Boroecia borealis (Sars 1865) Sars 1865
- Dataset
- Morphology and distribution of pelagic ostracods of the genus Boroecia (Ostracoda: Halocyprididae) in the Central Arctic
- Rank
- SPECIES
Classification
- kingdom
- Animalia
- phylum
- Arthropoda
- class
- Ostracoda
- order
- Halocyprida
- family
- Halocyprididae
- genus
- Boroecia
- species
- Boroecia borealis
description
MALE MALE Carapace: Carapace: length 3.16 – 3.23 mm length 2.25 – 2.43 mm shoulder vault rounded shoulder vault wing-shaped with sharp edge left valve with one tooth and right valve with 3 teeth in each valve with 4 teeth in posterior-dorsal angle posterior-dorsal angle posterior margin slightly convex and sloping downward to posterior margin visibly convex and unsloping or barely antero-ventral side sloping downward to antero-ventral side sculpture slightly developed sculpture distinct Rod-shaped organ: Rod-shaped organ: capitulum equal to length of second segment of 1 st antenna capitulum longer than second segment of 1 st antenna First antenna: First antenna: length limb about 70, 90 and 90 % length of e-, b- and d-setae length limb about 60, 70 and 80 % length of e-, b- and d-setae respectively respectively a-seta with large proximal tubercle a-seta with midsize or small proximal tubercle length a-seta less 50 % length of limb and about 1.4 times as length a-seta more 50 % length of limb and about 1.2 times as long as c-seta long as c-seta b-bristle with thin pad b-bristle with thick pad c-seta shorter than second segment and somewhat more than c-seta longer than second segment and about 30 % length of e- 20 % length of e-seta seta d-seta with 3 – 4 distal spines and less 80 % length of e-seta d-seta with 20 distal spines and more 80 % length of e-seta e-seta with 44 – 50 paired spines and without anterior tubercle e-seta with 53 – 56 paired spines and with anterior tubercle distally distally Second antenna: Second antenna: height of protopodite somewhat more than 40 % of its length height of protopodite about 50 % of its length first exopodite segment without short distal seta first exopodite segment with short distal seta second endopodite segment with developed e-seta second endopodite segment with undeveloped e-seta base of hooks and second endopodite segment form distinct base of hooks and second endopodite segment do not form ventral corner ventral corner Mandible: Mandible: seta on exopodite about 1.75 length of distal endopodite seta on exopodite about 1.5 length of distal endopodite segment (on dorsal margin) segment (on dorsal margin) muscle band attached to endite of basale is wide muscle band attached to endite of basale is narrow tubed bristle of endite on basale shorter than its usual tubed bristle of endite on basale equal to length of its usual posterior seta posterior seta Maxilla: Maxilla: length of second endopodite segment about 75 % and 65 % length of second endopodite segment about 90 % and 80 % height of 1 st endopodite segment and length of main claw height of 1 st endopodite segment and length of main claw respectively respectively distal seta of 1 st endopodite segment about 85 % length of 2 nd distal seta of 1 st endopodite segment about 70 % length of 2 nd segment segment Sixth limb: Sixth limb: setae on epipodial plate about 80 % length of basale (on setae on epipodial plate as long as basale (on ventral margin) ventral margin) Seventh limb: Seventh limb: length of 1 st exopodite segment somewhat less 3.5 times of its length of 1 st exopodite segment more 5.5 times of its height height ...... continued on the next page TABLE 4. (Continued) Boroecia maxima Boroecia borealis Caudal lip: Caudal lip: length of limb (distance between 1 st and 8 th bristles) about length of limb (distance between 1 st and 8 th bristles) about 90 % length of 2 nd claw 80 % length of 2 nd claw 2 nd claw less than 70 % length of 1 st claw 2 nd claw more than 70 % length of 1 st claw FEMALE FEMALE Carapace: Carapace: length 3.35 – 3.66 mm length 2.65 – 2.94 mm height about 30 % of length height about 40 % of length shoulder vault rounded shoulder vault wing-shaped with sharp edge left valve with one tooth and right valve with 3 teeth in each valve with 4 teeth in posterior-dorsal angle posterior-dorsal angle posterior margin slightly convex and sloping downward to posterior margin visibly convex and unsloping or barely antero-ventral side sloping downward to antero-ventral side sculpture slightly developed sculpture distinct First antenna: First antenna: length of limb about 80 % length of its dorsal seta length of limb equal to length of its dorsal seta e-seta about 3 times as long as sensory setae e-seta about 2 times as long as sensory setae sensory setae about 70 – 80 % length of limb sensory setae about 90 – 100 % length of limb Second antenna: Second antenna: 1 st exopodite segment without short distal seta 1 st exopodite segment with short distal seta length of g-seta equal to length of protopodite length of g-seta about 90 % length of protopodite Mandible: Mandible: seta on exopodite about twice as long as distal endopodite seta on exopodite about one and half as long as distal segment (on dorsal margin) and less 50 % length of endopodite segment (on dorsal margin) and more 50 % length endopodite of endopodite muscle band attached to endite of basale is wide muscle band attached to endite of basale is narrow main terminal claw longer than endopodite main terminal claw shorter than endopodite length of longest ventral seta on basale more than the height length of longest ventral seta on basale less than the height of of this segment this segment tubed seta of endite on basale shorter than its usual posterior tubed seta of endite on basale equal to length of its usual seta posterior seta Maxilla: Maxilla: longest seta of 1 st endopodite segment more than 2 times its longest seta of 1 st endopodite segment less than 2 times its length length 1 st endopodite segment with 2 distal spines 1 st endopodite segment with 3 distal spines Fifth limb: Fifth limb: basale about 90 % length of 1 st segment and with 10 ventral basale equal to length of 1 st segment and with 9 ventral setae setae Sixth limb: Sixth limb: basale with 5 ventral setae basale with 4 ventral seta seta of exopodite longer than half length of basale seta of exopodite shorter than half length of basale basale about 80 % length of setae on epipodial plate basale about 60 – 70 % length of setae on epipodial plate Distribution of Boroecia species in the Central Arctic. The Arctic Basin is known to be one of the coldest regions of the World Ocean. However, by no means is the entire water column characterized by subzero temperatures. The relatively warm waters of the Gulf Stream flow via the North Atlantic Current into Norwegian and thence into the North Cape and West Spitsbergen currents, advecting warm water and the elements of boreal fauna and flora into polar latitudes (Vinogradov 1968, Meincke et al. 1997). In almost all areas of the Central Arctic the water column includes a warm layer of North Atlantic Waters with positive water temperatures and relatively high salinities, primarily located in depths of 200 – 900 m (excluding the area to the north off Spitsbergen) (Treshnikov et al. 1976) and having a thickness of 600 – 700 m (Klepikov et al. 1985, Spall 2013). This layer contains the greatest species diversity of plankton (Brodsky 1956, Brodsky & Pavshtiks 1976; Vinogradov 1968; Virketis 1957; Chavtur 1978, 1992). Within this layer, water temperatures are about 2.5 º C in the Eurasian subregion, 0.8 º C at the North Pole, but only 0.4 º C in the American subregion (Treshnikov et al. 1976). Understanding distribution of Boroecia species in these waters is problematic. The species are rather similar in appearance and most authors have not given adequate morphological information about the species they were reporting on. Boroecia maxima and B. borealis often occur at the same locality and have thus often been confused and even treated as being identical species.
