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1.
The microstructure, shape and appearance of the growth rings in statoliths of Nassarius reticulatus (L.) were investigated. This species possesses two statocysts, each containing a single spherical statolith of calcium carbonate of up to 0.22 mm in diameter in the largest animals. The relationship between statolith diameter (SD) and total shell height (TSH) is exponential [ln(TSH)=26.3SD–0.842], although the function is site specific. Statoliths of the largest whelks (>29 mm) contained three or four clearly defined rings, corresponding to TSH values of ~1.1, 4.6–5.3, 12.0–13.5 and 18.5 mm, respectively. The first ring likely represents the metamorphic ring that was deposited at the time of larval metamorphosis when the post-larval whelk adopted a benthic lifestyle. The estimated size of the whelks at formation of the second, third and fourth statolith rings closely matched the TSH inferred from the shell rings. It is concluded that the patterns of growth rings present in statoliths can provide information about the age and growth of N. reticulatus.Communicated by O. Kinne, Oldendorf/Luhe 相似文献
2.
Seasonal changes in catch rate, growth and mortality of Nassarius reticulatus from an intertidal lagoon and a wave-exposed beach at Rhosneigr (Anglesey, North Wales, UK) are described. The number of N. reticulatus caught in baited traps from the lagoon was significantly higher (>125 individuals trap−1) during the summer (>18°C), than at <12°C (<65 individuals trap−1), and the numbers caught in the lagoon were an order of magnitude greater than on the beach, >13 individuals trap−1 in July (>16°C), and <5 individuals trap−1 between December and April (<9.5°C). Predictions of shell growth attained by N. reticulatus annually in the lagoon using graphical modal progression analysis (MPA) of length frequency data, were similar to the growth
of marked and recaptured lagoon N. reticulatus. Predictions of shell growth using computerised length frequency distribution analysis (LFDA), however, did not reflect the
growth as accurately as MPA. Modal progression analysis demonstrated that N. reticulatus from the lagoon achieved a higher asymptotic maximum shell length (L
∞) and a lower growth constant (K) than animals from the beach. Shell growth was seasonal with growth of the lagoon individuals slowing down towards the end
of September and resuming in early April, about a month later than the beach individuals. Mortality of N. reticulatus was greater during the summer, and survival was lower in the lagoon than on the beach. Recruitment patterns were similar in
the lagoon and on the beach, and MPA and LFDA predicted that larval N. reticulatus settled between late summer and early autumn, with juveniles (7–8.9 mm) appearing in the population the following year, between
February and April. Growth of male and female N. reticulatus in the laboratory was similar and was temperature and size dependent. The different growth patterns between N. reticulatus from the two habitats, predicted using MPA, were maintained when individuals were reared under laboratory conditions for ∼6 months;
N. reticulatus <21 mm from the beach grew faster than individuals from the lagoon, although N. reticulatus >21 mm from the lagoon grew faster and attained a larger length (26 mm) than individuals from the beach (24 mm). Low food
availability did not affect N. reticulatus survival in the laboratory but significantly suppressed shell growth. 相似文献
3.
C. A. Richardson H. Kennedy C. M. Duarte D. P. Kennedy S. V. Proud 《Marine Biology》1999,133(2):205-212
The calcitic and aragonitic shell of the fan mussel Pinna nobilis L. contains a record of the environmental changes experienced during its growth. Stable-isotope analyses of oxygen (18O:16O) in shell carbonate from the calcitic outer shell-layer have been used to validate the periodicity of clearly defined concentric
rings on the aragonitic posterior adductor-muscle scar and to estimate the age and growth of fan mussels growing in Posidonia oceanica (L.) meadows at four locations on the south-east Spanish Mediterranean coast. The stable oxygen-isotope records obtained
at intervals along a profile across the shell surface enabled seasonal changes in water temperature to be established, and
hence seasonal patterns of shell growth to be inferred. Muscle-scar rings were found to be deposited annually in the shell
in the spring and early summer (a period of increasing water temperatures), and represent an interruption in the migration
of the posterior adductor muscle along the inner surface of the shell. In small pinnids (<25 cm) accretion of the shell is
rapid during the first year, but in the second year it is distinctly slower than at the same time the previous year. This
slowing down in growth during the second year coincides with the appearance of the “first” distinct muscle-scar ring, indicating
that Pinna nobilis does not form a muscle-scar ring during its first year of shell growth. Maximum growth rates were recorded amongst pinnids
from Carboneras, where they achieved a length of 59 cm in 8 yr, whilst those from Aguamarga were estimated to be the oldest
(attaining a length of 45 cm in 13 yr).
