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Two new species of the planktonic copepod genus Tortanus, subgenus Atortus, are described from inter- to sub-tidal water of South Andaman Island, India. The new species are assigned to the tropicus group sensu Othman (1987) and distinguished from the other members of the group by the characteristic morphology of the pair of posterior dorsolateral processes on the fifth pedigerous somite in the female and the antennule and leg 5 in the male. An analysis of previous records of the tropicus species group indicates their sporadic occurrence combined with high species richness in Southeast Asia, suggesting future discovery of even more species by sampling with finer geographic and habitat coverage.

Trophic preference (i.e., food resources and trophic levels) of different copepod groups was assessed along a salinity gradient in the temperate estuarine Gwangyang Bay of Korea, based on seasonal investigation of taxonomic results in 2015 and stable isotope analysis incorporating multiple linear regression models. The δ13C and δ15N values of copepods in the bay displayed significant spatial heterogeneity as well as seasonal variations, which were indicated by their significant relationships with salinity and temperature, respectively. Both spatial and temporal variations reflected those in isotopic values of food sources. The major calanoid groups (marine calanoids and brackish water calanoids) had a mean trophic level of 2.2 relative to nanoplankton as the basal food source, similar to the bulk copepod assemblage; however, they had dissimilar food sources based on the different δ13C values. Calanoid isotopic values indicated a mixture of different genera including species with high δ15N values (e.g., Labidocera, Sinocalanus, and Tortanus), moderate values (Calanus sinicus, Centropages, Paracalanus, and Acartia), and relatively low δ15N values (Eurytemora pacifica and Pseudodiaptomus). Feeding preferences of different copepods probably explain these seasonal and spatial patterns of the community trophic niche. Bayesian mixing model calculations based on source materials of two size fractions of particulate organic matter (nanoplankton at < 20 µm vs. microplankton at 20–200 µm) indicated that Acartia and Centropages preferred large particles; Paracalanus, Calanus, Eurytemora, and Pseudodiaptomus apparently preferred small particles. Tortanus was typically carnivorous with low selectivity on different copepods. Labidocera preferred marine calanoids Acartia, Centropages, and harpacticoids; on the other hand, Sinocalanus and Corycaeus preferred brackish calanoids Paracalanus and Pseudodiaptomus. Overall, our results depict a simple energy flow of the planktonic food web of Gwangyang Bay: from primary producers (nanoplankton) and a mixture of primary producers and herbivores (microplankton) through omnivores (Acartia, Calanus, Centropages, and Paracalanus) and detritivores (Pseudodiaptomus, Eurytemora, and harpacticoids) to carnivores (Corycaeus, Tortanus, Labidocera, and Sinocalanus).

This study reports on the planktonic copepod, Tortanus ( Atortus ) murrayi Scott A., 1909 from South Andaman, Northeast Indian Ocean. This is a new distributional record of murrayi species group of recticauda species complex from the Indian Ocean. T . ( A .) murrayi is a well-known species, yet, the taxonomic features of mouthparts and swimming legs were never previously illustrated and is achieved herein.

Two new species of the planktonic copepod genus Tortanus, subgenus Atortus, are described from inter-to sub-tidal water of South Andaman Island, India. The new species are assigned to the tropicus group sensu Othman (1987) and distinguished from the other members of the group by the characteristic morphology of the pair of posterior dorsolateral processes on the fifth pedigerous somite in the female and the antennule and leg 5 in the male. An analysis of previous records of the tropicus species group indicates their sporadic occurrence combined with high species richness in Southeast Asia, suggesting future discovery of even more species by sampling with finer geographic and habitat coverage. Deux nouvelles espèces du genre de copépode planctonique Tortanus, sous-genre Atortus, sont décrites des eaux inter- à sub-tidales de l'île Andaman du Sud, Inde. Les nouvelles espèces sont assignées au groupe tropicus sensu Othman (1987) et se distinguent des autres membres du groupe par la morphologie caractéristique de la paire de processus dorsolatéraux postérieurs situés sur le cinquième somite pédigère chez la femelle et par l'antennule ainsi que la patte 5 chez le mâle. Une analyse des mentions antérieures des espèces du groupe tropicus indique leur présence sporadique combinée avec une richesse en espéces élevée en Asie du Sud-Est, suggérant la découverte future d'encore plus d' espèces par un échantillonnage utilisant une couverture plus fine au niveau géographique et de l'habitat.

