PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON 110(4):569-580. 1997. Aglaodiaptomus atomicus, a new species (Crustacea: Copepoda: Calanoida: Diaptomidae) from freshwater wetland ponds in South Carolina, U.S.A., and a redescription of A. saskatchewanensis (Wilson 1958) Adrienne E. DeBiase and Barbara E. Taylor The University of Georgia, Savannah River Ecology Laboratory, RO. Drawer E, Aiken, South Carolina 29802, U.SA. — Abstract. A new calanoid copepod, Aglaodiaptomus atomicus, is de- scribed from freshwater wetland ponds in Aiken County, South Carolina, U.S.A. It is common in Aiken and Barnwell Counties. It has been collected from shallow, acidic wetland ponds, most of which dry periodically. Agla- odiaptomus atomicus resembles A. saskatchewanensis, which is redescribed from Saskatchewan, Canada, and Louisiana, U. S. A. The male of A. atom- icus differs from all of its congeners by possessing a distinctively large distolateral process on the right leg 5, exopod 1. The female differs from its closest congener, A. saskatchewanensis, in possessing nearly symmetrical thoracic wings. In A. saskatchewanensis the wings are distinctly asymmet- , rical. A survey of freshwater wetland ponds on more detailed description of A. saskatch- the upper coastal plain of western South ewanensis is presented here, as well as a Carolina revealed an apparently unde- description of the new species, A. atomi- scribed calanoid copepod species. This spe- cus. cies, which was incorrectly reported as Diaptomid copepods vary in the follow- Diaptomus conipedatus Marsh, 1907 by ing morphological characteristics: body Mahoney et al. (1990), is one of the most length, features of the thoracic somites common calanoid copepod species occur- (especially the 6th somite), length, number ring in Carolina bays and other isolated, of and armature of the antennules in both shallow, wetland ponds in Aiken and Barn- sexes, number of somites of the female well Counties, South Carolina. It most urosome, and segmentation, shape and or- closely resembles Aglaodiaptomus sas- namentation of the fifth leg of both sexes katchewanensis Wilson, 1958. However, (Wilson 1959). The mouth parts and legs detailed comparisons with specimens of A. 1-4 of the species presented in this paper saskatchewanensis proved it to be a sepa- correspond to those of Leptodiaptomus si- & rate, undescribed species. ciloides (Comita Tommerdahl 1960). In her original description of Agla- Descriptions and measurements of whole odiaptomus saskatchewanensis, Wilson copepods were made in glycerine. Dissect- (1958) provided an illustration of only the ed specimens were mounted either in lac- male fifth leg and a partial description of tophenol or in CMC-9. Most were stained the species. Few additional details were with Chlorazol Black E before being A added to her 1959 key (Wilson 1959). mounted. — 570 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON Family Diaptomidae Baird 1850 (1+a), XV(1), XVI(l+a), XVII(l), XVIII Genus Aglaodiaptomus Light, 1939 (1), XIX(l+a), XX(1), XXI(l), XXII(2), Aglaodiaptomus saskatchewanensis XXIII(2), XXIV(2), XXV(5+a). Setae on (Wilson 1958) segments 17, 19, 20, 22 with hooked ends Figs. 1-3 (Fig. IE); length of seta approximately 3A that of respective segment. Diaptomus saskatchewanensis Wilson, Leg 2 endopod 2 with Schmeil's organ 1958:490-491, 493-495, fig. 3.—Diap- (not figured). tomus (Aglaodiaptomus) saskatchewan- Leg 5 (Fig. IF): Coxa with posterior lat- ensis Robertson, 1972:202. Aglaodiap- & eral protrusion ending in sensillum. Basis tomus saskatchewanensis, Chengalath with short lateral seta. Exopod segments 1 Shih, 1994:2422. and 2 approximately equal in length. Claw — Material. Saskatchewan: 8 6 6> 6 9 9; of exopod 2 slightly curved with denticles farm reservoir near Lucky Lake, Saskatch- on inner and outer margins. Exopod 3 not ewan, Canada, 107°20'N, 50°10'W, 16 Jun articulated. Lateral spine of exopod 2 about USNM 1948; 210784; coll. J. R. Nursall. 3A the length of outer seta of exopod 3. Ex- Louisiana: 33 6 8, 28 9 9; shallow road- opod 3 inner seta plumose, twice the length side pond 19.4 km south of Natchitoches, of outer seta. Endopod single-segmented, Natchitoches Parish, Louisiana, U.S.A., equal in length to exopod 1, two plumose USNM 31°60'N, 93°05'W, 10 Apr 1953; setae and pointed protrusion at tip (Fig. 278233; co—ll. W. G. Moore. 