Nauplius VI Research Articles

Life stage-specific effects of tire particle leachates on the cosmopolitan planktonic copepod Acartia tonsa

Tire wear particles (TWP) are a major source of microplastics in the aquatic environment and the ecological impacts of their leachates are of major environmental concern. Among marine biota, copepods are the most abundant animals in the ocean and a main link between primary producers and higher trophic levels in the marine food webs. In this study, we determined the acute lethal and sublethal effects of tire particle leachates on different life stages of the cosmopolitan planktonic copepod Acartia tonsa. Median lethal concentration (LC50, 48 h) ranged from 0.4 to 0.6 g L−1 depending on the life stages, being nauplii and copepodites more sensitive to tire particle leachates than adults. The median effective concentration (EC50, 48 h) for hatching was higher than 1 g L−1, indicating a relatively low sensitivity of hatching to tire particle leachates. However, metamorphosis (from nauplius VI to copepodite I) was notably reduced by tire particle leachates with an EC50 (48 h) of 0.23 g L−1 and the absence of metamorphosis at 1 g L−1, suggesting a strong developmental delay or endocrine disruption. Leachates also caused a significant decrease (10–22%) in the body length of nauplii and copepodites after exposure to TWP leachates (0.25 and 0.5 g L−1). We tested a battery of enzymatic biomarkers in A. tonsa adult stages, but a sublethal concentration of 50 mg L−1 of tire particle leachates did not cause a statistically significant effect on the measured enzymatic activities. Our results show that tire particle leachates can negatively impact the development, metamorphosis, and survival of planktonic copepods. More field data on concentrations of TWPs and the fate and persistence of their leached additives is needed for a better assessment of the risk of tire particle pollution on marine food webs.

Development of the muscular and nervous systems during the larval ontogeny of the stalked barnacle, Octolasmis angulata Aurivillius 1894 (Cirripedia: Thoracicalcerea: Poecilasmatidae)

The advancements in microscopic techniques have stimulated great interest in the muscular and neural architectures of invertebrates, specifically using muscle and neural structures to infer phylogenetic relationships. Here, we provide the data on the development of the muscular and nervous systems during the larval development of stalked barnacle, Octolasmis angulata using the phalloidin F-actin and immunohistochemical labelling (e.g. acetylated α-tubulin and serotonin) and confocal laser scanning microscopy analysis. All naupliar stages shared the same muscle and neural architectures with only the discrepancy in size. The nauplii have a complex muscle arrangement in their feeding apparatus and naupliar appendages. Most naupliar muscles undergo histolyse during the cyprid metamorphosis. The cyprid muscles form beneath the head shield at the end of nauplius VI. The naupliar and cyprid central nervous systems exhibit the typical tripartite brain comprising the protocerebrum, deutocerebrum and tritocerebrum. The serotonin-like immunoreactivity is mainly found in the naupliar brain, mandibular ganglia, cyprid brain and posterior ganglia. Our study revealed that numerous muscle and neural architectures in the naupliar and cyprids have phylogenetic significance, but future studies on the myoanatomy and neuroanatomy of other barnacle species are necessary to determine the homology of these structures.

Transcriptome and Proteome Studies Reveal Candidate Attachment Genes during the Development of the Barnacle Amphibalanus Amphitrite

The acorn barnacle, Balanus amphitrite, is the main biofouling organism in marine environments. In the present study we profiled the transcriptome and proteome of B. amphitrite at different life stages (nauplius II, nauplius VI and cyprid) from the Red Sea, where the average water surface temperature is 34°C and the salinity reaches 41‰. We identified 65,784 expressed contigs, and a total of 1,387 expressed proteins measured by quantitative proteomics. We found that osmotic stress, salt stress, hyperosmotic response and the Wnt signaling pathway were strongly up-regulated during the planktonic stage, while the MAPK pathway, lipid metabolism, and cuticle development genes were down-regulated. In the transition stage between the nauplius VI and the cyprid, genes that are involved in blood coagulation, cuticle development and eggshell formation were highly up-regulated, while the nitric oxide pathway, which stimulates the swimming and feeding response in marine invertebrates, was down-regulated. We are able to report for the first time that sound sensory system proteins are highly abundant in the nauplius VI stage, implying that these proteins are good targets for the development of new antifouling compounds. The results presented here together with the new genome-wide datasets for a non-model specie represent an important resource for the study of biofouling and development.

