Jiang-Shiou Hwang

Cymbopogon citratus-synthesized gold nanoparticles boost the predation efficiency of copepod Mesocyclops aspericornis against malaria and dengue mosquitoes

Plant-borne compounds can be employed to synthesize mosquitocidal nanoparticles that are effective at low doses. However, how they affect the activity of mosquito predators in the aquatic environment is unknown. In this study, we synthesized gold nanoparticles (AuN) using the leaf extract of Cymbopogon citratus, which acted as a reducing and capping agent. AuN were characterized by a variety of biophysical methods and sorted for size in order to confirm structural integrity. C. citratus extract and biosynthesized AuN were tested against larvae and pupae of the malaria vector Anopheles stephensi and the dengue vector Aedes aegypti. LC₅₀ of C. citratus extract ranged from 219.32 ppm to 471.36 ppm. LC₅₀ of AuN ranged from 18.80 ppm to 41.52 ppm. In laboratory, the predatory efficiency of the cyclopoid crustacean Mesocyclops aspericornis against A. stephensi larvae was 26.8% (larva I) and 17% (larva II), while against A. aegypti was 56% (I) and 35.1% (II). Predation against late-instar larvae was minimal. In AuN-contaminated environment,predation efficiency against A. stephensi was 45.6% (I) and 26.7% (II), while against A. aegypti was 77.3% (I) and 51.6% (II). Overall, low doses of AuN may help to boost the control of Anopheles and Aedes larval populations in copepod-based control programs.

Sex Steroids in Scleractinian Coral, Euphyllia ancora: Implication in Mass Spawning

Abstract The objectives of this study were to investigate the presence and annual cycle of sex steroids in scleractinian coral, Euphyllia ancora. The free and conjugated forms of sex steroids in coral and spawning seawater were investigated, and aromatase activity in the coral tissue was identified. Polyps collected from corals and seawater were extracted with diethyl ether, and purified by alumina column and reversed-phase HPLC; testosterone and estradiol-17β (E2) was measured by a validated RIA. E2 and testosterone in their free and glucuronide forms were consistently detected in coral tissue throughout the year. Peak concentrations of free E2, E2 glucuronide, and testosterone glucuronide were obtained in the coral tissue just prior to spawning. The presence of specific aromatase activity was demonstrated in coral tissue. Free E2 and E2 glucuronide concentrations were higher than androgen (testosterone and testosterone glucuronide) in coral tissue and spawning seawater. Higher concentrations of free E2 than E2 glucuronide were detected in coral tissues throughout the year. In contrast, higher concentrations of E2 glucuronide than free E2 and testosterone glucuronide were found in seawater during mass coral spawning. No steroid sulfate could be detected in the coral tissue and seawater. We suggest that the release of E2 glucuronide may play an important role in coral mass spawning.

Taxonomic Composition and Grazing Rate of Calanoid Copepods in Coastal Waters of Northern Taiwan

Taxonomic composition and grazing rate of calanoid copepods in coastal waters in the northern tip of Taiwan was studied in May 1996. During the study period chlorophyll a concentrations in the upper 2 m of the water column were low. Twenty-five species of calanoid copepods were identified. Acrocalanus gracilis, Canthocalanus pauper, Temora discaudata, Temora turbinata, and Undinula vulgaris were found over the entire study area. Gut pigment content of 17 species was measured with the gut fluorescence method. The variability of the gut pigment contents for a single species among the sampling stations comprised about a factor 2 to 4. Ingestion rates and clearance rates were calculated from gut pigment data. The highest values were observed in Temora discaudata, Temora turbinata, and Undinula vulgaris.

Host selection by shrimps symbiotic with sea anemones: A field survey and experimental laboratory analysis

In three coastal areas of the Republic of China, we found six species of anemoneshrimps and five of host sea anemones in 13 symbiotic combinations; four of the 13 combinations were previously documented. In the laboratory, we tested host preference of the three common shrimps, Periclimenes ornatus Bruce, P. brevicarpalis (Schenkel), and Thor amboinensis (De Man), for anemones of three species. Periclimenes ornatus unequivocally preferred Entacmaea quadricolor (Ruppell and Leuckart), the only anemone with which it occurs in northern Taiwan and from which the experimental specimens had been collected. We therefore consider P. ornatus a specialist on E. quadricolor. Results of experiments with P. brevicarpalis and T. amboinensis were ambiguous: for both, outcome of some experiments was affected by identity of the anemone from which the shrimp had been collected, and in other experiments, T. amboinensis exhibited no preference. We therefore consider Thor a generalist symbiont, and P. brevicarpalis intermediate in specificity. In experiments to determine sensory cue(s) used by the shrimps to locate hosts, none could locate an anemone by vision alone. A significant proportion of shrimp of all three species was chemically attracted to anemones of at least one species; as in the preference experiments, source of the shrimp affected the results for P. brevicarpalis and T. amboinensis. The proportion of shrimp chemically attracted to an anemone in the experiments on sensory cues was lower than the proportion attracted in the host preference experiments. We, therefore, infer that shrimp use more than one sensory modality to locate a host anemone.

