Bijdragen lot de Dierkunde, 49 (2): 219-226 1979 Amsterdam Expeditions to the West Indian Islands, Report 5. Notodiaptomus caperatus, a new calanoid copepod from phreatic groundwater in Barbuda (Crustacea: Diaptomidae) by Thomas E. Bowman Department of Invertebrate Zoology, Smithsonian Institution, Washington, DC 20560, U.S.A. Abstract Description. — Female: Length 1.6-1.7 mm. In dorsal view body widest at posterior from well in is Notodiaptomus caperatus n. sp., a Barbuda, cephalosome and pediger 1, gradually narrowing described and illustrated. It is the first diaptomid from the 4 and 5 5 Lesser Antilles and the first West Indian diaptomid having posteriorly. Pedigers separate. Pediger affinities with South American species. produced into small wings; left wing directed slightly obliquely, armed with 2 conical spines; right wing directed nearly laterad, armed with 2 INTRODUCTION conical spines. Urosome 2-merous, most or all of 2nd segment Recently Dr. Jan H. Stock (Zoologisch Museum, telescoped into genital segment. Genital segment University of Amsterdam) sent to me for study a 1.5 as of anterior nearly X long as rest urosome; sample of calanoid copepods that he had collected part expanded laterally into lobe on either side; in phreatic groundwaters of Barbuda, the north- with right lobe steeper sides, bearing conical spine easternmost of the Leeward Islands of the Lesser at summit; left lobe with unarmed summit, but Antilles. The copepods proved to be the new with conical spine at posterior base. In lateral view diaptomid described below, the first from the genital segment produced into posteroventral Lesser Antilles. pouchlike protuberance, anterior to which are several vertical folds. Caudal ramus symmetrical, TAXONOMIC PART half slightly more than as wide as long. Antenna 1 reaching slightly beyond caudal rami; Notodiaptomus Antenna caperatus n. sp. segments 11-21 each with 1 seta. 2 with 2-4. Figs. inner and outer lobes of endopod with 9 and 7 setae respectively. Maxilliped with lobes of 1st Material examined. — Sta. 78/19, of University basipod well developed; 4th lobe with only 3 Amsterdam Expeditions to the West Indian Islands. Barbuda, and of setae row spinules on distal margin. Guava Farm, S.E. of Codrington (17°37'39"N6l°48'51"W), 1-4 with normal of (fig. 1), from round, almost covered well, water table at Legs armature spines and of water 0.75 3 m, depth m, chlorinity 1400 mg/1, leg. 2 with cuticular setae. Leg triangular lobe on H. J. Stock, 9 April 1978: 30 $ £ (holotype in Zoologisch posterior surface of 2nd Museum Amsterdam endopod segment. (ZMA), coll. no. ZMA Co. 102.655a; 1st ZMA Co. 10 Leg 5, with 19 paratypes, 102.655b; paratypes in United basipod prominent posterior States National DC coll. Museum, Washington (USNM) no. conical spine; 2nd basipod with short lateral seta. USNM 172318; 12 9 9 (10 ZMA Co. paratypes, 102.655c; First exopod segment 2 X as long as wide. Second 2 paratypes, USNM 172318); 45 copepodids of various without lateral claw stages (ZMA Co. 102.655d). exopod segment seta; mod- armed middle erately stout, on parts of both mar- 4 in *) Report no. appeared Verslagen en technische gege- with gins close-set spinules. Third exopod segment vens, Instituut voor Taxonomische Zoologie (Zoologisch Universiteit 20. slightly longer than medial seta to Museum), van Amsterdam, no. wide; fused Downloaded from Brill.com10/02/2021 03:16:23PM via free access 220 TH. E. BOWMAN - NOTODIAPTOMUS FROM BARBUDA Fig. 1. Map of Barbuda (from Russell & McIntire, 1966) showing the location of station 78/19 (indicated by a star), where collected. Notodiaptomus caperatus n. sp. was Downloaded from Brill.com10/02/2021 03:16:23PM via free access BIJDRAGEN TOT DE DIERKUNDE, 49 (2) - 1979 221 2. and left Fig. Notodiaptomus caperatus n. sp.: a, , dorsal; b, pediger 5 urosome, side; c, same, light side; d, 5 and of same, dorsal; e, , lateral;f, pediger urosome, dorsal; g, right wing of pediger 5, lateral; h, left wing pediger 5, lateral; i, antenna 1, segments 11-19. Downloaded from Brill.com10/02/2021 03:16:23PM via free access 222 TH. E. BOWMAN - NOTODIAPTOMUS FROM BARBUDA than of lateral — From Latin segment at base, more 2 X length Etymology. the caperatus seta. Endopod reaching beyond middle of 1st meaning wrinkled, referring to the folds on the 2nd exopod segment, 2-merous; segment longer female genital segment. with than 1st, distal margin oblique, armed row of fine setae. Relationships. — The Barbudan diap- tomid is provisionally assigned to the South Amer- in Male: Length 1.4-1.5 mm. Prosome shape as ican genus Notodiaptomus Kiefer, 1936, which of 5 the female. Right posterior corner pediger corresponds to nordestinus group of Wright left rounded; corner slightly angular; both corners (1935). The limits of South American diaptomid armed with terminal knob have been established and spinule-tipped having genera not firmly, setule dorsal it. Genital future studies alter the to segment asymmetrical, revisionary may generic with higher bulge on left side bearing postero- assignment of the Barbudan species. dorsal Posterior of curved to As with other N. be seta. part urosome diaptomids, caperatus may right. identified by a combination of distinguishing Right antenna 1 with spines on segments 8, 10, characters rather than by one or two characters. 