共查询到20条相似文献,搜索用时 31 毫秒
1.
Copepod grazing impact on planktonic communities has commonly been underestimated due to the lack of information on naupliar
feeding behaviour and ingestion rates. That is particularly true for small cyclopoid copepods, whose nauplii are mainly in
the microzooplankton size range (<200 μm). The trophic role of Oithona spp. nauplii was investigated off Concepción (central Chile, ~36°S) during the highly productive upwelling season, when maximum
abundances of these nauplii were expected. Diet composition, ingestion rates, and food-type preferences were assessed through
grazing experiments with different size fractions of natural planktonic assemblages (<3, <20, <100, and <125 μm) and cultures
of the nanoflagellate Isochrysis galbana. When the Oithona spp. nauplii were offered a wide range of size fractions as food (pico- to microplankton), they mostly ingested small (2–5 μm)
nanoflagellates (5–63 × 103 cells nauplius−1 day−1). No ingestion on microplankton was detected, and picoplankton was mainly ingested when it was the only food available. Daily
carbon (C) uptake by the nauplii ranged between 28 and 775 ng C nauplius−1, representing an overall mean of 378% of their body C. Our relatively high ingestion rate estimates can be explained by methodological
constraints in previous studies on naupliar feeding, including those dealing with “over-crowding” and “edge” effects. Overall,
the grazing impact of the Oithona spp. nauplii on the prey C standing stocks amounts up to 21% (average = 13%) for picoplankton and 54% (average = 28%) for
nanoplankton. These estimates imply that the nauplii of the most dominant cyclopoid copepods exert a significant control on
the abundances of nanoplankton assemblages and, thereby, represent an important trophic link between the classical and microbial
food webs in this coastal upwelling system. 相似文献
2.
Respiration rates and elemental composition (carbon and nitrogen) were determined for four dominant oncaeid copepods (Triconia borealis, Triconia canadensis, Oncaea grossa and Oncaea parila) from 0–1,000 m depth in the western subarctic Pacific. Across the four species of which dry weight (DW) varied from 2.0
to 32 μg, respiration rates measured at in situ temperature (3°C) increased with DW, ranging from 0.84 to 7.4 nl O2 individual−1 h−1. Carbon (C) and nitrogen (N) composition of the four oncaeid species ranged from 49–57% of DW and 7.0–10.3% of DW, respectively,
and the resultant C:N ratios were 4.8–8.3. The high C contents and C:N ratios were reflected by large accumulation of lipids
in their body. Specific respiration rates (SR, a fraction of body C respired per day) ranged between 0.5 and 1.3% day−1. Respiration rates adjusted to a body size of 1 mg body N (i.e. adjusted metabolic rates, AMR) of the four oncaeid species
[0.6–1.1 μl O2 (mg body N)−0.8 h−1 at 3°C] were significantly lower than those (1.7–5.1) reported in the literature for oithonid and calanoid copepods at the
same temperature. The present results indicate that lower metabolic expenditure due to less active swimming (pseudopelagic
life mode) together with rich energy reserve in the body (as lipids) are the characters of oncaeid copepods inhabiting in
the epi- and mesopelagic zones of this region. 相似文献
3.