discussion
Remarks. The name Conchoecia borealis is also mentioned in the following literature: Vanhöffen (1897), Nordgaard (1899), Müller (1901, 1912), Ostenfeld (1906, 1931), Ostenfeld & Wesenberg-Lund (1909), Damas & Koefoed (1907), Jörgensen (1912); Jespersen (1923), Davidson (1924), Yashnov (1927), Kielhorn (1952), Hulings (1966, 1967), Shih & Laubitz (1978), Richter (1994). However, these publications have no taxonomical information (descriptions and figures are absent). Therefore we are not sure if the identification of these authors is correct. The specimens investigated by us differ somehow from the descriptions of B. borealis by Brady & Norman (1896), Vávra (1906), Skogsberg (1920), Sars (1922) and Poulsen (1973). A list of distinguishing characteristics is given in Table 3. Since this species is morphologically quite similar to B. maxima, we provide a comparison of characteristics between these species (Tab. 4). Beside the records mentioned above, this species was reported from the China Seas (Chen & Lin 1995), which seems very doubtful considering the distribution mentioned by other authors. B. borealis was found from - 1.66 ° to 17.7 ° C and from 32.7 ‰ to 35.14 ‰ (Fowler 1903; Virketis 1957; Deevey 1968; Angel & Fasham 1975; Shih & Laubitz 1978; Angel 1979 b; Bashmanov & Chavtur 2008). number of postero-dorsal teeth on valves: - left (male) 4 (?) 3 4 - right (male) 3 2 4 number of distal spines some on anterior side 6 spines on 5 – 6 spines on posterior side - on b-seta (male) posterior side - on d-seta (male) about 25 about 60 about 20 - on e-seta (male) 50 – 55 50 50 – 55 53 – 56 length of row of spines on e-seta (male) more than twice as long as more than twice as more than 1.5 as long as pad on pad on b-seta long as pad on b-seta b-seta length a-seta (male) about 1.5 length of c-seta; about 1.2 length of c-seta; about about 40 % length of e-seta 35 % length of e-seta length b-seta (male) as long as d-seta or somewhat somewhat longer than d-seta; more; about 70 % length of e-seta more 80 % length of e-seta …… continued on the next page TABLE 3. (Continued) Characteristics Skogsberg Vavra 1906 Poulsen 1973 Sars Brady & Norman Present 1920 1866 1896 paper length c-seta (male) about 25 % length of e-seta; as about 30 % length of e-seta; long as 2 nd segment of limb longer than 2 nd segment of limb length of part e-seta distally paired about 40 % length of this seta about 30 % length of this seta spines (male) length of dorsal seta (female) about 80 % length of limb as long as limb length of sensory setae (female) about 80 % length of limb; more than 90 % length of limb; somewhat more than 30 % length about 50 % length of e-seta of e-seta Length of e-seta (female) about twice as long as limb about 2.5 times as long as limb about twice as long as limb Second antenna: proximal part hook on right limb (male) with 2 verrucae and one thin only with 2 verrucae only with 2 with one verruca and one thin spine verrucae spine FIGURE 12. Boroecia borealis (Male: A – C, IBM 2832; D, E, G, M, IBM 2831; F, H – L, 2834). A, lateral view of the right valve; B, ventral view of the valves; C, posterior view of the valves; D, E, posterior margin of the right and left valves; F, arming of the b-seta; G, distal part of the Rod-shaped organ and 1 st antenna; H, I, 1 st antenna; J, arming of the e-seta; K, Rodshaped organ (black blob at the capitulum is probably sclerite); L, distal part of the d-seta; M, endopodite of the right 2 nd antenna. FIGURE 13. Boroecia borealis (Male: A, D, IMB 2834; C, F, IBM 2831; B, E, G – J, IBM 2833). A, 2 nd antenna; B, C, exopodite and endopodite of the right 2 nd antenna; D – F, clasping organ of the right 2 nd antenna; G, clasping organ of the left 2 nd antenna; H, mandible; I, J, exopodite and epipodite of the mandible. FIGURE 17. Boroecia borealis (Female: A – C, IBM 2836; D, E, IBM 2835; F, G, IBM 2837; H – J, IBM 2840). A, lateral view of the right valve; B, ventral view of the valve; C, posterior view of the valves; D, E, posterior margin of the right and left valves; F, capitulum of the Rod-shaped organ; G, Rod-shaped organ at 1 st antenna; H, 1 st antenna (dorsal seta not