Long-distance dispersal via ocean currents connects Omani clownfish populations throughout entire species range.

notes: PMCID: PMC4167857types: Journal Article; Research Support, Non-U.S. Gov'tOpen-access articleDispersal is a crucial ecological process, driving population dynamics and defining the structure and persistence of populations. Measuring demographic connectivity between discreet populations remains a long-standing challenge for most marine organisms because it involves tracking the movement of pelagic larvae. Recent studies demonstrate local connectivity of reef fish populations via the dispersal of planktonic larvae, while biogeography indicates some larvae must disperse 100-1000 s kilometres. To date, empirical measures of long-distance dispersal are lacking and the full scale of dispersal is unknown. Here we provide the first measure of long-distance dispersal in a coral reef fish, the Omani clownfish Amphiprion omanensis, throughout its entire species range. Using genetic assignment tests we demonstrate bidirectional exchange of first generation migrants, with subsequent social and reproductive integration, between two populations separated by over 400 km. Immigration was 5.4% and 0.7% in each region, suggesting a biased southward exchange, and matched predictions from a physically-coupled dispersal model. This rare opportunity to measure long-distance dispersal demonstrates connectivity of isolated marine populations over distances of 100 s of kilometres and provides a unique insight into the processes of biogeography, speciation and adaptation.NERCRoyal Society ExchangeEPHE Fellowshi

Seasonal variations of surface mesozooplankton community structure in the Sea of Oman and the Arabian Sea

The different characteristics and atmospheric forces over the Sea of Oman and the Arabian Sea are assumed to influence zooplankton seasonality and community structure. This work aimed to characterize the abundances and seasonality of coastal and surface mesozooplankton communities in the Sea of Oman (Muscat) and the Arabian Sea (Salalah), and the effects of environmental factors on their distribution. Zooplankton samples two contrasting coastal regions; 22 in the Sea of Oman, and 20 in the Arabian Sea, were collected during 2013-2014 from the surface and analyzed. Total zooplankton abundance was divided by the number of samples to obtain the monthly average abundance per meter cube (ind•m-3) of sea water. A total of 91 species were observed from all 42 samples of which 58 were copepods, among which 47 were calanoid copepods. Species composition varied significantly between the two locations. The similarity between the two communities was highest (samples were closest to each other) during the winter, and showed the largest differences in composition in the summer. The seasonal changes in community structures were most significant for copepods and calanoid copepods (p= 0.0002 and p= 0.0003 respectively) and less significant for non-copepods (p= 0.0057). Only few species (17 in the Sea of Oman and 20 in the Arabian Sea) represented more than 90% of the total zooplankton abundance. There was a distinct pattern of seasonal variation in the abundance of zooplankton in the Arabian Sea, especially copepods and meroplankton, but there was no such pattern in the Sea of Oman. Some successful species such as Temora turbinata and Penilia avirostris in the Sea of Oman, and Oithona spp. in the Arabian Sea seem able to exploit a wide range of prey from phytoplankton to small ciliates and thus feed through the microbial loop

Laser microprobe mass spectrometry of quaternary phosphonium salts: direct versus matrix-assisted laser desorption

AbstractThe use of laser microprobe mass spectrometry (LMMS) for the structural characterization of thermolabile quaternary phosphonium salts has been evaluated. A comparison has been made between LM mass spectra obtained by direct analysis of “neat” organic salts and the corresponding “matrix-assisted” LM mass spectra. Main limitations of LMMS for the direct analysis of neat organic salts (i.e., no matrix) result from (1) formation of artifact ions that originate from thermal degradation and surface recombination reactions and (2) poor shot-to-shot reproducibility of the spectra. Dilution of the organic salts in a suitable, UV-absorbing matrix (e.g., nicotinic acid) significantly enhances the quality of the LM mass spectra. Improvements are: (1) an increase of the ion yield of preformed cations, 92) reduction or elimination of thermal decomposition and other deleterious surface reactions, and (3) a much better shot-to-shot spectral reproducibility. An interesting analytical feature is that these LM mass spectra, which contain only a few matrix peaks, can be obtained for subnanogram amounts of sample.The results also show that triphenylphosphonium salts with polycyclic aromatic substituents can be used as “molecular thermometers” to probe both the temperatures experienced by the sample molecules during the laser-induced sesorption ionization process and the internal energies of the desorbed ion species. In this way, quaternary phosphonium salts can be used for evaluating whether improvements have been achieved by applying different sample tretments. Comparison of four different matrices (i.e., nicotinic acid, ammonium chloride, glycerol, and 3-nitrobenzylalcohol) indicates that the effectiveness of a matrix to reduce thermal degradation and to decrese the internal energies of the ions depends on the UV-absorption characteristics and the volatilization/sublimation temperature of the matrix material

