Labidocera Aestiva Research Articles

Population composition of calanoid copepods of the Chennai coast, Tamil Nadu

The study aims to determine the population composition of calanoid copepods from Ennore, Marina and Kovalam stations of the Chennai coast during the period of October 2018 to September 2019. Zooplankton samples were collected from 3 stations monthly. Temperature, pH, dissolved oxygen and salinity of water samples were measured. In the present study, 24 calanoid copepod species were recorded from 3 stations. Index of dominance of calanoid copepod was high in the month of October 2018 at Ennore and Kovalam stations and in the month of November 2018 was high at Marina, however, index of diversity and evenness of calanoid copepod was high in the month of March 2019 at all the stations. Labidocera aestiva showed high average density (68.99±11.11 nos/m 3 ), followed by Subeucalanus crassus (34.40±6.75 nos/m 3 ). Principal Component Analysis (PCA) of calanoid copepods between the species showed postive as well as negative correlations at the three sampling stations. The calanoid copepods were high (1253.80±11.66 nos/m 3 , 1221.20±13.49 nos/m 3 and 938.90±9.45 nos/m 3 ) in the month of March 2019 at Marina, Kovalam and Ennore stations, respectively. Calanoid copepods densities were statistically analyzed whereas, PCA highlighted about relationship among the species.

Effects of Dispersant and Oil on Survival and Swimming Activity in a Marine Copepod

Knowledge of lethal and sublethal effects of crude oil and dispersants on mesozooplankton are important to understanding ecosystem impacts of oil spills in marine environments. Here we (1) establish median lethal concentrations for water accommodated fractions of Corexit EC9500A dispersant, MC-252 crude oil (WAF), and dispersed crude oil (CEWAF) for the coastal copepod Labidocera aestiva, and (2) assess acute effects on L. aestiva swimming activity. Mortality assays with L. aestiva support that copepods are more sensitive than other zooplankton taxa to dispersant toxicity, while WAF and CEWAF are generally similar in their toxicity to this copepod species and other zooplankton. Acute effects on L. aestiva activity included impaired swimming upon WAF and CEWAF exposure. These results highlight that copepods are particularly sensitive to dispersant exposure, with acute effects on survival most evident with dispersant alone, and on swimming behavior when dispersant is mixed with crude oil.

Oogenesis in calanoid copepods

Summary An ultrastructural investigation of ovary structure and oogenesis was conducted on ten species of cold and warm water calanoid copepods from six families with broad distributions ranging from coastal to mesopelagic habitats. They include Calanus finmarchicus, C. hyperboreus, C. glacialis, Euchaeta marina, Centropages furcatus, C. velificatus, Labidocera aestiva, Acartia tonsa, Pleurommama xiphias, and Undinula vulgaris. All ten species show similarities with respect to ovarian morphology and oogenesis. Oogenesis is asynchronous with all stages of oocytes present within each sexually mature female. The oocytes differentiate to diplotene of the first meiotic division and undergo a growth phase within the ovary before initiating vitellogenesis within the diverticulae. Vitellogenesis involves both an autosynthetic (endogenous) and a heterosynthetic (exogenous) process resulting in the deposition of two different types of yolk bodies. Endogenous yolk formation is initiated by the proliferation of vesicular endoplasmic reticulum (ER) through the blebbing of the outer lamina of the nuclear envelope. These ER vesicles contain a variable number of granules that arise before the vesicles detach from the nuclear envelope. Parallel arrays of annulate lamellae (AL) also appear in this region and their swollen, distal cisternae release ER vesicles into the surrounding ooplasm that are indistinguishable from those generated by the nuclear envelope. Golgi complexes proliferate and produce secretory products that fuse with both the ER cisternae and newly formed yolk bodies. Simultaneous biosynthetic activity of the ER, AL, and Golgi results in the formation of Type I yolk bodies, and primary and secondary cortical vesicles that likely participate in the formation of the egg envelope. In the later stages of vitellogenesis, extraoocytic yolk precursors originating in the hemocoel pass through the follicle cells that encompass the oocytes in an endocytotic process that releases precursors into the pervitelline space. Oocytes then incorporate these precursors endocytotically resulting in the gradual assembly of Type II yolk bodies. To our knowledge, this is the first ultrastructural study to describe the biosynthesis of specific products (yolk bodies and cortical granules) by annulate lamellae in any metazoan oocyte. Vitellogenesis in calanoid coperpods is significantly different from that described in any other crustacean group. Further investiation of this process in related crustaceans might provide useful phylogenetic insights.

Spectral sensitivity of vertically migrating marine copepods.

