Report of Epibiont Diatom P. pacificum on the Cyclopoid Copepod D. affinis from the Southwestern Shelf Waters of India (Eastern Arabian Sea)

Pseudohimantidium pacificum, an epizoic diatom has been reported from different parts of the global oceans, however, has not been reported from the shelf waters of India. This symbiotic association of P. pacificum with a specific copepod species (Ditrichocorycaeus affinis) was repeatedly noticed from the shelf waters of the Arabian Sea during the winter monsoon from three locations in the South East Arabian Sea. Our study suggests towards host specificity of P. pacificum and additionally reveals their preference towards male hosts which is consistent with the earlier reports from other regions. Most importantly, this report extends the range of geographic distribution of the epibiont and this is the third report on this epibiont from the Indian Ocean region. It also suggests that epibiosis in marine zooplankton is much frequent phenomenon that has the potential to play an important role in the marine zooplankton population dynamics.

No impact of biocontrol predator on development time or size of surviving Aedes albopictus under optimal nutritional availability

BackgroundCyclopoid copepods have been applied successfully to limit populations of highly invasive Aedes albopictus mosquitoes that can vector diseases, including chikungunya, dengue, yellow fever, and Zika, to humans. However, there is concern that changes in certain vector traits, induced by exposure to copepod predation, might increase the risk of disease transmission. In this study, we tested whether cyclopoid copepod predation has sublethal effects on the development time or adult size of Ae. albopictus under the scenario of an invasion in southeast England, which lies at the northern edge of the vector’s expanding global range.MethodsThird instar Ae. albopictus larvae, hereafter referred to as “focal individuals”, were placed in individual Petri dishes, each containing four newly-hatched Ae. albopictus larvae, which were counted, removed, and replaced daily. All focal individuals were provided with fish food ad libitum, and half were exposed to Megacyclops viridis copepod predators. The day of pupation was recorded for each focal individual, and the wing length of each focal adult was also measured.ResultsExposing late instar Ae. albopictus to predation decreased their chances of surviving to adulthood. Mortality of the focal individuals was 12.9% in the predator treatment, and 2.9% in the controls. Three focal larvae that died in the predator treatment showed signs of melanization, indicative of wounding. Among surviving Ae. albopictus, no significant difference in either pupation day or wing length was observed due to copepod predation.ConclusionsWe found that M. viridis predation on smaller Ae. albopictus larvae does not significantly affect the pupation day or adult size of surrounding larger larvae that are less vulnerable to copepod attacks. This study controlled for density effects on size by maintaining a constant number of newly-hatched prey larvae surrounding each focal larva. Those working to control Ae. albopictus populations in the field should be made aware that increased adult body size can occur if copepod biocontrol agents are applied at lower than necessary levels. The absence of a significant sublethal impact from M. viridis copepod predation on surviving later-stage larvae in this analysis supports the use of M. viridis as a biocontrol agent.Graphical abstract

Morphology and Ecological Characteristics of Paracyclops Novenarius Reid, 1987: A Cyclopoid Copepod Inhabiting a Highly Contaminated Aquifer in Central-North of Mexico

This work reports the freshwater copepod Paracyclops novenarius, in a water body with high arsenic concentrations. Morphologic analysis, abundances, body size of the copepod and physical and chemical variables of the water (including arsenic concentrations) were evaluated in two different climatic seasons (rainy and dry). Morphological analysis showed that the high arsenic concentrations do not affect the morphology of P. novenarius, including all its development and adult instars. The highest abundances of this species were found in the dry season for all development stages, with values ​​of 1.51 and 1.50, 4.46, 0.21 ind/L-1, for nauplii, copepodites, females, and males, respectively. However, these values are lower than other aquatic systems of the region and the world, without polluting agents. The highest arsenic concentration was found in the dry season (58 mg/L-1) and the lowest during the rainy (54.5 mg/L-1). The body size of the analyzed organisms was larger in rainy compared to dry, with an average of 637.2 ± 42 µm for females and 650 ± 37 µm for males. A Mann-Whitney U test showed significant differences in lengths by season and by arsenic concentration (U = 1284.5, U = 1284.5; p < 0.05). The results of this study could provide information for environmental impact assessments on aquatic systems.

Microalgal Diet Influences the Nutritive Quality and Reproductive Investment of the Cyclopoid Copepod Paracyclopina nana

Copepods represent an interesting alternative or a complement live food to brine shrimps and rotifers commonly used in aquaculture. They constitute the natural prey of many fish species and therefore do not require a potential nutritional enrichment. But an optimization of the microalgal diets used to feed copepods is essential to improve their mass culture. This study examined the effects of seven microalgal diets, namely single-species diets of Rhodomonas salina (R), Tisochrysis lutea (T), and Pavlova lutheri (=Diacronema lutheri) (P), two-species diets (R + T, T + P, and R + P), and a three-species diet (R + T + P), on the fatty acid and monosaccharide composition of the cyclopoid copepod Paracyclopina nana as well as its reproductive investment. Experiments were run during 15 days in 10-L beakers; starting with nauplii collected from a large 300-L batch culture. Copepods fatty acid contents were studied, particularly the relative amounts of docosahexaenoic acid (DHA) and eicosa-pentaenoic acid (EPA). The R + T, R, and T diets induced the highest total fatty acid amount in copepods. R + T and R also generated the lowest DHA/EPA ratios in copepods due to high EPA contents. The highest value of total monosaccharides was found in copepods fed with R + T + P. Diets R + T and R induced the greatest prosome volumes and clutch volumes in ovigerous females. Both prosome volume and clutch volume in P. nana ovigerous females were correlated to the individual EPA amount. The results demonstrated that all diets including R. salina enhanced the productivity of P. nana in mass culture, particularly when combined with T. lutea. R. salina, and T. lutea induced complementary fatty acid and monosaccharide profiles, confirming that R + T represents the best microalgae combination for productive culture of P. nana. Conversely, P. lutheri did not enhance the nutritional profile nor the fecundity of P. nana in the culture. This study is the first to demonstrate that R. salina is a suitable microalga for productive mass culture of P. nana for use as live food in aquaculture.