Copepod communities related to water masses in the southwest East China Sea

The East China Sea is characterized by a complex hydrographic regime and high biological productivity and diversity. This environmental setting in particular challenged a case study on the use of mesozooplankton community parameters as indicators of water masses. In order to reveal spatial patterns of zooplankton communities during summer, a large scale oceanic transect study was conducted. Two transects were taken in the southwest East China Sea region, covering for the first time the China shelf, slope, and the estuaries of the Yangtze river and of the Minjiang river, the northern Taiwan Strait, and the Kuroshio Current region. A total of 77 copepod species were quantified. Copepod abundance was significantly higher in the estuary of the Yangtze River runoff mixture waters and lowest at the Kuroshio Current Region. The calanoid Parvocalanus crassirostris was the most frequently occurring and abundant species retrieved from 27 samples of a total of 39 samples. The use of multivariate cluster analysis separated the Mainland China Shelf from the northern Taiwan Strait and the Kuroshio Current Region at the first hierarchical level. The use of an indicator value method (IndVal) associated with each cluster of stations revealed characteristic species assemblages. Two hierarchical levels defined 4 assemblages within geographical sectors representing copepod assemblages of the Kuroshio Current Region, of the northern Taiwan Strait and the southern China Shelf near the estuary of the Minjiang River and northern stations near the estuary of the Yangtze River. Overall, there was a strong correspondence between the distribution of certain copepod species and water masses. Differences between the Mainland China shelf, the northern Taiwan Strait and the Kuroshio Current Region were characterized by differences in species composition and abundance. Water mass boundaries in the study area were exclusively indicated by distinct differences in species composition, emphasizing a correlation between copepod communities and water masses of the southwest East China Sea in summer.

Costs and benefits of the symbiosis between the anemoneshrimp Periclimenes brevicarpalis and its host Entacmaea quadricolor

Shrimp of the species Periclirnenes brevicarpalis (family Palaemonidae, subfamily Pontoniinae) are obligate associates of sea anemones. To assess the nutritional relationship between the shrimp and one of its hosts. Entacrnaea quadricolor (family Actiniidae), w e conducted 10 replicate 30 d experiments. An experiment comprised 6 treatments: a pair of fed shrimp, a pair of unfed shrimp. a fed pair of shrimp plus an anemone, an unfed pair of shrimp plus an anemone, a fed anemone, and an unfed anemone. Shrimp survival was 6 (of 20) for unfed shrimp lacking an anemone, 17 for fed shrimp lacking an anemone, and 19 for shrimp with a host, whether fed or not. Longevity of unfed anemoneshrimp kept alone (23 d ) was significantly less than that of shrimp in the other treatments (28 or 29 d) . Larvae were released by all female shrimp with an anemone but by only 7 of 10 unfed and 8 of 10 fed ones kept alone Magnitude of growth, interval between molts, and number of larval releases were all dependent on whether a shrimp had been kept with an anemone but were independent of whether ~t had been fed. Shrimp clipped and ate anemone tentacles: unfed anemones with shrimp lost most or all of thelr tentacles, and many fed ones did so as well, but anemones kept without shrimp did not. Magnitude of tentacle loss was dependent on whether the anemone had been with shrimp but was independent of whether it had been fed Thus, there IS a benefit to the shrimp from this association and potentially a cost to the anemone, but anemones w ~ t h shrimp in nature always appear to have normally long and numerous tentacles.

Changes in the swimming behavior of Eurytemora affinis (Copepoda, Calanoida) in response to a sub-lethal exposure to nonylphenols.

Estuarine waters are continuously loaded with chemicals which affect the physiology of aquatic organisms to various extents. They also have adverse effects on a wide range of behaviors. Nonylphenols and related compounds are biodegradation products of the nonionic surfactants nonylphenol polyethoxylates. They are commonly found in the aquatic environment. We observed immediate alterations of the free swimming activity of the calanoid copepod Eurytemora affinis from the Seine estuary in response to a sub-lethal concentration of nonylphenols (4-NP and NP1EC) at environmentally realistic concentrations (2 μg/L). Swimming speed and activity increased for both males and females. The use of copepod kinematic proved to be a sensitive indicator of sub-lethal exposure to pollutants.

