Eurytemora carolleeae, Alekseev, Victor R. & Souissi, Anissa, 2011

Alekseev, Victor R. & Souissi, Anissa, 2011, A new species within the Eurytemora affinis complex (Copepoda: Calanoida) from the Atlantic Coast of USA, with observations on eight morphologically different European populations, Zootaxa 2767, pp. 41-56 : 43-52

Eurytemora carolleeae sp. nov.

( Figs 2–7 , 8 A, 9A–D)

Type material. Holotype, ZIN RN 55052, a female dissected on 1 slide; from the Chesapeake Bay, USA (39°23.81'N, 76°03.32'W), collected by Dr Kimmel, 16 April 2008.

Allotype, ZIN RN 55053, a male dissected on 1 slide; from the Chesapeake Bay, USA (39°23.81'N, 76°03.32'W).

Other paratypes, ZIN RN 55054/1–10, 15 females and 15 males from the Chesapeake Bay, USA (39°23.81'N, 76°03.32'W), dissected on 10 slides (3 individuals per 1 slide)

Description. Female ( Figs. 2–5 ). Body transparent, genital double-somite yellowish brown. Length measurements: Full body length without caudal setae 1160 µm, with caudal setae 1655 µm.; cephalosome 418 µm and 4 free thoracic segments 1/2/3/4 = 90/70/70/40 µm. Urosome 460 µm, genital double-somite 130 µm, 3 following somites 1/2/3 = 80/60/60 µm and caudal rami 130 µm.

Cephalothorax ( Fig. 2 A) as long as wide, with maximum width close to middle, frontal part of cephalothorax oval.

Last thoracic somite with 1–2 small spines on wing-like outgrowths of lateral margin. Genital double-somite 1.5 times as wide as long, due to wing-like outgrowths in anterior part of the somite, with two relatively long spines on both sides, with seminal receptacle as shown in Figs. 2 B–C.

Caudal rami ( Fig. 2 B) divergent, 6.2 times as long as wide, with long and strong hair-setae on both sides, as well as on last abdominal somite.

Length proportions of terminal setae, beginning from outermost caudal seta:1/1.3/1.15/1. Length proportions of dorsal and lateral setae to outermost seta 0.25 and 0.6 times respectively. All caudal setae with clearly observable segment-like divisions.

Antennules ( Fig. 3 A) of 25 segments, reaching end of third free thoracic somite, setation of segments beginning from first segment: 0/4/4/3/1/3/1/4/1/3/1/3/3/2/3/2/3/2/2/3/1/1/2/3/7. Most segments with 2 and more setae provided with 1 aesthetasc, last (distal) segment with 6 setae and 1 aesthetasc.

Antenna ( Fig. 4 A) biramous, composed of 2-segmented protopod, 2-segmented endopod and 6-segmented exopod. First exopod segment with 3 setae, second segment with 2 setae, 3–5 segments with 1 seta each, 6 (distal) segment with 4 setae. First endopodal segment with 2 setae, second with 9 setae laterally and 7 setae at distal end.

Mandible ( Fig. 3 D) composed of coxa with gnatobasis, one of its tooth (outermost) significantly larger than other and separated from them. Coxa in middle with biramous mandibular palp, basis with 4 setae, 8-segmented exopod and 5-segmented endopod. Distal segment of exopod with two sub-equal setae, other segments bearing single long seta each. Distal segment of endopod with 2 long setae and 1 short seta, other segment with 2 long setae each.

Maxillula ( Fig. 4 B) biramous and composed of precoxa with medial arthrite bearing 10 strong claw-like spines, 6 relatively long setae; coxa with elongated endite bearing 5 long and one short setae and outer outgrowth with 7 very strong sub-equal in length setae and 2 thin setae. Basis composed of basal endite, 1-segmented endopod with 10 long subequal setae and 4-segmented exopod bearing 5–5–4–7 (distally) long setae.

Maxilla ( Fig. 4 C) uniramous, composed of precoxa with 2 endites; distal endite bearing 3 long setae, first segment with 3 setae, coxa with two endites bearing 3 long setae each and 5-segmented endopod including basal endite with 3 setae and 4 short segments bearing 2 and 3 long distal setae.

