Cyclops bohater Koźmiński, 1933

Hołyńska, Maria & Dimante-Deimantovica, Inta, 2016, Redescription and taxonomic notes on Cyclops bohater Koźmiński, 1933 and Cyclops lacustris G. O. Sars, 1863 (Arthropoda, Crustacea), with an identification key to the Cyclops species of Fenno-Scandinavia, European Journal of Taxonomy 212, pp. 1-31 : 3-14

Cyclops bohater Koźmiński, 1933

Figs 1 ̅6

Cyclops bohater Koźmiński, 1933: 105 ̅106, 111̅113, 123̅124, 135, 138̅139, figs 5–6, pl. 3, tab. 3.

Cyclops bohater ̅ Lindberg 1957: 96 ̅97, fig. 55. — Einsle 1975: 100 ̅102, 147, fig. 3; 1993: 136̅137, fig. 80; 1996a: 28̅31, fig. 18. —? Stanković & Ternjej 2007: 189 ̅199, figs 2̅12, tab. 2. — Deimantovica 2010 (part) (records from Lake Brigene only).

non Cyclops bohater ponorensis Naidenow & Pandurski, 1992: 27 ̅30, fig. 1, tabs 1̅2; synonymized by Pandurski (1997) as C. abyssorum divergens Lindberg, 1936 .

non Cyclops bohater – Deimantovica 2010: 216 ̅222, figs 2̅5, tabs 1, 3–4.

Type material

Lectotype (designated here)

POLAND: ♀, Wigry lakes, ~ 132 m a.s.l., Lake Okrągle (~ 0.14 km 2 surface area) close to the southern bay of Lake Wigry proper, 54º01' N, 23º01' E, 1 Mar. 1927, leg. and det. Z. Koźmiński ( NHMUK 2016 . 38). Paralectotypes

POLAND: 1 ♀ in alcohol ( NHMUK 2016. 39) and 1 Ƌ dissected ( NHMUK 2016. 40), same locality and collecting date as lectotype; 1 ♀ dissected on two slides ( SMNK: 4396̅4397) and 1 undissected ♀

( SMNK: 4398), “Wigryseen”, 54º01' N, 23º06' E, 31 Jan. 1928, leg. et det. Koźmiński, “ paratype ”, prep. Fr. Kiefer 13 Dec. 1939.

Other material examined

AUSTRIA: 1 ♀, Lake Wörth (Carinthia), 46º38' N, 14º09' E, 439 m a.s.l., Knut Lindberg’s Collection, nr. 25, “Autriche AUT.1” ( ZMLU).

LATVIA: 1 CIV ♀ toto ( MIZ 2/2016/1) and 9 CIV parts (A2, Mxl, P1), Latgale region, Augshzeme, Lake Brigene, ~ 148 m a.s.l., 55º45’ N, 26º33’ E, 12 May 2008, leg. I. Deimantovica ( MIZ 2/2016/2-10). SWEDEN: 1 ♀ ( MIZ 2/2016/11), Largen, 59º35' N, 18º31' E, ~ 35 km NE of Stockholm, 3Aug. 2011, leg. Oslo University; one ♀ dissected ( MIZ 2/2016/12) and 1 undissected ♀ in alcohol ( IDD), 3 ƋƋ dissected, same locality, 8 Nov. 2012, leg. I. Dimante-Deimantovica & B. Walseng, ( MIZ 2/2016/13-15).

Description

Female

Body length 1960̅ 2500 µm (lectotype, 2370 µm) ( Fig. 1A ). Cephalothorax length/width 1.05̅1.14 (lectotype, 1.10), cephalothorax width/genital double-somite width 2.6̅2.9 (lectotype, 2.9), prosome length/urosome length 1.5̅1.8 (lectotype, 1.8). Pediger 2 ( Fig. 1A ) bearing distinct posterolateral lobes and conspicuously wider than succeeding somites. Pediger 5 laterally protruding, “wing-like” ( Fig. 1B , arrowed).

