温度和盐度对青蛤孵化及幼虫、稚贝存活与生长变态的影响

在9个温度梯度(10-34℃)和10个盐度梯度(盐度3‰-50‰)条件下,研究了温度和盐度对青蛤孵化及幼 虫、稚贝生存与生长变态的影响。结果表明,青蛤孵化和浮游幼虫生长的适温范围为24-32℃,最适温度均为26- 30℃,稚贝生长的适温范围为22-32℃,最适温度为24-30℃。在最适温度下,D形幼虫变态率达80．7％-88．2％, 浮游幼虫和稚贝的存活率分别为86．2％-88．7％和81．5％-84．0％;孵化及浮游幼虫的生长适宜盐度为15‰- 30‰,稚贝为10‰-35‰,最适盐度均为20‰-25‰。在最适盐度下,D形幼虫的成活率、变态率、生长速度皆最高, 分别达到86．9％、77．5％和9．38×11．0μm/d,匍匐幼虫经14-14．5d发育至双管期稚贝,至双管期稚贝的成活率 82．5％-85．0％,日平均生长达13．1μm以上。与大多数滩涂贝类一样,青蛤属于广温广盐性贝类,且稚贝对低盐的 适应能力强于对高盐的适应能力。     

饥饿和再投喂对青蛤(Cyclina sinensis)幼虫生长、存活及变态的影响

在温度18.2～20.6℃,盐度23～25,pH 7.96～8.14 的条件下,研究了饥饿和再投喂对青蛤幼虫生长、存活及变态的影响.结果表明:在饥饿状态下,幼虫具有生长现象,且随着饥饿时间的延长,壳长逐渐接近一个常值而不再生长;幼虫可以由面盘幼虫发育到足面盘幼虫.随饥饿时间延长存活率下降;且足面盘幼虫及其变态规格、单水管稚贝规格随着饥饿时间延长而减小;幼虫的不可逆点(PNR)为12.48d;延迟变态时间长达12.7d.饥饿后再投喂相同的时间,幼虫能够恢复生长,存活的幼虫能够变态;稚贝表现出补偿生长现象,以壳长作为衡量标准,完全补偿生长能力依次为:S10＞S11＞S12＞S1＞S2＞S3;超补偿生长能力依次为:S9＞S8＞S7＞S6＞S5＞S4.     

香港巨牡蛎和长牡蛎幼虫及稚贝的表型性状

为了评估香港巨牡蛎和长牡蛎在北方沿海的早期表型性状,于2010年7月,以2009年6月在青岛繁育的两种牡蛎为材料,在大连研究了温度(Mt:(22±1.0)℃及Ht:(28±1.0)℃)、盐度(S₂₀:20±1.0及S₃₀:30±1.0)及中间育成环境(ID:室内及OD:室外)对两种牡蛎幼虫及稚贝表型性状的影响。结果表明:香港巨牡蛎壳宽显著大于长牡蛎(P<0.05),壳高及怀卵量显著小于长牡蛎(P<0.05),壳长、鲜重及壳重两者间无显著差异(P>0.05)。在温度和盐度相同情况下,长牡蛎卵径、受精率、孵化率及D形幼虫均大于香港巨牡蛎;香港巨牡蛎幼虫浮游前期生长较慢,而后快于长牡蛎。两种牡蛎幼虫存活能力在15日龄时高温组>中温组;相同温度下,香港巨牡蛎中盐组>高盐组,长牡蛎高盐组>中盐组。幼虫变态期间,较低的温度延迟了变态时间,降低了变态率,使得两种幼虫变态规格大型化。温度是影响幼虫生长、存活、变态的最主要因素,其次为盐度,交互作用几乎尚未起到作用。中间育成阶段,室外比室内培育效果更好,且香港巨牡蛎稚贝壳高在60日龄以后显著大于长牡蛎(P<0.05),环境是影响稚贝生长的最主要因素;无论室内还是室外两种牡蛎稚贝的存活率均在90%以上,且各实验组间无显著差异(P>0.05)。     