shown) and shaft of the Rod-shaped organ; I, 2 nd antenna; J, exopodite of the 2 nd antenna. FIGURE 18. Boroecia borealis (Female: A – E, IBM 2840; F, G, IBM 2835). A, B, endopodite of the 2 nd antenna; C, mandible (setae not shown); D, epipodite, basale, exopodite and endopodite of the mandible; E, distal part of the mandible; F, basal endite and cutting edge, distal and proximal tooth-lists of the coxale on the mandible; G, distal part of maxilla. FIGURE 19. Boroecia borealis (Female: A, D, E, IBM 2840; B, C, IBM 2835). A, basale and endopodite of the maxilla; B, C, 2 nd and 3 rd coxale endites of the maxilla; D, fifth limb; E, upper lip. FIGURE 20. Boroecia borealis (Female: A, IBM 2838; B – F, IBM 2840). A, 1 st precoxale endite of the maxilla; B, C, precoxale, coxale and basale from exterior (B) and interior (C) of the right fifth limb; D, E, sixth limb; F, seventh limb. Boroecia maxima Boroecia borealis
distribution
Distribution of Boroecia borealis. The distribution map of Boroecia borealis is somewhat different from that of B. maxima. It is obvious that the central region of the Arctic Ocean is devoid of this species. It is distributed along the edge of the shelf region but it does not occur over the shelf region itself. It is absent from most of Russia’s northern seas, with depths less than 150 – 200 m (see figure) The main distribution, or better the main area where these animals have been collected, seems to be the Greenland Sea Gyre and regions at the edge of the shelf region from the Fram Strait up to the Chukchi Sea. No reliable data on the occurrence of this species around the Canadian Archipelago and in the northern Greenland Sea are available (see figure). Only Shih & Laubitz (1978) present information on findings of presumend B. borealis, i. e. areas of sampling (69 º – 74 ºN and 95 º – 139 º W), depths of sampling (25 – 800 m deep), water temperature (from - 1.66 º to 0.6 º C) and salinity (from 32.7 to 34.8 ‰). They do not give morphological data on the species and their data are not consistent with other well-funded research data on this species. Therefore, we think that these authors either mixed B. borealis with the closely related cold-water species B. maxima or, which is even more probable, just identified the latter species as the former one. Their material needs re-identification, therefore we still cannot claim that B. borealis inhabits this area.
distribution
Distribution of Boroecia maxima. Boroecia maxima is the most abundant species of halocyprids in the mesoplankton of the Arctic Ocean and its adjacent cold waters (often contributing 70 – 90 % of total halocyprid populations). It inhabits the entire Central Arctic (Brodsky & Nikitin 1955 (recorded as Ostracoda), Bogorov 1946; Virketis 1957, 1959; Melnikov 1980 (recorded as Conchoecia sp.); Melnikov & Kulikov 1980 (recorded as Conchoecia sp.); Sars 1900; Müller 1931; Grainger 1965; Leung 1972, 1973; Chavtur 1978, 1992, 2001; Chavtur & Bashmanov 2005; Angel 1979 a) from the surface to 2000 (3900) m depth. (Fig. 11). North of 84 – 85 º N, only one other deep-sea species, Proceroecia vitjazi, co-occurs with B. maxima at depths of 1000 m in subpolar waters (unpublished data). Martin Angel (pers. communication) reports another novel, as yet undescribed species Boroecia in the deep sea below 750 m. Shallow depths in the Bering Strait and in adjacent Chukchi and northern Bering Seas are an ecological barrier to the dispersion of oceanic species occurring at depths deeper than 200 m, and not only excludes the spread of B. maxima into the North Pacific, but also the entry of North Pacific species into the Arctic. The distribution pattern of B. maxima in the Arctic reflects the bathymetry of the Arctic Ocean (Figs. 11, 22). Nevertheless, it is remarkable that this species is not found over the shelf along the Russian coastline and the Chukchi Sea. It does occur in the delta of the Mackenzie River, where the salinity is also rather low. This indicates that depth and temperature are the main factors limiting its distribution rather than salinity. Note that the shelf near the Mackenzie River is narrow, and offshore the water deepens rapidly.