Brackish-water calanoid copepods, defined as those predominantly inhabiting oligo- and mesohaline waters, were investigated at 45 rivers in western Japan during 2006–2009 to review their faunas and, for comparison, 4 rivers of Korea in 2006. Eight species (Acartia ohtsukai, A. sinjiensis, A. tsuensis, Pseudodiaptomus inopinus, P. ishigakiensis, Sinocalanus sinensis, S. tenellus and Tortanus derjugini) were identified as brackish-water calanoid copepods from Japan. Among them, P. inopinus was most often collected; it occurred in 38 rivers. Acartia tsuensis and A. sinjiensis were also frequent species in Japan. Pseudodiaptomus ishigakiensis discovered from Kyushu Island is new to the mainland of Japan. From the rivers of Korea six species were identified (A. ohtsukai, A. sp., P. inopinus, P. sp., S. tenellus and T. dextrilobatus). Based on the present and previous studies, a total of 13 brackish-water calanoid copepods have been recorded from Japan and Korea, of which eight species, including three continental relicts (A. ohtsukai, S. sinensis and T. derjugini) in Kyushu Island, are common to both regions. Among them, only two species (P. inopinus and S. tenellus) are distributed widely on both Japanese and Korean coasts of the Tsushima (Korea) Strait. This indicates that the faunas of brackish-water calanoid copepods are very different between Japan and Korea despite the short geographical distance (about 170 km) and that the Tsushima Strait has played the role of an effective barrier for their dispersion.

The morphology and host-specificity of the histophagous apostome ciliate Vampyrophrya pelagica infecting pelagic copepods in the Seto Inland Sea, Japan, were intensively investigated. Four stages were reconfirmed in the life cycle of the ciliate. A mature cell within the phoront bears cilia ready for quick excystation, and unique lamellar structures in the cytoplasm appear to be precursors of food vacuole membranes. These lamellar structures completely disappear in the fully grown trophont. The phoronts were attached to the ventral surface of the copepod prosome or legs, but were almost totally absent on the urosome. The number of phoronts per copepod was up to 43 for the adult female of Paracalanus parvus s.l. Phoront attachment was found irrespective of developmental stage and sex of P. parvus s.l., although the early copepodid stages were less frequently infected than the later stages, and the adult female was more intensively infected than the adult male. There was a marked seasonal change in prevalence and host-specificity of the phoronts. From middle summer to early winter, P. parvus s.l., Acartia pacifica, Tortanus forcipatus, Euterpina acutifrons, and Corycaeus affinis were frequently infected, while Oithona spp. and Microsetella norvegica were rarely infected, whereas from late winter to early summer, phoronts were detected only on the large-sized calanoids, Calanus sinicus and Euchaeta plana. This may be explained by a combination of longevity and molting of copepods, turnover time of the apostome life cycle which depends on water temperature, and seasonal changes in the abundance and food selectivity of predatory chaetognaths. Considering the high prevalence of apostome ciliates on not only copepods but also other crustaceans in the world oceans, the ecological influence of these ciliates on marine ecosystems should be re-evaluated.

We show how four co-occurring calanoid copepod species modulate their responses to two contrasting hydrodynamic stimuli. Species-specific patterns in escape behavior included quantitative differences in performance to each stimulus type. Using high-speed video, we compared escape reactions in Acartia hudsonica, Centropages hamatus, Tortanus discaudatus, and Temora longicornis. Responses to a flow field created by a suction tube involved reorientation away from the source of suction followed by a series of vigorous power strokes. Responses to brief computer-controlled hydrodynamic stimuli had short latencies (a few milliseconds) and consisted of a reorientation followed by a few pereiopod power strokes. Two species responded to this stimulus with higher escape speeds. The other two species gave a larger response to the suction stimulus by producing long escape trajectories. Each species perceived the magnitude of the threat in a different way and employed a different strategy in the escape response.