不同盐度、pH条件下氨氮对管角螺稚贝毒性影响

在水温28.5℃,采用实验生态学方法研究了不同盐度、pH条件下氨氮对管角螺(Hemifusus tuba)稚贝[壳高(11.3±0.11)mm,n=30]毒性的影响。结果表明,(1)盐度对氨氮的毒性有较大影响,随着盐度的降低,氨氮在水体中的毒性增强;盐度为16、19、23和28,总氨氮对稚贝的96h半数致死浓度(96hLC50)分别为36.5、43.7、52.6和58.8mg/L,安全浓度(SC)为3.7、4.4、5.3和5.9mg/L。(2)氨氮在水体中的毒性随pH的升高而增强,pH为7.6、8.0、8.4和8.8时,总氨氮对稚贝的96hLC50依次为58.3、54.5、50.6和20.2mg/L,对应的SC依次为5.8、5.5、5.1和2.0mg/L。氨氮在pH8.8时对稚贝的96hLC50急剧下降,其毒性是在pH7.6时的2.9倍。     

大竹蛏胚胎发生及稚贝发育研究

在人工培育条件下,对大竹蛏(Solen grandis)胚胎发生及稚贝发育进行显微观察,探究大竹蛏胚胎及幼虫发育规律。结果表明,大竹蛏胚胎及幼虫发育过程为：受精卵、卵裂、囊胚期、原肠期、担轮幼虫、D形幼虫、稚贝。在水温为22.4℃时,受精后20~24h发育成D形幼虫,5~7d变态为稚贝,38d稚贝贝壳已具备成贝形态,壳长壳高比为2.60。从受精卵到附着所需积温为3088.79~5005.19℃?h。稚贝先形成出水管后形成进水管,最终形成“一管双孔”。壳长与壳高关系式为     

菲律宾蛤仔(Ruditapes plilippinarum)大连群体两种壳型家系生长发育比较

通过对菲律宾蛤仔大连群体壳宽的选择,于2006年5月建立了壳宽型(WS)和壳扁型(PS)两个家系.对两种壳型亲本的鲜重、性比、产卵量及其子代的生长与存活进行了比较.结果表明:两种亲贝的鲜重差异显著(P＜0.05),WS、PS亲贝的雌雄比例分别为0.88 : 1、0.62 : 1,产卵量分别为124.19万/粒和408.50万/粒;两家系子代的卵径、D形幼虫大小、变态规格无显著差异(P＞0.05),但单水管、双水管稚贝的大小差异显著(P＜0.05);幼虫浮游期间(0～16日龄),WS和PS幼虫平均生长速度分别为(9.46±1.56)ìm d-1和 (9.60±0.38)ìm d-1,差异不显著(P＞0.05).12日龄前,WS和PS幼虫存活率差异不显著(P＞0.05),但16日龄时,WS幼虫存活率明显低于PS (P＜0.05).变态期间(16～24日龄),WS家系的生长速度((2.64±0.34)ìm d-1)显著地小于PS家系((3.91±0.67)ìm d-1) (P＜0.05),WS家系的变态率(5.32%±1.53%)也显著地小于PS家系(15.68%±3.06%) (P＜0.01).PS家系在稚贝的室内培育期间(24～60日龄)和生态池育成阶段(60～180日龄)的生长速度均显著地快于WS家系(P＜0.05);PS家系的存活率也均显著地高于WS家系(P＜0.05).     

pH和氨氮对橄榄蚶耐受性的影响

采用实验生态学方法,研究了pH和氨氮对橄榄蚶稚贝和成贝存活和耐受力的影响.结果表明:pH显著影响橄榄蚶稚贝和成贝的成活率,橄榄蚶稚贝适宜pH范闱为7.9～9.4,pH为8.5时存活最好,橄榄蚶成贝的适宜pH范围为5.2～9.4.氨氮浓度和毒性试验时间的相互作用显著影响橄榄蚶稚贝和成贝的成活率,氨氮浓度越高,其毒性越强.稚贝48 h、96 h的半致死浓度(TLm)为58.6 mg·L-1、50.0 mg·L-1,安全浓度(SC)为5.9 mg·L-1、5.0 mg·L-1、成贝48 h、96 h的TLm为618.7 mg·L-1、556.9 mg·L-1、SC为61.9 mg·L-1、55.7 mg·L-1.     

