Bythotrephes arcticus Lilljeborg 1901

• Main Author: Korovchinsky, Nikolai M.
• Format: Text
• Language: unknown
• Published: Zenodo 2016
• Subjects: Biodiversity; Taxonomy; Animalia; Arthropoda; Branchiopoda; Diplostraca; Cercopagidae; Bythotrephes; Bythotrephes arcticus; Kola Peninsula; Murmansk; Norway; Seta; Gam; Vestnik; Porsanger; Juv; Karesuando; Pustozersk; Huitfeldt; Borok; Arktis*; karelien; Kildin; kola peninsula; ob river; Subarctic; Tundra; Norrbotten; Siberia
• Online Access: https://dx.doi.org/10.5281/zenodo.6085645; https://zenodo.org/record/6085645

Bythotrephes arcticus Lilljeborg, 1901 (Figs. 1–6) Bythotrephes longimanus Leydig, 1860: Stenroos 1897: 67 –68 (partim); Ekman 1904: 28 –29. Bythotrephes longimanus var. arcticus Lilljeborg, 1901: Lilljeborg 1901: 612 –613, Tab. 81, Figs. 9 –12; Mordukhai-Boltovskoi & Rivier 1987: 152, Fig. 44 A-B; Rivier 1998: 173, Fig. 215 a, b. Bythotrephes longimanus var. arctica Lilljeborg: Levander 1901: 24. Bythotrephes arctica Lilljeborg: Sars 1903: 186, Pl. 8, fig. 6. Bythotrephes longimanus arcticus Lilljeborg: Ischreyt 1930: 321, Fig. 13 d; Manuilova 1964: 292–293, Fig. 160 – 6; Vekhov 1981: 74, Fig. 2; 1987: 28, Fig. 1. Bythotrephes crassicauda Lilljeborg: Ischreyt 1934: 277, Abb. 16 d; 1937: 56; 1939: 127. Bythotrephes longimanus crassicaudus Lilljeborg: Litvinchuk 2001: 129. Bythotrephes crassicaudus Lilljeborg, 1890: Litvinchuk 2002: 84–86, 118 – 119, 127 – 128, Figs. 8, 10, 35, 36, 41 B, 42 B; 2007: 191–192, Figs. 3 B, 4 B; Litvinchuk & Litvinchuk 2016: 67–73, Fig. 9. Type material. Syntypes. All specimens certainly used by Lilljeborg (1901) for investigation and description of B. arcticus and labeled “ B. crassicauda ” or “ B. longimanus arcticus ” can be considered as belonging to the type series of the taxon (ICZN, 72.4. 1., 72.5.) and named syntypes (ICZN, 73.2.). Lectotype . A parthenogenetic female with body length 4.34 mm (Karesuando, Norrbotten, Sweden, 30.7. 1875, collected by Lilljeborg, sample N 2669) deposited in a tube with alcohol in the Museum of Evolution of Uppsala University (№ UPSZTY 163492). Paralectotypes are deposited in the same Museum: slides № UPSZTY 2730, 2826– 2830; samples № UPSZTY 163493– 163505. Material examined. Russia: Kola Peninsula (Murmansk region): 1) A slide (MEUU, N 633 c with specimens from sample N 2318) labeled “ Kola Penins., Karabella, 31 / 7 77, Sandeb. exp., Bythotrephes crassicauda n. sp. glacialis ” (the last name has probably been crossed out by Lilljeborg) (in a Museum catalog this material is designated as “ B. longimanus arcticus, syntypes ”), 2 ad, dried ( paralectotypes) 2) a slide (MEUU, N 633 d with a specimen from sample N 2319) labeled “ Bythotrephes crassicauda n. sp., Kola Penins. Karabella, 5 / 9 77, Sandeb. exp.”, 1 ad dried and deformed ( paralectotype ); 3) sample (MEUU, N 2672) designated in a Museum catalog “ B. l. arcticus, USSR, Kola peninsula, Karabella, 31.7. 1877, Sandeberg”, numerous specimens (ad, gam, males) ( paralectotypes, ); 4) sample (ZIN, without number) labeled “ Bythotrephes, Alexandrovsk (Murman), 1899, A. Linko”. 