Maxilliped ( Fig. 4 D) uniramous and 9-segmented, composed of short precoxa with 1 seta and long coxa with 3 hill-shaped endites bearing 2–3–3 setae; basis more wide in distal part whit 3 long setae and with group of long hairs; endite with 3 long setae followed with 5-segmented endopod armed with 2–3–4–3–4(distally) setae.

Swimming legs P1–4 ( Figs. 5 A–D) consist of coxa and basis bearing 3-segmented exopod and 1 (P1) or 2-segmented endopod (P2–4). Coxae connected with smooth coxal membrane. First and second exopodal segments in each leg with 1 spine outside and 1 seta inside. In P1 endopod with 6 setae, in P2–P3 first segment with 3, distal segment with 6 setae, in P4 first segment with 2, distal segment with 5 setae. Formula for spine (Arabic) and seta (Roman) for distal exopodal segments in P1–4 as follows: 3V–3V – 2V–3V. All setae in swimming legs with clear seen segment-like divisions ( Fig. 5 D, indicated with arrow). Distal spines in exopod P4 very strong in middle part, sub-equal or slightly shorter than nearest setae and shorter than distal segment length ( Fig. 5 D). Lateral edge of coxa in P1–2 with groups of long hair-setae. Both sides of P1–P4 covered with very short hair-setae.

Rudimentary P5 ( Fig. 2 C) uniramous and 4-segmented, narrow coxal plate bearing 1-segmented basis with strong inner outgrowth and 2 spines, distal spine slightly longer than first one. One-segmented exopod with long apical seta and lateral spine about half of apical seta. Tiny spine inserted between these two appendages about 10% or less of short spine length and shorter than distal spine width in insertion place.

Egg sac with up to 60 eggs.

Male. Body length 1720 µm, with caudal setae 1780 µm, in live and freshly conserved specimens blue-grey in colour or colorless.

Cephalothorax as long as wide, with maximum width close to caudal end, anterior part of cephalothorax round shaped.

Last thoracic somite without wings and spine on lateral margin ( Fig. 6 A)

Abdomen 5-segmented.

Caudal rami: 9 times as long as wide without setules or hair–like seta on dorsal and ventral side but with long hair-seta on inner part of cauda. Terminal setae ratio beginning from outermost caudal seta: 1/1.15/1.25/1. Lateral seta about 0.8 times longer than outermost seta, dorsal seta very short, located near innermost seta insertion place ( Fig. 6 A).

Right Antennule ( Fig. 3 B) 21-segmented, 4 and 6 segments without setae, 7–12 segments with strong spines, strongest spine (twice as long as any other spine) at segment 12; 19–20 segments with denticulate plates at inner edges, distal segment with several sensitive papilla. Other segments with regular setae as in Fig. 2 . Left antennule 25 segmented armed as in female (see Fig. 2 ).

Antenna biramous (not shown) with 2-segmented protopod, 2-segmented endopod and 6segmented exopod. Setation as in female (see Fig. 4 A).

Mandible of same construction as in female, gnatobasis with outermost tooth–like processor significantly larger than other and separated from them with a gap indicated in picture Fig. 3 C with arrow.

Maxillula ( Fig. 6 C) biramous, basically as in female, with precoxa bearing 8 strong clow-like spines, 6 relatively long setae. Coxa with elongated endite bearing 6 long setae and outer outgrowth with 9 very strong subequal in length setae. Basis composed of basal endite, 1-segmented endopod with 10 long subequal setae and 4 segmented exopod bearing 5–5–4–7(distally) long setae.

Maxilla ( Fig. 6 E) similar to female: precoxa with 2 endites; distal endite with 3 long setae, first segment with 3 setae, coxa also with two endites bearing 3 long setae each and 5 segmented endopod including basal endite with 3 setae and 4 short segments bearing 2 setae; distal segment with 4 setae.