Received: 26 January 1998 / Accepted: 8 October 1998 相似文献
4.
M. Peharda C. A. Richardson I. Mladineo S. Šestanović Z. Popović J. Bolotin N. Vrgoč 《Marine Biology》2007,151(2):629-638
Age, growth and population structure of Modiolus barbatus from Mali Ston Bay, Croatia were determined using modal size (age) classes in length frequency distributions, annual pallial
line scars on the inner shell surface, internal annual growth lines in shell sections of the middle nacreous layer and Calcein
marked and transplanted mussels. The length frequency distributions indicated that M. barbatus attain a length of ∼40 mm in 5–6 years indicating that a large proportion of the population in Mali Ston Bay is <5 years
old. Some mussels of ∼60 mm were predicted to be 14 years old using the Von Bertalanffy growth (VBG) equation. Up to the first
6 pallial line scars were visible in young (<6 years) mussels but in older shells the first scars became obscured by nacre
deposition as the mussel increased in length and age. The age of the older shells (>6 years) was determined from the middle
nacreous lines in shell section, which formed annually in winter between February and March; the wider dark increments forming
during summer (June to September). The oldest mussel, determined from the middle nacreous lines, was >12 years, with the majority
of mussels aged between 3 and 6 years of age. The ages of mussels ascertained using the growth lines were not dissimilar to
the ages predicted from the length frequency distributions. Age at length curves produced using modal size class data were
not different from the data obtained using the pallial scar rings and internal growth lines. Taken together these data suggest
that M. barbatus attains a length of 40 and 50 mm within 5 and 8 years, respectively. Eighty one percent of individual M. barbatus injected with a Calcein seawater solution (300 mg Calcein l−1), into their mantle cavity successfully deposited a fluorescent line, which was visible in suitably prepared shell sections
under ultra violet light. Incorporation of Calcein into the mussel shells was seasonally variable with the lowest frequency
of incorporation in mussels marked in February and recovered in May. Seasonal shell growth was observed with significantly
higher growth rates in mussels marked in May and removed in August (ANCOVA, F
3,149 = 23.11, P < 0.001). Mussels (∼18 to 22 mm) marked in May and recovered in August displayed maximal growth rates of >2.5 mm month−1 compared with a mean mussel growth rate of 1.2 ± 0.6 mm month−1. At other times of the year mussel shell growth ranged from immeasurable to 1.48 mm month−1. 相似文献
5.
Pablo E. Penchaszadeh Carlos Sánchez Antelo Soledad Zabala Gregorio Bigatti 《Marine Biology》2009,156(9):1929-1939
The edible volutid snail Adelomelon ancilla occurs on the Argentine coast and may have the capacity to serve as source of support for local fisheries. However, knowledge
of its reproduction is lacking. Over 3 years (from September 2000 to July 2004) we studied the oviposition at Golfo Nuevo,
Patagonia by diving. Monthly collections were performed to examine gonadal stages histologically during 2002–2003. Gamete
development stages corresponded with the expected period for oviposition occurring from July to November, a time of increasing
day length. Oviposition also took place in March when water temperature attained a maximum of 18°C. Following the spawning
period, remaining gametes were resorpted in both sexes. Males contained sperm throughout the year, parasperm and eusperm forms
were found within the same acinus. Oogonia/oocytes ranged from 20 to 240 μm in diameter during oogenesis. Females commenced
laying egg capsules from a shell length of 114 mm. Reproduction is compared with other fishable volutid snails from the Argentine
shelf, and suggests the need to apply certain fishing restrictions if the resource begins to be utilized commercially. The
imposex condition was found in snails from some shipping areas. The frequency of this condition declined with distance from
the port. 相似文献
6.