Light is a critical factor in the proximate basis of diel vertical migration (DVM) in zooplankton. A photobehavioral approach was used to examine the spectral sensitivity of four coastal species of calanoid copepod, representing a diversity of DVM patterns, to test whether species that migrate (nocturnal or reverse DVM) have response spectra that differ from non-migratory surface dwellers. The following species were given light stimuli at wavelengths from 350 to 740 nm, and their photoresponses were measured: Centropages typicus (nocturnal migrator), Calanopia americana (nocturnal migrator), Anomalocera ornata (reverse migrator), and Labidocera aestiva (non-migrator). Centropages typicus and A. ornata had peak responses at 500 and 520 nm, respectively, while Calanopia americana had maximum responses at 480 and 520 nm. Thus, the species that undergo DVM have peak photobehavioral responses at wavelengths corresponding to those available during twilight in coastal water, although the range of wavelengths to which they respond is variable. Non-migratory surface-dwelling L. aestiva had numerous response peaks over a broad spectral range, which may serve to maximize photon capture for vision in their broad-spectrum shallow-water habitat.

Zooplankton responses to hypoxia: behavioral patterns and survival of three species of calanoid copepods

Seasonally recurrent and persistent hypoxic events in semi-enclosed coastal waters are characterized by bottom-water dissolved oxygen (d.o.) concentrations of < 2.0 ml l−1. Shifts in the distribution patterns of zooplankters in association with these events have been documented, but the mechanisms responsible for these shifts have not been investigated. This study assessed interspecific differences in responses to hypoxia by several species of calanoid copepods common off Turkey Point, Florida, USA: Labidocera aestiva (Wheeler) (a summer/fall species), Acartia tonsa (Dana) (a ubiquitous year-round species), and Centropages hamatus (Lilljeborg) (a winter/spring species). Under conditions of moderate to severe hypoxia 24-h survival experiments were conducted for adults and nauplii of these species from August 1994 to October 1995. Experiments on adults used a flow-through system to maintain constant d.o. concentrations. Adults of A. tonsa showed no decline in survival with d.o. as low as 1.0 ml l−1, sharp declines in survival at d.o. = 0.9 to 0.6 ml l−1, and 100% mortality with d.o. = 0.5 ml l−1. Adults of L. aestiva and C. hamatus were more sensitive to oxygen depletion: both species experienced significant decreases in survival for d.o. = 1.0 ml l−1. Nauplii of L. aestiva and A. tonsa showed no significant mortality with d.o. = 1.1 to 1.5 ml␣l−1 and d.o. = 0.24 to 0.5 ml l−1, respectively. In addition, experiments investigating behavioral avoidance of moderate to severe hypoxia were carried out for adults of all three species. None of the three species effectively avoided either severely hypoxic (d.o. < 0.5 ml l−1) or moderately hypoxic (d.o. ≈ 1.0 ml l−1) bottom layers in stratified columns. These results suggest that in␣nearshore areas where development of zones of d.o. < 1.0 ml l−1 may be sudden, widespread, or unpredictable, patterns of reduced copepod abundance in bottom waters may be due primarily to mortality rather than avoidance.

Subitaneous, diapause, and delayed-hatching eggs of planktonic copepods from the northern Gulf of Mexico: morphology and hatching success

Experiments were conducted to examine the morphology and hatching success of eggs, either spawned by freshly caught planktonic copepods or recovered from bottom sediments in the northern Gulf of Mexico. Collections were made between August 1992 and September 1995. Eggs of nine species were described and these differed in their diameter, color and surface attributes. Three types of eggs were distinguished: subitaneous, diapause, and delayed-hatching. Three species, Labidocera aestiva Wheeler, Acartia tonsa Dana, and Centropages velificatus (Oliveira) produced only subitaneous eggs. Hatching success varied greatly among these species. Two species, Labidocera mirabilis Fleminger and Centropages hamatus (Lilljeborg) produced diapause eggs and subitaneous eggs. The length of the refractory phase of the diapause eggs differed greatly both within and between these two species. A third type of dormant egg, delayed-hatching, was recognized in Labidocera scotti Giesbrecht and Pontella meadi Wheeler. The existence of delayed-hatching eggs may be an adaptive response of subtropical species to less seasonal fluctuation. Based upon morphological characteristics of the eggs and rearing of nauplii to an identifiable stage, benthic dormant eggs of eight species of calanoid copepods were also identified.

