| Caprella acanthogaster belongs to Crustacea Amphipoda and is considered asbiofouling organism for it usually inhabitat on the surface of maricultural red andbrown algae, sea urchin etc, and the maricultural facility such as cultural rope, scalloplatern net, and could feed organic detritus and the seeding of algae. In the northerncoastal of China, the species is found attaching on the surface of maricultural seaweedGracilaria lemaneaformis and influences the growth of cultivated seaweed seriously.Therefore, from September2012to September2013, basic reproduction biology,ecology and the control method were studied in Ailian Bay in this paper. The mainlyresults were as follows:1. Seasonal succession of biofouling community in Sungo Bay, ChinaThe seasonal succession and vertical distribution of biofouling community wereinvestigated monthly from September2012to September2013. A total of28macro-biofouling species were identified, including Algae, Spongia, Annelida,Mollusca, Bryozoa, Crustacea and Urochordata. The main attachment season wasduring July to November2012, and the highest biomass of biofouling organism wasextented in September and October2012, whichwas due to the higher biomass ofBryozoa sp., Laminaria japonica and Styela canopus. There were not significantlydifferent on vertical distribution of the biofouling species, but with significantlydifferent among the different areas. The number of biofouling species was more insummer and autumn than that of in winter and spring.The abundance of C. acanthogaster had significantly relationship with sea watertemperature, salt, and the concentration of ammonium, chla. In different areas, theabundance is different. In macroalgal area (site A), it was distributed throughout theyear but winter and the abundancewas maximum in summer, which amounted to90800ind·m-2, amount of which, including14400ind·m-2sexual maturity. However,in shellfish-algae cultured area (site B) and non-cultured area (site C), C.acanthogaster only could be found in summer.2. Reproductive biology of Caprella acanthogaster The reproductive biology of the marine amphipod C. acanthogaster wasconducted at14℃and20℃in laboratory. The results showed that:(1) Theembryonic developmental process went through nine stages: fertilized egg, cleavagestage, morula stage, blastula stage, gastrula stage, limb-bud stage, heart-beating stage,juveniles were fully developed and juveniles. The time of embryonic developmentfrom fertilized egg to juveniles hatching from egg membrane was196hoursand117hours at14℃and20℃, respectively.(2) The temperature had a significant influenceon maturation time and body length at sexual maturity(P＜0.05). Nonetheless, it wasno significant effect (P＞0.05) on body length of juveniles. The body length ofjuveniles, body length at sexual maturity and maturation time were1.52±0.17mm,10.14±1.24mm,33.20±3.27days at14℃, respectively. while that were1.37±0.07mm,6.66±0.75mm,18.17±2.56days at20℃.(3) There was a positive correlation betweenthe number of eggs (NE) and the body length (BL) at the same temperature. Therelationship between NE and BL was EN=7.7399BL-39.661(R2=0.7463) at14℃and EN=13.685BL-78.153(R2=0.7675) at20℃, respectively.3. Impacts of Caprella acanthogaster’s feeding on maricultural GracilarialemaneaformisThe feeding rate of different size of C. acanthogaster on seaweed Gracilarialemaneaformis at different temperature was measured in laboratory. The resultsshowed:(1) Both water temperature and the body size had significantly influence onits feeding rate (P<0.01). The feeding rate of C. acanthogasterincreasedwith theincreasing of water temperature at14~18℃and then decreased with temperature at18~22℃.(2) The loss weight percent (W) of G. lemaneaformiswas increased with theincreasing of density (D) of C. acanthogaster. And the relationship between W and Dcouldbe represented by Logarithmic curve equation: W=alnD+b.4. Control efficiency of ammonium bicarbonate (NH4HCO3) on Caprellaacanthogaster attached on cultivated seaweed Gracilaria lemaneaformisHigh-concentrations of ammonia solution have toxic or lethal effects on animals.They could be potentially used as antifoulant. On the other hand, ammonia can beabsorbed by G. lemaneaformis. In this investigation, C. acanthogaster was exposed tosolution of various concentrations (C) of ammonia including0.5,0.6,0.7,0.8,0.9,1.0,2.0,3.0,4.0and5.0g·L-1, with0g·L-1as the blank control. The detachment rate (D)and mortality rate (M) was calculated at short-time (5mins), medium-time (10mins), and longer-time (15mins) periods, respectively. The results showed that,(1) BothNH4HCO3concentration and treatment time had significant effect on rates ofdetachment (D) and mortality (M)(P<0.05);(2) The rates increased with the elevationof NH4HCO3concentrations and duration of exposed time. In the same exposure timegroup, the relationship between D or M and NH4HCO3concentration couldberepresented by the S-shaped curve equation：ln D=a+(b/C), or ln M=c+(d/C);(3)100%lethal concentrations of NH4HCO3for5,10,15mins were7.36,6.17,3.68g·L-1,respectively. |
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