In situ feeding patterns of ephyrae of the jellyfish Aurelia aurita (Linnaeus) revealed the importance of relatively large (>1 mm) prey in the diet of these scyphozoan predators. These studies
were carried out in Narragansett Bay, Rhode Island, USA in March and April, from 1993 through 1996. Rotifers were the only
small prey ingested in quantity, and then only when they were unusually abundant in the plankton. Copepod nauplii, similar
in size to rotifers and equally abundant, were rarely consumed. Since copepods evince rapid escape responses, this observation
suggested a role for prey escape in determining prey vulnerability, while the predominance of large prey in the diet suggested
a role for prey size. Using two dimensional video observations of free-swimming ephyrae and their prey in the laboratory we
tested hypotheses about the mechanisms underlying these dietary patterns, comparing mechanisms for capture of large versus
small prey and for prey of equal size but differing escape behaviors. Capture efficiencies of ephyrae feeding on large prey
were 4 to 12 times greater than for small prey taxa. Capture efficiencies for prey of equal size also differed significantly,
indicating that other factors influence the outcome of predator–prey interactions. Most prey captures occurred while the ephyrae
were swimming and creating fluid flows that entrained prey into the subumbrellar region. Even copepod nauplii were frequently
drawn into the subumbrella of swimming ephyrae despite average potential escape velocities (25.7 mm s−1) that exceeded mean maximum velocity of fluid flows around the ephyrae (13.1 mm s−1). Large prey were more likely than small prey to contact nematocyst-bearing surfaces both before and after entrainment in
flow fields. With regard to behavior, prey escape speeds were not the only predictor of prey vulnerability. Prey that continued
swimming after entrainment (rotifers and brine shrimp) were captured more often than prey of equal size that ceased normal
swimming (copepod nauplii and barnacle nauplii). Copepod nauplii were the prey least likely to be captured because they either
“played dead” and were expelled from the subumbrella of the ephyrae before contacting a surface, or they eventually escaped
at high velocity. These observations indicate that size-selective predation by ephyrae of A. aurita can be influenced by a variety of behavioral responses of the prey.
Received: 9 April 1997 / Accepted: 5 September 1997 相似文献
4.
Growth rates and development times were determined for nauplii of the genera: Acartia, Centropages, Corycaeus, Oithona, Paracalanus, Parvocalanus and Temora in nearshore waters of Jamaica from in situ microcosm incubations. At these high local temperatures (∼28 °C), total naupliar
development time was short: 3 to 4 d inshore and 4 to 5 d offshore. Mean instantaneous growth rates (g) ranged from as high as 0.90 d−1 for Parvocalanuscrassirostris to as low as 0.41 d−1 for Corycaeus spp. In general, nauplii of cyclopoid copepods appeared to grow more slowly than those of calanoids of the same size. Naupliar
growth rates were significantly related to body size (r
2 = 0.43 to 0.50), but were unrelated to chlorophyll concentration in any measured size-fraction. This suggests that nauplii
are generally not limited by resources, but are growing at their maximum temperature and size-dependent rates.
Received: 30 May 1997 / Accepted: 13 May 1998 相似文献
5.
Survival, developmental and consumption rate (Artemia nauplii ingested per day) as well as predation efficiency (ingested per available Artemia nauplii) were studied during the larval development of the shallow-water burrowing thalassinid Callianassa tyrrhena (Petagna, 1792), which exhibits an abbreviated type of development with only two zoeal stages and a megalopa. The larvae,
hatched from berried females from S. Euboikos Bay (Aegean Sea, Greece), were reared at 10 temperature–food density combinations
(19 and 24 °C; 0, 2, 4, 8 and 16 Artemia nauplii d−1). Enhanced starvation resistance was evident: 92 and 58% of starved zoeas I molted to zoea II, while metamorphosis to megalopa
was achieved by 76 and 42% of the hatched zoeas at 19 and 24 °C, respectively. The duration of both zoeal stages was affected
by temperature, food density and their interaction. Nevertheless, starvation showed different effects at the two temperatures:
compared to the fed shrimp, the starved zoeae exhibited accelerated development at 19 °C (8.4 d) but delayed metamorphosis
at 24 °C (5.9 d). On the other hand, both zoeal stages were able to consume food at an increased rate as food density and
temperature increased. Predation efficiency also increased with temperature, but never exceeded 0.6. Facultative lecithotrophy,
more pronounced during the first zoeal stage of C.tyrrhena, can be regarded as an adaptation of a species whose larvae can respond physiologically to the different temperature–food
density combinations encountered in the wide geographical range of their natural habitat.
Received: 28 February 1998 / Accepted: 21 October 1998 相似文献
6.
