Eurycercus longirostris Hann 1982

Eurycercus longirostris Hann, 1982

Figs 6–7

Eurycercus longirostris Hann, 1982, p. 587 –595, Figs 1 –25; Elías-Gutiérrez et al. 1997, p. 65, 67–68, Figs. 9 –13; Bekker et al. 2010, p. 2501, Fig. 12.

Eurycercus vernalis Hann, 1982, p. 595 –596.

Type locality. "Big Turkey Lake, Lagrange Co" (Hann 1982), Indiana, U.S.A. Approximate geographic coordinates: 41.59, -85.19.

Holotype. A parthenogenetic female, 1.44 mm, in alcohol, USNM 181893.

Paratypes. A parthenogenetic female on a slide in glycerine jelly, USNM 181895. Two parthenogenetic females in alcohol, and one parthenogenetic female in glycerine jelly on a slide, NHM 1980.371, 1980.372. A parthenogenetic female in alcohol, and one parthenogenetic female in glycerine jelly on a slide, CMN C-1981-217. An ephippial female in glycerine jelly, USNM 181896. “In addition, one exuvia mounted in polyvinyl lactophenol on a slide has been deposited in each of the three museums listed above. All other specimens are in the author's collection” (Hann 1982).

Allotype. A mature male in glycerine jelly, USNM 181894.

Material examined here: Canada. British Columbia. Morei Lake, coll. in 02.07.2005 by M. Belyaeva & S. Ishida, DJT 3-618 (59.955, -132.024). Manitoba. Fish House Pond, Boat doek at Delta Marsh Field Station, coll. in 19.09.1982 by M. M. Boucherle, DGF 6770 (49.97, -98.29); Weir Channel, Churchill, coll. in 16.08.2006 by M. Eíias-Gutiérrez, AAK M-0898 and AAK M-0891 (58.672, -94.161). Newfoundland and Labrador. Ocean Pond, coll. in 03.07.2005 by L.J. Hovind & M. Faustova, AAK M-0487 (47.4442, -53.4118). Nova Scotia. A lake, west side of Hgy. 349, 0.5 miles N of Williamswood / Harrietsfield boundary, coll. in 31.10.1984 by D. G. Frey, DGF 7328 (44.55, -63.64). Ontario. Pond 3 miles E Manitoba / Ontario border, on Trans-Canada Hwy, coll. in 29.08.1974 by D. G. Frey, DGF 3660 (49.73, -95.11); Pond on Opeongo Road, Algonquin Park, coll. in 08.10.1982 by S & F, DGF 6446 (45.56, -78.6); Sydenham Lake, Sydenham, coll. in 11.10.1982 by S & F, DGF 6490 (44.4226, - 76.5559). Yukon. Squanga Lake, coll in 02.07.2005 by M. Belyaeva & S. Ishida, DJT 3-624, DJT 3-625 and AAK M-0477 (60.4478, -133.603).

