport and still resulted in a west-east gradient, presumably because of frequent destratification in the shallow Mobile Bay system.

No abstract

No abstract

No abstract

No abstract

The ctenophore Mnemiopsis leidyi is one of the most successful marine bioinvaders on record. Native to the Atlantic coast of the Americas, M. leidyi invaded the Black Sea, Caspian and Mediterranean Seas beginning the in late 1980s, followed by the North and Baltic Seas starting in 2006, with major concomitant alterations in pelagic ecology, including fishery collapses in some cases. Using extensive native range sampling (21 sites), along with 11 invasive sites in the Black, Caspian, Mediterranean, North and Baltic Seas, we examined M. leidyi worldwide phylogeographic patterns using data from mitochondrial cytochrome b (cytb) and six nuclear microsatellite loci. Cytb and microsatellite data sets showed different levels of genetic differentiation in the native range. Analyses of cytb data revealed considerable genetic differentiation, recovering three major clusters (northwestern Atlantic, Caribbean, and South America) and further divided northwestern Atlantic sampling sites into three groups, separated approximately at Cape Hatteras on the US Atlantic coast and at the Floridian peninsula, separating the Gulf of Mexico and Atlantic coasts. In contrast, microsatellite data only distinguished samples north and south of Cape Hatteras, and suggested considerable gene flow among native samples with clear evidence of isolation by distance. Both Electronic supplementary material The online version of this article (