Impact of anoxia and sulfide on the viability of eggs of three planktonic copepods

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 146:291-295 (1997) - doi:10.3354/meps146291 Impact of anoxia and sulfide on the viability of eggs of three planktonic copepods Marcus NH, Lutz RV, Chanton JP Eggs of 3 calanoid copepods Acartia tonsa, Centropages hamatus and Labidocera aestiva were exposed to either anoxia or anoxia/sulfide. Mean sulfide concentrations ranged from 283 to 352 M. Viability, determined at 4 d intervals for 32 d and judged as hatching success under normoxia was variable, but generally declined with increasing time of exposure. Values for hatching success were transformed to probits to determine the median lethal times of exposure to anoxia and anoxia/sulfide and 95% confidence limits. We observed no significant difference in the mortality of eggs exposed to anoxia/sulfide compared to anoxia alone and suggest that eggs switch to anaerobic metabolism when exposed to anoxia. Copepods · Resting eggs · Anoxia · Sulfide Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 146. Publication date: January 30, 1997 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1997 Inter-Research.

Effects of anoxia on the viability of subitaneous eggs of planktonic copepods

The effect of anoxia on the viability (as evidenced by hatching) of newly spawned and fully developed subitaneous eggs of three species of copepods, Acartia tonsa (Dana), Centropages hamatus (Lilljeborg), and Labidocera aestiva (Wheeler) was determined for eggs produced in the laboratory by adults collected from inshore waters of the northeastern Gulf of Mexico between January and August 1992. Hatching success decreased to 50% or less when eggs were exposed to oxygen concentrations <0.06 mll-1 for more than 12 d, except for newly spawned eggs of L. aestiva, which still showed 50% survival after 32 d of exposure to anoxia. For all three species, newly spawned eggs survived exposure to anoxia longer than fully developed eggs. The results indicate that the increasing occurrence of anoxia in estuarine and coastal waters could have a major impact on the population growth of these important food web organisms.

Hatching and viability of copepod eggs at two stages of embryological development: anoxic/hypoxic effect

The effects of low oxygen concentrations on the hatching and viability of copepod eggs at two stages of embryological development were investigated. Fully developed eggs from Acartia tonsa (Dana) and Labidocera aestiva (Wheeler) collected between July and September 1991 at Turkey Point, Florida, USA, hatched at lower oxygen concentrations than newly spawned eggs given the same incubation periods. Since many of the newly spawned eggs subsequently hatched when exposed to normoxic conditions, it is likely that the exposure to low oxygen delayed embryonic development. At oxygen concentrations where no initial hatching occurred, the subsequent hatching success of fully developed eggs of A. tonsa was higher than that of newly spawned eggs, indicating that newly spawned eggs were more sensitive to low oxygen concentrations. No such difference was observed for the eggs of L. aestiva.

Labidocera aestiva and L. scotti in Tamiahua Lagoon, Veracruz, Mexico

Labidocera aestiva and L. scotti in Tamiahua Lagoon, Veracruz, Mexico

Experimental records of the effects of food patchiness and predation on egg production of Acartia tonsa

The effects of predation and spatial patchiness in food distribution on egg production of the marine calanoid copepod Acartia tonsa were investigated in the laboratory. A postexperiment egg production method was developed to override the decline in number of copepods due to predation. The copepods were able to remain in food patches about 41–47% of the time, and consequently egg production rates were higher than expected from the average food concentration. Predation by the calanoid copepod Labidocera aestiva tended to increase egg production rates of A. tonsa. The interaction of patchiness and predation resulted in relatively less time spent by A. tonsa in the food patches, probably as a consequence of conflict between hunger level and predation risk.

Potential effects of a resuspension event on the vertical distribution of copepod eggs in the sea bed: a laboratory simulation

Adult female Acartia tonsa and Labidocera aestiva were obtained from inshore marine waters near Turkey Point, Florida (29°54.5′N;84°31′W) during April and May 1991. For each species, eggs spawned overnight in the laboratory were collected, mixed with sediment, and added to a plastic tube (26 to 29 cm longx5 cm diam) to yield a 2 cm-thick layer. This tube was connected to a 245 cm-long tube, seawater was added and the contents were thoroughly mixed by turning the assembly end-over-end several times. The vertical distribution of eggs in the sediments following resuspension varied according to the grain size of the sediments. For sediments of ≥125 μm particle-diameter, 68 to 72%, and 70 to 73% of the eggs of A. tonsa and L. aestiva, respectively, occurred in the upper 4 mm.For sediments ≥63 to <125 μm particle-diameter, 34 to 36% of the eggs of A. tonsa and L. aestiva, respectively, occurred in the upper 4 mm. For sediments of <63 μm particle-diameter, egg distribution was uniform for both species throughout the 2 cm layer. The results indicate that the vertical distribution of eggs in the sea bed following a resuspension event should be highly dependent upon the grain-size composition of the sediments.