Haruna Amano Toshiaki Fujita Naoshi Hiramatsu Sayumi Sawaguchi Takahiro Matsubara Craig V. Sullivan Akihiko Hara 《Marine Biology》2007,150(6):1215-1225
Coralliophila abbreviata (Lamarck) is a corallivorous gastropod that lives and feeds on several species of scleractinian coral in the Western Atlantic
and Caribbean. Previous studies of C. abbreviata have revealed that snails on branching acroporid corals are larger and consume more tissue than those on massive and plating
corals. To ascertain whether snail life-history and fitness are differentially affected by the coral host, an analysis of
the age structure and female reproductive output of snail populations on three coral host taxa (Acropora palmata, Diploria spp., and Montastraea spp.) was conducted at four shallow (2–7 m depth) reef sites off Key Largo, Florida in June through August, 2004. Snails
were, on average, almost twice as large on A. palmata than on Diploria spp. and Montastraea spp., averaging 30.3 mm shell length, compared to 17.2 and 17.6 mm, respectively. Brood size increased as a power function
with female shell length. Females on A. palmata were significantly larger than females on the other two hosts and, therefore, produced more offspring per female. The number
of growth striae on the inner surface of the operculum was used to estimate snail age. Estimates of growth rate were obtained
by fitting the Gompertz growth function to size-at-age plots and mortality was estimated using growth parameters and size-frequency
data. The data suggest that C. abbreviata inhabiting A. palmata are larger than on alternative hosts due to a combination of a faster growth rate and longer life-span. The species is believed
to be a protandrous hermaphrodite. The timing of sex change varied among hosts; snails on A. palmata changed sex later at larger sizes relative to those on the other two hosts. Based on these results, it seems probable that
C. abbreviata has developed reaction norms for life-history traits, allowing snails to adjust and maximize fitness in the different environments
associated with various coral hosts. 相似文献
7.
A comparison of shell growth in Donax trunculus (collected between 1988 and 1990 of Cullera, Spain) has been carried out using an analysis of cohort progression in monthly length frequency distributions, hyaline surface shell growth rings and internal microgrowth bands. In the Mediterranean there are two periods of recruitment of D. trunculus, one in the summer (July to September) and the other in winter (December to February). Clams recruited to the population in winter display a clear cessation in shell growth during the following summer which may possibly be correlated with spawning, whereas individuals of the summer recruited cohort show no growth cessation the following summer and continue to deposit shell during this period. The normally opaque shell of D.trunculus reveals the presence of translucent hyaline growth rings when the shells are backlit by a strong light source, and these have been shown to be laid down in the shell during summer months. Formation of a hyaline ring is accompanied by a narrowing of the microgrowth patterns present in shell sections. Both the hyaline rings and the length frequency distributions have been used to determine the age and growth rate of D. trunculus. 相似文献
8.
A. I. Arkhipkin 《Marine Biology》1997,129(1):103-111
Statolith microstructure was studied in 56 Ancistrocheirus lesueurii (25 to 423 mm of mantle length, ML) caught in the central-east Atlantic. Statolith growth increments were grouped into three
main growth zones, distinguished mainly by increment width. The second transition in the statolith microstructure (from Zone
2 to Zone 3) coincides with the life history shift from epipelagic and upper mesopelagic to a bathyal habitat. Second-order
bands (mean 27.65 growth increments) and sub-bands (mean 13.6 growth increments) within statolith microstructure appeared
to be related to the lunar cycle. Striking sexual dimorphism is reflected in the age and growth rates: males live ca. 1 yr,
while females only start maturing at this age and obviously live >1.5 yr. A. lesueurii is a slow growing squid, attaining 25 to 30 mm ML at the age of 100 d. After ontogenetic migrations into bathypelagic waters
at ML > 30 to 35 mm, growth rates gradually decrease to the minimum known values for squids. Based on back-calculated hatching
dates, A. lesueurii hatches throughout the year with a peak between November and March.
Received: 28 August 1996 / Accepted: 31 January 1997 相似文献
9.