Genital double-somite ( Fig. 1B ) slightly shorter than, or as long as wide. Seminal receptacle as typical in genus, transverse ridge present next to copulatory pore. Posterior margin of anal somite ( Fig. 1C ) with continuous row of spinules, anal sinus without surface ornamentation, anal operculum weakly developed. Caudal rami ( Fig. 1C ) 5.0̅6.5 times as long as wide, medial margin bearing hairs. Midline crest running almost full length of ramus on dorsal surface. Few spinules present on lateral margin in anterior third, indicating presumptive insertion site of the ancestral anterolateral accessory seta (I). Spinules also present at insertion of caudal setae II and III. Seta II inserted at distance of 0.21̅0.23 ramus length measured from posterior end. Relative length of caudal setae VII, VI, V, IV, and III: 1.0̅1.2 (dorsal seta broken in lectotype), 1.7̅2.2 (lectotype, 2.2), 3.7̅4.4 (lectotype, 4.0), 2.8̅3.6 (lectotype, 3.5), 1.0. Seta VI (medialmost) 1.1̅1.3 (lectotype, 1.2) times as long as caudal rami, seta V (longest) 0.66̅0.80 (lectotype, 0.72) times as long as urosome. Caudal setae homonomously setulose, setae IV and V with breaking plane.

Antennule ( Fig. 1D ̅G) 17-segmented (I̅V, VI̅VII, VIII, IX̅XI, XII̅XIII, XIV, XV̅XVI, XVII, XVIII, XIX, XX, XXI, XXII, XXIII, XXIV, XXV, XXVI̅XXVIII) and reaching middle of pediger 2 to middle of pediger 3. Seta formula as common in plurisegmented Cyclopinae : 8, 4, 2, 6, 4, 1+sp, 2, 1, 1, 0, 1, 1+ae, 0, 1, 2, 2+ae, 7+ae. Aesthetasc on segment 12 ( Fig. 1E ̅F) reaching distal margin of segment 13 to middle of segment 14, aesthetasc length 2.2̅2.8% of body length (n = 3; lectotype, 2.24%). Aesthetasc on segment 16 not reaching middle of segment 17, aesthetasc length 2.1̅2.7% of body length (n = 3; lectotype, 2.1%). Spinules only present on ventral surface of segment 1. Last three segments of antennule with hyaline membrane.

Antenna composed of coxobasis and three-segmented endopodite, and bearing 3, 1, 9 (8 in Lake Largen, Sweden ̅ MIZ 2/2016/11) and 7 setae, respectively. Inner medial seta of coxobasis ( Fig. 2A ̅B) with short setules, outer medial seta naked. Exopodite seta reaching beyond enp3 and bearing setules conspicuously longer in proximal than in distal section of seta. Frontal surface of coxobasis ( Fig. 2A ) with few spinules in ~4/10 of segment and longer spinules more proximally next to lateral margin, and distinctly long spinules in oblique/longitudinal row near middle line in proximal third of segment. Caudal surface of coxobasis ( Fig. 2B ) with double (single in Lake Largen, Sweden, ̅ MIZ 2/2016/12) row of long spinules near long proximal spinules on lateral margin, elongate spinules (7̅13) in longitudinal row(s) near lateral margin distally to double row, and oblique field of small spinules proximally to insertions of medial setae. Additional groups, such as small spinules medially to proximal double row ( Fig. 2B , arrowed) and row of tiny spinules along presumptive proximal margin of basipodite (Lake Wörth, Austria), sometimes present.

