VARIATIONS IN THE PHYSIOLOGICAL STATE OF THE COMMON COCKLE (CERASTODERMA EDULE (L.)) IN THE LABORATORY AND IN SOUTHAMPTON WATER

Various physiological indices (i.e. body condition index, scopefor growth and net growth efficiency) have been used to examinethe metabolic state of the common cockle (Cerastoderma eduleL.) at different sites in Southampton Water, U.K. The resultsshow that there is a measurable difference in the conditionindex of cockles collected from different localities. Thesedifferences can be broadly related to the level of contaminationof the site with metals and hydrocarbons. All the indices suggestthat cockles inhabiting the eastern, less polluted side of SouthamptonWater are in a better metabolic state than in those from somesites on the western side close to industrial areas. Growthand longevity also appear to be site related. (Received 25 September 1989; accepted 25 March 1990)     

EFFECTS OF SEASON AND SIZE (AGE) ON HEAVY METAL CONCENTRATIONS OF THE COMMON COCKLE (CERASTODERMA EDULE (L.)) FROM SOUTHAMPTON WATER

The tissue concentrations of six metals (Cu, Cd, Fe, Pb, Niand Zn) have been examined in the cockle, Cerastoderma edulefor variation in relation to age, season and location of theanimal. Comparison is made of animals from seven sites in SouthamptonWater, U.K. which have differing sediment metal loads. Softtissues are observed to have lower metal concentrations in summerthan in winter/spring. Tissue metal load, per unit dry weight,also decreases with size/age of the animals. No direct correlationwas observed between sediment metal load and tissue levels,but animal concentrations were generally higher where sedimentswere contaminated. The findings are discussed. (Received 25 September 1989; accepted 25 March 1990)     

A QUANTITATIVE STUDY OF A CERASTODERMA -- NEPHTHYS COMMUNITY IN THE LIMFJORD, DENMARK, WITH SPECIAL REFERENCE TO PRODUCTION OF CERASTODERMA EDULE

Cerastoderma edule is the dominant member of a non-random Cerastoderma—Nephthyscommunity, occupying a physically, homogeneous, submerged sandbankin the Limfjord, Denmark. C. edule is patchily distributed withinthis community, growth rates showing a clear density-dependence.Individual production is about 35%lower in high density patchesthan outside them; at low density annual individual flesh dryweight increment is 295 mg. Seasonal variation in water, ash,lipid, protein and glycogen contents is studied, and a sizedependent(= density-dependent) relationship is shown to exist for someparameters. Population production, estimated by a new graphicalmethod, and taking into account gametic and shell protein production,attains 150 g dry flesh weight, m^–2.yr^–1 at meanpopulation density rising to 250 g dry flesh weight. m^–2.yr^–1in the high density patches. ¹Present address: Institut für Physiologische Chemie, Abt.Zellbiochemie, Universitat Hamburg, Martinistrasse 52, 2000Hamburg 20 (Received 10 March 1980;     

REPRODUCTIVE CYCLES OF CERASTODERMA GLAUCUM(BRUGUIERE) AND C. EDULE (L.) WITH SPECIAL REFERENCE TO THE EFFECTS OF THE 1981-82 SEVERE WINTER

Gonadal changes in two species of Cerastoderma occurring indiscrete populations in South Wales were monitored by stereologicalanalysis during the breeding seasons of 1981 and 1982. Fecundityand spawning efficiencies were determined quantitatively. Therelationship between reproductive activity and changes in meatcondition are discussed. Both species are opportunistic breeders. Their normal patternsof reproduction are similar, consisting of minimum activityin winter and peak activity during spring/early summer. Thetwo species were affected differently by the severe winter of1981–82—C. glau-cum exhibited a single, ‘epidemic’spawning and resumed gametogenesis after a 4-month resting period.C. edule adopted a ‘polycyclic’ pattern withouta resting period. Both of these unusual reproductive strategies,augmented by reduced predation resulted in heavy spatfalls. (Received 20 March 1985; revised 20 March 1985;     