Triterpenoids in Echinoderms: Fundamental Differences in Diversity and Biosynthetic Pathways

Echinoderms form a remarkable phylum of marine invertebrates that present specific chemical signatures unique in the animal kingdom. It is particularly the case for essential triterpenoids that evolved separately in each of the five echinoderm classes. Indeed, while most animals have ∆5-sterols, sea cucumbers (Holothuroidea) and sea stars (Asteroidea) also possess ∆7 and ∆9(11)-sterols, a characteristic not shared with brittle stars (Ophiuroidea), sea urchins (Echinoidea), and crinoids (Crinoidea). These particular ∆7 and ∆9(11) sterols emerged as a self-protection against membranolytic saponins that only sea cucumbers and sea stars produce as a defense mechanism. The diversity of saponins is large; several hundred molecules have been described in the two classes of these saponins (i.e., triterpenoid or steroid saponins). This review aims to highlight the diversity of triterpenoids in echinoderms by focusing on sterols and triterpenoid glycosides, but more importantly to provide an updated view of the biosynthesis of these molecules in echinoderms

PROBAVNI SUSTAV KOŠTUNJAČA PERSORBIRA MIKROČESTICE

The ability of the teleost gut to absorb microparticulate material was examined following rectal intubation (3.5 g kg -1 ) of commercial grade cornstarch (≈21 mm diameter), or potato starch (≈43 mm diameter). Tissue samples were taken from the mid - and hind-gut of control and treated fish 18 h postintubation. Collected samples were processed using standard plastic and staining protocols and resultant photomicrographs examined by computer-assisted image analysis. Cornstarch particles (8-14 mm), were observed to pass from gut lumen to the lamina propria via a paracellular or persorptive route only. No evidence for the like passage of potato starch was found.Mogućnost probavnog sustava koštunjavičastih vrsta riba da apsorbiraju sitne čestice pojedinih tvari bila je istraživana s pomoću rektalne intubacije (3, 5 g kg -1 ) komercijalnoga škroba kukuruza (promjera ≈21 mm) i škroba krumpira (promjera ≈ 43 mm). Uzorci tkiva uzeti su iz srednjeg i stražnjeg dijela crijeva kontrolne i tretirane skupine riba, i to 18 sati nakon intubacije. Sakupljeni su uzorci spremljeni u standardne plastike i obojeni prema protokolu, te fotomikrografski snimljeni na računalu. Čestice škroba kukuruza (8-14 mm) zapažene su da iz lumena crijeva prolaze u laminu propriju samo paracelularnim ili persorptivnim putem. No, nije zapažen prolazak čestica škroba krumpira

Short-Lived Aggregations of Filograna/Salmacina Tube Worms in the Gulf of Oman

Dense aggregations of serpulid worms were encountered in the Daymaniyat Islands (Gulf of Oman) from 10 to 20 m depth, over the period January–March, 2021. The species responsible for these aggregations belongs to the Filograna/Salmacina-complex (Annelida: Serpulidae). This species has been present in the area and observed along the Oman coastline, but high-density aggregates like this have not been reported before. The most probable cause of the aggregations, supported by field observations and Aqua-MODIS satellite data, was natural eutrophication with a subsequent algal bloom linked to the local winter monsoon. This observation emphasises the importance of documenting biodiversity and dynamics of reef communities along the Oman coastline

Aggregations of a Sessile Ctenophore, Coeloplana sp., on Indo-West Pacific Gorgonians

We document the benthic ctenophores Coeloplana sp. and Vallicula multiformis from Oman, extending their geographic range. A new Coeloplana species was found forming aggregations on gorgonians of two octocoral host genera, Melithaea and Euplexaura, representing associations previously unknown to occur in the Indo-West Pacific region. Our findings also illustrate the concurrent presence of the ectocommensal ophiuroid Ophiothela mirabilis, which adversely affects other Coeloplana species in the tropical West Atlantic, where it is considered invasive. This exploration contributes to our understanding of the biogeography, species distribution, and ectosymbiotic associations of these genera, setting the stage for a comprehensive species description and in-depth analysis of host relationships in future studies