materials_examined
Material examined. Drift Ice Station “ Severnyi Polyus ” - 2 (SP- 2), Station 5, 78 º 53 ˙ N, 194 º 30 ˙ E, depth 260 – 950 m, Nansen’s Net (S = 0.5 m ²), August 1950: IBM 2831, adult male (length 2.25 mm); IBM 2832, adult male (2.43 mm); IBM 2835, adult female (2.75 mm); IBM 2836, adult female (2.82 mm). RV ” Polarstern ” 27 th Cruise, Station AGT 0 47, 77 º 11.67 ˙ N, 126 º 19.17 ˙ E, depth 1079 m, 9 September 1993, Nectobenthic Trap: IBM 2834, adult male (2.36 mm); Station AGT 0 48, 77 º 07.83 ˙ N, 126 º 25.04 ˙ E, depth 500 m, 9 September 1993, Nectobenthic Trap: IBM 2839, adult female (2.80 mm); IBM 2840, adult female (2.94 mm). 77 º 11.67 ˙ N, 126 º 19.17 ˙ E, depth 1079 m. RV “ Berg ” 15 th (?) Cruise, Station 50, sample 154, Norwegian Sea (? сoordinates), depth 300 – 500 m, 15 June 1954, Nansen’s Net (S = 0.5 m ²): IBM 2837, adult female (2.66 mm); IBM 2838, adult female (2.65 mm). These specimens have been deposited in the Museum of the Institute of Marine Biology (Vladivostok, Russia). Supplementary description of adult male. Carapace (Fig. 12 A – E). Length 2.25 – 2.43 mm (literature 1.80 – 2.60 mm). Greatest height about 0.99 – 1.15 mm at posterior half and width 0.79 – 0.97 mm at midlength. Dorsal and ventral margin straight or barely concave at midlength. Anterior margin evenly rounded. Posterior margin visibly concave and not or barely sloping downward to antero-ventral side. Postero-dorsal corner on each valve with 4 teeth. Shoulder vault well developed wing-shaped with sharp edge along the greater part of its length. Each valve with well developed dorso-medial gland represented by a series of long glandular cells situated about 1 / 3 from posterior corner. Lateral gland on posterior margin of each valve consisting of 4 groups of glandular cells and situated about 2 / 3 from posterior corner. Surface of carapace with distinct sculpture (like rhombic cells). Rod-shaped organ (Fig. 12 G, K). Capitulum section slightly concave dorsally, somewhat longer than second segment of 1 st antenna, and about 45 % length of shaft. First antenna (Fig. 12 I – J, L). Length 0.8 mm about 60 %, 70 % and 80 % length of e-, b- and d-setae respectively. The a-seta provided with little proximal tubercle, longer than ½ length of limb, about ⅓ and ½ length of e-seta and c-seta respectively. The b-seta somewhat longer than d-seta and about 80 % length of e-seta and armed with long thick pad; its terminal part distally of pad with some spinules. The c-seta longer (about 110 %) than second segment of limb and about 30 % length of e-seta. The d-seta 80 % length of e-seta distally with about 20 anterior spinules and 20 posterior short setules. The e-seta about 1.5 of length of limb, with rounded bend (without distinct angle) and a tubercle at ⅔ of its length, proximally of bend along 1 / 3 of its length with two rows with each 53 – 56 (in literature 50 – 55) closely placed winged spines, distal part of seta sword-shaped. Surface of limb bare. Second antenna (Figs. 12 M, 13 A – G). Height of protopodite exceeding slightly half its length. Protopodite as long as its longest natatory seta and about twice as long as exopodite. First segment of exopodite relatively thick (20 % and more of its length), about 70 % of its whole length and with short distal seta. The a-seta on endopodite about ¾ of length of b-seta. The e-seta tiny. The f-seta about 70 % length of g-seta. Sensory h-, i- and j-setae terminally rounded and about 50 % length of g-seta. The g-seta barely shorter than protopodite (about 85 – 90 % of its length). The f- and g-setae sword-shaped distally. Hook appendage near second endopodite segment without distinct ventral protuberance. Proximal part of hook appendage about ½ length of its distal part on left and right endopodite. Right hook appendage relatively well developed, sharply curved, with long straight proximal section furnished