1G). — Female. Length, excluding caudal se- Male. Length, excluding caudal setae, tae, of specimens from Saskatchewan, of specimens from Saskatchewan, range: range: 1.24-1.64 mm (n = 6), from Loui- 1.24-1.44 mm (n = 8), of specimens from siana, range: 1.34-1.64 mm (n = 28). Body Louisiana, range: 1.28-1.64 mm (n = 33). broadest at pedigers 1 and 2 in dorsal view Body (Fig. 2A) as in female, with 5-seg- (Fig. 1A). Pedigers 4 and 5 incompletely mented urosome. Thoracic wings (Fig. 2B) separated with faint sutures visible laterally. asymmetrical, right wing developed into Pediger 5 small with posteriorly-directed elongated lobe, left wing small. Each wing wings (Fig. IB). Left wing with large dor- with 2 sensilla; sensilla of right wing twice somedial lobe (Fig. 1C) reaching beyond as large as left. Urosome (Fig. 2B): segment posterior margin of wing in dorsal view 1 asymmetrical in dorsal view, left margin (Fig. IB). Right wing has 2 poorly-devel- shorter than right; left posterior corner bifid oped lobes (Fig. ID). Each lobe on both with obliquely directed lobe tipped with wings tipped with short sensillum. Urosome sensillum, right posterior corner simple, of 3 segments (Fig. IB). Genital segment also tipped with sensillum. Segments 2-4 with slight asymmetrical lateral protrusions; approximately equal in size; ventral sensilla left protrusion more rounded than right. on segments 2 and 3 visible under high Both protrusions tipped with sensillum. magnification (not figured). Segment 4 Caudal rami (Fig. IB) nearly twice as long asymmetrical, left margin shorter than right. as broad; inner margins hairy. Caudal rami with hairs on inner margins. Antennules 25-segmented, extending to Antennules (Fig. 2A, C-E) extend to middle of caudal setae (Fig. 1A). Append- proximal margin of caudal rami. Right an- ages per segment as follows (Roman nu- tennule geniculate between segments 18-19 meral = segment, Arabic numeral = num- and 20-21. Segments 18-19 (Fig. 2D), 20- ber of setae, sp = spine, a = aesthetasc): 21 (not figured) and 22-23 (Fig. 2E) fused. 1(1+a), II(3+a), 111(1 +a), IV(1), V(l+a), Large parallel spiniform processes on seg- VI(1), VII(l+a), VIII(l+sp), IX(2+a), ments 10, 11; additional large spine on seg- X(l), XI(2), XII(l+sp+a), XIII(l), XIV ment 13 (Fig. 2C). Spines on segments 10 VOLUME NUMBER 110, 4 571 Fig. 1. Aglaodiaptomus saskatchewanensis Wilson, 1958. Paratype female (USNM 278233): A, Habitus, dorsal, distal segments ofantennule indicated by arrow; B, Urosome, dorsal; C, Left thoracic wing and urosome, lateral; D, Right thoracic wing and urosome, lateral; E, Antennule, segments 19, 20; F, Leg 5, anterior, setae of exopod 3 (thin arrows), lateral seta of exopod 2 (thick arrow); G, Leg 5 endopod, distal end. and 11 equal in length, shorter than spine Left leg 5 (Figs. 3A-E): Leg (excluding on segment 13. Spines on segments 15-17 spines) extending slightly beyond right ba- with bifurcated tip (Figs. 2C, D). Segment sis. Coxa, small process tipped with sensil- 17 (Fig. 2D) with flat, digitiform seta ex- lum near outer posterodistal margin. Basis tending to center of segment 18-19. Addi- with short lateral seta. Exopod segment 1 tional modified seta arising from proximal longer than segment 2; inner margin with Va of segment 18-19, running length of seg- pad; distal corner of pad hairy (Fig. 3B). ment. Segment 22-23 (Fig. 2E) with curved Exopod 2 articulating at distolateral margin distal process; process about as long as seg- of exopod 1. Inner margin of exopod 2 with ment 24. hairs extending the length of the segment PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON 572 Fig. 2. Aglaodiaptomus saskatchewanensis Wilson, 1958. Paratype male (USNM 278233): A, Habitus, dor- sal, distal segments of antennule indicated by arrow; B, Urosome, dorsal; C, Right antennule, segments 8-16; D, Right antennule, segments 16-19; E, Right antennule, segments 23-25. (Fig. 3B); hairs extend to cover % of ante- with crenate longitudinal groove; remaining rior surface (Fig. 3C). Outer distal quadrant surface of endopod with small rows or clus- % of exopod 2 covered with minute protuber- ters of short