Effects of ultraviolet-B enhancement on marine trophic levels in a stratified coastal system 总被引:3,自引:0,他引:3
A. A. Keller P. Hargraves H. Jeon G. Klein-MacPhee E. Klos C. Oviatt J. Zhang 《Marine Biology》1997,130(2):277-287
We examined the effects of enhanced UV-B radiation (relative to ambient) on marine trophic levels inhabiting a stratified
coastal ecosystem, using living models (13 000 liter marine enclosures) of a temperate estuarine water column. The experiment
was carried out in June and July 1994 on a plankton community drawn from lower Narragansett Bay, Rhode Island, USA. The effects
of altered UV-B radiation (elevated 50% over ambient, tenfold DNA-weighted) on three trophic strata: the primary producers
(photosynthetic algae), primary herbivores (copepods), and fish eggs and larvae (Anchoa mitchilli Cuvier and Valenciennes) were examined. The goal was to determine if UV-B–induced alterations at the base of the food chain
had impacts on other elements of the trophic web. Phytoplankton abundance (P=0.02) and biomass (P=0.007) were significantly reduced in UV-B–enhanced treatments, above but not below the thermocline (2.25 m), during the second
week of the study. Copepod nauplii were significantly less abundant in UV-B–enhanced mesocosms than in control treatments
during the third and fourth weeks of the study (P=0.01). A portion of the impact on nauplii may be a result of alterations at the base of the food web. The greater mortality
of nauplii in UV-B–enhanced systems did not translate to reduced abundance of copepodite (P=0.83) or adult (P=0.29) copepods. No significant effects were observed for microzooplankton (P=0.15). Neither the mortality rates nor the growth rates of larval anchovy were significantly affected by the experimental
increase in UV-B (P>0.05). Despite the tenfold increase in biologically damaging UV-B, effects were not seen at higher trophic levels, most likely
because of the rapid extinction of UV-B in the highly colored coastal water.
Received: 13 November 1996 / Accepted: 18 July 1997 相似文献
7.
Growth and development rates were determined for nauplii of Calanus finmarchicus (Gunnerus) in the near-shore waters of a western Norwegian fjord from in situ mesocosm incubations. The major food source
for the nauplii was diatoms, but Phaeocystis sp., dinoflagellates and ciliates were also part of the diet. At local temperatures ranging from 4.8 to 5.2 °C the cumulative
median development time from hatching to Nauplius VI was 19 d. The time taken to molt to the next naupliar stage was approximately
constant (3 d) from Stages IV to VI, but Stage III needed the longest development time (5 d). The instantaneous growth rate
in terms of body carbon was negative from hatching to Nauplius Stage II, but as high as 0.25 to 0.30 d−1 from Stage III to V. Enhancement of food resources by nutrient addition led to no significant change in specific growth rates.
Additionally, the cohorts from different nutrient regimes showed almost equal development time, size and body carbon within
stages. Length–weight relationships of nauplii from the two different food resources were: W
low resources = 4.17 × 10−6 × L
2.03 (r
2 = 0.84) and W
high resources = 4.29 × 10−6 × L
2.05 (r
2 = 0.92), where weight (W) is in micrograms of C and body length (L) in micrometers. The natural body morphology of naupliar stages I to VI is illustrated with digital images, including the
final molt from Nauplius VI to Copepodid Stage I. In general, development of the nauplii was faster than that of the copepodids
of C. finmarchicus, and structural growth was exponential from naupliar stages III to VI. This study validates our earlier results that nauplii
of C. finmarchicus can obtain high growth and nearly maximal developmental rates at relatively low food levels (∼50 μg C l−1), suggesting that nauplii exhibit far less dependence on food supply than copepodids.
Received: 30 July 1999 / Accepted: 7 March 2000 相似文献
8.