合浦珠母贝幼虫变态中的形态、器官变化及运动与摄食观察

为揭示合浦珠母贝幼虫至稚贝生长发育过程中其外部形态变化及内部器官改变的内在规律, 掌握其形态和器官与运动和摄食行为之间的关联。在光学显微镜下对整个幼虫生长发育及变态过程中的外部形态、内部器官特征进行了系列观察和性状测量; 利用非线性回归参数拟合, 描述各形态性状生长特点及不同属性之间的联系; 观察不同发育阶段其运动与摄食过程。结果显示, 幼虫在正常生长过程中, 其壳长生长方式为加速正增长、壳高为减速正增长、绞合线长为加速负增长, 壳高相对于壳长的生长为快速生长、绞合线长相对于壳长为慢速生长。幼虫生长至壳长为(209.26±9.22) μm时, 内部器官发生改变, 面盘开始逐渐退化从而发育成鳃, 斧足逐渐形成; 壳长生长至(234.30±14.00) μm时, 次生壳开始长出, 外部形态逐渐向稚贝转变。稚贝阶段, 其鳃丝长、鳃丝间距和鳃丝数量相对于壳长的生长均表现为慢速生长。幼虫在水中的运动和摄食过程主要依靠面盘外周纤毛的摆动来完成, 俯视观幼虫绕不规则圆沿顺时针方向运动, 垂直观幼虫螺旋上升或下降。稚贝阶段, 依靠斧足的往复伸缩来完成爬行, 依靠鳃的过滤完成摄食。在幼虫变态过程中, 面盘退化至鳃具备滤食功能期间, 变态幼虫运动功能降低, 摄食能力丧失, 依靠自身能量储备来完成生长和器官发育, 这一过程是苗种培育中的重要关键点。     

盐度对墨西哥湾扇贝幼虫和稚贝生长与存活的影响

2000年4月和2001年4月在浙江省玉环县抛西水产育苗场研究了海水盐度对墨西哥湾扇贝浮游幼虫和稚贝生长和存活的影响。结果表明：浮游幼虫的适宜盐度为16．54—36．58,最适生长盐度为23．38—30．02;稚贝的适宜盐度为23．38—42．70,最适生长盐度为23．38—36．58。     

褶纹冠蚌钩介幼虫非寄生变态发育观察及早期稚蚌的生长

为揭示褶纹冠蚌钩介幼虫变态发育特征及过程,采用体外培养方法实现了褶纹冠蚌钩介幼虫的非寄生变态发育。运用光学显微镜和扫描电子显微镜对变态发育过程中幼虫外部形态、内部器官发育进行了系列观察,对非寄生变态发育的稚蚌后期生长发育进行跟踪研究,并分析了底泥和光照两种环境因子对稚蚌存活及生长的影响。结果显示:在整个培养过程中,钩介幼虫的外部形态及大小未出现显著性变化,而斧足、鳃丝、外套膜及内脏团等组织器官逐步形成;在培养第3天,幼虫可见斧足雏形,鳃丝、外套膜纤毛尚未发现;在培养第6天,斧足成形,可见斧足侧沟,外套膜纤毛稀疏,鳃丝出现;培养第9天,斧足纤毛、外套膜纤毛增多,鳃丝密集。稚蚌投喂30d后,鳃丝基本成形。养殖试验结果表明:底泥对稚蚌存活和生长具有显著影响（P < 0.01）,而光照无显著性影响（P>0.05）。该结果为蚌科钩介幼虫变态发育生物学研究积累了基础资料,也通过对稚蚌生长的评估证实了体外培养是蚌类人工繁育及保护的有效技术途径。     