Effect of temperature on statolith growth of the European squid Loligo vulgaris during early life 总被引:1,自引:0,他引:1
R. Villanueva 《Marine Biology》2000,136(3):449-460
Over the past decade, statolith interpretation has resulted in a major advance in our knowledge of squid population-dynamics,
but the way in which environmental conditions affect the statolith increment-deposition ratio remains virtually unknown. The
object of the present study was to determine the effect of temperature on this process, using tetracycline marks to validate
statolith growth in Loligo vulgaris Lamarck, 1798 under rearing conditions equivalent to severe winter (11 °C) and summer (19 °C) temperature regimes. Tetracycline
marking was performed every 10 d (at 10, 20, 30, 40, 50 and 60 d of age). The newly hatched squid paralarvae were slightly
smaller in summer than those hatched in winter. Survival rates were similar in both cultures, but growth rates (wet mass)
of summer squids were double those in winter. At hatching, statoliths were already longer in the summer squids, and growth
rates were 2% d−1 as opposed to 0.9% d−1 for winter statoliths. For the dorsal dome area of the statolith, where more increment counts were made, statolith growth
was of 3.25 μm d−1 in summer, and daily increment deposition was confirmed in 87% of the statoliths. The slow growth of statoliths at winter
temperatures yielded a mean growth of 1.1 μm d−1– insufficient to discern the increments using light microscopy. Subsequent SEM observation enabled only 21% of the winter
statoliths to be read; these also indicated a deposition rate of one increment d−1. Since the life span of L. vulgaris is ≃1 yr, squids will experience at least one winter during their life cycle, and this might be visible on the statolith.
Received: 28 June 1999 / Accepted: 20 December 1999 相似文献
10.
Juvenile squids were grown in individual 2.6-l floating enclosures and were fed either a high- or a low-ration diet of fish
and the crustacean Acetes. Squids were maintained for a maximum of 44 days in two experiments. The high-ration individuals reached a significantly
larger size in both experiments (27, 25.5 mm mean mantle length, ML) compared to their low-ration siblings (19 mm mean ML)
in both experiments. The statolith increment widths prior to the start of the experiment were significantly wider (between
3 and 4 μm) compared to the increment widths after the start of the experiment (between 2 and 3 μm) both for the low- and
the high-ration squids. High-ration squids also had significantly wider increments and larger statoliths than their low-ration
siblings. Even though we detected consistent trends in daily statolith increment widths for the different feeding regimes,
we could not detect variation in increment widths at a daily level of resolution (i.e. as a result of differences in day-to-day
food intake at an individual level). This was probably due to the relatively consistent diet experienced by each individual.
These experiments revealed that ration level influences squid growth rate, statolith size and daily statolith increment width.
Received: 30 March 2000 / Accepted: 30 October 2000 相似文献
11.
Life history of the golden ring cowry Cypraea annulus (Mollusca: gastropoda) on Okinawa Island,Japan
M. Katoh 《Marine Biology》1989,101(2):227-234
Two mark-recapture studies, regular population censuses, field observations, and laboratory culture were used to study the life history of the tropical marine gastropod Cypraea annulus Linnaeus, 1758 from Cape Maeda, Okinawa Island, from April 1984 to March 1986. In the field, the average rate of increase in shell length of marked juvenile snails was 1.0±0.3 mm wk-1 (N=13), with a maximum of 1.5 mm wk-1 (initial shell length 10.6 to 17.2 mm). In the laboratory, the maximum growth rate of juveniles was 3.0 mm wk-1 with food ad libitum. Snails with primordial teeth on the shells grew at a rate of 0.1 to 0.5 mm wk-1 for about 2 wk. The adults continued to grow at a similar rate for an additional 3 to 6 wk, and ceased detectable growth when some females started spawning egg masses. In the littoral zone on Okinawa Island, snails reproduced throughout the year. Egg masses brooded by three females (shell length 17.4 to 21.3 mm) in the field contained 90 000 to 133 000 ova. In the laboratory, brooding periods of three females lasted 6,8, and 9 d. The estimated average frequency of spawning was 5 egg masses female-1 yr-1. The mean shell length of adult females (20.3 mm) was significantly larger than that of adult males (19.6 mm). The life-history strategy of C. annulus is characterized by rapid growth, high fecundity, and repeated spawning throughout the year. 相似文献
12.