First record of the freshwater copepod Mesocyclops paranaensis Dussart & Frutos, 1986 (Copepoda: Cyclopoida: Cyclopidae) from Colombia

The Neotropical free-living freshwater cyclopoid copepod Mesocyclops paranaensis Dussart & Frutos, 1986 was found in a small temporal pond in La Guajira, northern Colombia. Hitherto, it has been reported from Argentina, Paraguay, and Brazil. This is the first record of this species in Colombia, its northernmost finding in South America, and the fourth locality in which this species has been recorded from. Mesocyclops paranaensis can be distinguished from its closest congeners by a unique combination of the characters of the female, including: 1) leg 4 intercoxal sclerite with two large, acute projections; 2) P3, P4 intercoxal sclerite caudal surface lightly pilose; 3) seminal receptacle with narrow lateral arms and weakly convex anterior margin; 4) second antennary endopodite with seven setae, and insertion of antennary exopodal seta with adjacent spinules; 5)frontal surface of P1 basipodite ornamented with long spinules; 6) posterior margin of anal somite with continuous row of spinules; and 7) inner margin of caudal ramus hirsute. The Colombian population shows some subtle morphological differences with respect to previous reports.

Effects of Different Diets on Population Growth of Cultured Cyclopoid Copepod, Mesocyclops leuckarti (Claus, 1857)

In recent times aquaculture has become an increasingly important part of the world economy. Copepods play major roles in pond ecosystems serving as food for small fish, micro-predators on fish and other organisms, fish parasites, intermediate hosts of fish parasites and hosts and vectors of human diseases like cholera. Growth, reproduction and biochemical composition were analyzed for the copepod Mesocyclops leuckarti fed on four diets and their ratio like Bakers yeast (B), Baker’s yeast+ Wheat flour (BW, 1:2), Bakers yeast + Chicken manure (BC, 1:2) and Bakers yeast + Chicken manure + Wheat flour (BCW, 1:2:2). The mean peak density of the copepod population was 569 individual/lit, for all four diets used. The highest was 587 individual/lit, on diet having combination of Bakers yeast, Chicken manure and Wheat flour (BCW). A small copepod Mesocyclops leuckarti tends to have a short life span and it was found to be important food items for fish larvae.

Effect of Different Salinity Levels on Population Dynamics and Growth of the Cyclopoid Copepod Oithona nana

Copepods are one of the most abundant and diverse live food sources for mesopelagic and bathypelagic fishes and crustaceans. They could contribute to the overlap of the transition period from live feed to an artificial weaning diet in marine larvae production. However, the culture conditions still need optimization to provide sufficient production to cover the increasing demand for marine hatcheries. Therefore, the present study investigated the effects of different salinity levels (5, 10, 15, 20, 25, and 30 ppt) on the population growth, growth rate, and population composition (males, females, copepodite, and nauplii ratio) of the marine copepod, Oithona nana. The experiment continued for 15 days, under laboratory-controlled conditions of temperature (27 ± 1 °C), pH (7.7 ± 0.15), and continuous gentle aeration in 30 L glass aquaria. The copepod culture aquaria were supplemented with a mixture of soybean and yeast (0.5 g 10−6 individual−1 24-h−1) as a feed source. The highest significant population growth and population growth rate of O. nana were achieved with a salinity level of 20 ppt. Regarding population composition, O. nana cultured at the salinity level of 20 ppt recorded the highest significant percentages of copepodite and nauplii. The results concluded that copepod, O. nana, is capable of withstanding abrupt changes in the salinity, but there are limits to their tolerance, with an optimal salinity level of 20 ppt. This salinity level achieved the highest population growth and the highest percentages of copepodite and nauplii of marine Copepoda, O. nana.

Size, not temperature, drives cyclopoid copepod predation of invasive mosquito larvae

During range expansion, invasive species can experience new thermal regimes. Differences between the thermal performance of local and invasive species can alter species interactions, including predator-prey interactions. The Asian tiger mosquito, Aedes albopictus, is a known vector of several viral diseases of public health importance. It has successfully invaded many regions across the globe and currently threatens to invade regions of the UK where conditions would support seasonal activity. We assessed the functional response and predation efficiency (percentage of prey consumed) of the cyclopoid copepods Macrocyclops albidus and Megacyclops viridis from South East England, UK against newly-hatched French Ae. albopictus larvae across a relevant temperature range (15, 20, and 25°C). Predator-absent controls were included in all experiments to account for background prey mortality. We found that both M. albidus and M. viridis display type II functional response curves, and that both would therefore be suitable biocontrol agents in the event of an Ae. albopictus invasion in the UK. No significant effect of temperature on the predation interaction was detected by either type of analysis. However, the predation efficiency analysis did show differences due to predator species. The results suggest that M. viridis would be a superior predator against invasive Ae. albopictus larvae due to the larger size of this copepod species, relative to M. albidus. Our work highlights the importance of size relationships in predicting interactions between invading prey and local predators.