1 ad of first generation; 5) sample (ZIN, N 6852) labeled “ Bythotrephes longimanus Leydig, Verhne- Kildinskoe lake, coll. Knipovitch, 1898, det. Verestchagin”, 2 ad, 2 males; 6) a slide (ZIN, without number) labeled “ Bythotrephes, Kildin, 1898, N. Knipovitch”, 1 ad, dried; 7) a slide (ZIN, N 73 – 15) labeled “ Bythotrephes longim v., swamps of Kildin Island, det. Verestchagin”, 1 ad, deformed; 8) a slide (ZIN, without number) labeled “ Bythotrephes longim, Lake Kildinskoe, Knipovitch 1894, det. Verestchagin”, 1 gam. Arkhangel’skaya region, Bol’shezemelskaya tundra (north-east of European Russia) : 9) sample (NMK, N 2143), Nenetsky autonomous area, Srednayay Haryala, Lake Lolyalaty (67 ° 4 ’ N; 56 ° 3 ’ E), 11.7. 2000, coll. A.V. Rzhavsky, numerous ad, 1 male; 10) sample (NMK, N 2144), the same area, spring near Lake Lolyalaty, coll. A.V. Rzhavsky, 2 ad; 11) sample (ZIN, N 6853) labeled “ Bythotrephes longimanus Leydig, Pechersky area, Pustozersk VII, coll. Zhuravsky, det. G. Verstchagin”, 2 males; 12) two slides (ZIN, N 45 -06) labeled “ Bythotrephes longimanus, Arkhangel’skaya guberniya, Pustozersk, Zhuravsky”, 2 ad; 13) basin of the River Tchernaya, lake 1 (68 ° 22 ’ 18.5 ’’ N; 56 ° 49 ’ 19.5 ’’ E) and lake 2 (68 ° 29 ’ 59.4 ’’ N; 56 ° 40 ’ 35.4 ’’ E), 9.7. 2013, leg. E.B. Fefilova, 8 ad, numerous juv; 14) the same region, Lake Dubovskoi (67 ° 36 ’032’’ N; 62 ° 54 ’ 12.5 ’’ E), 20.7.2012, 1 gam, 2 males, leg. E.B. Fefilova; 15) two slides (ZIN, without numbers) labeled “ Bythotrephes , tundra near mouth of the River Pechera, Peltsam”, 2 ad. Western Siberia : 16) sample (ZIN, N 250-1936), Ob River, sor Vusrenohnor, Yurty Karvoki, 7.3.1931, 12 ad; 17) sample (ZIN, N 6849) labeled “v -? Bythotrephes longimanus, River Sos’va near Berezov town, 16.7. 1896, coll. Varpahovsky, det. Verestchagin”, 1 ad; 18) a slide (ZIN, without number) labeled “lake near village Puiko, Yamal, det. G. Verestchagin”, 1 ad; 19) Lake Yan in the basin of the River Pur near town Tarko-Sale, 3 ad, 1 male, 5 juv. Eastern Siberia : 20) sample (ZIN, N 6851) labeled “ B. longimanus v -?, Turuhansk, coll. Ulrih, det. Verestchagin”, 6 ad, 14 males, some juv; 21) a slide (ZIN, without number) labeled “ Bythotrephes longim. v?, Turuhansk, Ulrih”, 1 ad; 22) a slide (ZIN, without number), the same label, 2 gam; 23) a slide (ZIN, without number), the same label, 1 ad. Kazakhstan: 1) sample (ZIN, N 6848) labeled “ Byth. arcticus Lilljeb, Akmolinskaya region, Lake Sabanty Kul, 6.6. 1899, coll. Ignatov, det. G.O. Sars”, 6 ad, deformed; 2) a slide (ZIN, without number) labeled “ Bythotrephes arcticus, Akmolinskaya region (st. 15), P. Ignatov”, 3 ad, deformed. Sweden: 1) a slide (MEUU, N 633 a with specimens from sample N 2669) labeled “ B. longimanus arcticus, Sw, Lpl, Karesuando, 30 / 7 1875, Lillj.”, 2 ad ( paralectotypes ); 2) a slide (MEUU N 633 b with specimens from sample N 2673) labeled “ B. l. arcticus, Sw, Lpl, Karesuando, 30.7. 1875, Lillj.”, 4 ad ( paralectotypes ); 3) a slide (MEUU, N 633 e with specimens from sample N 2320) labeled “ Bythotrephes crassicauda, Sw, Lpl, Karesuando, 30 / 7 75, Lillj.” with 2 dissected males ( paralectotypes ); 4) a slide (MEUU, N 633 f with specimens from sample N 2321) labeled “ Bythotrephes crassicauda, Sw, Lpl, Karesuando, 30 / 7 75, Lillj.”, 2 ad, dissected ( paralectotypes ); 5) sample (MEUU, N 2648) labeled “ B. l. arcticus (junior), Sw, Sk, Vombsjön, 8.7. 