Larval development of the pedunculate barnacles Octolasmis angulata Aurivillius 1894 and Octolasmis cor Aurivillius 1892 (Cirripedia: Thoracica: Poecilasmatidae) from the gills of the mud crab, Scylla tranquebarica Fabricius, 1798

Detailed studies of larval development of Octolasmis angulata and Octolasmis cor are pivotal in understanding the larval morphological evolution as well as enhancing the functional ecology. Six planktotrophic naupliar stages and one non-feeding cyprid stage are documented in details for the first time for the two species of Octolasmis. Morphologically, the larvae of O. angulata and O. cor are similar in body size, setation patterns on the naupliar appendages, labrum, dorsal setae-pores, frontal horns, cyprid carapace, fronto-lateral gland pores, and lattice organs. Numbers of peculiarities were observed on the gnathobases of the antennae and mandible throughout the naupliar life-cycle. The setation pattern on the naupliar appendages are classified based on the segmentation on the naupliar appendages. The nauplius VI of both species undergoes a conspicuous change before metamorphosis into cyprid stage. The cyprid structures begin to form and modify beneath the naupliar body towards the end of stage VI. This study emphasises the importance of the pedunculate barnacle larval developmental studies not only to comprehend the larval morphological evolution but also to fill in the gaps in understanding the modification of the naupliar structures to adapt into the cyprid life-style.

Larval vision contributes to gregarious settlement in barnacles: adult red fluorescence as a possible visual signal

Gregarious settlement, an essential behavior for many barnacle species that can only reproduce by mating with a nearby barnacle, has long been thought to rely on larval ability to recognize chemical signals from conspecifics during settlement. However, the cyprid, the settlement stage larva in barnacles, has one pair of compound eyes that appear only at the late nauplius VI and cyprid stages, but the function(s) of these eyes remains unknown. Here we show that cyprids of the intertidal barnacle Balanus (=Amphibalanus) amphitrite can locate adult barnacles even in the absence of chemical cues, and prefer to settle around them probably via larval sense of vision. We also show that the cyprids can discriminate color and preferred to settle on red surfaces. Moreover, we found that shells of adult B. amphitrite emit red auto-fluorescence and the adult extracts with the fluorescence as a visual signal attracted cyprid larvae to settle around it. We propose that the perception of specific visual signals can be involved in behavior of zooplankton including marine invertebrate larvae, and that barnacle auto-fluorescence may be a specific signal involved in gregarious larval settlement.

A description of the larval development of Megabalanus azoricus (Pilsbry, 1916) reared in the laboratory

This study provides the first description of the larval development of the commercially exploited barnacle Megabalanus azoricus. It describes the changes in larval size and shape as well as the general morphology and duration of each larval stage. Embryos were obtained from gravid specimens collected at São Miguel Island and reared through six naupliar stages to the cypris stage in laboratory conditions. The planktotrophic nauplii reached the cypris stage after 14 days of hatching in individual cultures at 20 °C under natural illumination and fed with phytoplankton (Chaetoceros gracilis, Isochrysis sp., and Tetraselmis sp.). The nauplius of M. azoricus has a normal size compared with nauplii of other congeneric species, ranging between the 261 μm (nauplius I) and 912 μm (nauplius VI). This work provides the first description of larvae of the genus Megabalanus for the Portuguese oceanic islands and provides comparisons with congeneric species in other parts of the world.

Influence of water temperature on the larval development of Neoverruca sp. and Ashinkailepas seepiophila—Implications for larval dispersal and settlement in the vent and seep environments

Deep-sea hydrothermal vents and cold seeps are scattered and limited habitats, and species that are confined to these benthic habitats often have a planktonic larval stage in their life history to maintain dispersal and gene flow among discrete populations. We have reared the larvae of Ashinkailepas seepiophila, inhabiting inactive vents and active cold seeps, through their entire larval development under atmospheric pressure. Using two temperatures (4°C, 10°C) we examined whether larval development resembles other vent species in being affected by thermal stimulation. Under laboratory conditions, A. seepiophila completed larval development in 65 days at 4°C. This is considerably shorter than the 100 days previously reported to be required at the same temperature by Neoverruca sp., a species confined to inhabiting active vents. Also in contrast to Neoverruca sp., A. seepiophila did not drastically shorten the developmental period from nauplius VI to cyprid when exposed to temperature of 10°C. We conclude that there is no need for late naupliar stages of A. seepiophila to develop into cyprids more quickly at elevated temperatures because this species does not inhabit active vents. The difference in response to water temperature during larval development may contribute to the separated distribution of the two species at active vents (Neoverruca sp.) and inactive vents and cold seep (A. seepiophila) environments.