Labrum ( Fig. 2C ) bearing teeth on arcuate distal margin, lateral lobes with small spinules. Distal hairs long and arranged in two groups. Epistoma and vertical cleft ( Fig. 2C ) naked, except for few hair-like elements on one side only next to epistoma (observed in lectotype, but missing in ♀ from Lake Wörth, Austria). Mandibular palp ( Fig. 2D ) with two long and one short seta, no surface ornamentation next and proximal to palp. Maxillule: setation of precoxal arthrite as typical in plurisegmented Cyclopinae . Palp with spinules ( Fig. 2E , arrowed), and bearing long proximal seta, three setae on lateral lobe and three apical setae; proximal seta and at least one of lateral lobe setae with distinctly long setules ( Fig. 2E , arrowed). Maxilla ( Fig. 3A ): precoxopodite and coxopodite fused on frontal surface but separated on caudal surface; syncoxopodite, basipodite and two-segmented endopodite with 5, 2, 2 and 3 setae, respectively. Claw-like attenuation of basipodite with spinules on both concave (inner) and convex (outer) margin. Basipodite seta inserted in front of claw-like attenuation, bearing long setules on both concave and convex edge in proximal half, and tiny spinules on convex margin in distal half of seta. Maxilliped ( Fig. 3B ) composed of syncoxopodite, basipodite and two-segmented endopodite with 3, 2, 1 and 3 setae, respectively. On caudal surface of basipodite spinules arranged in two groups. First endopodal segment and basipodite bearing hair-like spinules on frontal surface. Syncoxopodite frontally adorned with medium-sized or small spinules midway between median and distalmost setae, and tiny spinules more proximally next to finger-like membraneous element.

P1̅P4 setation formula shown in Table 2.

Medial spine of P1 basipodite with heteronomous setulation: setules long in proximal 4/10 ( Fig. 3C , arrowed), and short spinule-like more distally. Medial spine reaching slightly beyond distal margin of enp2 to proximal ¼ of enp3. Long spinules ( Fig. 3C , arrowed) arranged in arc on frontal surface of P1 basipodite between insertions of exo- and endopodite. Intercoxal sclerites naked on frontal and caudal surfaces in P1̅P3, and sparsely pilose on caudal surface in P4. Obtuse protuberances of P4 intercoxal sclerite low, hardly reaching beyond distal margin of segment, or extending well beyond it ( Fig. 3D ). Medial expansion of basipodite pilose in P1̅P3, and naked ( Fig. 3D ) or bearing few short apical hairs (Lake Largen, Sweden ̅ MIZ 2/2016/12; and Lake Wörth, Austria) in P4. Caudal surface ornamentation of P4 coxopodite (spinule groups are coded according to Einsle 1996a, see Fig. 3D ) composed of: undulate line of medium-sized spinules near proximal margin (group A), with 9̅16 spinules in lateral section, and 10̅13 spinules in medial section; rows of spinules of unequal size along distal margin, with 3̅7 spinules in medial row (group C) and 1̅4 spinules in lateral row (group D); and oblique field of long spinules at laterodistal angle (group E); spinules sometimes present at lateroproximal angle (group B) (Lake Wörth, Austria) and/or lateral margin (group F) (Lake Wörth, Austria; paralectotype ̅ SMNK: 4398). Coxopodal seta conspicuously longer (~1.9×) than height of medial expansion of basipodite. Distal margin of first and second exopodal segment of P4 naked on caudal surface ( Fig. 3D ), or bearing spinules. P4 enp3 2.6̅2.9 times as long as wide; of apical spines medial one 1.6̅2.3 times as long as lateral, and 0.94̅1.10 times as long as segment.

P5 ( Fig. 1B ) segmentation and setation as typical in genus. Distal segment 2.0̅2.3 times as long as wide. Medial spine inserted near half-length of segment (0.45̅0.55 segment length measured from proximal margin), medial spine 0.5̅0.9 times as long as distal segment. Lateral seta on proximal segment relatively long, 0.6̅0.9 times as long as apical seta and 1.9̅3.0 times as long as distal segment. Apical seta 3.1̅4.0 times as long as distal segment. Spinules present at insertion of median spine and apical seta, but absent at insertion of lateral seta.