The impact of different plant extracts on biological parameters of Housefly [Musca domestica (Diptera: Muscidae)]: Implications for management

Housefly is a significant domestic pest, which causes nuisance. The use of insecticides is discouraged to manage housefly; therefore, alternative management strategies are inevitable. The current study investigated the impact of different plant extracts, i.e., Moringa oleifera (moringa), Allium sativum (garlic) and Piper nigrum (black pepper) on biological parameters of house fly. Two different concentrations (i.e., 25 and 50%) of the extracts were blended in larval diet made through mixing of wheat bran, yeast and dried milk powder. The results indicated significant differences for larval duration. Maximum larval duration was recorded for garlic followed by black pepper and moringa, respectively. In case of pupal duration, non-significant differences were observed among plant extracts. Increase rate of oviposition was noticed with moringa at 25% concentration, while decreased oviposition rate was noted for garlic with 50% concentration. Egg hatching percentage remained non-significant for the botanical extracts. The highest survival was observed with moringa, while garlic resulted in the lowest survival. The highest repellency was noticed for garlic followed by black pepper, whereas moringa resulted in the lowest repellency after 30, 60 and 90 min. Prolonged developmental time was observed for bot concentrations of garlic, whereas moringa noted the shortest developmental time. Thus moringa was found to be a promoter of housefly development. Minimum adult emergence was found with both concentrations of garlic followed by 50% concentration of black pepper. The 50% concentration of black pepper promoted the population of adult males, while both concentrations of moringa and 25% concentration of black pepper encouraged the population of female adults. Study outcomes depicted that tested botanical extracts had significant potential for disturbing biological parameters of housefly. The garlic extracts can potentially be used to manage housefly. However, further investigations on the larval and adult mortality are needed.     

Sequential predator effects across three life stages of the African tree frog, <Emphasis Type="Italic">Hyperolius spinigularis</Emphasis>

While theoretical studies of the timing of key switch points in complex life cycles such as hatching and metamorphosis have stressed the importance of considering multiple stages, most empirical work has focused on a single life stage. However, the relationship between the fitness components of different life stages may be complex. Ontogenetic switch points such as hatching and metamorphosis do not represent new beginnings—carryover effects across stages can arise when environmental effects on the density and/or traits of early ontogenetic stages subsequently alter mortality or growth in later stages. In this study, I examine the effects of egg- and larval-stage predators on larval performance, size at metamorphosis, and post-metamorphic predation in the African tree frog Hyperolius spinigularis. I monitored the density and survival of arboreal H. spinigularis clutches in the field to estimate how much egg-stage predation reduced the input of tadpoles into the pond. I then conducted experiments to determine: (1) how reductions in initial larval density due to egg predators affect larval survival and mass and age at metamorphosis in the presence and absence of aquatic larval predators, dragonfly larvae, and (2) how differences in mass or age at metamorphosis arising from predation in the embryonic and larval environments affect encounters with post-metamorphic predators, fishing spiders. Reduction in larval densities due to egg predation tended to increase per capita larval survival, decrease larval duration and increase mass at metamorphosis. Larval predators decreased larval survival and had density-dependent effects on larval duration and mass at metamorphosis. The combined effects of embryonic and larval-stage predators increased mass at metamorphosis of survivors by 91%. Larger mass at metamorphosis may have immediate fitness benefits, as larger metamorphs had higher survival in encounters with fishing spiders. Thus, the effects of predators early in ontogeny can alter predation risk even two life stages later.     