1880, Lillj.”, 1 juv ( paralectotype) 6) sample (MEUU, N 2650) labeled “ B. l. arcticus, Sw, Hls, Råbosjön, 28.8. 1895, E. Lönnberg”, numerous ad, gam, males ( paralectotypes ); 7) sample (MEUU, N 2651) labeled “ B. l. arcticus, Sw, Jmt, Undersüker Ottsjön, 21.8. 1889, Schött H.”, 1 ad, 1 gam, 1 male, 3 juv ( paralectotypes ); 8) sample (MEUU, N 2658) labeled “ B. longimanus, Sw, Jmt., Östersund brook, 9.08. 1889, coll. Lillj.”, 1 ad ( paralectotype ); 9) sample (MEUU, N 2669) designated in a Museum catalog “ B. l. arcticus, Sw, Lpl, Karesuando, 30.7. 1875, Lillj.”, numerous ad, gam, males ( paralectotypes, a lectotype was selected from this sample—see above); 10) sample (MEUU, N 2655) labeled “ B. l. arcticus, Sw, Sk, Vombsjön, Cederström G.C. ”, 1 ad ( paralectotype ); 11) sample (MEUU, N 2674) labeled “ B. l. arcticus, Sw, Lpl, Karesuando, 31.7. 1875, Lillj.”, numerous ad, gam, males ( paralectotypes ). Norway: 1) sample (MEUU, N 2657) labeled “ B. l. arcticus, Norw, Tönset, Tönsettjarn, 28.7. 1881, Esmark B.”, about 20 ad, gam, males ( paralectotypes ); 2) sample (MEUU, N 2659) labeled “ B. l. arcticus, Norw, Tönset Lonsö, 28.7. 1881, B. Esmark”, 1 ad, 1 gam, 1 male ( paralectotypes ); 3) sample (MEUU, N 2668) labeled “ B. l. arcticus, Norw, Porsanger, 21.7. 1887, G. Kolthoff”, numerous ad and males ( paralectotypes ); 4) sample (MEUU, N 2670) labeled “ B. l. arcticus, Norw, Porsanger Stora, Tumsö, 1.8. 1887, G. Kolthoff”, numerous ad, gam, males ( paralectotypes ); 5) sample (MEUU, N 2675) labeled “ B. l. arcticus, Norw, Porsanger lake, 4.8. 1887, G. Kolthoff”, numerous ad, gam, males ( paralectotypes ); 6) sample (MNB, N 18908) labeled “ Bythotrephes longimanus Leydig, 1860, Norwegen, aus Forellenmägen, leg. Huitfeldt-Kaas, ded. Weltner, Oct. 1900 ”, numerous ad, males. Data on body and body parts measurements of specimens of some populations are presented in Table 1. Data from other populations have been taken into consideration for comparison. BL, mm HL:BL TlL:BL CPL:BL PCL:BL CPCL:BL% ICD: BL ICTh:BL % % % % % % Bythotrephes arcticus 1. Lake Lolyalaty (Arkhangel’skaya region, Bol’shezemelskaya tundra, NE European Russia), females, n = 15 3.5 –4.0 35.7–44.4 86.7–110.3 155.8–216.1 13.0– 17.6 9.9–14.7 11.3 –17.0 8.5–14.8 3.7 41.3 95.9 188.5 15.5 11.9 13.9 10.5 2.6 6.9 3.6 1.3 1.4 1.4 1.7 6.3 7.2 1.9 8.3 11.7 10.2 16.5 2. Sor Vusrenohnor, Yurty Karvoki, Ob River (Western Siberia), females, n = 13 3.5–4.8 37.9–45.7 70.2–85.8 143.5-201.8 9.2–18.7 6.6–13.9 8.7–16.7 5.8–8.6 4.1 42.0 79.0 168.5 12.8 9.8 12.2 7.1 2.4 4.9 15.6 2.6 2.1 2.6 0.9 5.6 6.3 9.3 20.4 21.2 21.4 12.6 3. Karesuando (Norrbotten, Sweden), females, n = 15 3.6–5.4 33.8–43.6 65.1–82.5 114.7-183.4 8.6–19.3 4.5–12.2 8.0– 15.6 5.6 –8.0 4.9 38.0 71.3 131.5 11.8 8.7 12.1 6.8 2.8 4.6 17.7 2.8 2.0 2.2 0.8 7.4 6.4 13.4 23.4 23.3 18.1 12.4 4. Combined data on six populations, females, n = 25 2.8–6.1 31.0– 51.5 63.1–92.5 80.7 –190.0 7.2–18.6 5.2 –16.0 9.9–15.9 5.5–9.9 4.6 39.9 78.8 132.6 12.7 9.2 12.1 7.7 3.5 2.6 34.5 2.8 2.5 1.6 1.2 8.8 3.3 26.0 22.3 27.5 13.0 15.6 5. Combined data for males, n = 16 2.5–4.4 35.6–46.5 51.1–80.3 141.8 –214.0 10.8–21.6 8.5–18.4 8.2–13.5 6.1–10.6 3.6 39.8 65.2 172.2 16.2 14.1 10.6 8.8 3.3 7.8 24.6 2.9 2.8 1.9 1.3 8.2 11.9 14.3 17.7 19.7 18.0 14.8 Bythotrephes transcaucasicus, Lake Chaldyr (Turkey), n = 16 2.3–4.2 34.0– 38.5 68.0– 77.9 127.1 -157.9 6.0– 11.1 5.0– 9.6 7.6–9.9 4.4–7.2 3.8 36.8 73.5 145.5 8.5 7.4 8.8 5.8 1.4 2.6 8.6 1.5 1.3 0.7 0.8 3.8 3.5 5.9 17.8 17.1 7.4 12.9 Diagnosis. Body elongated and divided into four parts: head, thorax, abdomen and postabdomen with long caudal process (Fig. 1 A). Its longitudinal axis is conspicuously incurved when anterior part of head is located at almost right angle to the thorax. Also, highly movable abdomen can be either in a straight line with the thorax or at an angle to it. Head large with rounded anterior part filled by the enormously developed compound eye and bearing small antennules ventrally. Posterior part of head bears long swimming antennae and mouth parts consisting of mandibles, maxillules (mx I), and upper lip (labrum). Thorax with strongly developed muscular ventral side bearing four pairs of thoracic limbs of different size directed antero-ventrally or ventrally. Dorsally, thorax bears sack-like carapace transformed into brood pouch sometimes reaching large size. Abdomen (metasome) is elongated, cylindrical, inconspicuously three-segmented and flexible, connected with small postabdomen, bearing ventrally a pair of straight claws and posteriorly a very long straight caudal process with a pair of similar claws proximally. Generally body length of females (without caudal process) can reach 6.0 mm or slightly more (in the examined specimens it ranges from 2.3 to 6.1 mm), while the length of caudal process may be shorter or surpasses the body length considerably. Description. Parthenogenetic female. Head. Comparatively very large (31.0– 51.5 % of body length) and subdivided into two parts: rounded anterior part mostly filled by large compound eye and posterior part bearing dorsally a large saddle-shaped neck organ, swimming antennae and mouth parts. Large pigment spot occupies about one-third or at most a half of the eye’s volume (see also Ekman (1904)). Ocellus (naupliar eye) is absent (Elofsson 1966). Antennules. Small and situated on the ventral side of the anterior head part beneath the eye. They are bulbous (Fig. 1 B) and sit on the joined basis slightly split anteriorly. Terminally they bear five regular aesthetascs in two groups, with three and two in each one, one shorter and thinner aesthetasc-like structure situated in a group with two regular aesthetascs, and having slightly widened apical end with dark granular structure inside (“accessory simple seta” according to Scourfield (1896)). Swimming antennae. Comparatively long, with elongated cylindrical basipodite (Fig. 1 A) which has a dorsal thin naked seta on its folded proximal part. Of two antennal branches, the lower three-segmented one (endopodite), sitting on the apical basipodital prominence, is slightly longer than upper branch. The upper branch is foursegmented and lower branch is three-segmented. Proximalmost segment of the upper branch is rudimentary and clearly visible only externally, all