Maxilliped ( Fig. 6 D) 9-segmented, composed of short precoxa with 1 seta and long coxa with 3 hill-shaped endites bearing 2–2–3 setae; basis more wide in distal part with 3 long setae and with group of long hair-setae near setae insertion place. Endopod 5-segmented with 2–2–4–3–4(distally) setae.

Swimming legs P1–4 ( Figs. 7 A–D) constructed basically like in female. Formula for spine (Arabic) and seta (Roman) for distal exopod segments in P1–4 as follows: 3V–3V – 2V–3V. All setae in swimming legs with clear seen segment-like divisions. Distal spines in exopod P1–4 not so strong in middle part as in female, slightly shorter than nearest setae and longer than distal segment length ( Fig. 7 D). Lateral edge of coxa in P1–4 with groups of long hair-setae. Both sides of P1–P4 covered with very short hair-setae.

Rudimentary legs P5 ( Fig. 6 B): right leg with basipodal segment cylindrical in shape and with small hill on inner side pointed with long spine, distal bent segment with several sensitive pores and two short spines in middle. Left leg basipod also cylindrical about 1.45 times as long as wide, next exopodal segment with two long spine in middle part, distal segment with strong long spine in middle and hook in end similar in construction to E. affinis .

Etymology. The new species is named in honor of Dr. Carol Lee, Wisconsin University, Madison, USA, in recognition of her pioneering work on cryptic species within the E. affinis complex.

Remarks. The new species was discriminated from E. affinis ( Poppe, 1880) that inhabits European coastal brackish and fresh water habitats. Eurytemora carolleeae sp. nov. differs from E. affinis by a combination of characters that includes in both sexes: clearly seen segment-like divisions in setae on P1–P4 and caudal rami; mandible with large outside orientated tooth separated with a gap from other teeth ( Figs. 3 A, 9).

Females E. carolleeae are equiped with wing-like outgrowths of the genital double-somite that significantly increases the proportion between anterior and posterior parts of the somite ( Fig. 9 C; Table 2 ). This species has P5 with a very small (tiny) spine in the second exopodal segment placed between two distal spines. The length of this tiny spine is less than the width of the nearest spines, or about 10 % of the short distal spine length ( Table 2 ).

ities. Mean + standard deviation (Min–Max).

Species AREA Female Male

Caudal rami, Leg 5, Caudal rami, P5 basipod left, L/W tiny spine/spine1 L/W L/W In males of E. carolleeae the caudal rami are naked on both dorsal and ventral sides, left rudimentary P5 with exopod of cylindrical shape, and length/width proportion not less than 1.25 times ( Table 3 , Fig. 9 ).

In E. affinis only a small proportion of adults in some local populations (see below) have setae on swimming legs with unclear segment-like divisions. They have mandible with more or less equal teeth; the outside tooth is not separated from neighboring teeth by a gap.

Female E. affinis , in contrast to the newly described species, has a genital somite with only small upper outgrowths (if present) which do not look like wings; the ratio between anterior and posterior parts in the genital somite is significantly less than 1.5 (see Table 2 ). In P5 the tiny spine is much longer than width of the nearest distal spines and usually is more than 15 % of the short distal spine length ( Table 4 ).

Male E. affinis always has caudal rami with at least several spines on the dorsal surface. In P5 the left exopodal segment has a triangular shape outgrowth that decreases length/width proportion in this segment up to 1 or even less (see Table 3 ).

Figures

FIGURE 2. Eurytemora carolleeae sp. nov., female, ZIN 55050 (holotype): A, habitus, dorsal view; B, urosome, ventral view; C, genital double-somite with P 5, ventral view. Scale bar: A, B, 300 µm; C, 150 µm.

FIGURE 3. Eurytemora carolleeae sp. nov. A, male antennula; B, female left antennula; C, male gnathobasis of mandible; D, female mandible with palp. Arrows indicate separate processor on gnathobasis. Scale bar: A, B, 125 µm; C, D, 62.5 µm.

FIGURE 4. Eurytemora carolleeae sp. nov., female, ZIN 55050 (holotype): A, antenna; B, maxillula, ventral view; C, maxilla; D, maxilliped. Scale bar: 50 µm. Arrow indicating seta segmentation.