Male

Body length 1525̅ 1685 µm ( Fig. 4A ), cephalothorax length/width 1.1̅1.3, prosome length/urosome length 1.6̅1.8. Pediger 2 without distinct posterolateral lobes, but sometimes significantly wider than succeeding prosomal segments (Lake Largen, Sweden) ( Fig. 4B ). Pediger 5 ( Fig. 4C ) laterally not protruding. Caudal rami without dorsal crest, 4.2̅5.1 times as long as wide, pilose on medial margin. Short transverse row of spinules present in anterior third at presumptive insertion site of ancestral anterolateral accessory seta (I), as well as at insertion of caudal seta II and III. Seta II inserted at distance of 0.24̅0.26 ramus length measured from posterior end. Relative length of caudal setae VII, VI, V, IV, and III: 1.1̅1.2, 2.1̅2.2, 3.4̅4.0, 2.9̅3.3, 1.0. Seta VI 1.6̅1.8 times as long as caudal rami, seta V 0.8̅0.9 times as long as urosome.

Antennule 17-segmented (verified on dorsal surface): I̅V, VI̅VII, VIII, IX, X, XI, XII, XIII, XIV, XV, XVI, XVII, XVIII, XIX̅XX, XXI̅XXIII, XXIV̅XXV, XXVI̅XXVIII. Armature formula 8+3ae, 4, 2, 2+ae, 2, 2, 2, 2, 1+sp+ae, 2, 2, 2, 2+ae, 2, 1+ae, 4+ae, 7+ae (setation of segment 13 and segment 17 were verified in males from Lake Largen, Sweden). Modified setae: one and two striated plates present on segment 14 and 15, respectively; and one cone-like element present on segment 14 and 15 each.

Antenna segmentation and setation as in female, except for enp2, which bears 8 or 7 setae. Spinule ornamentation of antennal coxobasis similar to that in female ( Fig. 4D ̅E), of medial setae inner one bearing short setules and outer seta naked. Mouthparts ( Figs 4F , 5A ̅B) similar to those in female, but

spinules tiny or absent on maxillulary palp, and maxilliped syncoxopodite adorned with single group of spinules midway between median and distalmost setae.

P1̅P4 segmentation and setation as in female ( Table 2). Medial spine of P1 basipodite ( Fig. 5C ) with few long setules proximally and short spinules more distally, and reaching distal margin of enp2 to proximal ~1/6 of enp3. Long spinules arranged in arc on frontal surface of P1 basipodite between insertions of exo- and endopodite. Lateral spine of P2 exp1 more slender than other spines of exopodite, and bearing long setules ( Fig. 5D cf. Fig. 5E ). Intercoxal sclerites naked in P1̅P3 and sparsely pilose on caudal surface in P4. Caudal surface ornamentation of P4 coxopodite ( Fig. 5F ) similar to that in female, but spinules/hairs missing on lateral margin. Coxopodal seta conspicuously longer (~1.7̅1.8×) than height of medial expansion of basipodite. Medial expansion of basipodite apically pilose in P1̅P4. P4 enp3 2.9̅3.2 times as long as wide. Of apical spines medial one 1.9̅2.1 times as long as lateral spine and as long or slightly (~1.1×) longer than segment.

P5 ( Fig. 4C ) distal segment 2.0̅2.4 times as long as wide, medial spine inserted near half-length of segment (0.47̅0.58 segment length measured from proximal margin), medial spine 0.56̅0.71 times as long as distal segment. Lateral seta on P5 proximal segment 0.68̅0.81 times as long as apical seta and 2.9̅3.6 times as long as distal segment. Apical seta 4.1̅4.8 times as long as distal segment. Spinules present at insertion of median spine and apical seta, but absent at insertion of lateral seta.

P6 ( Fig. 4C ) composed of three elements; median- and lateral seta 0.94̅1.05 times and 1.9̅2.4 times as long as median spine, respectively. P6 flap naked.

Copepodid IV instar (Lake Brigene, Latvia)

Copepodid shows some important species diagnostic characters, such as: inner medial seta of antennal coxobasis with short setules and outer medial seta naked; proximal seta of maxillulary palp and at least one seta of lateral lobe of palp with long setules; medial spine of P1 basipodite with few distinctly longer setules proximally and short spinules distally; long spinules arranged in arc on frontal surface of basipodite between insertions of exo- and endopodite; P5: spinules present at insertions of medial spine and apical seta, but absent at insertion of lateral seta; lateral seta (110 µm) relatively long (0.79× apical seta length).