other segments of both branches are much more developed. Small spine with a row of neighboring minute prominences on the end of second segment of upper antennal branch (Fig. 1 F), similar apical prominences and spines on the distal segments of both branches (Figs. 1 D, 1 E). Small proximalmost segment of upper branch lacks setae, while other segments possess two-segmented swimming setae of more or less similar size except distalmost of them which are shorter. All setae bilaterally armed with rows of uniform thin setules. General formula of antennal setae: 0–1 – 2–5 / 1 – 1–5. Mouth parts. They are represented by upper lip (labrum), mandibles, and maxillules (maxilla I). The upper lip (Fig. 1 C) is composed of two parts: a posterior thick and slightly flattened triangular lobe and anterior large proboscis-like outgrowth. The latter is separated from the former one by a deep indention of the cuticle. The triangular lobe bears numerous papillae along its posterior-interior (oral) margin while the outgrowth is armed with tiny spinules. Mandibles are bilobed and adapted for biting (Fig. 4 H), with a toothed, blade-like posterior lobe and small anterior lobe (mandibular process) armored with a cluster of about 30 long outgrowths, differing in size and bearing some prominences distally (Figs. 4 J, 4 K). Posterior lobe is strongly sclerotized and divided into two toothshaped parts, the larger (posterior) of which has a small additional tooth about midway along its border (Fig. 4 H). Maxillules (mx I) look like two cylindrical structures situated posterior to mandibles. Distally, they bear a short central seta and some papillae near it. Maxillae (mx II) are absent; the openings of maxillar glands are situated near the bases of tl I laterally (see Olesen et al., 2003). Carapace. It looks like a comparatively low bag-like structure, strongly modified into a closed brood pouch (Fig. 1 A) widely connected at its base with the dorsal side of thorax. Thoracic limbs. Four pairs of strongly chitinized, stenopodous limbs are densely situated along the muscular ventral side of thorax and directed antero-ventrally (Figs. 1 A, 3 A). All of them have complex and variously setaceous armament along their inner side. Limbs of the three anterior pairs are five-segmented and those of the last fourth pair are three-segmented. Protopodites of all of them, covered by comparatively softer cuticle, are inconspicuously delimited into two parts (segments), coxa and basis, while the endopodites of limbs of the three anterior pairs are composed of three well developed segments and those ones of the fourth pair are unisegmented (Figs, 1 I, 2 A, 2 H, 2 I). First pair of limbs (tl I) are especially long and strong; their length can surpass the body length but are usually shorter (63.1–110.3 % of body length) (Figs. 1 A, 1 I, 3 A). Terminally, the inner side of their protopodite bears a small triangular lobe, the pseudognathobasic process (see the explanation of the term in Korovchinsky (2015)), armed laterally and distally with two outgrowths with apical setae and numerous spinulae (Fig. 3 B). The external part of the protopodite is longer than the internal one and bears apically a small conical