spinules. Outer of anterior ances in both anterior and posterior views. face of endopod (Fig. 3E) crenulate; small Terminal seta about as long as segment and pad on inner distal edge covered with tiny plumose, terminally placed on inner mar- spinules. gin; short, rounded digitiform process Right leg 5 (Fig. 3A): Coxa with disto- placed on outer distal margin, covered with medial lobe on posterior surface tipped with short hairs. Endopod as long as exopod; sensillum. Basis with narrow, inwardly outer margin of posterior face (Fig. 3D) rounded longitudinal hyaline membrane on VOLUME NUMBER 110, 4 573 Fig. 3. Aglaodiaptomus saskatchewanensis Wilson, 1958. Paratype male (USNM 278233): A, Leg 5, pos- terior; B, Left leg 5 exopod 2, posterior; C, Left leg 5 exopod 2, anterior; D, Left leg 5 endopod, posterior; E, Left leg 5 endopod, anterior. posteromedial face; fine setule on lateral exopod 2, distal Vi of inner surface with fine margin slightly distal to mid-length of seg- teeth. Terminal claw as long as exopod 1; ment margin. Endopod greatly reduced, distal 3A ofinner surface lined with fine den- with fine setae on distomedial surface. Ex- ticles. — opod 1 with distally directed process on dis- Distribution and ecology. Only three tolateral corner, less than Va length of seg- records exist beyond the Louisiana and ment. Exopod 2, slightly longer than exo- southern Saskatchewan collections used for pod 1 Lateral spine inserted at 34 the length Wilson's (1958) description. Reed (1959) . of the segment, spine about Vi as long as collected specimens from Frobisher Lake 574 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON on the upper Churchill River in Saskatch- 81°27'-81°47'W). All collected February ewan, extending the range of A. saskatch- and December 1990 with 102 (xm mesh dip & ewanensis northward. Patalas Salki net by A. E. DeBiase. — (1984) recorded it in Southern Indian Lake, Co-occurring Diaptomidae. Flamingo Manitoba, another lake along the Churchill Bay: Aglaodiaptomus clavipoides Wilson, River. Robertson (1972) reported A. sas- 1955, A. stagnalis Forbes, 1882, Leptodiap- katchewanensis from southeastern Oklaho- tomus moorei Wilson, 1954, Onychodiap- ma in oxbow lakes, farm reservoirs, ditches tomus sanguineus Forbes, 1876; Bay 11: and swampy areas. Hesperodiaptomus augustaensis Turner, 1910, O. sanguineus', Bay 40: no other Family Diaptomidae Baird 1850 diaptomids; other SRS ponds: A. clavipo- Genus Aglaodiaptomus Light, 1939 ides, A. stagnalis, H. augustaensis, L. Aglaodiaptomus atomicus, new species moorei, Onychodiaptomus birgei Marsh, 4-6 Figs. 1894, O. sanguineus, Skistodiaptomus pal- Diaptomus conipedatus Mahoney et al., lidus Herrick, 1879, up to five of these spe- cies per pond. 1990: 247, 252, Fig. 2. — Diaptomus sp. DeBiase & Taylor, 1993: Female. Length, excluding caudal se- 388; Boileau & Taylor, 1994:193, 195- tae: 1.65-2.00 mm (n = 25). Body broadest 196, 197-199, Figs. 1-3. at pedigers 1 and 2 in dorsal view (Fig. 4A). — Pedigers 4 and 5 incompletely fused. Weak- USNM Type material. Holotype, 6, USNM ly asymmetrical thoracic wings; left dorso- 259989; allotype 9, 259990, each medial lobe (Fig. 4C) slightly more devel- dissected on slide in lactophenol; paratypes: oped than ventrolateral lobe; each lobe 5 6 6 5 9$, each dissected on slide in lac- USNM tipped with small sensillum. Lobes of right tophenol, and 20 6 6 20 9 9, wing (Fig. 4B) of equal size, each tipped 267334; all from South Carolina, Aiken with small sensillum. Urosome of 3 seg- County, Flamingo Bay (Bay 3), 33°20'N, m ments (Fig. 4D). Genital segment twice as 81°41'W, Savannah River Site, 300 west side of Road F at about 0.8 km south of long as broad, with very slight, rounded lat- eral expansions at mid-length, each with intersection of Roads 2 and F. All collected short, laterally-directed spine. Left expan- 7 Feb 1994 with 102 |xm dip net by A. E. sion slightly more distally placed than right. DeBiase. All undissected paratypes pre- Caudal rami about V/i times longer than served in ethanol. — broad; inner margins hairy. Additional, non-type material. 