The fate of key species, such as the barnacle Amphibalanus improvisus, in the course of global change is of particular interest since any change in their abundance and/or performance may entail
community-wide effects. In the fluctuating Western Baltic, species typically experience a broad range of environmental conditions,
which may preselect them to better cope with climate change. In this study, we examined the sensitivity of two crucial ontogenetic
phases (naupliar, cypris) of the barnacle toward a range of temperature (12, 20, and 28°C) and salinity (5, 15, and 30 psu)
combinations. Under all salinity treatments, nauplii developed faster at intermediate and high temperatures. Cyprid metamorphosis
success, in contrast, was interactively impacted by temperature and salinity. Survival of nauplii decreased with increasing
salinity under all temperature treatments. Highest settlement rates occurred at the intermediate temperature and salinity
combination, i.e., 20°C and 15 psu. Settlement success of “naive” cyprids, i.e., when nauplii were raised in the absence of
stress (20°C/15 psu), was less impacted by stressful temperature/salinity combinations than that of cyprids with a stress
history. Here, settlement success was highest at 30 psu particularly at low and high temperatures. Surprisingly, larval survival
was not highest under the conditions typical for the Kiel Fjord at the season of peak settlement (20°C/15 psu). The proportion
of nauplii that ultimately transformed to attached juveniles was, however, highest under these “home” conditions. Overall,
only particularly stressful combinations of temperature and salinity substantially reduced larval performance and development.
Given more time for adaptation, the relatively smooth climate shifts predicted will probably not dramatically affect this
species. 相似文献
9.
At specific locations within the Baltic Sea, thermoclines and haloclines can create rapid spatial and temporal changes in
temperature (T) and salinity (S) exceeding 10°C and 9 psu with seasonal ranges in temperature exceeding 20°C. These wide ranges in abiotic factors affect
the distribution and abundance of Baltic Sea copepods via species-specific, physiological-based impacts on vital rates. In
this laboratory study, we characterized the influence of T and S on aspects of reproductive success and naupliar survival of a southwestern Baltic population of Temora longicornis (Copepoda: Calanoida). First, using ad libitum feeding conditions, we measured egg production (EP, no. of eggs female−1 day−1) at 12 different temperatures between 2.5 and 24°C, observing the highest mean EP at 16.9°C (12 eggs female−1 day−1). Next, the effect of S on EP and hatching success (HS, %) was quantified at 12°C for cohorts that had been acclimated to either 8, 14, 20 or 26 psu
and tested at each of five salinities (8, 14, 20, 26 and 32 psu). The mean EP was highest for (and maximum EP similar among)
14, 20 and 26 psu cohorts when tested at their acclimation salinity whereas EP was lower at other salinities. For adults reared
at 8 psu, a commonly encountered salinity in Baltic surface waters, EP was relatively low at all test salinities—a pattern
indicative of osmotic stress. When incubated at 12°C and 15 different salinities between 0 and 34 psu, HS increased asymptotically
with increasing S and was maximal (82.6–84.3%) between 24 and 26 psu. However, HS did depend upon the adult acclimation salinity. Finally,
the 48-h survival of nauplii hatched and reared at 14 psu at one of six different temperatures (10, 12, 14, 16, 18 and 20°C)
was measured after exposure to a novel salinity (either 7 or 20 psu). Upon exposure to 7 psu, 48-h naupliar mortality increased
with increasing temperature, ranging from 26.7% at 10°C to 63.2% at 20°C. In contrast, after exposure to 20 psu, mortality
was relatively low at all temperatures (1.7% at 10°C and ≤26.7% for all other temperatures). An intra-specific comparison
of EP for three different T. longicornis populations revealed markedly different temperature optima and clearly demonstrated the negative impact of brackish (Baltic)
salinities. Our results provide estimates of reproductive success and early survival of T. longicornis to the wide ranges of temperatures and salinities that will aid ongoing biophysical modeling examining climate impacts on
this species within the Baltic Sea. 相似文献
10.