outgrowth (Fig. 2 M–right). The first segment of the endopodite is long (19.9–34.9 % of body length) and bears 6–10 (usually 7–8) anterior lateral setae (their number of limbs of one individual can vary) with a posterior row of incurved spines, and anterior and lateral rows of fine setulae (Figs. 3 C, 3 D). Distally, this segment bears a shorter anterior seta of the same type and a long posterior finely setulated seta (Figs. 1 I, 1 J, 1 K, 3 E). The second segment of the endopodite is conspicuously shorter (9.3–19.8 % of body length) and bears only two apical setae similar to those on the end of the previous segment, but shorter (Figs. 1 I, 1 L). The terminal third segment of the endopodite is also long (17.0– 37.4 % of body length), almost equal or slightly surpassing the length of the first segment (1.09–1.13: 1.0), and always bears apically four long roughly spinulated setae, two of them terminally and two subterminally (Fig. 1 I). Basally, these setae are armed by a row of smaller spines, while distally, by larger lanceolate spines situated in two rows and directed terminally (Fig. 3 F). Second pair of limbs (tl II) considerably shorter; their protopodite, again externally, is conspicuously longer and bears a conical outgrowth (Figs. 2 A, 2 M-middle, 3 A). The first, basal segment of their endopodite, bears a row of 7–10 (mostly 7–8) rather long anterior lateral setae of type “B” (their number also can vary in one individual) (Figs. 2 A, 2 B, 3 G, 3 H). Also there are 2–3 posterior lateral setae of the same type on this segment. Terminal setae of the segment are different; the anterior one of type “C” is shorter and roughly armored (Figs. 2 A, 2 C, 3 I), while the posterior one is longer and finely setulated. Internally, this segment bears stout cylindrical pseudognathobasic process, possessing some prominences of different size, one small, thin seta, and a pore apically (Figs. 2 A, 3 L). The second segment of the endopodite is short with only two setae, the anterior of which is of “C”- type while the posterior seta is longer and finely setulated. The distal, third segment of the endopodite of the limb bears four setae, two : Published as part of Korovchinsky, Nikolai M., 2016, Redescription of Bythotrephes arcticus Lilljeborg, 1901 (Crustacea: Cladocera: Onychopoda) and confirmation of an independent species status of the distant Transcaucasian populations of the genus Bythotrephes Leydig, pp. 247-270 in Zootaxa 4138 (2) on pages 249-261, DOI: 10.11646/zootaxa.4138.2.2, http://zenodo.org/record/255713 : {"references": ["Lilljeborg, W. (1901) Cladocera Sueciae oder Beitrage sur Kenntnis der in Schweden lebenden Krebstiere von der Ordnung der Branchiopoden und der Unterordnung der Cladoceren. Nova acta regiae societatis scientatis scientiarum upsaleinsis, ser. 3, 19, 1 - 701.", "Stenroos, K. E. (1897) Zur Kenntnis der Crustaceen-Fauna von Russisch-Karelien. Cladocera, Calanidae. Acta Societatis pro Fauna et Flora Fennica, 15, 1 - 72.", "Ekman, S. (1904) Die Phyllopoden, Cladoceren und freilebenden Copepoden der nord-schwedischen Hochgebirge. Ein Beitrag zur Tiergeographie, Biologie und Systematik der arktischen, nord- und mittel-europaischen Arten. Zoologische Jahrbucher. Abteilung fur Systematik, Geographie und Biologie der Tiere, 21, 1 - 179. http: // dx. doi. org / 10.5962 / bhl. title. 