Phylogenetic relationships within the taxon Tisbe (Copepoda, Harpacticoida) as evidenced by naupliar characters1

All six naupliar stages of six species of Tisbe Lilljeborg, 1853 are compared: Tisbe gracilis (T. Scott, 1895), T. cucumariae Humes, 1957, T. furcata (Baird, 1837), T. bulbisetosa Volkmann-Rocco, 1972, T. bolothuriae Humes, 1957 and T. battagliai Volkmann-Rocco, 1972. The nauplii of T. cucumariae are described and differences to those of the other species are specified. The appendages of only nauplius VI are figured. T. bolothuriae and T. battagliai ire characterized by the reduction of oral structures. A cladogram depicting relationships within Tisbe is deduced from a comparison and evaluation of these naupliar characters. The cladogram supports some previous findings, viz. the close relationship of T. bolothuriae and T. battagliai as well as of T gracilis and T. cucumariae but deviates in other respects from the cladogram deduced by Dahms et al. (1991, this volume) from adult characters. The discrepancies are discussed.

Time-series measurements of oxygen consumption of copepod nauplii

The goal of this study was to determine over time with high temporal resolution the oxy- gen consumption rates of nauplii of marine planktonic copepods while feeding on phytoplankton at environmental concentrations. The determination of the nauplii's oxygen consumption was achieved by applying a fluorescence-based non-invasive technology. The hourly oxygen consumption at 21°C ranged from near 18 nl O2 Nauplius IV -1 to about 33 nl O2 Nauplius VI -1 of the calanoid Eucalanus pileatus. The nauplii's feeding activity was reflected by an average reduction of food concentration of about 50% of the initial abundance and a production of 2.2 pellets nauplius -1 h -1 . The nauplii's aver- age food consumption, at a rate equal to 17.7% of body weight d -1 , did not cover their metabolic expenses of 29.7% of body weight d -1 . Their feeding performance could have been to some extent limited by the size of the experimental vessels. Microscopic observations showed that the motion of late nauplii of E. pileatus was continuous (i.e. as previously observed) in vessels of 250 ml and larger. The main finding of this study is that the metabolic activity of minute metazooplankton organisms, while they are feeding, can now be determined with good precision over a period of hours without any invasion of the experimental vessels.

Toxic effects of copper on larval development of the barnacle Balanus amphitrite

Experiments were conducted to assess the effects of copper on larval development in the barnacle Balanus amphitrite. In the first experiment, we compared the sensitivity of three naupliar stages to copper stress. Molting inhibition occurred at copper concentrations ranging from 32 μg l −1 in nauplius II to 128 g l −1 in nauplius VI. EC 50 for molting ranged from 97 μg l −1 in nauplius II to 129 g l −1 in nauplius VI. Decreased survival occurred at 128 μg Cu l −1 in all of the naupliar stages tested, with LC 50 ranging from 145 in nauplius II to 213 μg l −1 in nauplius VI. In the second experiment, we examined effects of copper on the development from nauplius II to cyprid. The larvae reached cypris stage only in treatments of ⩽16 μg Cu l −1. Our study therefore showed that molting was a more sensitive endpoint than survival, nauplius II was the most sensitive naupliar stage, and that whole larval development assay was more sensitive than assays using a particular larval stage. The results were discussed with respect to the use of this species in toxicity tests.

Growth and development rates of Calanus finmarchicus nauplii during a diatom spring bloom

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: Wlow resources = 4.17 × 10−6 × L2.03 (r2 = 0.84) and Whigh resources = 4.29 × 10−6 × L2.05 (r2 = 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.

Morfologia dos estágios de Náuplios e Copepodito i de Perulernaea gamitanae thatcher & paredes, 1985 (Crustacea: Cyclopoida: Lernaeidae), parasita do Tambaqui Colossoma macropomum (cuvier, 1818), (Osteichthyes: Characidae), cultivados em laboratório(1)

Os estágios de náuplios e copepodito I de Perulernaea gamitanae Thatcher & Paredes, 1985 foram estudados a partir de cultura de ovos obtidos de fêmeas adultas, parasitas de tambaqui, Colossoma macropomum (Cuvier, 1818) (Osteichthyes: Characidae), provenientes de tanques de cultivo em Manaus, Amazonas, Brasil. As larvas foram mantidas no laboratório à temperatura de 28ºC. O desenvolvimento de P. gamitanae de náuplio I até náuplio VI durou cinco dias e cada estágio era precedido de uma muda. As principais diferenças entre cada estágio foram o aparecimento de setas no segmento terminal da antênula, acréscimo no número de setas furcais, variação no comprimento e na forma do corpo. No sexto dia eclodiu o primeiro estágio de copepodito, que sobreviveu sete dias sem sofrer muda. Descrições morfológicas pormenorizadas e ilustrações foram feitas para todos os estágios de náuplios c para o primeiro estágio de copepodito.