Other features: Anal somite with continuous row of spinules along posterior margin. Caudal rami relatively short (175 µm), bearing medial hairs, longitudinal crest absent on dorsal surface. Short transverse row of robust spinules present in anterior third at presumptive insertion site of anterolateral accessory seta (I), and caudal seta II and III. Seta II (50 µm) inserted at distance of 0.31 ramus length measured from posterior margin. Length of setae VII, VI, V, IV and III, 153 µm, 260 µm, 565 µm, 425 µm, and 137 µm, respectively.

Antennule ( Fig. 6A ̅C) 10-segmented, homologous with ancestral segments I̅V, VI̅XI, XII̅XIII, XIV, XV̅XVI, XVII̅XX, XXI̅XXIII, XXIV, XXV, XXVI̅XXVIII. Seta formula 5, 6, 2, 2, 2, 3, 2+ae, 2, 2+ae, 7+ae. Anterodistal seta on segment 4 (XIV), spine-like in the adult, relatively long, reaching slightly beyond distal margin of succeeding segment ( Fig. 6A , arrowed). Length of aesthetascs on segment 7 (XXI̅XXIII) and 9 (XXV), 60 µm and 62 µm, respectively ( Fig. 6 B–C). Second endopodal segment of antenna bearing 7 setae. P1̅P4 rami two-segmented ( Fig. 6D ̅E), setation shown in Table 3.

P 4: intercoxal sclerite naked, medial expansion of basipodite apically pilose; medial apical spine of endopodite much longer (3.6×) than lateral apical spine. P5 distal segment relatively short (length, 36 µm; width, 28 µm), medial spine (24 µm) inserted at distance of 0.72 segment length, measured from proximal margin. P6 armed with medial spine (50 µm) and lateral seta (81 µm).

Remarks

Cyclops bohater was originally described from Lake Wigry (max. depth 73 m, surface area 21.15 km 2) and some smaller lakes (Okrągle, Długie, Muliczne and Rzepiskowe) within the vicinity of L. Wigry in the Suwałki-Augustów Lake District, NE Poland ( Koźmiński 1933). The holotype of C. bohater was not designated in the original description ( Koźmiński 1933), and we are not aware of any institution where it might be deposited. The Hydrobiological Station at Wigry Lakes, where Zygmunt Koźmiński worked and his copepod material might be left, was completely destroyed during World War II ( Gieysztor 1963). We have not found any type(s) at the Museum and Institute of Zoology PAS (Warsaw) either, though part of Koźmiński’s samples (e.g., those from the Tatra Mts. and Warsaw region) are deposited here. However, some specimens from the terra typica and identified by Koźmiński himself as C. bohater fortunately have remained in the collections of Staatliches Museum für Naturkunde in Karlsruhe and Natural History Museum in London. The collecting data of these specimens suggest that they might constitute the material which Koźmiński’s original description was based on; therefore, we selected one of those specimens as the lectotype of the species (NHMUK 2016.38). In choice of the lectotype the NHM series was preferred to the material from Karlsruhe Museum, because more characters (incl. those of the mouthparts and the morphometric traits) could be verified in the NHM specimens which were dissected by us, and the collecting data of the NHM material were fully consistent with the information provided in the original description.

Ecology

Permanent lakes and ponds, eutrophic to oligotrophic. The species is rather rare in the surface plankton, both the larvae and adult seem to prefer the deep or near-bottom waters ( Koźmiński 1933, 1936; Wierzbicka 1936). The same distribution pattern was observed in a population in Lake Largen, Sweden (Dimante-Deimantovica & Walseng, unpublished data). Adults and copepodids occurred in large number in the littoral zone of a clay pit pond in Poland (Warsaw) in March, but disappeared from the littoral in late spring ( Wierzbicka 1960). Einsle (1988) reported on the permanent near-shore occurrence of the species in Lake Constance (Obersee).