The pattern of diel vertical migration and the trophic interactions of moon jelly (Aurelia sp.) were investigated in the sea lakes of Mljet Island (Adriatic Sea) where this scyphomedusa is present throughout the
year. Water column characteristics, plankton and in situ behaviour of Aurelia were followed over several 24-h cycles (6–8 times during each cycle) from the surface to the bottom (44 m). Aurelia exhibited a consistent pattern of diel vertical migration. Most of the time Aurelia were located at the bottom of the thermocline layer at temperatures lower than 19°C. Aurelia migrated towards the surface at dusk when the majority was found within the thermocline or just above it. During the night
the medusae sank into the deepest layers below 25 m. The main medusa food items inferred from stomach contents were small
adult copepods like Oithona nana and Paracalanus parvus and copepodites of small calanoids and cyclopids. In addition, in situ feeding experiments indicated high clearance rates
for nauplii and naked ciliates and clear response of bacterial populations pointing to indirect cascade effects of Aurelia on microbial in addition to classical food web. 相似文献
11.
Measurement of copepod predation on nauplii using qPCR of the cytochrome oxidase I gene 总被引:1,自引:0,他引:1
Edward G. Durbin Maria C. Casas Tatiana A. Rynearson David C. Smith 《Marine Biology》2008,153(4):699-707
A method to directly measure predation rates by older stage copepods upon copepod nauplii using species-specific primers for
the mitochondrial cytochrome oxidase subunit one gene (mtCOI) and real-time quantitative PCR (qPCR) was developed. The general
approach is to determine the mtCOI gene copy number of an individual prey organism and the copy number of the same gene in
the stomachs of predatory copepods collected in the field. From the knowledge of DNA disappearance rates in the stomachs,
ingestion rates can be calculated. In October 2006, laboratory experiments were carried out with Acartia tonsa N1 and N2 as prey and adult female Centropages typicus as predator. The copepods were collected in Narragansett Bay, USA. A. tonsa mtCOI copy numbers copepod−1 were determined for stages N1–C1 and for adults. A. tonsa DNA was detectable in the guts of the predators for as long as 3 h. Exponential rates of decline in prey DNA from the stomachs
of the predators are similar to those measured for gut pigments. Because of the very small amount of DNA in an individual
N1 or N2 nauplius, procedures were developed to maximize the quantitative extraction and recovery of DNA and to increase the
sensitivity of the method. Two quite divergent haplotypes of A. tonsa were found in Narragansett Bay, which required separate qPCR primers; one was present in summer (July) and the other in fall
and winter (October and February). With modification, the methods in this study can likely be applied to a range of predator–prey
systems. 相似文献
12.
Along the mid-Atlantic coast of the US, the ctenophore Mnemiopsis leidyi (Agassiz) appears to be increasing in abundance and undergoing shifts in its historical seasonal distribution. We provide
new data on shifting ctenophore abundance in Long Island estuaries and its implications for top-down control of the plankton
community. Peak mean biovolume estimates of M. leidyi in Long Island estuaries in 2006 revealed ctenophore abundance values that were a factor of two to five times greater than
previous studies conducted two decades ago. Furthermore, peak M. leidyi densities in 2006 occurred 2–3 months earlier than previously documented, suggesting a shift in the seasonal maxima of M. leidyi. Application of daily ingestion rates to zooplankton abundance indicates that, at its highest densities M. leidyi can remove an overall average of 20–89% per day of bivalve veligers and other zooplankton taxa, including adult copepods,
nauplii, and tintinnids. Increasing ctenophore abundance, especially during a period when they were not historically abundant
(i.e., June) may have significant consequences for species which spawn at this time. For example, current populations of M. leidyi represent a major source of larval mortality for bivalves which may inhibit recovery of shellfish populations and reinforce
their low abundance state in Long Island estuaries. 相似文献
13.