Laboratory culture of the larvae of Conus textile Linné (Gastropoda: Toxoglossa)

The larvae of the Indo-Pacific gastropod Conns textile Linné were reared in the laboratory from hatching through metamorphosis. Larvae fed a mixed phytoplankton culture of Isochrysis galbana and Phaeodactylum tricornutum grew at a rate of 0.06 mm/day and began metamorphosing 16 days after hatching. Unfed control cultures yielded no metamorphically competent larvae. Laboratory-reared larvae metamorphosed spontaneously on the walls of the fïberglass rearing tanks when their average shell length was 1.5 mm. Measurements made on field-collected Conns textile juveniles indicate that the larvae metamorphose at the same size in the laboratory as they do in nature.Rates of larval shell length increase and dry weight increase paralleled each other until metamorphosis. At this point, shell growth slowed while dry weight increased suddenly. It is suggested that this weight increase reflects calcification and strengthening of the fragile larval shell upon entering the benthic environment.     

Survival, development and food energy partitioning of nase larvae and early juveniles at different temperatures

Survival was generally high, 94–100%, for newly hatched larvae of the nase Chondrostoma nasus held at 10, 13, 16, 19, 22, 25 and 28° C up to day 66 post-fertilization. The developmental rate decreased with age and increased with temperature. Specific growth rates increased with temperature; within one temperature range growth rate decreased with ontogenetic development. Food consumption and respiration increased with temperature and body size. A temperature increase from 25 to 28° C resulted in slightly reduced survival, minor acceleration of developmental growth and respiration rates, and impeded skeleton formation. Growth efficiency of consumed energy decreased throughout the larval period from 55 to 67% at the first larval stage (L1) to 36–48% at the first juvenile stage (J₁). A similar trend for assimilation efficiency and its utilization for growth was observed. The constant temperatures required by larval nase ranged from a minimum 8–10° C to a maximum 25–28° C. A shift of optimum temperatures, 8–12, 13–16, 15–18, 19 and 22° C for nase spawning, embryonic development, yolk feeding larvae, early externally feeding larvae and, late larvae and juveniles, respectively, paralleled the spring rise in the river water temperature. Larval and juvenile nase show high survival, growth and energy conversion efficiencies compared with other fish species. On the other hand, low survival rates and growth can be attributed to external perturbations; thus, young nase may be considered a good indicator of the environmental and ecological integrity of river systems.     

Relationships between larval nutritional experience, larval growth rates, juvenile growth rates, and juvenile feeding rates in the prosobranch gastropod Crepidula fornicata

Planktonic larvae experiencing short periods of starvation or reduced food supply often grow and develop more slowly, have poor survival, fail to metamorphose, metamorphose at smaller sizes, or grow slowly as juveniles. In this study, we examined the impact of short periods of food limitation at various stages of larval development on larval and juvenile growth in Crepidula fornicata. In addition, we considered whether juveniles that were stressed as larvae grew poorly because of reduced rates of food collection due to impaired gill function. For 5 experiments, larvae were either starved for several days beginning within 12 h of hatching or were starved for the same number of days following 1 or more days of feeding at full ration (cells of the naked flagellate Isochrysis galbana, clone T-ISO, at 18×10⁴ cells ml⁻¹). In one experiment, larvae were transferred for 2 or 4 days to seawater with extremely low phytoplankton concentration (1×10⁴ cells ml⁻¹). In all experiments, larvae were returned to full ration following treatment. Control larvae were fed full ration from hatching to metamorphosis. When larvae reached shell lengths of about 900 μm they were induced to metamorphose and then reared individually at full ration in glass bowls, with phytoplankton suspension replenished daily. Larval and juvenile growth rates were determined by measuring changes in shell length (longest dimension) over time. Juvenile feeding rates were determined by monitoring changes in phytoplankton concentration over 2–3 h at the end of the growth rate determinations. In general, larval growth rates for the first 2 days after the resumption of feeding were inversely proportional to the length of time that larvae were starved. However, larval growth rates ultimately recovered to control levels in most treatments. Starving the larvae caused a significant reduction in initial juvenile growth rates (first 3–4 days post-metamorphosis) in most experiments even when larval growth rates had recovered to control levels prior to metamorphosis. Juvenile growth rates were not significantly reduced when larvae were subjected to reduced food availability (1×10⁴ cells ml⁻¹), even for treatments in which larval growth rates were compromised. Mean weight-specific filtration rates for juveniles were significantly reduced (p<0.05) following larval feeding experience in only one or possibly 2 of the 4 experiments conducted. Our data suggest that although larvae of C. fornicata may fully recover from early nutritional stress, the resulting juveniles may exhibit poor initial growth due to impaired gill function, reduced digestive capability, or reduced assimilation efficiency.     