59325", "Mordukhai-Boltovskoi, P. D. & Rivier, I. K. (1987) Predatory Cladocera: Podonidae, Polyphemidae, Cercopagidae, and Leptodoridae of the world fauna. Guide-books on the fauna of the USSR 148, 1 - 182. [in Russian]", "Rivier, I. K. (1998) The predatory Cladocera (Onychopoda: Podonidae, Polyphemidae, Cercopagidae) and Leptodoridae of the World. Guides to the identification of the microinvertebrates of the continental waters of the World 13. Backhuys Publishers, Leyden, 213 pp.", "Sars, G. O. (1903) On the Crustacean fauna of Central Asia. Part II. Cladocera. Ezhegodnik Zoologitcheskogo Museja Imperatorskoy Akademii Nauk, 8, 157 - 194.", "Ischreyt, G. (1930) Uber Korperbau und Lebenweise des Bythotrephes longimanus Leydig. Archiv fur Hydrobiologie, 21, 241 - 323.", "Vekhov, N. V. (1981) Some features of the biology of Bythotrephes longimanus (Cladocera, Cercopagidae) of tundra lakes. Vestnik zoologii, 5, 72 - 75. [in Russian]", "Ischreyt, G. (1934) Beitrag zur vergleichenden Morphologie und Systematik der Polyphemiden. Zeitschrift fur Wissenschaftliche Zoologie, 146, 236 - 282.", "Litvinchuk, L. F. (2001) Morphological variation of the predatory cladocerans of family Cercopagidae. Trudy Zoologitcheskogo Instituta RAS, 289, 125 - 132.", "Litvinchuk, L. F. (2002) Systematics and distribution of water fleas of the family Cercopagidae (Crustacea, Cladocera) in the north-west of Russia. PhD Thesis, Zoological Institute, St. - Petersburg, 258 pp. [in Russian]", "Litvinchuk, L. F. & Litvinchuk, S. N. (2016) Morphological diversity and widespread hybridization in the genus Bythotrephes Leydig, 1860 (Branchiopoda, Onychopoda, Cercopagidae). Archiv of Biological Sciences, Belgrade, 68, 67 - 79. http: // dx. doi. org / 10.2298 / ABS 150505010 L", "Elofsson, R. (1966) The nauplius eye and frontal organ of the non-malacostraca (Crustacea). Sarsia, 25, 1 - 128. http: // dx. doi. org / 10.1080 / 00364827.1966.10409568", "Scourfield, D. J. (1896) The olfactory setae of the Cladocera. Journal of the Quekett Microscopical Club, ser. 2, 6, 280 - 288.", "Olesen, J., Richter, S. & Scholtz, G. (2003) On the ontogeny of Leptodora kindtii (Crustacea, Branchiopoda, Cladocera), with notes on the phylogeny of the Cladocera. Journal of Morphology, 256, 235 - 259. http: // dx. doi. org / 10.1002 / jmor. 10043", "Korovchinsky, N. M. (2015) Redescription of Bythotrephes longimanus Leydig, 1860 and B. cederstromii Schodler, 1877 (Crustacea: Cladocera: Onychopoda), with notes on the morphology and systematics of the genus Bythotrephes Leydig, 1860. Zootaxa, 3955, 1 - 44. http: // dx. doi. org / 10.11646 / zootaxa. 3955.1.1", "Vekhov, N. V. (1987) Peculiarities of distribution, biology, and morphological variability of Bythotrephes longimanus (Leydig) s. lat. in the European Subarctic. Biological Sciences, 2, 27 - 35. [in Russian]", "Litvinchuk, L. F. (2007) Systematics and biology of the genus Bythotrephes. In: Smirnov, N. N., Korovchinsky, N. M. & Krylov, A. V. (Eds.), The w ater fleas: systematics and biology. IBIW, Borok, 173 - 198. [in Russian]"]}