with verruca and short spine, distally with subterminal ridges and two exceedingly small hyaline spines. Left hook appendage relatively small, straight or slightly curved, with bare proximal section (without verruca and spine) and distally also with two fine spines and with subterminal ridges. Ventral surface of first endopodite segment densely covered with tiny setules. Mandible (Figs. 13 H – J, 14 A – D). Seta of exopodite about 1.5 the length of distal endopodite segment. Length of first, second and third segments of endopodite about 50 %, 25 % and 25 % its length, respectively (on dorsal margin). First segment on dorsal margin with one distal plumose seta, on ventral margin with 4 setae with short setules, of which one distal seta very long. Dorsal margin of second segment with one (longest) strong claw-like seta (about 65 – 70 % length of endopodite) and two setae; ventral margin with two setae (longest about 75 – 80 % length of endopodite). Third segment with 7 terminal seta: 5 short setae and two strong long claw-like setae (longest seta about 80 % length of endopodite). Length of basale about 70 % or somewhat longer than endopodite, and height about 80 – 85 % of its length. Tooth-row of basale endite with 6 triangular teeth, with one lateral evenly rounded tooth and two equal posterior setae, one of which tubular. Muscle band attached to posterior margin of basal endite relatively narrow. Masticatory pad with 4 strong and long teeth, with numerous long and some short setules and 4 rounded flaps. Epipodite narrow, with noticeable verruca with moderately long seta. Maxilla (Fig. 14 E – G). Seta of basale about subequal to length and width of first endopodite segment. This segment with 6 ventral, 3 dorsal and one medio-distal setae with short setules, width about 70 % and 40 % of its length and its longest ventral seta, respectively. Medio-distal seta of this segment more than 70 % of the length of the segment. Length of second segment about 3 times or less of its height, about 90 % width of first segment and about 80 % length of main claw. Distal surface of first segment armed with 3 relatively long spines. Coxale endite provided with 15 and precoxale endite with 9 setae and teeth. Fifth limb (Fig. 15 A – C). Epipodial plate with 4, 5 and 4 (and one additional short seta) plumose setae in each distal, middle and proximal group of setae, respectively. First endite of precoxale with one long plumose seta and one short seta, second endite covered with short spines (on external side) and with two plumose setae (one medium long and one long) and one minute bare seta. Coxale armed with two strong claw-like setae, two plumose and 4 setae with short setules; its inner surface provided with some relatively long spines. Basale is less than 80 % of the length of first segment of endopodite and bears 8 setae with short setules, one plumose ventral seta, and one dorsal plumose seta; its width about 80 % of length. Exopodite represented by long seta. First segment of endopodite with two ventral and one dorsal setae with short setules; its width about 30 % of length. Longest claw-like seta of second segment about 55 – 60 % length of endopodite. External side of precoxale, coxale and basale covered with long setules. Sixth limb (Figs. 15 D, 16 A). Epipodial plate with 5, 5 (rarely 4) and 6 (and one additional short seta) plumose setae in each of distal, middle and proximal group of setae, respectively; length of these setae (except of short seta) about 80 % length of basale (on ventral margin). Protopodite provided with two distal plumose setae. Basale with 3 ventral, 2 ventro-lateral and one dorso-lateral plumose setae. Exopodite represented by one short bare seta. First segment of endopodite with one ventral seta and second segment with one dorsal and one ventral setae. Terminal setae about twice as long as length of endopodite. Seventh limb (Fig. 16 