虫酰肼对甜菜夜蛾汰选种群生长发育及生殖的影响

研究虫酰肼对甜菜夜蛾汰选种群生长发育及生殖的影响。结果显示:经虫酰肼处理后,甜菜夜蛾SS种群和RR种群卵的孵化抑制中浓度分别为179.38和160.71mg/kg,孵化幼虫的存活抑制中浓度分别为18.64和30.53mg/kg,虫酰肼对甜菜夜蛾卵的孵化率影响较小,而对孵化后幼虫的存活率影响较大。处理初孵幼虫6d后,2种群幼虫存活率及化蛹率随处理浓度的增加而降低,幼虫历期最高饲毒浓度与最低饲毒浓度相比分别延长了2.71d和6.19d,同一浓度下,RR种群幼虫历期比SS种群缩短了0.94～2.59d。处理甜菜夜蛾3龄幼虫12h后,随虫酰肼浓度的增加,2种群化蛹率逐渐降低,雌雄蛹重均有递减的趋势,雌蛹比例随浓度的增加变化较小,但SS种群雌蛹比例≤50.00%,而RR种群雌蛹比例≥50.00%,雌雄成虫羽化率总体上依次递减,处理浓度大于1.00mg/kg时虫酰肼对甜菜夜蛾成虫羽化的影响较大。     

不同浓度氨氮对轮叶黑藻的生理影响

在实验室条件下,比较研究了不同浓度（0.5、1、2、4、8、16mg/L）的氨氮（NH4＋-N）对沉水植物黑藻（Hydrilla verticillata）的生理生化影响,测定了黑藻生物量、叶绿素、可溶性糖、蛋白质含量和过氧化物酶（POD）、超氧化物歧化酶（SOD）、谷氨酰氨合成酶（GS）的活性变化。实验结果表明低浓度的氨氮（0.5、1、2mg/L）对轮叶黑藻的生长稍有促进作用,但培养液中氨氮浓度超过4mg/L时,黑藻的相对生长率（R）明显下降,当浓度达到16mg/L时,黑藻在20多天内全部死亡。在低浓度氨氮条件下,黑藻叶绿素和可溶性糖含量随氨氮浓度增加呈上升趋势,当培养液中氨氮浓度超过4mg/L时,叶绿素和可溶性糖含量在第24、32、40天取样时较对照组明显降低。低浓度氨氮处理组（0.5、1、2mg/L）的蛋白质含量先下降后又上升,而对照组的蛋白质含量一直在上升,高浓度氨氮处理组（8、16mg/L）的蛋白质含量则呈明显下降趋势。POD、SOD和GS活性变化趋势基本一致,在高浓度氨氮条件下增加显著,并表现为先上升再下降的格局,在第16天或第24天达到最大值。研究结果提示在富营养化条件下氨氮氨氮条件下增加显著,并表现为先上升再下降的格局,在第16天或第24天达到最大值。研究结果提示在富营养化条件下氨氮浓度的升高将影响其生理功能,过高浓度的氨氮对轮叶黑藻是一种逆境胁迫,可抑制其生长甚至导致植物死亡。轮叶黑藻对氨氮浓度变化虽有一定耐性,但耐性会随时间延长而变弱。     

Ovipositional and ovicidal effects of the microbial agent Bacillus thuringiensis israelensis on Culex quinquefasciatus say (Diptera: Culicidae).