Recruitment of capelin in the Barents Sea fail when juvenile herring and cod are abundant and the potential for feeding competition
of wild sympatric capelin and herring larvae and small cod juveniles were investigated. The frequency of gut evacuation after
capture of capelin larvae were also studied in mesocosms. Small capelin larvae (<35 mm length) fed on small prey including
phytoplankton, invertebrate eggs and nauplii, bivalves, other invertebrate larvae and small copepods. Calanus copepodites were only observed in large capelin larvae (>26 mm length). Calanus copepodites were the major food sources for contemporary herring larvae (25–35 mm length) and Calanus and euphausiids were the major prey for small juvenile herring (37–60 mm length) and cod (18–40 mm length). Capelin larvae
reared in mesocosms evacuated the guts shortly after capture. Capelin larvae had a smaller mouth and fed on smaller prey than
herring and cod of the same length. This implies that the small capelin larvae, in contrast to sympatric small herring and
cod, are not tightly linked to the food chain involving Calanus and euphausiids. Thus, exploitative competition between capelin larvae and planktivorous fish that rely on Calanus and euphausiids in the Barents Sea may be relaxed. 相似文献
14.
To investigate copepod nauplii ingestion rates on phytoplankton, we have adapted the traditional gut fluorescence technique
as it can be used with lower gut pigment concentrations. With the improved technique, laboratory experiments were performed
to estimate functional responses for nauplii of Calanus helgolandicus and Centropages typicus. Nauplii were raised from eggs to copepodites and the experiments were performed with stages NIV-NV. Gut evacuation rates
and ingestion rates were measured on Isochrysis galbana at different concentrations. Specific ingestion rates ranged between 0.038–0.244 μg C μg−1 nauplii C d−1 for C. typicus and 0.041–1.412 μg C μg−1 nauplii C d−1 for C. helgolandicus. Both species showed a type III functional response, reaching a saturation concentration at around 600 μgC l−1 for C. typicus and 800 μgC l−1 for C. helgolandicus.
An erratum to this article can be found at 相似文献
15.
Mie H. Sichlau Jørgen L. S. Hansen Thorbjørn J. Andersen Benni W. Hansen 《Marine Biology》2011,158(3):665-676
Distribution, abundance and age of diapause eggs from three species of calanoid copepods (in particular from Acartia spp. most likely Acartia tonsa, and Centropages hamatus and less numerous from Temora longicornis) were recorded in sediment profiles by enumerating hatched nauplii from incubated sediment samples. Phytoplankton pigments
and 210Pb and 137Cs analyses indicated that the sedimentation regimes were different between two southern and two northern stations of the
island Funen, Denmark. Significant variations in vertical distribution, abundance and mortality of diapause eggs were found
between the stations. Dating of the sediment cores suggested a ~70-year maximum age of viable eggs on the northernmost stations,
and ~28 year at the southernmost stations. The eggs exhibited a significantly higher mortality rate at the southernmost stations
compared with the northernmost, 0.35–0.53 year−1 vs. 0.07–0.08 year−1 with no systematic pattern among species. The differences in abundance, mortality and age of the diapause eggs are suggested
to be due to the sediment characteristics in which they are buried. 相似文献
16.
Whilst a range of animals have been shown to respond behaviourally to components of the Earth’s magnetic field, evidence of
the value of this sensory perception for small animals advected by strong flows (wind/ocean currents) is equivocal. We added
geomagnetic directional swimming behaviour for North Atlantic loggerhead turtle hatchlings (Caretta
caretta) into a high-resolution (1/4°) global general circulation ocean model to simulate 2,925-year-long hatchling trajectories
comprising 355,875 locations. A little directional swimming (1–3 h per day) had a major impact on trajectories; simulated
hatchlings travelled further south into warmer water. As a result, thermal elevation of hatchling metabolic rates was estimated
to be between 63.3 and 114.5% after 220 days. We show that even small animals in strong flows can benefit from geomagnetic
orientation and thus the potential implications of directional swimming for other taxa may be broad. 相似文献
17.
The contents of free amino acids (FAA) and total protein, together with growth and gut-content, of turbot (Scophthalmus maximus L.) larvae reared at 14, 18 and 22 °C were studied from first-feeding to approximately 140 effective day-degrees post hatch
(Deff
∘). Artemia franciscana nauplii and two species of rotifers were used as prey. Protein content accounted for about 42 and 26% of dry body mass in
the A. franciscana nauplii and the rotifers, respectively. The FAA pool constituted 5.6 and 4.8% of the total amino acids in the same animals.