鲁北的贝沙岗与贝沙植被类型

有关鲁北贝沙岗的植被,已往对它缺乏系统研究。本文概述了在鲁北渤海湾浅海这一特异环境条件下,植被的组成成分、生态特性、外貌结构和系统类型。     

THE INFESTATION OF MYTILUS EDULIS LINNAEUS BY POLYDORA CILIATA (JOHNSTON) IN THE CONWY ESTUARY, NORTH WALES

The incidence of the shell-boring parasite Polydora ciliatain Mytilus edulis from the Conwy estuary, North Wales is described.Amongst mussels >40 mm in shell length both the occurrenceand abundance of P. ciliata increased steeply with host size.Infestation was highest amongst mussels near the mouth of theestuary where around 60–65% of the population was parasitized;no systematic relationship between the incidence of P. ciliataand tidal elevation was observed. Mussel condition was negativelycorrelated with the degree of infestation. Moderately and heavilyinfested mussels, however, never accounted for more than ca.10% of this population and the overall detrimental effects ofP. ciliata on growth and production is thus probably quite small.Whilst heavily infested mussels were evidently more vulnerableto predation, the shore crab, Carcinus maenas, selected smaller,non-infested mussels whenever these were available. No obviousrelationships were found between the presence of P. ciliataand the incidence of either pearls or pea crabs. (Received 14 January 1991; accepted 2 April 1991)     

THE USE OF MOLLUSCAN SHELL GROWTH PATTERNS IN ECOLOGY AND PALEOECOLOGY

The influence of substratum, depth of water, turbidity, and temperature on daily growth patterns has been studied by transplanting juvenile Mercenaria mercenaria (Linnaeus) from the laboratory to intertidal and subtidal environments.
The study of seasonal growth variations in a population of Gemma gemma Totten from Long Island Sound shows that shell growth patterns may be used to determine the season of death and age of dead shells.
Deep-water species (e.g. Nucula cancellata Jeffreys, Malletia sp., and Calyptogena ponderosa Boss) exhibit growth increments that are more uniform in thickness and less sharply defined than those in shallow-water species.     

珠江口崖门鲈鱼年龄和生长的研究

本文依据1983年6月至1986年1月对290尾鲈鱼年龄和生长的调查资料,阐明鲈鱼鳞片年轮特征并计算出鲈鱼体长与鳞长、体长与体重的关系式。研究表明:3龄以前属幼鱼阶段,体长和体重的相对增长率较大,生长指标较高,3龄以后进入成鱼生长阶段。其生长适合von Bertalanffy生长方程,体重生长曲线的拐点位于3.05龄。因此以3龄、体重3.5公斤左右的鲈鱼作为商品鱼加以捕捞,经济效益最高。     

SPECIES OF THE GENUSLECIDEA(LECANORALES) ON GYPSUM IN SPAIN

The genusLecideain the lichen flora of the gypsum soils of Spain is represented by two species:L. gypsicolaLlimona andL. circinarioidesCasares & Hafellner sp. nov., which are described in this article. Chemical, anatomical and ecological differences are also described, as is the taxonomic value of the morphological characteristics of the mature ascoma.     

GROWTH OF THE GREEN ALGA CODIUM FRAGILE IN A CONNECTICUT ESTUARY1

An in situ comparison of environmental and physiological factors was undertaken in 1971–72 (15 months) in the Niantic River estuary to elucidate some of the important aspects, of the growth and development of the seaweed Codium fragile. In general, Codium in the estuary has a growing season of from 6 to 9 months. Growth increments during this period are relatively constant. Temperature and salinity are the main limiting factors to growth, although low summer concentrations of inorganic nitrogen may also be involved. Reproduction by means of swarmers occurs only in late summer or autumn. Codium appears highly adapted to the role of a colonizing species. It not only possesses the capability to occupy the harshest of environments, but also a system of reproductive alternatives which facilitates rapid colonization. The availability of substrate for attachment is the chief factor limiting its spread in this estuarine system.     

