Mastigodiaptomus reidae, Eliâas-Gutieârrez, Suaârez-Morales M., 2000

Eliâas-Gutieârrez, Suaârez-Morales M., 2000, Two new Mastigodiaptomus (Copepoda, Diaptomidae) from southeastern Mexico, with a key for the identi ® cation of the known species of the genus, Journal of Natural History 34 (5), pp. 693-708 : 700-705

Mastigodiaptomu s reidae n. sp.

(®gures 23±39)

Material examined

HOLOTYPE: adult male, collected 3 October 1998, from a small pond in ChicanaÂ, Campeche, Mexico, deposited at The Natural History Museum , London, registered under number 1998.2718 . ALLOTYPE: adult female, collected 3 October 1998, in the same locality, deposited at The Natural History Museum, London, registered under number 1998.2719 .

PARATYPES: one adult female, and one adult male, same locality, deposited at the MuseÂum National d’ Histoire Naturelle, Paris, catalogue numbers MNHN-Cp1689 and MNHN-Cp1688. One adult female, and one adult male, same locality, deposited at the National Museum of Natural History , Smithsonian Institution, Washington DC, catalogue numbers USNM-26148 8 and 261489, respectively. One adult female, and one adult male from same locality, deposited at El Colegio de la Frontera Sur under number ECO-CH-Z00410 . Original samples are deposited at El Colegio de la Frontera Sur, Unidad Chetumal , Quintana Roo, Mexico .

Type locality. A pond (surface<1 ha) located in the archaeological site of Chicana (18ss30¾ 50 ² N, 89ss28¾ 54 ² W) in the State of Campeche, within the Biosphere Reserve of Calakmul, Mexico .

Description

Female (®gure 26). Mean length excluding furcal rami 1.54Ô 0.05 mm, range 1.47±1.60. Body slender, prosome slightly narrower anteriorly, symmetrical. Rostrum as in ®gure 29. Thoracic wings weakly developed, asymmetrical, right shorter than left. Right wing with two spine-like processes, both posteriorly directed. Left wing with a nearly transversal posterior margin, ending in a single spine, directed outwards; another spine on inner end of wing, directed posteriorly. Urosome with three somites, relative lengths: 72.9 5 8.35 5 18.7 = 100. Genital double-somite slightly asymmetrical, with one slender spine on anterior third of both lateral margins, right spine inserted in a slightly more proximal position than left (®gure 26). Genital double-somite ventrally expanded, with low protuberances around genital opening (®gure 28). Anal somite more than twice as long as previous somite. Caudal rami about as long as wide, inner margin setose. Caudal rami with three terminal, one dorsal, and two lateral setae, all setae biserially plumose, more than 2.5 times as long as caudal rami.

Antennules (®gure 27) relatively short, 25-segmented, barely reaching posterior margin of genital double somite (®gure 28). Seta on segments 3, 7 and 9 very long. Armature per segments as follows: 1 (1 +ae), 2 (3 +ae), 3(1 +ae), 4 (1), 5(1), 6 (1 +ae), 7(1), 8 (1 +sp), 9(2), 10 (1), 11(2), 12(1 +sp), 13 (1), 14 (1 +ae), 15(1), 16 (1), 17(1), 18 (1), 19(1), 20 (1), 21 (1), 22 (2), 23 (2), 24 (2), 25 (4 +ae).

Antenna (®gure 31) as in M. maya , but outer lobe of distal portion of terminal endopod with one short posterior and six anterior setae, and with subterminal cluster of four or ®ve small hair-like spinules; internal with two short and seven long setae.

Mandible (®gure 30) with six teeth on gnathobase, at least one is bi-pointed; ventral outermost tooth longer and wider. Distal end of inner margin with short setulated spine-like projection. Basis with four setae; endopod two-segmented, proximal segment with four setae; distal segment longer, with seven setae. Exopod four-segmented, with normal 1,1,1,3 setation pattern.

Maxillule (®gure 32) with praecoxal arthrite bearing 14 spiniform setae. Coxal epipodite with nine setae, coxal endite with ®ve setae. Basis with one wide and long internal lobe bearing two setae, second endite with two setae, basal exite reduced, represented by a small lobe bearing a single seta. Endopod reduced, three-segmented, articulating with the basis, proximalmost segment with four setae, second with one seta, distalmost with three apical setae. Exopod with six setae, with a row of small spines on proximal third. Maxilla as in M. maya but endopod four-segmented, setation pattern 1,1,1,3.