The northern propellerclam Cyrtodaria siliqua is a common bycatch in the Arctic surfclam, Mactromeris polynyma fishery on Banquereau Bank in Eastern Canada. Samples of the propellerclam from this exploited fishery were used to determine
the life history characteristics of the population. The age structure of the population is dominated by old animals to ages
exceeding 100 years. We validated the age estimates for the propellerclam through analysis of bomb-produced radiocarbon in
the shell growth increments deposited before, during and after the atmospheric atomic bomb testing periods of the 1950s and
1960s. Radiocarbon from shells with presumed birth dates between the late 1950s and 1970s clearly reflected the sharp increase
in oceanic radiocarbon attributable to previous nuclear testing, indicating that age estimates based on shell increment counts
are accurate. Estimates of von Bertalanffy growth parameters revealed that the growth rate of the population was relatively
rapid for the first 20 years of life, slowing down to very low growth rates thereafter. Sexual maturity was estimated as being
reached at 28.6 mm in length and 4.7 years in age. Size–weight morphometric relationships were also calculated. 相似文献
13.
I. Sötje F. Neues M. Epple W. Ludwig A. Rack M. Gordon R. Boese H. Tiemann 《Marine Biology》2011,158(5):1149-1161
The rhopalia and statocysts of Periphylla periphylla (Péron and Lesueur in Ann Mus Hist Nat Marseille 14:316–366,1809) and Chironex fleckeri Southcott (Aust J Mar Freshw Res 7(2):254–280 1956) were examined histologically and showed several homologous characteristics. Differences in sensory area distribution could
be connected to a slightly different functionality of equilibrium sensing. In P. periphylla, the statoliths (crystals) grow independently of each other; whereas in C. fleckeri, one large crystal covers the smaller ones. The structures of both statoliths were examined in detail with single-crystal
diffraction, microtomography and diffraction contrast tomography. The single compact statolith of C. fleckeri consisted of bassanite as was previously known only for other rhopaliophoran medusae. An origin area with several small oligocrystals
was located in the centre of the cubozoan statolith. The origin areas and the accretion of statoliths are similar in both
species. Our results lead to the assumption that the single bassanite statolith of C. fleckeri (Cnidaria, Cubozoa) is a progression of the scyphozoan multiplex statolith. It is therefore suggested that the Cubozoa are
derived from a scyphozoan ancestor and are a highly developed taxa within the Rhopaliophora. 相似文献
14.
Increasing threats to deep-sea corals highlight the need to expand knowledge of these taxa so that conservation measures can
be developed. The present study focused on the reproductive patterns of the deep-sea solitary coral Flabellum angulare. A series of samples (n = 398) collected in 2006–2008 in the northwest Atlantic at depths of 925–1,430 m revealed that gametogenesis was synchronous
among males and females and fluctuated seasonally. Initiation of gamete synthesis was estimated to be in August–September
and spawning in June. Further analysis and daily monitoring of 30–60 individuals maintained in a flow-through mesocosm showed
that gamete release occurred in March–June with a peak in May. Release of oocytes coincided with rising seawater temperatures
and high deposition rates indicative of elevated water column productivity. Oocytes (900–1,200 μm diameter) were released
through the oral cavity, generally in bundles of 3–5 surrounded by mesenterial filaments and attached to a thread (30–50 mm
long). As oocytes became free in the water column, ovulation occurred followed by fertilization. Eggs/embryos initially remained
on the tentacles of the spawner before either falling onto the substratum or floating to the surface. The embryos developed
into planula larvae measuring 2–3 mm in length within about 24 h. Together, these findings shed new light on the strategies
used by deep-sea corals to maximize their reproductive success. 相似文献
15.