B). Limb relatively slim. Length of first segment about 3.5 times of its width; greatest width at proximal part. Second segment provided with 2 – 4 spinules, its short seta about 1.3 times length of limb (long seta broken). Caudal furca (Fig. 16 C). Set with 6 pairs of claw-like setae, two pairs of regular setae and one unpaired seta dorsally of smallest seta pair. 4 th seta considerably longer than 5 th seta. Length of limb (distance between 1 st and 8 th setae) about 60 and 80 % length of 1 st and 2 nd setae, respectively. Length of 2 nd seta about 80 % of 1 st seta. Inner surface densely covered with fine setules. Copulatory appendage (Fig. 16 D – G). Limb straight and relatively narrow, varying in shape and with 6 oblique muscle bands; about 28 – 34 % of carapace length. Its end obliquely truncated or almost rounded. Greatest width about 20 % or somewhat more of its length and positioned at mid-length. Upper lip is lost. Adult female. Carapace (Fig. 17 A – E). Length range 2.65 – 2.94 mm (in literature 2.0 – 3.0 mm). Greatest height about 1.19 – 1.44 mm at posterior half and width about 1.06 – 1.18 mm at mid-length. Dorsal and ventral margin strait or barely concave at mid-length. Anterior margin evenly rounded. Posterior margin visibly convex and barely or not sloping downward to antero-ventral side. Postero-dorsal corner on right valve with one tooth and on left valve with 3 teeth. Shoulder vault well developed and rounded. Lateral gland on posterior margin of each valve consists of 4 groups of glandular cells and situated about ⅔ from posterior corner. Surface of carapace with distinct reticular sculpture (like rhombic cells). Rod-shaped organ (Fig. 17 F – H). About 1.5 times or barely longer than length of 1 st antenna. Shaft extends somewhat beyond end of terminal end of 1 st antenna. Capitulum narrow, slightly concave dorsally, about 50 % length of shaft, with numerous long spines in proximal half and along ventral side and with pointed tip placed near ventral side. First antenna (Fig. 17 G, H). Limb narrow (height about 20 % of its length). Dorsal seta about as long as length of limb, and armed with short setules. The e-seta about twice (or somewhat less) as long as limb and sensory a – dsetae, with anterior and posterior short setules in its medial part, and distally slightly sword-shaped. Sensory setae terminally rounded and with equal thickness along their length. Lower surface of first and second segments and upper surface of first segment covered with some short setules; first segment has dark brown spots. Second antenna (Figs. 17 I, J; 18 A, B). Height of protopodite about 50 % of its length. Protopodite as long as longest natatory seta and somewhat longer than g-seta. Exopodite narrow, relatively long and about 55 % length of protopodite. First exopodite segment about 70 % of exopodite and with distal seta. Height of this segment about 15 – 20 % of its length. All setae of second endopodite segment terminally pointed. The f- and g-setae slightly widened distally and with anterior short setules. The f-seta about 70 % length of g-seta. Sensory setae with usual thickness along their length and terminally rounded; h- and j-setae about 55 % length of g-seta and somewhat shorter than iseta. Ventral surface of first endopodite segment densely covered with tiny setules. Mandible (Figs. 18 C – F). Seta of exopodite about one and half the length of distal endopodite segment. Length of first, second and third segments of endopodite about 50 %, 25 % and 25 % of their length. First segment dorsally with distal seta, ventrally with 3 relatively short and one long (about 85 % length of endopodite) setae with short setules. Dorsal margin of second segment with two short seta and one long claw-like seta (about 60 – 65 % length of endopodite), ventral margin with two normal setae, of which longest seta about 70 – 75 % length of endopodite. Third segment