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Background The silver nanoparticles (AgNPs) are used in the production of numerous commercial and medical products and are found to have adverse effects on animals. The sessile marine polychaete worm, Hydroides elegans, was examined for the influence of AgNPs on external fertilization and early developmental stages. Results Toxicity of AgNPs at various concentrations were examined on germ cells, fertilization rate, and early developmental stages. The EC50 was evaluated as 3 nM AgNPs; however, the survivability varied at each developmental stage, reducing with increasing stages of development, indicating a bioaccumulation effect of AgNPs. The lag in time of development suggested an impediment in dividing cells and the nuclear dysfunction assessed by DNA damage using comet assay. Conclusion The observations documented have provided an insight on hazardous effect of AgNPs on susceptible cells and reproductive efficiency on other organisms including human.

Larvae of many sessile marine invertebrates settle in response to surface microbial communities (biofilms), but the effects of soluble compounds from biofilms in affecting larval behavior prior to settlement, attachment, and metamorphosis have been little studied. This question was addressed by videotaping the behavior of competent larvae of the serpulid, Hydroides elegans, above settlement-inducing biofilms. Adult worms were collected in Pearl Harbor, Hawaii, USA in November 2012 and spawned almost immediately. Six-day old larvae were placed in five replicated treatments in small cups: (1) with a natural biofilm; (2) with a natural biofilm on an 8-µm screen, 1 mm above the bottom of a clean cup; (3) with a natural biofilm beneath a clean screen; (4) in a clean cup; and (5) in a clean cup with a clean screen. Using the videotapes, larval swimming speeds and trajectories were quantified within 5 min of the larvae being placed in a treatment. Only larvae that touched a biofilm, i.e., in treatments (1) and (2), slowed their swimming speed and increased the amount of time spent crawling rather than swimming. This shows that under these conditions, any soluble cues emanating from a biofilm do not affect settlement behavior. Furthermore, after 24 h close to 100 % of larva in the two accessible biofilm treatments had metamorphosed and

The uptake of anthropogenic CO2 emissions by oceans has started decreasing pH and carbonate ion concentrations of seawater, a process called ocean acidification (OA). Occurring over centuries and many generations, evolutionary adaptation and epigenetic transfer will change species responses to OA over time. Trans-generational responses, via genetic selection or trans-generational phenotypic plasticity, differ depending on species and exposure time as well as differences between individuals such as gender. Males and females differ in reproductive investment and egg producing females may have less energy available for OA stress responses. By crossing eggs and sperm from the calcareous tubeworm Hydroides elegans (Haswell, 1883) raised in ambient (8.1) and low (7.8) pH environments, we observed that paternal and maternal low pH experience had opposite and additive effects on offspring. For example, when compared to offspring with both parents from ambient pH, growth rates of offspring of fathers or mothers raised in low pH were higher or lower respectively, but there was no difference when both parents were from low pH. Gender differences may result in different selection pressures for each gender. This may result in overestimates of species tolerance and missed opportunities of potentially insightful comparisons between individuals of the same species.

The serpulid polychaete Hydroides elegans Haswell, 1883 is an early colonist of new substrata in Pearl Harbor, Oahu, Hawaii. When metamorphically competent, larvae of H. elegans will settle rapidly upon an acceptably biofilmed surface, but not on a clean surface. In this study we found the ability of larvae to respond selectively to inductive surfaces to be retained for at least 3 wk. Of a series of bacterial strains isolated from Hawaiian marine biofilms, 13 induced larval settlement, 11 gave moderate or mixed results, and 10 others did not stimulate the settlement of H. elegans. The amount of settlement induced by monospecific strains was rarely as great as with natural, multispecies films. Most of the isolated bacteria were motile Gram-negative rods, but Gram-positive strains were also present, and diverse metabolic types were represented in the study. Biofilms killed by treatment with heat, ultraviolet radiation or chemical fixatives were no longer inductive. Soluble, dialyzable, heat-stable bacterial products induced settlement and metamorphosis more slowly. The range of bacteria producing an inductive signal suggests either that there are multiple cues, or that the cue is common to many bacteria. Chemical signals characteristic of early microbial biofilms may indicate freshly available substrata with optimal potential for the growth and survival of H. elegans.

1. Lake Timsah, which lies almost half-way the Suez Canal, is highly populated with fouling assemblages consisting of algae, sponges, coelenterates, tube worms, bryozoans, barnacles, amphipods, molluscs and ascidians. 2. Tube worms (Hydroides elegans), barnacles (Balanus eburneus andB. amphitrite) and amphipod tubes represented the major fouling constituents. 3. Heaviest settlement occurred from May to September and during this period a panel immersed only for one month was covered with a thick layer of fouling organisms. Fouling was slight in the coldest months (December–February). 4. The majority of foulers appeared at short-term exposure but sponges,Styela partita and molluscs arrived after longer periods. No correlation could be established between the density of fouling and the duration of exposure. 5. The uppermost two metres were the most populated part of the lake and fouling nearly vanished below 5 m depth largely due to the high salinity and turbidity.