20 6 6 USNM Antennules 25-segmented, reaching 20 9 9, 267333, South Carolina, Barnwell County, Bay 40, 33°16'N, slightly beyond distal end of caudal rami 81°46'W, Savannah River Site, 25 m north (Fig. 4A). Appendages per segment as fol- of Road F-6 and 500 m east of Road F; 20 lows (Roman numeral = segment, Arabic 6 6 20 9 9, USNM 267332, South Caro- numeral = number of setae, a = aesthetasc, = lina, Aiken County, Bay 11, 33°1'N, sp spine): 1(1+a), II(3+a), 111(1+a), 81°36'W, Savannah River Site, 400 m west IV(1), V(l+a), VI(1), VE(l+a), Vm(l+sp), m of SC 125, about 500 south of Gate 6. IX(2+a), X(l), XI(2), XII(l+sp+a), XIII All paratypes undissected and preserved in (1), XIV(l+a), XV(1), XVI(l+a), XVII(l), ethanol. Also 500+ 6 6 9 9, dissected on XVIII(l), XIX(l+a), XX(1), XXI(l), XXII slides in glycerin, and 2000+ 66 99 + (2), XXIII(2), XXIV(2), XXV(5+a). As in copepodids, undissected in formalin, from A. saskatchewanensis, setae (see Fig. IE) 25 additional ponds in South Carolina, Ai- on segments 17, 19, 20, 22 with hooked ken and Barnwell Counties (all located on ends; length of setae approximately 34 that Savannah River Site, 33°05'-33°24'N, of respective segments. VOLUME NUMBER 110, 4 575 Fig. 4. Aglaodiaptomus atomicus, new species. Paratype female (USNM 267334): A, Habitus, dorsal, distal segments of antennule indicated by arrow; B, Right thoracic wing and urosome, lateral; C, Left thoracic wing and urosome, lateral; D, Urosome, dorsal; E, Leg 5, anterior, setae of exopod 3 (thin arrows), lateral seta of exopod 2 (thick arrow); F, Leg 5 endopod, distal end. Leg 2 endopod 2 with Schmeil's organ er seta. Endopod reaching slightly beyond (not figured). distal end of exopod 1; tipped with two plu- Leg 5 (Fig. 4E): Coxa with posterior lat- mose setae and pointed protrusion (Fig. eral protrusion tipped with sensillum. Basis 4F). — with lateral seta. Exopod 1 approximately Male. Length, excluding caudal setae: equal in length to exopod 2. Exopod 2 claw 1.50-1.85 mm (n = 25). Prosome segmen- slightly curved with denticles on inner and tation as in female (Fig. 5A). Thoracic outer margins. Exopod 3 not articulated. wings reduced, with small dorsolateral and % Lateral spine of exopod 2 about the ventromedial sensilla; sensilla of right wing length of outer seta of exopod 3. Exopod 3 twice as long as left. Left posterior corner inner seta plumose, twice the length of out- of urosome segment 1 bifid, tipped with PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON 576 Fig. 5. Aglaodiaptomus atomicus, new species. Paratype male (USNM 267334): A, Habitus, dorsal, distal segments of antennule indicated by arrow; B, Urosome, dorsal; C, Right antennule, segments 7-16; D, Right antennule, segments 17-19; E, Right antennule, segments 23-25. sensillum; right posterior corner simple, some (Fig. 5A). Right antennule geniculate with sensillum that is slightly larger than between segments 18-19 and 20-21. Seg- left. Urosome 5-segmented (Fig. 5B). Seg- ments 18-19 (Fig. 5D), 20-21 (not figured) ments 2-3, ventral margin lined with fine and 22-23 (Fig. 5E) fused. Long, parallel hair-like setae visible in lateral view under spines (Fig. 5C) on segments 10, 11, and high magnification (not figured). Fourth 13. Spines on segments 15 and 16 bifur- segment asymmetrical, right margin longer cated (Fig. 5C). Modified digitiform seta than left. Caudal rami with fine setules lin- (Fig. 5D) emerging from proximal Va of ing inner margins. segment 17 and extending to mid-length of Antennules extend to mid-length of uro- segment 18-19. Additional modified seta , VOLUME NUMBER 110, 4 577 emerging from proximal Va of segment 18- after the Savannah River Site (SRS), where 19, extending length of segment. Curved this species was first recognized. The SRS distal process (Fig. 5E) on segment 22-23 is a production facility for nuclear materials about Vi as long as segment 24. and was originally operated by the United Left leg 5 (Figs. 6A-E): Leg (excluding States Atomic Energy commiss—ion. spines) extending approximately to distal Distribution and ecology. Aglaodiap- edge of basis. Lateral lobe of coxa minute, tomus atomicus is known only from Caro- m tipped with sensillum. Basis with fine lat- lina bays and other shallow (usually <1 eral seta. Exopod 1 longer than exopod 2, deep) isolated wetland ponds in Aiken and with hairy pad on distomedial coiner. Exo- Barnwell Counties, South Carolina. The pod 2 (Figs. 