Low temperature limits the rate of biochemical reactions and aerobic scopes of cold water ectotherms. To compensate for this
limiting effect, animals living in cold environments often possess physiological or morphological adaptations to maintain
vital functions. Cross-latitudinal comparison of aerobic capacities is one method to test which factors constrain activity
in thermally distinct environments particularly when congeneric studies are carried out on related species with conservative
ecology and habitat. Burrowing is a major aerobic activity of bivalve molluscs that is described here for the first time for
the tropical mangrove species Laternula truncata and Laternula boschasina and then compared with their Antarctic congener Laternula elliptica. About 80% of L. truncata (16.3–46.1 mm shell length) and 63% of L. boschasina (11.3–27.7 mm shell length) buried within 24 h at 28°C. The burrowing rate index (BRI = [3√wet weight/time to bury]×104) ranged between 1.1 and 20.2 for L. boschasina and 1.1–32.9 for L. truncata. These values are 2–3 orders of magnitude less than other tropical bivalve molluscs and are amongst the lowest recorded for
any bivalve. Comparisons with the Antarctic L. elliptica showed little or no differences in BRI (Q
10 of 1.0–1.2 for specimens of the same size). This is contrary to the general pattern over a wide range of bivalves, where
BRI increases with a Q
10 of between 2.9 and 6.4 between high latitudes and the equator. L. elliptica has 25–30% longer relative foot length than tropical congeners of the same size, which could be a morphological adaptation
compensating for reduced burrowing speeds in a colder environment. Burrowing rates within the genus Laternula could, however, also be maintained by differing habitat, ecological and physiological constraints on burrowing capability. 相似文献
16.
Shelled molluscs frequently exhibit a record of damage on exterior surfaces that can evidence past predation attempts and
may affect survival and growth. In South Carolina populations of the ribbed marsh mussel, Geukensia demissa, >90% of the individuals and up to 60% of the total shell area are damaged. A trend toward greater amounts of damage occurred
on mid-marsh compared to oyster reef mussels from the barrier beach side of inlets. Shell damage effects on survivorship and
shell and tissue growth were assessed seasonally during multi- and single-season field experiments. Mussels from a common
mid-marsh site were divided into size classes (~50 or 70 mm), treated to create two damage levels (undamaged and damaged),
and replaced within mid-marsh exclusion cages to minimize additional shell damage. In both multi- and single-season experiments
increased shell damage resulted in significantly greater mortality. Linear shell growth was unaffected by increased damage,
but 50 mm mussels grew twice as fast. Shell mass increased 16–50% in the multi-season and single-season winter period, but
decreased 7–12% during the single-season summer period. Tissue mass significantly decreased 31–43% in 50 mm damaged mussels,
but increased by 33% for 70 mm mussels in both multi-season and the single-season winter period experiments. Shell damage
did reduce tissue mass 43% in 70 mm single-season summer mussels. Experimental results indicate shell damage from a simulated
increase in predation can affect negatively both survival and growth of marsh mussels. Seasonal timing of shell damage and
initial mussel size also influenced the effects of sublethal predation on shell and tissue growth. The previously unrecognized
importance of sublethal predation and the resultant significant negative effects of shell damage on survival and growth will
affect the distribution and population dynamics of G. demissa in coastal marshes and will influence the overall contribution of ribbed mussels to estuarine ecosystems. 相似文献
17.
D. J. Brousseau 《Marine Biology》1979,51(3):221-227
Field studies were conducted in Gloucester, Massachusetts, USA, to determine linear shell growth rates for Mya arenaria. These rates were then compared with those reported for the same species from other locations. Most shell deposition occurred from March through November of each year. Winter interruptions in growth were not as marked in the small clams as in the larger ones (>60.0 mm). Annual variations in growth were slight during the period 1973–1974. Growth of mature clams (>35.0 mm) slowed during the spawning season. No significant sexual dimorphism in mean annual growth rates was detected. Winter rings were shown to be a reliable method for determining age in clams from Gloucester. Age-size relationships, based on two independent measures of annual growth, winter rings and tagging experiments, were computed using the Von Bertalanffy growth equation. No well-defined latitudinal patcerns in growth could be established for M. arenaria. 相似文献
18.
The euphausiids Thysanoessa inermis (Kroyer 1846), Thysanoessa spinifera (Holmes 1900), and Euphausia pacifica (Hansen 1911) are key pelagic grazers and also important prey for many commercial fish species in the Gulf of Alaska (GOA).
