Artificial substrates preference for proliferation and immigration in Aurelia aurita(s. l.) polyps

The increasing amounts of artificial marine substrates, in many parts of the world have been proposed as a potential driver of Aurelia spp. blooms, on account of providing extra habitats for the settlement and the proliferation of the benthic stage(polyps). Previous experiments have mainly focused on the substrate choices of Aurelia spp. planulae. However, substrate preferences for the proliferation and immigration of polyps have not been reported. We monitored the propagation and immigration of Aurelia aurita(s. l.) polyps on two natural and nine artificial substrates at constant temperature(20±0.5°C) and salinity(30±0.5) in beakers and a glass aquarium in the laboratory, respectively. The results showed that, among artificial substrates, the highest number for polyp proliferation and immigration was found on nets, rigid polyvinyl chloride plates(RPVC), and wood. The lowest density of polyps was present on iron plates. Among natural substrates, the asexual reproduction rate of polyps on Patinopecten yessoensis(Jay, 1857) shells was significantly higher than Azumapecten farreri(Jones & Preston, 1904). On the account of the distinction in the roughness, chemical properties and biofilms of these material surfaces, bare artificial or natural substrates discriminatively affect the proliferation and the immigration of Aurelia spp. polyps at laboratory. These observations suggest that, even in the natural environment, different materials and texture may influence the composition and the abundance of the fouling communities and the assemblages of polyps and, indirectly, have effects on the amounts of released medusae.

Survival of Red King Crab （Paralithodes Camtschaticus） Juveniles on Natural and Artificial Substrates

Understanding settlement tendencies and substrate preference is essential for king crab stock enhancement because structurally complex habitats provide red king crab juveniles with shelter and protect them from predation and cannibalism during critical stages of their lives. The growth and survival rates of juvenile red king crab （Paralithodes carntschaticus） from the first juvenile instar stage after settlement from the free-swimming glaucothoe （stage C 1）, to the third juvenile instar （stage C3）, that were reared in aquaria with natural rock, shell, and artificial substrate from June 8 to July 15, 2008 at the Alutiiq Pride Shellfish Hatchery in Seward Alaska were evaluated. The percent of crabs surviving to the C3 juvenile stage was the highest （34%） for the artificial substrate, the lowest （24%） for the shell substrate, and intermediate （27%） for the rock substrate. No significant differences were found in the wet weight and carapace width （P〉0.05） among these three treatments, although the crabs were reared in the natural shell substrate, were heavier, （4.1±0.3 mg） than those reared in the natural rock （3.9±0.1 mg）, and artificial substrates （3.8±0.7 mg） and crabs reared in the natural rock substrate were larger （1.8±0.2 mm） than those reared in the natural shell （1.7±0.2 mm）, and the same as those in the artificial substrates （1.8±0.2 mm）. These results may be due to the short length of the experiment relative to the life cycle of the species. Further research is needed to understand the optimal environmental conditions for juvenile crabs and determine how their crucial habitats, which may be easily disturbed by human activities, can be conserved.

Protozoan colonization on artificial substrates in relation to water quality in a tropical Indian harbour

A field study was conducted to evaluate the protozoan colonization patterns on artificial substrates in relation to organic pollution within a tropical harbour. The composition of protozoans and their succession rates on artificial substrates(polyurethane foam units) were compared between two field stations(A and B), and their presence were considered with regards to the prevailing water quality conditions at the study sites. Altogether 44 genera of flagellates and ciliates were documented. The common genera of flagellates encountered included Monas, Polytoma, and Chromalina. Among the ciliates, the predominant genera were Tetrahymena, Vorticella, Lagynophyra, and Heloiphyra. These groups exhibited characteristic successional patterns in relation to ambient water quality. At Station A, located close to the sewage outfall, the water quality parameters included poor Secchi disc transparency(0.48m), dissolved oxygen of 1.93 mg/ml, salinity of 18 psu, and temperature 31.3 ℃. Here, the nanoflagellates( spumella ) colonized first, followed by microcilliate( Tetrahymena ) and sessile form( Vorticella ). Station B, located on the seaward side, was characterized by relatively less stressed environmental conditions with transparency 1.85m and dissolved oxygen value of 6 04 mg/ml. Salinity of 27.27 psu, and mean temperature of 30 ℃ were recorded at “B'. At this station, the nanoflagellate Polytoma was first documented to colonize on the substrates, followed by microcilliate( Lagynophrya ) and suctorid( Heliophyra ). These findings support the use of protozoans as indicator species for evaluating the hazards posed by organic pollution to natural estuarine communities.

Fitness and predation potential of Macrolophus pygmaeus reared under artificial conditions

The biological parameters of Macrolophus pygmaeus Rambur afler prolonged rearing in the absence of plant materials were compared with those of conventionally plant-reared predators. When eggs of Ephestia kuehniella Zeller were provided as food, developmental and reproductive fitness of M. pygmaeus reared for over 30 consecutive generations using artificial living and oviposition substrates was similar to that of predators kept on tobacco leaves. Plantless-reared fifth instars of the predator also had similar predation rates on second instars of the tobacco aphid, Myzus persicae nicotianae Blackman, as their peers maintained on plant materials. In a further experiment, predation on aphid prey by fifth instar M. pygmaeus fed one of two egg yolk-based artificial diets was compared with that of nymphs fed E. kuehniella eggs. Despite their lower body weights, preda- tors produced on either artificial diet killed similar numbers of prey as their counterparts reared on lepidopteran eggs. Our study indicates that artificial rearing systems may be useful to further rationalize the production of this economically important biological control agent.