Larvicidal activity of Morinda citrifolia L. (Noni) (Family: Rubiaceae) leaf extract against Anopheles stephensi, Culex quinquefasciatus, and Aedes aegypti

Morinda citrifolia leaf extract was tested for larvicidal activity against three medically important mosquito vectors such as malarial vector Anopheles stephensi, dengue vector Aedes aegypti, and filarial vector Culex quinquefasciatus. The plant material was shade dried at room temperature and powdered coarsely. From the leaf, 1-kg powder was macerated with 3.0 L of hexane, chloroform, acetone, methanol, and water sequentially for a period of 72 h each and filtered. The yield of extracts was hexane (13.56 g), chloroform (15.21 g), acetone (12.85 g), methanol (14.76 g), and water (12.92 g), respectively. The extracts were concentrated at reduced temperature on a rotary vacuum evaporator and stored at a temperature of 4°C. The M. citrifolia leaf extract at 200, 300, 400, 500, and 600 ppm caused a significant mortality of three mosquito species. Hexane, chloroform, acetone, and water caused moderate considerable mortality; however, the highest larval mortality was methanolic extract, observed in three mosquito vectors. The larval mortality was observed after 24-h exposure. No mortality was observed in the control. The third larvae of Anopheles stephensi had values of LC50 = 345.10, 324.26, 299.97, 261.96, and 284.59 ppm and LC90 = 653.00, 626.58, 571.89, 505.06, and 549.51 ppm, respectively. The Aedes aegypti had values of LC50 = 361.75, 343.22, 315.40, 277.92, and 306.98 ppm and LC90 = 687.39, 659.02, 611.35, 568.18, and 613.25 ppm, respectively. The Culex quinquefasciatus had values of LC50 = 382.96, 369.85, 344.34, 330.42, and 324.64 ppm and LC90 = 726.18, 706.57, 669.28, 619.63, and 644.47 ppm, respectively. The results of the leaf extract of M. citrifolia are promising as good larvicidal activity against the mosquito vector Anopheles stephensi, Aedes aegypti, and Culex quinquefasciatus. This is a new eco-friendly approach for the control of vector control programs. Therefore, this study provides first report on the larvicidal activities against three species of mosquito vectors of this plant extracts from India.

The complete mitogenome of the hydrothermal vent crab Xenograpsus testudinatus (Decapoda, Brachyura) and comparison with brachyuran crabs.

In this study, we analyzed the complete mitochondrial (mt) genome of a hydrothermal vent crab Xenograpsus testudinatus (Decapoda: Brachyura) obtained from the hydrothermal vents off Kueishantao Island, Taiwan, which extend from the deep sea Okinawa Trench. The mitogenome of X. testudinatus was 15,796 bp in length and contained the same 37 genes (e.g. 2 rRNAs, 22 tRNAs, and 13 PCGs) found in other metazoan mitogenomes. Analysis of the structural mt gene order in X. testudinatus revealed that the 13 PCGs, excluding a translocation of ND6-Cyt b cluster, were similarly ordered when compared to the pancrustacean ground pattern; however the tRNAs were severely rearranged. Phylogenetic analysis of decapod mitogenomes showed that the molecular taxonomy of the vent crab was in accordance with its morphological systematics. Together, these findings suggest that the vent crab studied here has little mitochondrial genetic variation when compared with morphologically defined conspecifics from other marine habitats.

Aristolochia indica green-synthesized silver nanoparticles: A sustainable control tool against the malaria vector Anopheles stephensi?

Malaria is a life-threatening disease caused by parasites transmitted to people and animals through the bites of infected mosquitoes. We biosynthesized silver nanoparticles (AgNP) using Aristolochia indica extract as reducing and stabilizing agent. AgNP were characterized by UV-vis spectroscopy, FTIR, SEM, EDX and XRD. In laboratory, LC50 of A. indica extract against Anopheles stephensi ranged from 262.66 (larvae I) to 565.02 ppm (pupae). LC50 of AgNP against A. stephensi ranged from 3.94 (larvae I) to 15.65 ppm (pupae). In the field, the application of A. indica extract and AgNP (10 × LC50) leads to 100% larval reduction after 72 h. In laboratory, 24-h predation efficiency of Diplonychus indicus against A. stephensi larvae was 33% (larvae II) and 57% (larvae III). In AgNP-contaminated environment (1 ppm), it was 45.5% (larvae II) and 71.75% (larvae III). Overall, A. indica-synthesized AgNP may be considered as newer and safer control tools against Anopheles vectors.