U.S.A. Alaska. Birch Lale, Anchorage, coll. 8.08.2011 by D. J. Taylor, A. A. Kotov, M. Ballinger & A. Medeiros, DJT20 _2011_ Ancourage _04 (61,14558, -149,9384). California. CPR Pond 2, coll. in 01.05.2001 by E. Gallo, AAK 2007-319; Lower Twin Lake in Robinson, Creek Valley, coll. in 12.09.1965 by D. G. Frey, DGF 1726 (40.5066, -121.3639). Colorado. Ponded Brooklet near Upper Red Rock Lake, coll. in 02.09.1975 by D. G. Frey, DGF 1704 (40.0816, -105.5412). Connecticut. Beach Pond, coll. in 14.06.2004 by D. J. Taylor & A. A. Kotov, AAK 2005-234 (41.5837, -71.7222). Indiana. Hammond Lake, coll. in 29.10.2006 by S. Ishida & K. Kim, AAK M-1124 (41.3647, -85.6775); Oliver Lake, coll. in 25.11.1966 by D. G. Frey, DGF 2342 (41.5724, -85.4051); Silver Lake, coll. in 29.10.2006 by S. Ishida & K. Kim, AAK M-1128 (41.08, -85.9). Maine. Meddybemps Lake, Hgy. 119, Moosehorn Wildlife Refuge, coll. in 09.11.1984 by G. Frey, DGF 7346 (45.07, -67.37); Sebago Lake, coll. in 11.08.1966 by D. G. Frey and 09.1981 by D. B. Berner, DGF 1911, DGF 1874 and AAK 1999-103 (43.778, - 70.518). Massachusetts. Pequot Pond, coll. in 26.06.2004 by A. A. Kotov & W. Piel, AAK M-0076 (42.18, - 72.692). Michigan. Douglas Lake, Marl Bay, coll. in 29.07.1961 by D. G. Frey, DGF 0295 (45.58, -84.69); Hamilton Lake, coll. in 07.07.1966 by D. G. Frey, DGF 1857 (45.7551, -87.7854); Twin Lake, coll. in 31.01.1975 by D. G. Frey, DGF 0303 (43.3676, -86.1716). Minnesota. Newton Lake in BWCA near Ely, coll. in 08.08.1979 by D. G. Frey, DGF 5250 (47.9768, -91.7273). Mississippi. Pearl River System, Chien's Sta. 3, 1.2 miles SW of jct. 411 on State Road 12 near McCool, coll. in 09.05.1974 by D. G. Frey, DGF 3413 (33.21; -89.36); Roadside ditch, Hwy 39W, ca. 4 miles S of Indianola, coll. in 13.03.1978 by D. G. Frey, DGF 4583 (33.5, -90.6). New Hampshire. Otter Pond near Sunapee Lake, coll. in 24.06.2004 by W. Pill & A. A. Kotov, AAK 2005-255 (43.4303, -72.0587); Sunapee Lake at Brich Point, coll. in 24.06.2004 by W. Piel & A. A. Kotov, AAK 2005-264 - 265 (43.3756, -72.07). New York. Fishpond near Atlantic city Reservoir, coll. in 01.05.1995 by H. Segers, AAK 1998-014 (39.44, -74.55); Lake Erie, coll. in 25.06.2006 by L. Hovind, AAK M-0272 (42.8503, -78.8742); Pond 3, Brigantine National Wildlife Refuge, coll. in 08.05.1995 by H. Segers, AAK 1998-016 (39.4, -74.4); Round Pond, Long Island, coll. in 12.06.2004 by D. J. Taylor & A. A. Kotov, AAK 2005-223 (40.9857, -72.2914). North Carolina. Lake Carolina, coll. in 07.06.2005 by L.J. Hovind, DJT 20-129 (35.475, -79.075); Pages Lake, coll. in 18.08.1958 by P. Patterson, DGF 0050 (35.1379, -79.4304); Panther Lake, 02.03.1979 by D. G. Frey, DGF 3759 (35.5678, -78.6955). Pennsylvania. Swingle Road Pond, coll. in 11.06.2004 by D. J. Taylor & A. A. Kotov, DJT 20-004 (41.4154, -75.3162); Swingle Road Pond, coll. in 06.2004 by D. J. Taylor & A. A. Kotov, AAK 2005-219 (41.4154, -75.3162). Rhode Island. Bowdish Reservoir, coll. in 14.06.2004 by D. J. Taylor & A. A. Kotov, AAK 2005-236 and DJT 20-037 (41.9242, -71.7826). Tennessee. Pool between road and Reelfoot Lake, 1 mile N of Dods, Tennessie Nat. Wildlife Ref., coll. in 11.10.1974 by D. G. Frey, DGF 3427 (36.4, -89.4). Vermont. Crystal Lake, coll. in 26.03.1975 by D. G. Frey, DGF 2600 (44.7338, -72.1539). Washington. Green Lake, Seattle, coll. in 22.10.1983 by D. G. Frey, DGF 6695 (47.6784, -122.3381); Slough, upper end of Lake Quinault, Rain Forest Camp, Olympic Peninsula, coll. in 27.06.1978 by D. G. Frey, DGF 4895 (47.49, -123.85). Wisconsin. Fox Lake, coll. in 23.06.1956 by D. G. Frey, DGF 0248 (43.5822, -88.919).