The magnitude of oviposition as well as the size, shape and the number of eggs per of egg rafts egg raft were determined after gravid Culex quinquefasciatus Say oviposited on water treated with water dispersible granules (WDG) of Bacillus thuringiensis ssp. israelensis (Bti) and on untreated water. The mean number of eggs/raft was lower in the treated than in the untreated water. Bti concentrations from 0.5 to 2.0mg/L affected the shape of egg rafts and number of eggs in each raft. As the concentration of Bti increased from 0.5 to 2.0 mg/L the shape of egg rafts became more irregular with fewer eggs in each raft. Exposure to Bti at 2- and 26-h reduced the hatching rates, and fewer eggs hatched at 26-h of exposure to Bti. As the concentration of Bti WDG increased from 0.5 to 2.0 mg/L, the hatching rate decreased. Eggs exposed for 2-h to 2.0mg/ L Bti had a hatch of 30% after 24 h, the rate increasing to 57% after 72 h. In contrast, in 26-h exposed eggs to 2.0 mg/L Bti, the hatching rate after 24 h was only 12% and this rate increased to 39% after 72 h. In larvae from eggs exposed for 2 h, the survival rate was 40% at 2.0 mg/L Bti and 87% in untreated controls. In contrast, the survival rates of larvae from 26-h exposed eggs was 91% in controls while it was 30% at 2.0 mg/L Bti. As the concentration of Bti increased from 0.5 to 2.0 mg/ 1 the survival rates of larvae decreased. The combined effects of reductions of egg rafts, low number of eggs per egg raft, and reduced hatching and survival rates could have significant cumulative effects on the yield of adult mosquitoes, and this could result in a greater control potential of this microbial agent.     

Changes in RNA,DNA, protein contents and growth of turbot Scophthalmus maximus larvae and juveniles

The growth potential of turbot Scophthalmus maximus larvae and juveniles was studied using nucleic acid‐based indices and protein variables. The experiment was carried out from 4 to 60 days post hatching (dph). A significant increase in instantaneous growth rate during metamorphosis and retarded growth rate during post‐metamorphic phase were observed. Ontogenetic patterns of DNA, RNA and protein all showed developmental stage‐specific traits. The RNA:DNA ratio decreased up to 12 dph, then increased rapidly till 19 dph and fluctuated until 35 dph followed by a decline to the end. The RNA:DNA ratio was positively correlated with growth rate of juveniles during the post‐metamorphic phase, whereas this ratio was not a sensitive indicator of growth during the pre‐metamorphic phase and metamorphosis. The protein:DNA ratio showed a similar tendency to the RNA:DNA ratio. Changes of DNA content and protein:DNA ratio revealed that growth of S. maximus performed mainly by hyperplasia from 4 to 12 dph and hypertrophy until 21 dph during the pre‐metamorphic larval phase. Growth was dominantly hypertrophical from the early‐ to mid‐metamorphosing phase and hyperplastic thereafter. The results show that the DNA content and protein:DNA ratio can evaluate growth rates of larval and juvenile S. maximus on a cellular level.     

An extraordinarily long larval duration of 4.5 years from hatching to metamorphosis for teleplanic veligers of Fusitriton oregonensis

Veliger larvae of the NE Pacific snail Fusitriton oregonensis were reared in culture for 4.5 to 4.6 years from hatching to metamorphosis and through postlarval growth to reproduction. Larval shells grew in length from 0.20 to 3.9 mm. Late veligers grew slowly, but shell sizes increased even in the 4th and 5th years. Widths of larval shells at late stages equaled or exceeded those of the protoconchs of two juveniles from the field. Cultured larvae did not metamorphose until presented with subtidal rocks and associated biota. There was no indication of larval senescence: the first 2 years of postmetamorphic shell growth were slightly faster, and time from metamorphosis to first reproduction (3.3 years) was slightly less than for an individual that had developed to metamorphic competence in the plankton. A 4.5-year larval phase exceeds previous estimates for teleplanic larval durations and greatly exceeds estimates of the time for transport across oceans. This extraordinarily long larval period may exceed the usual duration in nature but shows that larval periods can be much longer than previously suspected without complete stasis in growth and with little if any loss of viability.