11, 12, 13, 15, and 16. Spines on segments 10 The shape and armature of pediger 5 and the the in both and 11 subparallel to axis of antenna, those of genital segment, armature of antenna 1 and 16 that of and the of in both segment 12 especially quite small, sexes, structure leg 5 sexes, with incised taken will N. segment 13 suberect, large, slightly together, distinguish caperatus from tip. Segment 23 with strong recurved spinous other diaptomids. Perhaps the most striking char- than half of acteristics the wrinkled in the process more length segment. are genital segment with and and inner Right leg 5, 1st basipod moderately devel- female, the shape denticulate mar- in oped sensillum-bearing process. Second basipod gin of the distal process of the left leg 5 exopod medial with the male. about 1.5 X longer than 1st; margin cuticular thickening at midlength; distomedial part of posterior surface with crescentic patch of fine hairs. Second exopod segment about 1.5 X longer HABITAT with than 1st and 1.6 X longer than wide, H. rounded knob at base medially; lateral spine sub- Barbuda is "hollow as Swiss cheese" (J. Stock, in has terminal, more than half length of segment; litt.) and substantial underground water, claw third than but terminal nearly a longer exopod, no surface streams. Rainfall averages nearly arched with with recorded maximum gently recurved tip. Endopod 2- 100 cm/year, a of nearly of 1st 670 cm in 1913 and a minimum of about 55 cm merous, not quite reaching midlength armed is within 6 exopod segment; apical margin oblique, in 1930. The water table high, m of the with row of setules. surface on practically all lowland parts of the Left leg 5 slightly more slender than right, island. Two of the major wells provide more than reaching about midlength of 1st exopod segment 300,000 and 94,000 1/day (data from Martin- of right leg. First basipod about 1/4 longer than Kaye, 1956). The water is rather saline; Martin- 2nd. Exopod with widely separated proximal and Kaye (1956) gives measurements for salinity and distal pads. Proximal pad slightly smaller than between 352 2865 ppm (= mg/1) for the medial wells. bodies of distal, bilobed. Distal process subconical, major Larger underground water and denticulate in distal surface exist in number of but of margin nearly straight a caves, none lateral with contained part, margin bend near midlength. those sampled calanoids. medial Some Proximal process straight, slender, pointed, diaptomids prefer small, temporary bodies with minute margin a few spinules. of water, e.g. Hemidiaptomus amblyodon (Maren- Endopod reaching base of distal pad, becoming zeller) (see Dussart, 1967: 108, who terms such narrower I not slightly distally; apex slightly oblique, species "telmatoplanktonic"). However, am armed with of slender other row setules. aware of any diaptomid known only from Downloaded from Brill.com10/02/2021 03:16:23PM via free access - BIJDRAGEN TOT DE DIERKUNDE, 49 (2) 1979 223 10-16; b, d, Fig. 3. Notodiaptomus caperatus n. sp.: a, right antenna 1, segments same, segment 23; c, antenna 2; mandibularpalp; e, maxilliped, 1st basipod; f, leg 1; g, leg 2. Downloaded from Brill.com10/02/2021 03:16:23PM via free access 224 TH. E. BOWMAN - NOTODIAPTOMUS FROM BARBUDA 4. of lateral; Fig. Notodiaptomus caperatus n. sp.: a, leg 4; b, leg 5, posterior; b', endopod same, anterior; c, leg 5, 2nd and d, leg 5, posterior; e, left leg 5, anterior; f, right leg 5, basipod, 1st exopod, endopod, anterior. Downloaded from Brill.com10/02/2021 03:16:23PM via free access BIJDRAGEN TOT DE DIERKUNDE, 49 (2) - 1979 225 phreatic groundwater. C. B. Wilson (1936) re- Until now, no diaptomids have been reported from Herrick and the Lesser and the of ported Diaptomus albuquerquensis Antilles, presence a diap- tomid is that D. novamexicanus Herrick from underground on Barbuda remarkable, considering waters of Yucatan, but in open-air cenotes. Only the Amsterdam Expeditions sampled 580 stations one described diaptomid, the blind unpigmented on 29 islands for stygobionts and obtained cala- from Cueva noids 16 In Diaptomus cokeri Osorio-Tafall, 1942, only at 1 of the stations on Barbuda. Chica and Cueva de los Sabinos, San Luis Potosi contrast to the other West Indian diaptomids, N. but has affinities with South rather State, Mexico, appears to be a true troglobite, caperatus American least live than at some epigean diaptomids are able to North American species.