Euphausiacea diversity in a trans-oceanic transect through the South Atlantic Ocean: the first Atlantic record of Thysanopoda astylata Brinton, 1975

Abstract

Information about euphausiids in central South Atlantic Ocean is scarce; hence, we investigated species composition and distribution of euphausiids along a longitudinal transect in this region, with an emphasis on Thysanopoda. Zooplankton samples were collected from 44 stations during the first Transatlantic Commission (Brazil-Africa). Euphausiids comprised 21,390 individuals across larval stages (nauplius, calyptopis, and furcilia) and adults. Furcilia and adults were classified to species level when possible, with a total of 19 identified species. Overall, Euphausia species frequency of occurrence and abundance were highest in samples collected near the African coast, while Thysanopada species dominated near the Brazilian coast. Of the euphausiids caught, 158 were identified as Thysanopoda, including 2 specimens of T. astylata, 6 T. aequalis, 3 T. pectinata, 2 T. monacantha, 2 T. tricuspida, and 1 T. egregia; 118 damaged specimens could only be identified as Thysanopoda spp., and 24 as T. aequalis / T. astylata complex because of the lack of diagnostic structures. Thysanopada egregia was present in samples collected down to 96 m, which increases the vertical range for this species. This report constitutes the first record of Thysanopoda astylata Brinton, 1975 in Atlantic waters.

Further record of the deep-sea euphausiid, Thysanopoda cristata G. O. Sars, 1883 (Euphausiacea, Euphausiidae) from the southwestern Atlantic: with comments on morphological variations

“…Thysanopoda cristata was described by Sars ( 1883) based only on one adult male from off Mindanao in the Philippines (Pacific Ocean) (Station 213 at 3750 m), but it is known to be widely distributed in the Indo-Pacific (between 30°N and 40°S), South Africa (Natal coast), Baja California in Mexico, and in the Polar Arctic and Antarctic oceans Brinton, 1962;Grindley & Penrith, 1965;Taniguchi, 1974;Youngbluth, 1975). For the Atlantic Ocean, this species was reported only in the Sargasso Sea, Azores and possible observations in the tropical western Atlantic (covering the North and South Atlantic) (Gibbons et al, 1999;Lansac-Tôha & Freire, 1999;Muxagata et al, 2019). However, several of these records were provided in unpublished reports (dissertations and theses) containing only species lists, without taxonomic descriptions, and specimens not deposited in a zoological collection, nor included an estimate of a possible region of occurrence for the T. cristata found.…”

“…Around 60 species of krill are reported in the South Atlantic, from neritic to oceanic zones, including islands, archipelagos and atolls (Montú, 1977;Muxagata et al, 2019). In Brazilian waters, 22 species are currently recorded, distributed among Euphausia Dana, 1850 (6 species), Nematobrachion Calman, 1905 (3 species), Nematoscelis G. O. Sars, 1883 (4 species), Stylocheiron G. O. Sars, 1883 (4 species) and Thysanopoda (5 species) (Ramirez, 1971;Antezana & Brinton, 1981;Montú & Cordeiro, 1986;Gibbons et al, 1999;Lansac-Tôha & Freire, 1999).…”

“…Regarding Euphausiidae, the genus Thysanopoda H. Milne Edwards, 1830 is composed of 14 valid species with a broad distribution in all oceans (including Arctic and Antarctic regions), especially in meso-and bathypelagic zones (∼200 to 4000 m) (Brinton, 1962;Baker et al, 1990;Gibbons et al, 1999). According to Lansac-Tôha & Freire (1999) and Muxagata et al (2019), only five species of Thysanopoda have been recorded in the South Atlantic (T. aequalis Hansen, 1905;T. monacantha Ortmann, 1893;T.…”