with 7 terminal setae of which 5 normal short setae and two strong long claw-like setae (longest seta about 85 % length of endopodite). Length of basale about 60 % length of endopodite, and height about 120 % of its length. Tooth-row of basale endite with 6 triangular teeth, with one lateral evenly rounded tooth and two posterior setae, one of which tubular and shorter than other. Muscle band attached to posterior margin of basale endite relatively narrow. Masticatory pad with 4 rounded flaps. Coxale cutting edge with 9 triangular teeth and one large straight tooth. Proximal and distal tooth-lists of coxale armed with 12 teeth each. Epipodite similar to those of male. Maxilla (Figs. 18 G; 19 A – C; 20 A). Seta of basale about equal or somewhat shorter than length of first endopodite segment. This segment with 6 ventral setae (of which longest seta somewhat shorter than length of its segment), 3 dorsal and one medio-distal setae with short setules; width about 60 % of its length and 35 % of its longest ventral seta. Medio-distal seta of this segment about more than 80 % of its length. Length of second segment more than 3 times of its height and equal or lesser (about 90 %) than width of first segment. Main claw about 1.3 times the length of second segment. Distal surface of first segment armed with 3 relatively short spines. Coxale and precoxale endites provided with 14 – 15 and 9 setae and teeth, respectively. Fifth limb (Figs. 19 D; 20 B, C). Epipodial plate with 4, 5 and 4 (and one additional short seta) plumose setae in each distal, middle and proximal group of setae, respectively. First endite of precoxale with one long plumose seta and one short seta, second endite covered with short spines (on external side), two plumose setae (one medium length and one long) and one minute bare seta. Coxale armed with two strong claw-like setae, two plumose and 4 setae with short setules; its inner surface provided with some relatively long spines. Basale about 95 – 100 % or somewhat less than length of second segment, with 8 setae setae with short setules, one plumose ventral seta, and one dorsal plumose seta; its width about 80 % of length. First segment of endopodite with two ventral and one dorsal setae with short setules; its width about 35 % of length. Longest claw-like seta of third segment about 55 % length of endopodite. External side of precoxale, coxale and basale covered with long setules. Sixth limb (Fig. 20 D, E). Epipodial plate with 5, 5 (rarely 4) and 6 (and one addition short seta) plumose setae in each of distal, middle and proximal group of setae, respectively. Protopodite provided with two distal plumose setae. Basale with 2 ventral, 2 ventro-lateral and one dorso-lateral plumose setae; its length about 60 – 70 % of length of setae on epipodial plate (except of short seta). Exopodite represented by short bare seta (shorter than half length of basale). First segment of endopodite with one ventral seta and second segment with one dorsal and one ventral setae. Main terminal claw-like seta about 80 % length of exopodite. Seventh limb (Fig. 20 F). Relatively slim. Length of first segment about 3.5 times of its width; this segment has equal thickness throughout its length. Second segment provided with 2 – 4 spinules, its short seta about 1.2 times length of limb and about 30 % of long seta. Caudal furca. With 6 pairs of claw-like setae, two pairs of regular setae and one unpaired seta dorsally to smallest pair of setae. 4 th seta considerably longer than 5 th seta. Length of limb (distance between 1 st and 8 th setae) about 60 and 80 % length of 1 st and 2 nd setae, respectively. Length of 2 nd seta about 75 % length of 1 st seta. Inner surface densely covered with fine setules. Upper lip. (Fig. 19 F). Posterior ventral edge interrupted by flat U-shaped notch. Each side of notch with 18 – 20 relatively long, flaccid, spine-like processes.