6B,C) articulating at distola- ponds range in size from 0.1-50 ha. Most teral margin of exopod 1 processes placed of these are temporary ponds. Hydrology is ; subterminally. Inner process is about as controlled mainly by precipitation and long as exopod 2, outer margin covered evapotranspiration (Lide et al. 1995). Fill- with setules. Outer process about Vz length ing tends to occur during late autumn-early of inner process, covered with setules. Out- winter, and drying during late spring-early er distal quadrant of exopod 2 with minute summer. protuberances on posterior surface (Fig. The ponds usually lack fish, and all are 6B). Endopod about as long as exopod with acidic (pH 4.4-6.6). Aglaodiaptomus atom- long patch of small teeth on distal Vz par- icus most often occurs at pH 5.1-5.7, and alleling inner margin of posterior face (Fig. has a broad temperature range (10-35°C). — 6D). Outer margin crenulated (Figs. 6D, E); Discussion and comparisons. The male crenation more developed on anterior sur- of A. atomicus differs from all other con- face. geners by possessing a relatively large pro- Right leg 5 (Figs. 6A): Coxa with dis- tuberance on the outer distal corner of ex- tomedial lobe tipped with sensillum. Basis opod 1 of right leg 5. It is at least Va the ornamented only with bilobed protrusion on length of exopod 1, while this projection, median-posterior face, proximal lobe slight- when present on males of other species, is ly larger; outer seta on lateral margin of much shorter. The exception is A. dilobatus segment. Endopod reduced, represented by Wilson, 1958, which has a fairly long pro- laterally bent lobe, covered with fine setae. tuberance. However, the left leg 5 ofA. di- Process on distolateral corner of exopod 1 lobatus is morphologically different from about Va length of exopod 1. Exopod 1 that of A. atomicus. It possesses an exopod shorter than exopod 2, claw equal in length 1 which widens distally and a globular ex- to exopod 2. Lateral spine inserted at % opod 2. Both of these segments are rela- length of segment, about 2/z the length ofthe tively rectangular in A. atomicus. claw, inner surface with fine denticles. Ter- The female of A. atomicus most closely minal claw as long as exopod 2; distal Va of resembles A. forbesi Light, 1938, A. lintoni inner surface lined with fine denticles. Forbes, 1893 and A. saskatchewanensis. — Color. Body pale blue; legs, distal Vz of These species are difficult to tell apart, ex- antennule, and setae of caudal rami bright cept that the endopod of A. lintoni reaches red-orange. The blue pigment is lost during well beyond exopod 1, while it is approxi- preservation. Ifthe specimens are preserved mately as long as exopod 1 in the others. in formalin, the red pigment remains but Also, exopod 3 is more developed in A. lin- becomes purple-red. toni and A. forbesi. Aglaodiaptomus atom- — Type locality. Flamingo Bay (Bay 3), icus can be distinguished from A. saskatch- 33°20'N, 81°41'W, Savannah River Site, ewanensis by the thoracic wings. The wings Aiken County, South Carolina. of A. saskatchewanensis are asymmetrical, — Etymology. The species name is given with the left dorsal lobe more developed PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON 578 Fig. 6. Aglaodiaptomus atomicus, new species. Paratype male (USNM 267334): A, Leg 5, posterior; B, Left leg 5 exopod 2, posterior; C, Left leg 5 exopod 2, anterior; D, Left leg 5 endopod, posterior; E, Left leg 5 endopod, anterior. than the right dorsal lobe, while the lobes katchewanensis may also be separated geo- of A. atomicus are almost equally devel- graphically. As described in the "Distribu- oped on both sides. tion and ecology" section, A. saskatche- Aglaodiaptomus atomicus keys out to A. wanensis has been reported from a few saskatchewanensis in Wilson (1959). These widely separated locations from the south- species are easily separated by the orna- central and north-central regions of North mentation of the male antennules and leg 5 America, while A. atomicus was discovered and the female thoracic wings. Also, A. in southeastern North America. Most stud- atomicus is slightly larger. ies in central North America have concen- Aglaodiaptomus atomicus and A. sas- trated on large reservoirs and lakes. Studies