The dry body mass of turbot larvae was exponentially related to Deff
∘. Protein and FAA contents were linearly related to dry body mass, and were independent of rearing temperature between 14
and 18 °C. At the end of the experiment, however, turbot larvae at 22 °C had lower gut content values, retarded growth rates,
and decreased FAA contents and concentrations. Thus, at this high temperature, turbot larvae seem unable to catch and ingest
sufficient prey, or to sustain an amino acid assimilation rate from the intestine sufficient to meet metabolic demands.
Received: 2 January 1997 / Accepted: 25 September 1998 相似文献
18.
19.
In this study we report the abundance, fecundity and an index of the relative survival of Oithona similis (nauplii to copepodites) across a large latitudinal and temperature range within the Southern Ocean. The abundance of O. similis was strongly related to temperature and to depth-integrated (0–100 m) chlorophyll a, abundance increasing with increasing temperature (and therefore decreasing latitude) and Chl a. In situ egg production rates and fecundity per female were also significantly and positively related to temperature and
Chl a. Egg hatch times rapidly lengthen as temperature decreases and in sac spawning species the next batch of eggs cannot be produced
until the previous clutch hatch. Consequently, we predict that in O. similis, fecundity must decline rapidly at low temperatures, especially below 5°C. A model comparing maximum rates of fecundity with
in situ data suggested production rates were strongly food limited across our study region. However, the relationship of in
situ and maximum rates to temperature were similar, confirming the importance of temperature. Further, as time taken to develop
from egg to adult also rapidly extends with declining temperature, it is increasingly unlikely that O. similis will be able to maintain its population against mortality. Our findings have broad implications for the cold temperature
(and hence geographic) limits of O. similis, but also for the distribution of other sac spawning copepods and planktonic species generally. 相似文献
20.
Benni W. Hansen Guillaume Drillet Reinhardt M. Kristensen Thomas F. Sørensen Majken T. Tøttrup 《Marine Biology》2010,157(1):59-68
Close to 50 species of marine Calanoid copepods have been reported to produce diapause eggs (Engel and Hirche in J Plankton
Res 26:1083–1093, 2004); eggs that are viable but require a refractory phase before they hatch, sometimes after months. Diapause eggs are often
described as morphologically different with respect to egg membrane ultrastructure and having a thicker egg shell with surface
ornamentation as opposed to the smooth shell found in subitaneous eggs that hatch within days (Belmonte in J Mar Syst 15:35–39,
1998; Chen and Marcus in Mar Biol 127:587–597, 1997; Castro-Longoria in Crustaceana 74:225–236, 2001). Egg production rates, egg surface ornamentation, and hatching success were monitored in large aquaculture fish enclosures
during winter with close to zero water temperatures (N57°). Surprisingly, all female copepods (Acartia spp.—presumably A. tonsa, and Centropages hamatus) produced eggs all through the winter with no obvious pattern with respect to light, temperature and food availability, and
no diapause eggs were observed. However, individual females produced several categories of eggs with or without surface spines
even within the same egg batch as evidenced by scanning electron microscopy (SEM). Four egg categories were distinguishable:
‘no spines’, smooth eggs; ‘short spines’, 5–15 μm long; ‘truncated spines’, with the spine tips cut-off <10 μm long; and ‘long
spines’, up to 30 μm long. All egg categories remained unchanged with respect to surface structures from when we took them
out of the incubation bottles until they hatched. In general, the frequency of ‘no spines’ was 10–40%, and most eggs were
ornamented with ‘short-’ or ‘long spines’. Further, a given egg can be ornamented with all types of surface spines simultaneously,
which might even be a fifth egg category. The different egg categories were all able to hatch within days when exposed to
normoxic conditions suggesting that they were subitaneous. 相似文献