Mexico. State of Mexico. Lake La Luna, in the crater of the volcano Nevado de Toluca, coll. in 04.06.1994 by M. Elías-Gutiérrez, AAK 2002-106 (19.1036, -99.7556).

Diagnosis. Parthenogenetic female. Dorsal head pores on a bubble-like projection located immediately on head shield. In anterior view, body wide, not compressed laterally, median dorsal keel absent. Rostrum relatively long. Ocellus of moderate size. Lateral head pore circular. Labrum with a moderate median keel, with broadly rounded apex, reaching distal end of antenna I length. Postabdomen with sub-parallel dorsal and ventral margins, preanal teeth pointed. Spines at base of pre-claw portion predominantly single. Antenna I with antennular sensory seta arising somewhat basally to middle. Denticles in rows encircling antennular surface relatively large. On antenna II, spine situated on proximal segment of exopod equal to or somewhat shorter than second segment. Limb I IDL with a strong hook-like seta, the smallest IDL seta especially fine and short. IDL with about 4–11 distal spinules, 3–15 proximal spinules, 1–11 marginal spinules and 0–12 basal spinules. Eight setae in filter plate II, 9 setae in filter plate III; 9 setae in filter plate IV, 8 setae in filter plate V.

Short redescription. Parthenogenetic female. In lateral view body sub-ovoid in larger females (Fig. 6A), maximum height of the body in its middle portion (BH/BL= 0.57–0.59). Dorsal margin interrupted only by a bubble-like head pore. In anterior view, body wide, not compressed laterally, maximum width of body at level of mandibular articulation. Median dorsal keel is absent. A single midgut loop, posterior intestinal caecum present. Few eggs in the brood pouch.

Head large, with well expressed, relatively long rostrum (Fig. 6B). The anterior portion of headshield (= portion anterior to level of mandibular articulation) more than two times lager than posterior one, broadly rounded, with slightly projected rostral region (Fig. 6C). A single major “head pore” as a ringed, sub-oval field of special cuticle located on a dorsal bubble. A small, circular lateral pore located at either side of major pore, closer to it (Fig. 6D). Labrum fleshy body, with a medium-size median keel, terminating in a broadly rounded apex (Fig. 6B) and with paired lateral horn-like projections (Fig. 6E).

Valves generally ovoid (VL/BL= 0.78–0.87), armature of posterior valve margin as in previous species (Fig. 6F–H).

Postabdomen large (PL/BL= 0.41–0.44), relatively broad (PH /PL= 0.48–0.56), with sub-parallel dorsal and ventral margins (Fig. 6I). Distal anal embayment shallow. Armature of the preanal margin as a series of preanal teeth (NT=87–98); distalmost tip somewhat larger than others; small gap lacking any teeth at base of postabdominal setae; teeth in middle of preanal margin with sharp tips. Distalmost postanal teeth long, clustered; teeth at base of pre-claw portion mainly single (Fig. 6J, arrows). Postabdominal setae as in previous species. Postabdominal claw relatively robust (CL/PL= 0.22–0.24); basal spines, first (distal) long (DS/CL= 0.30–0.47), second (basal) short (BS/CL= 0.13–0.22; BS/DS = 0.38–0.44).

Antenna I (Fig. 6K) relatively short (AL/BL = 0.10–0.11; AL/DA=2.86–3.42), triangular in cross section; protruding beyond tip of rostrum. Antennular sensory seta relatively short (about third of antenna I length), arising basally to antenna I middle. Nine bisegmented aesthetascs, with pointed teeth around them. Numerous short rows of relatively large denticles encircling antennular surface.