ECOPHYSIOLOGICAL RESPONSES OF CERASTODERMA EDULE (L.) AND C. GLAUCUM(BRUGUIERE) TO DIFFERENT SALINITY REGIMES AND EXPOSURE TO AIR

The estuarine bivalve Cerastoderma edule and the lagoonal C.glaucum were exposed in the laboratory to different salinityregimes and the effects in the osmotic concentration of themantle cavity liquid, extrapallial fluid and haemolymph determined.The behavioural responses of the two cockles to changing salinityand exposure to air were investigated by monitoring valve movements. Both C. edule and C. glaucum are euryhaline osmo-conformerswhen exposed to different environmental salinities, but differencesare seen in their behavioural responses to sudden exposure tolow salinity and cyclic changes in salinity. C. glaucum postponedthe effect of sudden exposure to low salinity by complete valveclosure whilst C. edule partially closed its valves and intermittentlygaped during the same period. During exposure to a sinusoidalfluctuating salinity regime, C. edule responded first to thefalling salinity by retracting siphons and partially closingvalves. In contrast, C. glaucum responded more slowly to fallingsalinity than did C. edule. C. glaucum closed valves faster,accompanied by erratic adductions. During an acclimation period in a continuous automatic tidalsystem, C. edule and C. glaucum were entrained to the tidalrhythm of immersion and exposure to air and demonstrated differentresponses of valve gaping and adductions. This rhythm was lostupon continuous submergence indicating the rhythm is exogenouslyinduced. The two cockles gaped during exposure to air at lowtide, suggesting that both can respire in air, contrary to previousreports. The different physiological and behavioural responses of C.edule and C. glaucum to changing salinity and exposure to airwere found to be a reflection of their respective environments.C. edule is adapted to daily changes and stresses in its estuarinehabitat whilst C. glaucum is subjected to seasonal changes. (Received 19 September 1985;     

AGE AND GROWTH OF LITHOPHAGA LITHOPHAGA (LINNAEUS, 1758) (BIVALVIA: MYTILIDAE), BASED ON ANNUAL GROWTH LINES IN THE SHELL

The life span of Lithophaga lithophaga was found to be >54 years when the annual growth lines in longitudinal shellsections were counted. The age determination was confirmed bya) length frequency histograms, b) the time taken for the formationof annual and reproduction rings and c) by determining the agein different parts of the shell. The age of individuals of thesame length varies, for example, individuals with a length of5.0 ± 0.2 cm range in age from 18–36 years. Theoldest individuals were found at depths of 1–5 m. Maximumgrowth (75%) was observed from the end of spring to the beginningof summer. The increase in length of the borehole, which was1.5 times greater than the length of L. lithophaga, was continuousand occurred at a faster rate in winter. Parameters, such as,shell length, age, axes, the occurrence of abnormal, white andpearlcontaining forms and wetflesh weight varied significantlywith depth. There was no variation in the ratio of boreholevolume/shell volume. On the basis of the above parameters, andalso the population density, each depth at which samples werecollected, was graded. Depths of 2–4 m were found to bethe most suitable for growth and habitation. Depths of 0–1m were most inhospitable due to strong wave action and the directeffect of the atmosphere. (Received 15 August 1994; accepted 17 March 1995)     

SHELL GROWTH IN SOME NILE BIVALVES

The growth of three species of mussels in the White Nile nearKhartoum was studied from caged specimens and natural populations.True annual rings develop as a result of a silting-induced restingstate during the annual flood from July to October. False ringsalso develop, possibly as a result of unfavourable factors likethe change of habitat, inadequate food, handling of the mussels. Growth is inhibited during November-January as a result of thelower water temperature and reproduction. However, there wasevidence that during this period juveniles grew at a higherrate than the adults. It could be concluded that there is atrade-off between reproductive effort and growth in the adults;growth is inhabited until the eggs are released from the gonadsinto the demibranchs. The period from February to July is the growth season; it ischaracterised by high water temperature and high transparency.The mussels had already spawned by February. Significant incrementswere observed on the shells of caged specimens especially afterMay. These increments were, however, smaller than comparablegrowth in natural populations. This indicated that the cageshad suppressed the growth of the mussels. Growth rates are slow. Estimation of maximum sizes for the unionidsusing Ford-Walford plots was almost in full agreement with theactual maximum sizes. The poor agreement in the case of M. dubiais related to the fact that this species is not well establishedin the habitat. ¹Present Address: Biology Department, Royal Holloway and BedfordNew College, Egham, Surrey TW20 0EX (Received 4 April 1989; accepted 20 July 1989)     

