A new species of Tortanus (Atortus ) (Copepoda, Calanoida, Tortanidae) from the coastal waters of Nha Trang, Vietnam

Abstract

A new species of the copepod genus Tortanus, subgenus Atortus, is described from the coastal waters of Nha Trang, Vietnam. The new species is assigned to the tropicus species group sensu Othman (1987) and distinguished from the other members of the group by the morphology of the processes on the fifth pedigerous somite and the genital somite in the female, and the antennule and leg 5 in the male. An analysis of previous records of Atortus indicates highly sporadic occurrence, but a large number of species to be distributed in Southeast Asia. This obviously suggests future discovery of even more species, and also the need for sampling with better geographic and ecological coverage in this particular region. RÉSUMÉ Une nouvelle espèce du genre de copépode Tortanus, du sous-genre Atortus, est décrite des eaux côtières de Nha Trang, Vietnam. La nouvelle espèce est attribuée au groupe d'espèces tropicus sensu Othman (1987) et se distingue des autres membres du groupe par la morphologie des processus situés sur le somite portant la cinquième patte et le somite génital chez la femelle, et par l'antennule et la cinquième patte chez le mâle. Une analyse des précédents signalements de Atortus indique une présence hautement sporadique, mais un grand nombre d'espèces réparties dans le sud-est asiatique. Ceci suggère clairement la découverte future de plus nombreuses espèces, et aussi la nécessité d'un échantillonnage réalisé avec une meilleure couverture géographique et écologique dans cette région particulière.

Spreading factors of a globally invading coastal copepod

“…The genus Pseudodiaptomus comprises today 80 species, five of which have been described in the last 10 years (e.g., Nishida & Rumengan, 2005;Sakaguchi & Ueda, 2010;Srinui et al, 2013). Most of them are distributed in the Indo-Pacific area, occupying a few restricted regions, and the majority (~60 species) occupies only one geographical area or two adjacent ones (Table 1 in the Supplementary material).…”

Two new species of Tortanus (Atortus) (Copepoda, Calanoida, Tortanidae) from the Andaman Islands

“…The species of the tropicus group are unique among pelagic copepods with their highly limited geographic distribution (Ohtsuka & Kimoto, 1989;Nishida & Cho, 2005). According to Ohtsuka & Kimoto (1989), among the eight species that were known at that time, only T. longipes and T. rubidus had been recorded at multiple localities, while the other six species were known only from the type localities.…”

“…This peculiarity has continued to date, and all four subsequently discovered species (T. taiwanicus, T. vietnamicus, T. andamanensis, T. sigmoides) are also from single localities, indicating high probability of discovering undescribed species at newly studied localities. This may be partly due to their patchy distribution associated with habitats of complicated topography such as coral reefs and sea-grass beds, wherein conventional net-sampling may not be much effective (Ohtsuka & Kimoto, 1989;Ohtsuka & Reid, 1998;Ohtsuka et al, 2000;Nishida & Cho, 2005), but also due to the presumed extensive speciation of this group through geological vicariance events in this particular region (Ohtsuka & Kimoto, 1989;Nishida & Cho, 2005). For more effective sampling of this group of copepods, specific methods such as those by SCUBA diving (Ohtsuka & Kimoto, 1989) and night-time collection, with or without light (Jones & Park, 1968;Bowman, 1971), are recommended.…”

“…The following 12 species are the current members of this group: T. brevipes Scott, 1909, T. tropicus Sewell, 1932, T. longipes Brodsky, 1950, T. rubidus Tanaka, 1965, T. giesbrechti Jones & Park, 1968, T. bowmani Othman, 1987, T. ryukyuensis Ohtsuka & Kimoto, 1989, T. digitalis, T. taiwanicus Chen & Hwang, 1999, T. vietnamicus Nishida & Cho, 2005, and the present two species, of which T. brevipes is known only from the female. While Ohtsuka & Kimoto (1989) proposed the name "brevipes species complex" for this assemblage of species, referring to the concept of species complex as proposed by Fleminger et al (1982), the name "tropicus" proposed by Othman (1987) is followed here, since the male of T. brevipes has not yet been described (see also Nishida & Cho, 2005).…”

A new species of Tortanus (Atortus) (Copepoda, Calanoida, Tortanidae) from Minicoy Island, southeastern Arabian Sea

“…The subgenus Atortus, accommodating 32 nominal species (Mulyadi et al, 2017), is regarded as the most advanced and is distributed exclusively in the Indo-West Pacific region. It tends to occur in more or less oligotrophic, clear, high-salinity (34-40 PSU) waters sometimes strongly influenced by warm currents, or in coral reefs and seagrass beds (Ohtsuka and Kimoto, 1989;Ohtsuka and Reid, 1998;Ohtsuka et al, 2000;Nishida and Cho, 2005;Nishida et al, 2015;Mulyadi et al, 2017). It must also be mentioned that cooccurrence of multiple closely related species of Tortanus (Atortus) makes it difficult to determine their femalemale correspondence solely on the basis of morphology (Nishida et al, 2015;Mulyadi et al, 2017).…”