Antenna II relatively short; spine situated on proximal segment of exopod somewhat shorter than or equal to length of second segment (Fig. 6L). Setae 0-0-3/1-1-3; spines 1-0-1/0-0-1.

Thoracic limbs (Fig. 7A–L) basically similar with those in E. macracanthus, some differences described below. Limb I with IDL with a strong hook-like seta (Fig. 7A–D), but not so large as in E. macracanthus. In contrast to the latter, the smallest seta of IDL stronger in E. longirostris. IDL with long distal spinules (4–11), long proximal spinules (3–15), short marginal spinules (1–11) and short basal spinules (0–12). On exopodite III seta 7 short, eight soft setae on inner limb portion (Fig. 7G). On exopodite IV seta 1 relatively long (Fig. 7I). On exopodite V setae 5–7 increasing in size distally (Fig. 7J). Filter plate of gnathobase III, IV with 9 setae, and limb V with 8 setae.

Ephippial female, male. See Hann (1982).

Length. 1.17–2.00 mm in our material.

Comments. Hann (1982) described two species, E. longirostris and E. vernalis, and concluded that there are no evident morphological differences between them. Only ontogenetic changes were found to be different, as revealed by a statistical analysis of the instar variability. Unfortunately, such ontogenetic differences are difficult to interpret and diagnose. We concluded that the patterns of instar variability found by Hann (1982) lack discreteness when more populations are examined (Bekker 2011). So, we believe that absence of any diagnostic traits of Hann's (1982) two taxa is due to their synonymy.

We found a small divergence of COI sequences among populations from distant points of the USA, including Indiana (the type locality of E. longirostris) and North Carolina (the type locality of E. vernalis). We found a separate sub-clade in Rhode Island and Newfoundland, but its separation from E. longirostris could not be associated with Hann's (1982) separation of E. longirostris and E. vernalis.

Note that the opinion of Hann (1982) is influenced by Frey's (1982b) idea that populations of cladocerans in southern and northern regions of North America become reproductively isolated as their timing of gamogenesis diverges (in autumn in the North and in spring in the South), which leads to speciation. It is presently unclear if there are good examples of this mode of speciation in cladocera. Geographic clades are commonly found in cladocerans, but these are often West-East, not South-North (Taylor et al. 1998). For genetically differentiated northsouth species, it is unclear if differences in the timing of reproduction are a cause or an effect of speciation (Constanzo & Taylor 2010).

Case 24.2.1 of ICZN (2000) proposed that "When the precedence between names or nomenclatural acts cannot be objectively determined, the precedence is fixed by the action of the first author citing in a published work those names or acts and selecting from them; this author is termed the "First Reviser"”. We followed this code, and Eurycercus vernalis Hann, 1982 is found by us to be a junior synonym of E. longirostris Hann, 1982.

Distribution. It is a remarkable fact that the southernmost populations of E. longirostris occur in Central Mexico (Elías-Gutiérrez et al. 1997, 2008) which is the southernmost portion of the Nearctic, while in nearby Neotropical Mexico, Belize and Guatemala (Elías-Gutiérrez et al. 2006, 2008), Central America and the West Indies (Frey 1982a) E. longirostris is almost certainly absent. There is a big gap in the distribution of Eurycercus south to Central Mexico until Columbia (see Aranguren et al. 2010; Bekker et al. 2010). So, the taxa of Eurycercus might be subdivided into the Nearctic and the Neotropical.

We know that E. longirostris s.str. is widely distributed through whole U.S.A. and southern Canada (Hann & Karrow 1984; Chengalath 1987; Lemke & Benke 2004) and present even in Churchill (Manitoba, Canada) (Jeffery 2011) and the Yukon Territories (our data). But more Canadian populations need to be studied to further assess species diversity. At least, the molecular data suggests a more complicated situation (see two clades in the COI chapter in this article).

Ecology. It is widely distributed in water bodies of different types. We found that two "species" according to Hann (1982) appear to belong to a sole taxon. The range of thermal preferences of E. longirostris is quite wide as evidenced by a record from subarctic Churchill.