To understand the role of the euphausiids in material flows in this ecosystem their growth rates were examined using the instantaneous
growth rate (IGR) technique on the northern GOA shelf from March through October in 2001–2004. The highest mean molting increments
(over 5% of uropod length increase per molt) were observed during the phytoplankton bloom on the inner shelf in late spring
for coastal T. inermis, and on the outer shelf in summer for T. spinifera and more oceanic E. pacifica, suggesting tight coupling with food availability. The molting rates were higher in summer and lower in spring, for all species
and were strongly influenced by temperature. Mean inter-molt periods calculated from the molting rates, ranged from 11 days
at 5°C to 6 days at 8°C, and were in agreement with those measured directly during long-term laboratory incubations. Growth
rate estimates depended on euphausiid size, and were close to 0 in early spring, reaching maximum values in May (0.123 mm day−1 or 0.023 day−1 for T. inermis) and July (0.091 mm day−1 or 0.031 day−1 for T. spinifera). The growth rates for E. pacifica remained below 0.07 mm day−1 (0.016 day−1) throughout the season. The relationship between T. inermis weight specific growth rate (adjusted to 5°C) and ambient chlorophyll-a concentration fit a Michaelis–Menten curve (r
2 = 0.48) with food saturated growth rate of 0.032 day−1 with half saturation occurring at 1.65 mg chl-a m−3, but such relationships were not significant for T. spinifera or E. pacifica. 相似文献
19.
Experiments were conducted to determine the effect of four algal diets (Corallina spp., Gelidium pristoides, Ulva rigida and an equal volume mixture of these seaweeds) on growth and reproduction of the South African gastropod Turbo sarmaticus Linnaeus, 1758. The best growth rate of juveniles (up to 13.8 mm shell length and 34.26 g wet body weight increase in 12
months), reproductive fitness of mature specimens (gonad index up to 33%) and energy reserves (up to 4.76 mg glycogen/100 mg
foot tissue) were achieved when T. sarmaticus was fed U. rigida or a mixed diet. In addition, the gonad index of individuals fed these diets was almost twice that of similar-sized field
specimens. Juveniles fed Corallina spp. only, grew very little (only 2.4 mm shell length and 4.23 g wet body weight increase in 12 months). The reproductive
fitness of adults fed on such a diet was also poor (gonad index <4.5%) and energy reserves were low (<3.5 mg glycogen/100 mg
foot tissue). Along the southeastern coast of South Africa, T. sarmaticus has a distinct reproductive cycle with gametogenesis occurring from March/April until August/September, whilst maturity (gonad
index = 15%) was maintained until December, after which spawning occurred until March.
Received: 6 July 1998 / Accepted: 8 March 1999 相似文献
20.
Genetic variation and covariation during larval and juvenile growth in Mercenaria mercenaria 总被引:1,自引:0,他引:1
Quantitative genetic variances and covariances were estimated for shell length of the hard clam Mercenaria mercenaria (L.) at three larval stages (prodissoconch I, 2 d and 10 d post-fertilization) in 1987 and in 1988 after ca. 9 mo of growth. At each sample interval additive genetic variance was a highly significant component of the total size variation. Narrow sense heritability estimates for shell length ranged between 0.58 (±0.10) for prodissoconch I and 1.08 (±0.29) for 2-d-old larvae. There was significant and positive genetic covariance in prodissoconch I and 2-d larval shell length which resulted in a highly significant genetic correlation (r
g=0.74) between these two traits. This covariance is not surprising since the prodissoconch I comprises the majority of the larval shell of a 2-d-old larvae. The genetic covariances between 2-d-old and 10-d-old larvae and between 10-d-old larvae and 9-mo-old juveniles were low and not significantly different from zero. These results indicate that there is substantial genetic variation for shell growth in M. mercenaria but this variation is not stable during development; the genetic variation in shell growth at one stage of development is not strongly related to the genetic variation in growth during other ontogenetic periods. In this study there were no evident constraints to natural selection for increased shell growth rate during development, which coupled with the high levels of genetic variation may suggest that in nature high rates of larval growth may not be normally subject to significant selective pressure. 相似文献