Cyclops bohater usually has one generation per year: reproduction from November to February, youngest copepodid instars appear early spring, copepodid V instar enters summer diapause in May and stays in the sediment on the bottom of the lake until late autumn when the larvae moult to adults. ( Einsle 1988; Frisch 2002). A second summer generation appeared in the Wigry lakes ( Koźmiński 1933), and Einsle (1988) also hypothesized more than one generation in the permanently littoral populations.

Distribution

Verified occurrences from Northern ( Sweden, Latvia) and Central Europe ( Poland, Austria) ( Table 4). For a critical overview of the literature data on the geographic distribution of C. bohater , see the Discussion.

Figures

Fig. 1. Cyclops bohater Koźmiński, 1933, ♀. A. Habitus, dorsal. B. Pediger 5 and genital doublesomite, ventral, arrow points to lateral “wing-like” protrusion of pediger 5. C. Anal somite and caudal rami, dorsal. D−G. Antennule, ventral. D. Segments 1̅6 (I̅XIV). E. Segments 7̅14 (XV-XXIII). F. Segments 12̅14 (XXI̅XXIII). G. Segments 15̅17 (XXIV̅XXVIII). Except for A (NHMUK 2016. 39) all drawings show the lectotype (NHMUK 2016. 38). Scale bars: A = 1 mm; B̅G = 100 µm.

Fig. 2. Cyclops bohater Koźmiński, 1933, ♀. A−B. Surface ornamentation of antennal coxobasis. A. Frontal, arrow points to insertion site of long spinules missing in C. bohater. B. Caudal, arrow points to a group of spinules sometimes present. C. Labrum, epistoma and rostrum. D. Mandible, frontal, arrow points to insertion site of spinules missing in C. bohater. E. Maxillulary palp, arrows point to long setules of the setae, and spinulose ornamentation of the palp. All drawings show the lectotype (NHMUK 2016.38). Scale bars: A̅E = 100 µm.

Fig. 3. Cyclops bohater Koźmiński, 1933, ♀. A. Maxilla, caudal. B. Maxilliped, frontal. C. Leg 1, frontal, arrows point to the long setules of the medial spine/seta of basipodite, and long spinules on the basipodite between the insertions of exopodite and endopodite. D−E. Leg 4: EXP, P4 exp 3; ENP, P4 enp3. All drawings show the lectotype (NHMUK 2016. 38). Scale bars: A̅E = 100 µm.

Fig. 4. Cyclops bohater Koźmiński, 1933, Ƌ. A. Habitus, dorsal. B. Prosome with distinctly wide pediger 2. C. Pediger 5, genital segment, and first abdominal segment, ventral. D−E. Antennal coxobasis. D. Frontal. E. Caudal. F. Labrum. Except for B (Lake Largen, Sweden ̅ MIZ 2/2016/15) all drawings show a paralectotype (NHMUK 2016. 40). Scale bars: A̅B = 500 µm; C̅F = 100 µm.

Fig. 5. Cyclops bohater Koźmiński, 1933, Ƌ. A. Maxillulary palp. B. Maxilliped syncoxopodite, frontal. C. Leg 1, frontal. D. Leg 2, slender spine of first exopodal segment and robust spines of exopodal segments 2 and 3. E. Exopodal armature of leg 3. F. Leg 4 coxopodite, basipodite and intercoxal sclerite, caudal. All drawings show a paralectotype (NHMUK 2016. 40). Scale bars = 100 µm.

Fig. 6. Cyclops bohater Koźmiński, 1933, copepodid IV, ♀. A−C. Antennule, ventral. A. Segments 1̅5 (I̅XVI), arrow points to long anterodistal seta of ancestral segment XIV. B. Segments 6̅8 (XVII̅ XXIV). C. Segments 9̅10 (XXV̅XXVIII). D. Leg 2, caudal. E. Leg 3, caudal. All drawings show specimen from Latvia (Lake Brigene ̅ MIZ 2/2016/1). Scale bar = 100 µm.