Invasions of aquatic habitats by non-indigenous species (NIS), including zooplankton, are occurring at an alarming rate and are causing global concern. Although hundreds of such invasions have now been documented, surprisingly little is known about the basic biology and ecology of these invaders in their new habitats. Here we provide an overview of the published literature on NIS zooplankton, separated by life history (holoplankton vs. meroplankton), habitat (marine, estuarine, freshwater), and biological level of organization or topic (e.g. distribution and range extension, physiology, behavior, feeding, community impacts, ecosystem dynamics, etc). Amongst the many findings generated by our literature search, perhaps the most striking is the paucity of studies on community and ecosystem level impacts of NIS zooplankton, especially in marine and estuarine systems. We also present some results from two ongoing studies of invasive zooplankton in the northeast Pacific Ocean - Pseudodiaptomus inopinus in Washington and Oregon coastal estuaries, and Tortanus dextrilobatus in San Francisco Bay. Both of these Asian copepods have recently expanded their range and can at times be extremely abundant (10^sup 3^ m^sup -3^). We also examine some aspects of the trophic (predator-prey) ecology of these two invasive copepods, and find that they are likely to be important in the flow of material and energy in the systems in which they now pervade, although their impacts at the ecosystem level remain to be quantified. Finally, the findings of both our literature search and our two case studies of invasive zooplankton lead us to make several recommendations for future research.[PUBLICATION ABSTRACT]

Zooplankton abundance, biomass, and composition from the ports of Mumbai, India, were studied by selecting 14 stations in and around the area during three different periods between 2001 and 2002 (Nov 01, Apr 02, and Oct 02). The results are compared with the records available since the 1940s. Copepod species such as Canthocalanus sp., Paracalanus arabiensis , Cosmocalanus sp., Euterpina acutifrons , Nannocalanus minor , and Tortanus sp. which were not reported in the earlier studies were observed during the present investigation. Purely herbivorous forms like Nannocalanus minor , Paracalanus sp., and Temora discaudata were in reduced abundance during Apr 02 sampling which was coupled with reduction in the diatom population. Whereas increased abundance of some carnivorous and omnivorous forms during Apr 02 sampling can be related to the changes in the food web dynamics.

Despite a dramatic increase in the introduction of non-indigenous estuarine zooplankton in recent decades, the trophic implications of such introductions have rarely been quantified. Here we investigate predation rates of Tortanus dextrilobatus, a carnivorous copepod recently introduced to the San Francisco Estuary that achieves peak abundances in excess of 1000 ind./m super(3). The functional response of T. dextrilobatus feeding upon 2 copepod prey types--the non-indigenous cyclopoid Oithona davisae, and the 'native' calanoid Acartia (Acartiura) sp.--was described by a type II functional response (Ivlev function) at 2 experimental temperatures. In 3 of these 4 treatments, 90% I sub(max) was achieved within a naturally occurring range of prey densities. Taxon-specific seasonal size variation was identified, and carbon-based consumption values were used to determine temperature-dependent rates of predation on both prey types. These empirically derived consumption rates and temperature dependence values were then applied to broadscale surveys (1997 to 1999) of zooplankton community composition in order to estimate the predatory impact of T. dextrilobatus upon prey populations in the San Francisco Estuary. Predatory impact estimates (% population consumed/d) greater than 1% occurred on a regular basis when T. dextrilobatus was abundant, with maxima exceeding 20, 65, and 25% for O. davisae, Acartia (Acartiura) sp. and all Copepoda, respectively. These observations support the hypothesis that non-indigenous invertebrate zooplanktivores can play a significant role, at least seasonally or episodically, in the secondary production dynamics of aquatic ecosystems.