Effects of low oxygen concentrations on the hatching and viability of eggs of marine calanoid copepods

Hatching of the eggs of four species of copepods, Acartia tonsa, Labidocera aestiva, Tortanus discaudatus, and Centropages hamatus was suppressed at oxygen concentrations less than 0.02 ml O2/l. When such eggs were subsequently exposed to normal oxygen concentrations, hatching varied among the species, indicating variability in the capacity of eggs to survive exposure to low oxygen. Incubation of eggs at low oxygen concentrations resulted in an increase in the duration of embryonic development. Experiments were conducted in closed systems and oxygen concentration was determined by thermal conductivity using gas chromatography.

Viability of subitaneous copepod eggs following fish predation on egg-carrying calanoids

The viability of subitaneous eggs of the eggcarrying calanoid copepod Euryternora herdmani was examined following fish ingestion and evacuation. More than 90% of the copepod embryos recovered intact in the fecal material of Atlantic silversides Menidia rnenjdja hatched within 3 d of incubation at 12 C in both light/dark and completely dark regimes. Percentage hatch was comparable to that for uningested embryos removed from eggsacs and for uningested embryos within eggsacs both attached to, and excised from, maternal copepods. For E. herdmani, selective silvers~de predation on ovigerous females is countered by the capacity of their subitaneous eggs to resist digestion. Zooplankton features that influence prey selection by planktivorous fish include prey size (Ivlev 1961, Brooks 1968, Werner & Hall 1974, O'Bnen et al. 1976), pigmentation (Zaret & Kerfoot 1975, Hairston 1979a, b) and, in some egg-carrying copepods and cladocerans, the presence of highly visible eggs (Mellors 1975, Hairston et al. 1983). Prior to periods of intense fish predation, many crustaceans produce diapause eggs that are thick-walled, highly pigmented and digestion resistant (Proctor et al. 1967, Mellors 1975). It has been suggested that the production of diapause eggs acts as a survival strategy to offset the costs of selective feeding on egg-bearing females (Hairston & Munns 1984) and ultimately aids in the perpetuation of endemic populations (Uye 1985). There has been only one account of digestion resistance in nondiapause copepod eggs. Marcus (1984) showed that both subitaneous ('quick-hatch') and diapause eggs released by the marine copepod Labidocera aestiva are capable of surviving passage through the gut tracts of 2 benthic polychaete species. Egg mortality during gut transport however, was higher for ingested subitaneous embryos. Many other copepod Present address: Ocean Sciences Centre. Memorial University of Newfoundland, St. John's, Newfoundland, Canada

How long does it take copepods to make eggs?

During investigations of relationships between food concentrations and rates of egg production by the marine copepod Anomalocera ornata Sutcliffe, we discovered an artifact that may be common in such experiments. Although rates of egg production by individual copepods were highly variable and rates exhibited no relation to food concentration offered during experimental incubations, egg production rates of up to 338 eggs·female −1·day −1 were obtained with natural phytoplankton and up to 83–128 eggs female −1·day −1 with unialgal phytoplankton cultures. However, concurrent measurements of ingestion rates in experiments with cultures revealed that the copepods were not eating. This suggested that food used to produce eggs during experiments had been ingested in the sea prior to capture. To test this, we offered 14C-labelled mixtures of diatoms and rotifers to five copepod species, and measured the lag period for labelled eggs to appear. Times for maximum measured values of counts per minute per egg were 9.5 h for Acartia tonsa Dana, 16.5 h for Centropages veliflcatus De Oliviera, 65.5 h for Labidocera aestiva Wheeler, 89 h for Centropages typicus Krøyer, and 91 h for A. ornata. C. typicus and A. ornata continued to produce eggs in filtered seawater for periods of 66.8 and 44.5 h, respectively. We concluded there is considerable interspecific variability in the lag period for conversion of ingested food to egg production in marine copepods, and this lag time must be known in order to interpret relationships between food and copepod egg production.

Distribution and abundance of eggs of Labidocera aestiva (Copepoda: Calanoida) in the bottom sediments of Buzzards Bay, Massachusetts, USA

Grain-size composition of the sea-bed and density of eggs of Labidocera aestiva in bottom sediments in Buzzards Bay were determined at approximately monthly intervals from March 1983 through April 1984. The results of this study, together with those of Marcus (1984), show that during the fall and winter periods of 1982–1984 the proportion of eggs of L. aestiva occurring in the surficial sea-bottom sediments declined and the proportion of eggs in the deeper sediment layers increased. High positive correlations (r2=0.72 and 0.92) were observed during the early fall 1983 between egg abundance and the proportion of the total sediments represented by the mud fraction. During late fall, winter, and early spring 1983–1984, the coefficients of determination were much lower. Physical criteria (e.g. sedimentation and transport characteristics) can be used to accurately predict the distribution and abundance of recently spawned eggs on the sea-bottom.