FIGURE 5. Eurytemora carolleeae sp. nov., female, ZIN 55050 (holotype): A, left swimming leg 1, anterior view; B, swimming legs 2, anterior view; C, swimming legs 3, anterior view; D, swimming leg 4, anterior view. Scale bar: 100 µm. Arrow indicating seta segmentation.

FIGURE 6. Eurytemora carolleeae sp. nov., male, ZIN 55051 (paratype): A, habitus, dorsal view; B, leg 5, anterior view; C, maxillula, anterior view; D, maxilliped, anterior view; E, maxilla, anterior view. Scale bar: A, 325 µm; B, 250 µm; C – E, 125 µm.

FIGURE 7. Eurytemora carolleeae sp. nov., male, ZIN 55051 (paratype): A, swimming leg 1, anterior view; B, swimming leg 2, anterior view; C, swimming leg 3, anterior view; D, swimming leg 4, anterior view. Scale bar: 100 µm.

FIGURE 8. Eurytemora carolleeae sp. nov. (A) and E. affinis (Poppe, 1880) (B) from the Luga Bay, The Finish Gulf, Baltic Sea. (Photo: Mrs Natalia Sukhikh)

FIGURE 9. Eurytemora carolleeae sp. nov. (A – D) and E. affinis (Poppe, 1880) (E – F): A, female mandible, arrow indicating a gap; B, male mandible, arrow indicating a gap; C, female genital somite with wing-like outgrowth; D, male leg 5 with arrow indicating left basipod; F, female genital somite without wing-like outgrowth; F, male P 5, arrow indicating left basipod. (Photo: Mrs Natalia Sukhikh)

Tables

TABLE 2. Selected morphometric indexes in females of E. carolleeae sp. nov. and E. affinis (Poppe, 1880) from their type localities. Mean + standard deviation (Min – Max). In bold – significant difference with p <0.05. * Only in one female among 56 examined, possibly an aberrant specimen.

Species/Indexes	Caudal rami, L/W	Genital somite, W2/W1	Leg 5, tiny spine/spine1	Leg 4, Long spine/Distal Segment
E. carolleeae	6,06+0,531 (5–7,4)	1,54+0,103 (1,35–1,67)	0,11+0,029 (0,06– 0,2*)	0,85+0,068 (0,70– 0,99)
E. affinis	6,08+0,638 (5,2– 7,8)	1,24+0,075 (1–1,39*)	0,25+0,053 (0,18– 0,36)	0,94+0,066 (0,8 –1,07)

TABLE 3. Selected morphometric indexes for E. carolleeae sp. nov. and E. affinis (Poppe, 1880) in males from the type local-

Species/Indexes	Caudal rami, L/W	Leg 5 Basipod left, L/W	Leg 4, Long spine/Distal Segment	Leg 1, Long spine/Distal Segment
E. carolleeae	9,56+0,936 (8,06–11,07)	1,43+0,13 (1,27–1,6)	1,06+0,060 (0,95–1,14)	1,1+0,117(1–1,39)
E. affinis	7,77+1,037 (6–10,45)	0,96+0,049 (0,91–1,08)	1,14+0,052 (1,03–1,25)	1,21+0,081 (1,06–1,38)

TABLE 4. Selected morphometric indexes in female and male E. carolleeae sp. nov. (USA, Chesapeake Bay) and E. affinis (Poppe, 1880) (from several European localities). Populations from the type localities are indicated in bold.

E. carolleeae CHESAPEAKE BAY 6,0 6	0.095	9.56	1.43
E. affinis RIGA BAY 7.59	0.292	10.86	0.98
E. affinis SCHELDE 7.03	0.31	8.01	0.92
E. affinis SEINE 7.61	0.241	8.77	0.94
E. affinis LOIRE 6.26	0.196	7.93	1.1
E.affinis ELBE 6,0 8	0.25	7.77	0.96
E.affinis GUADALQUIVIR –	–	12.91	1
E. affinis GIRONDE 7.87	0.239	7.04	0.98