Selectivity in the natural diets of acartia tonsa dana (copepoda: calanoida): comparison of juveniles and adults

Selective feeding in nature was compared for adults and two stages [Nauplius VI (NVI) and Copepodite I (CI)] of juvenile Acartia tonsa Dana collected from the northern Gulf of Mexico, Florida, USA. High performance liquid chromatography (HPLC) was used to compare the concentrations of four carotenoid pigments from copepods in incubating chambers to those from the surrounding water column. Adult copepods ingested significantly more pigment than the juveniles, however no difference was found between the relative proportions of pigments ingested by the three stages. Adults were shown to feed selectively in 50% of the experiments, while juvenile stages fed selectively in 75 %. The results suggest that conclusions derived from studies on natural feeding of adult copepods cannot always be extrapolated to juveniles ofthat species.

Metamorphosis between naupliar and copepodid phases in the Harpacticoida

It has been argued that, among Crustacea, copepods show ‘the most complete example of metamorphosis’: from nauplius to copepodid. In groups with either specialized nauplii or copepodids of a particular shape, body form changes markedly from nauplius VI to copepodid I. During post-embryonic development, one pair of appendages is formed at each successive stage, even in cases where some of these precursors are not developed externally. The same holds for the copepodid phase in which one somite is added per moult from a proliferation zone anterior to the anal somite. Of the appendages, the antennules continue to acquire further segments, setae and spines in the course of post-embryonic development, whereas the antennae and mandibles change drastically by losing their naupliar masticatory parts and, in the case of the mandibles, by developing completely different replacement structures. The antennae lose their masticatory function and migrate pre-orally from their naupliar paroral position. Even more striking are the changes affecting the post-mandibular mouthparts. From functionless naupliar limb-buds, these achieve almost the adult state as early as C I without any precursors in previous stages, whereas precursors of swimming legs 1 and 2 are indicated at N VI in most cases but, together with legs 3-6, differentiate in each successive instar from C I onwards. The caudal rami change in shape and in the number and structure of their setae. Sexual dimorphism becomes apparent only in the copepodid phase (as early as in C I in one case). Intermoult stages are important for tracing the origin and homology of larval and juvenile structures. Although ‘metamorphosis’ from nauplius to copepodid is in m any cases accompanied by remarkable changes, there also are examples of continuity in morphological and behavioural features.

Vertical distributions of eggs, nauplii and copepodites of Calanus helgolandicus (Copepoda: Crustacea) in the Celtic Sea

The vertical distributions of eggs, nauplii, copepodites and adults of Calanus helgolandicus (Claus) from five oblique plankton-net hauls taken in May (1980), March and September (1981) and January (1982) at a site in the shelf sea to the south-west of the United Kingdom are described. The water depth is approximately 95 m and becomes thermally stratified during the summer months when a thermocline of ∼6 C° develops. In early spring when the water column was isothermal (∼8 °C), the development of the eggs and nauplii took place below 60 m and a single ontogenetic migration was observed between Nauplius VI (NVI) and Copepodite I (CI). As the temperature of the water increased, this migration occurred in progressively earlier naupliar stages. The eggs were distributed throughout the water column in the profile taken in early May when a 1 C° thermocline occurred between 30 to 40 m. The majority of the NI to NIV stages occurred below 40 m, with the ontogenetic migration taking place in the NIV stage; the NV and NVI stages were found above the thermocline. In September, the eggs were again distributed throughout the water column (101 490 m-2), with a maximum number of >4 500 m-3 occurring in the surface to 5 m depth interval. Nauplius I and II were found at all depths, demonstrating that hatching occurred throughout the water column. The ontogenetic migration in these late-summer profiles took place between the NII and NIII stages, the remainder of the nauplii being found above the thermocline in the top 20 m. This is the first time that an ontogenetic migration, similar to the developmental ascent observed in the naupliar stages of the euphausiid Euphausia superba in the deep ocean, has been shown for a copepod nauplius.