DIFFERENCES IN THE DURATION OF EGG DIAPAUSE OF LABIDOCERA AESTIVA (COPEPODA: CALANOIDA) FROM THE WOODS HOLE, MASSACHUSETTS, REGION.

The duration of diapause of Labidocera aestiva eggs collected from the field and reared in the laboratory was determined at 5°C. A clear seasonal trend was observed. Diapause eggs produced in the early fall required a much longer exposure to cold to yield a 50% hatch (CT50) (i.e., the duration of diapause was longer) than eggs produced later in the fall. Eggs produced by laboratory animals that were reared at 14°C, 8L-16D, required a shorter period of chilling to terminate diapause than the eggs of animals reared at 19° C, 12L-12D. Considerable variation in the CT50 value was also observed among laboratory cultures that were all reared under identical conditions, but which differed in terms of selection history. The results indicate that both the genotype of the egg and the conditions prevailing during oocyte formation influence the duration of diapause. Eggs that were stored at 5°C for periods longer than 300 days no longer hatched upon warming. It is suggested that the variation in the duration of diapause is an adaptation that promotes synchronization of hatching by ensuring that all individuals terminate diapause at approximately the same time, and survival during the winter by conferring cold-hardiness. Synchronizing the onset of post-diapause development is also discussed as an alternative mechanism for achieving synchronous hatching.

Effects of cupric and zinc ion activities on the survival and reproduction of marine copepods

The toxicity of copper and zinc to the estuarine copepod Acartia tonsa and to the two diatom food species Thalassiosira pseudonana and T. weissflogii was measured in nitrilotriacetate-trace metal ion buffer systems at 25‰ S. Overall, A. tonsa appeared to be more sensitive to cupric and zinc ion activity than either of the diatoms; however, its sensitivity varied among the different life stages examined. Adult survival was not affected within the zinc ion activity range 10-11 to 10-8M and cupric ion activity range 10-13 to 10-11M over a 96-h period, but a cupric ion activity of 10-10M caused total mortality of adults within 72 h. Egg-laying rate was most sensitive to zinc, and was reduced at zinc ion activities ≧10-10M. Naupliar survival after 96 h was reduced by zinc ion activities ≧10-8M and by cupric ion activities ≧10-11M, and was reduced to zero at a zinc ion activity of 10-7M and at a cupric ion activity of 10-10.5M. In an interspecies comparison of 96-h adult survival, Centropages typicus was more sensitive to copper and zinc than A. tonsa and the survival of Labidocera aestiva was dependent on the ratio of cupric to zinc ion activity. A comparison of our results with estimates of zinc and cupric ion activities in estuaries suggests that ionic activities of these metals are high enough in some polluted estuaries to affect the survival and reproduction of copepods.

Subitaneous and diapause eggs of Labidocera aestiva Wheeler (Copepoda : Calanoida): Differences in fall velocity and density

The sinking rate and density of subitaneous and diapause eggs of the calanoid copepod, Labidocera aestiva Wheeler, were determined in the laboratory using a settling chamber and density gradient centrifugation. The average fall velocities of subitaneous and diapause eggs were, respectively, 0.0463 and 0.0610 cm/s. Based upon Stokes' equation the values for fall velocity correspond to densities ranging from 1.081–1.133 g/cm 3 for subitaneous eggs and 1.101–1.181 g/cm 3 for diapause eggs. The range of density values determined by density gradient centrifugation were comparable. The significance of the results with regard to the distribution of subitaneous and diapause eggs on the sea bottom and the underlying biological basis of the density difference is discussed.

Recruitment of individuals into the plankton: The importance of bioturbation1

The eggs of many planktonic copepods sink to the bottom in coastal waters and become buried beneath several centimeters of sediment where they cannot hatch. Bioturbation by three polychaetes, Nephtys incisa, Cistenides gouldii, and Clymenella torquata, promoted the burial of diapause eggs of the planktonic copepod Labidocera aestiva in a laboratory study. More important feeding by the two conveyor‐belt‐feeding species, C. gouldii and C. torquata, promoted the return of buried eggs to the water and water‐sediment interface. The viability of the eggs was unaffected by the translocation process and in these new positions eggs were able to hatch. We suggest that in the field bioturbation directly influences the recruitment of individuals into planktonic populations.