长江口刀鲚耳石年轮确证和年龄与生长研究

洄游性刀鲚是长江中下游重要的渔业资源,20世纪70年代以来,其资源量严重下降。研究以耳石为年龄鉴定材料,对长江口刀鲚渔获物的年龄结构和生长进行研究,主要目的在于确证刀鲚耳石上年轮,分析刀鲚渔获物的年龄结构和生长特征,评价刀鲚资源状况。2006年4月至2007年8月在长江口逐月采样,共采集了576尾洄游性刀鲚。对矢耳石横截面分析发现,从耳石核出发,腹侧生长轴具有周期性的直-弯生长模式,直线生长发生在4到12月,弯曲生长在10月到第二年的6月;边缘轮纹增长率分析也表明,这种直-弯生长模式具有年周期性,可以用来鉴定年龄。弯曲生长向下一个直线生长的转换发生在4月至6月间,将此转换定义为年轮标志。年龄分析表明,长江口刀鲚渔获物包括0龄至4龄共五个年龄组,以1龄和2龄个体为主,雌雄个体年龄组成相似,生长趋势也比较接近,拟合的von Bertalanffy生长方程为SL=327.691-e-0.51(t+0.28)(n=576,r2=0.71,P3.36(n=576,r2=0.95,P<0.05)。与20世纪70年代渔获物调查结果相比,现在长江口刀鲚种群明显低龄化和小型化,表明刀鲚资源已严重过度利用。降低刀鲚的捕捞强度是刀鲚资源保护和恢复的基础。       

AGE,GROWTH, AND REPRODUCTIVE PATTERNS OF DALL'S PORPOISE (PHOCOENOIDES DALLI) IN THE CENTRAL NORTH PACIFIC OCEAN

Life history parameters were estimated for Dall's porpoise, Phocoenoides dalli, from biological specimens collected in the western Aleutian Islands, during 1981–1987. Of 2,033 males and 3,566 females examined, reproductive data were available for 1,941 males and 1,906 females; ages were determined for 813 males and 1,297 females. Female sexual maturity was based on the presence of one or more corpus on either ovary; 845 were sexually immature and 1,061 were sexually mature. Two estimates of female average age at sexual maturity (ASM) were 3.8 and 4.4 yr; average length at sexual maturity (LSM) was 172 cm. Males were considered sexually mature when evidence of spermatogenesis was detected; 1,136 were sexually immature and 805 were sexually mature. Two estimates of male ASM were 4.5 and 5.0 yr; LSM was 179.7 cm. Physical maturity was assessed for 246 males and 446 females by examining the degree of fusion in thoracic vertebral epiphyses. For both sexes, the average age at physical maturity was 7.2 yr. Average length at physical maturity was 202.6 cm for males and 192.7 cm for females. Average lengths of physically mature males (x?= 198.1 cm, SE = 0.8566) and females (x?= 189.7 cm, SE = 0.4002) were significantly different(P < 0.0001). Early postnatal growth was rapid in both sexes. A secondary growth spurt in both mass and length was characteristic for both sexes; the increase in length preceded the mass increase by 1–2 yr. Average length at birth (LOB) was approximately 100 cm; birth mass averaged 11.3 kg (SE = 0.0772). By the time the umbilicus had healed (<2 mo), the average length and mass had increased to 114.1 cm and 23.8 kg, respectively. Gestation period based on projections using LOB was 12 mo, but this was considered an overestimate. Calving was modal, centered in early July; an annual reproductive interval was indicated. Among the sexually mature females, 120 were pregnant, 55 were pregnant and lactating, 321 were pregnant with colostrum, and 33 were “resting.” By 3 July (95% CI =x? 1 d), 50% of births had occurred, during each of the seven years sampled. The ovulation rate was estimated at 0.914 ovulations per average reproductive year. Enlarged follicles and recent ovulations were observed in postpartum females in late July.     

长江口北支兴隆沙有孔虫组合与沉积环境分析

通过对长江口北支兴隆沙XL2孔25个沉积物样品的有孔虫定量分析,发现该孔自下而上有4个有孔虫组合带(含10个有孔虫组合亚带),有孔虫分异度偏低,丰度变化大,壳径偏小,含有壳径细小的浮游有孔虫,部分壳体有机械破坏现象,这些特点反映出埋葬群在形成过程中受潮流的搬运、机械分选和破坏作用.结合沉积物粒度分析和环境磁学分析,揭示了该孔沉积环境自下而上按潮流脊-潮汐水道-潮流脊-潮坪演变的模式,进而探讨了长江口北支沉积水动力和物源.