A Comparative Study of Some Larval Stages of Penaeus monodon and Penaeus merguiensis (Crustacea : Decapoda) from Indonesia

The nauplius VI, protozoea II and mysis II of Penaeus monodon and P. merguiensis from Indonesian waters have been described and illustrated. The similarities and the differences between the two species have been observed. The comparison between the present study and that by previous authors have been made. Setation on endopod of maxilliped I and maxilliped II of protozoea and mysis stages as specific characters for identification is suggested. Two species of economically important penaeid prawns, Penaeus merguiensis De Man, 1888, and, P. monodon Fabricius, 1798, are among the many penaeids found in Indonesian waters. Although it is well known that their larvae occur in the coastal waters and are often mixed together (Noor-Hamid, 1976), accurate identification of their wild larvae is now possible only for post-larvae and juveniles, and identification at earlier stages is not yet succeeded. Larval stages of these species have already been described by some authors based upon materials from India (Silas et al., 1978) and the Philippines (Motoh, 1979; Motoh & Buri, 1979). Their information is available for identification of these larvae in Indonesian waters to certain extent, but some problems, which are probably related to difference of material andjor accuracy in observation, must be cleared before it is applied to Indonesian materials. In the present paper, larval stages of these two species, especially nauplius VI, protozoea II and mysis II, are described and compared on the basis of specimens reared in the laboratory, paying special attention to the type and number of setae on the appendages. Larvae of two species of penaeid prawns, Penaeus monodon and P. merguiensis, reared from eggs spawned in the laboratory were received from the Brackishwater Aquaculture Development Centre, Jepara. The larvae were preserved in 10% formalin and were used for morphological observation. Dissection of appendages was performed in 10% glycerin and drawings were made with Projectina, a micro photographic and drawing instrument. For each larval stage of the two species, 10 specimens were randomly taken for measurements with a micrometer eyepiece. The identification of substages is based on that used by Motoh (1979). Body lengths of nauplii were measured along the midline from apical to caudal margins, exclud-

Energy budget for the larval development ofElminius modestus (Crustacea: Cirripedia)

Biomass (CHN), respiration rate and food uptake were estimated for the larval development ofElminius modestus at three temperatures (12, 18, 24°C). Mean values of dry weight, elemental composition and energy equivalents increased exponentially with the development from nauplius II to VI. Dry weight, elemental composition and energy content exhibited the highest values at 18°C. Respiration rates increased with the larval stages expressed by a power function, but increased logarithmically with the dry weight of the larvae. The cypris larvae showed a reduced respiration rate compared with nauplius VI. The ingestion rate was measured at a concentration of 100 cells ofSkeletonema costatum μl−1. At 12 and 18°C ingestion rates increased exponentially and at 24°C by a logarithmic function. The fittings were used to estimate the energy budget ofE. modestus during larval development. The energy content of the larvae increased during the development from nauplius II to VI by a factor of 21 at 12°C, 25 at 24°C and 31 at 18°C. The estimated energy content of the freshly metamorphosed barnacle is 100 mJ (12°C), 130 mJ (24°C) and 150 mJ (18°C). The assimilation- (A/I) and gross growth efficiencies (K1) increased strongly during the development from nauplius II to VI (A/I: 6–14% in nauplius II to 50–90% in nauplius VI; K1: 4% in nauplius II to 75% in nauplius VI). The net growth efficiency (K2) showed a relatively constant level ranging between 57 and 83%.

<i>Centropages abdominalis</i> SATOのノープリアス幼生

The Copepoda nauplii are herbivore, preyed by the larvae of Pisces, Crustacea, Sagittoidea and the others which prey upon the nauplii. They may assume an important rôle in the food chain in the sea. Centropages abdominalis SATO occurs usually in rather large numbers in January, in the north western coast of Kyushu. In this season the plankton community is dominated by Bacillariaceae, especially by Thalassiosira subtilis (OSTENFELD). In rearing the female specimens of C. abdominalis were placed in the jars filled with the water (Cl--19.06‰). Skeletonema costatum (GREVILLE) and Stephanophixis palmeliana (GREVILLE) GRUNOW were placed in the jars for a fresh supply of the food or oxygen. The number of eggs produced by C. abdominalis ranged from 120 to 130 with an average of 122 eggs per brood. The egg is semitranslucent with light green in colour. The pelagic egg is 0.075mm in diameter having many setae on the surface. The length of the setae is from 0.02mm to 0.04mm. The egg is very similar to Haliocladus (Radiolaria) in structure. The nauplius is pyriform, and slight pointed posteriorly and quite rounded anteriorly. The nauplius retains red brown in the posterior region. The dark red eye-spot is comparatively large at the proximal portion of the rostrum. The nauplius is very similar in structure to that nauplius of Centropages hamatus (LILLJEBORG) described by M. OBERG (1906). After hatching, the larva developed into the nauplius VI which is the final stage of nauplius within about 10 days at the water temperature 15.4°C.