Maxilliped (®gure 33) well developed. Coxa with several distinct lobes, proximalmost with two setae, second and third with two, distalmost with anterior protuberance projecting over next segment, with row of short spinules surrounding process, and four short setae. Basis with row of slender spinules on middle portion of inner margin, group of three setae on middle portion of inner margin. Endopod six-segmented, ®rst segment partially fused to basis, bearing two subequal setae. Second endopodal segment with three subequal setae, third and fourth with two setae, ®fth with one seta; terminal segment with three subequal setae.

First leg (®gure 34) with three-segmented exopod, and two-segmented endopod, coxa with stout setules on outer margin, plumose seta on internal margin, reaching proximal end of ®rst endopod. Second endopod segment of leg 2 with Schmeil’s organ mammiliform. Second, third and fourth legs (®gures 35±37) with threesegmented exopods and endopods. Armature formula for swimming legs:

coxa basis exopod endopod leg 1 0±1 0±0 I±1;0±1;I,3,2 0±1;1,2,3 leg 2 0±1 0±0 I±1;I±1;I,3,3 0±1;0±2;3,2,2 leg 3 0±1 0±0 I±1;I±1;I,3,3 0±1;0±2;3,2,2 leg 4 0±1 0±1 I±1;I±1;I,3,3 0±1;0±2;3,2,2

Leg 5 (®gure 39): coxa with strong spiniform lateral process. Basis with inner margin straight, naked, with short, slender lateral seta reaching proximal third of ®rst exopod segment. Posterior margin of basis with rounded process projecting over endopod. Endopod two-segmented, intersegmental division faint. Endopod long, four times long as wide, its distal end reaching level of second third of inner margin of ®rst exopod segment; armed with one long terminal spine and a group of short, subterminal stout setae. First exopod segment nearly as long as second, with smooth, straight lateral margins. Claw of second segment with blunt tip, inner and outer margins armed with row of teeth along both margins. Third exopod segment reduced, barely distinct from second, represented by short, strong, spiniform process near usual spine of second segment.

Male (®gure 23). Mean length (mm) 1.56Ô 0.09, range 1.45±1.62.

Body slender, with typical diaptomid shape. Rostrum as in ®gure 25. Pediger 4 wider than succeeding somite; pediger 5 tapering posteriorly, asymmetrical, with reduced lateral`wings’. Right wing with two spine-like processes, pointing posteriorly. Left wing reduced, with small lobe ending in a small spine, pointing posteriorly. Urosome asymmetrical, ®ve-segmented. First urosomite with relatively long posterior spine on right margin, with rounded protuberance on left margin. Relative lengths of urosomites being: 20.4 5 18.7 5 20.3 5 22,8 5 18.6 = 100. Preanal somite with a rounded process on left side of posterior margin, projecting over the anal somite. Caudal rami as for female. Inner and outer margins of caudal rami naked.

Antennules slightly shorter than in female, last antennular segment barely reaching posterior margin of preanal somite. Right antennule (®gure 24) geniculated between segments 17 and 18, with one seta on segments 3±7; setae on segments 3, 5, 7 and 9 large. Aesthetascs on segments 1±3, 5, 9, 12 and 14. Segment 8 with one short spine and one seta; 9 with one long and one short setae; 10 and 11 each with one stout spine, that on former short, barely reaching distal third of bearing segment, that on latter reaching slightly beyond middle of segment 12; segment 12 with one seta and a short, broad spine; 13 with one seta and one large, strong spine, its base almost as wide as bearing segment, spine reaching proximal third of segment 14. Segment 14 with large spine, slightly smaller than that of previous segment, with a short seta at its base plus one long seta at distal end reaching segment 16; segment 15 with one spine and two setae; 16 with broad-based spine process pointing distally, with one seta borne near its base. Segment 17 with spiniform process inserted on proximal portion; 18 and 19 with typical spine-like processes closely adjacent to inner margin of segment, segment 19 also with one short seta on middle portion and one on distal margin. Segment 20 with long, wide-based fang-like process on distal inner margin, almost reaching halfway along next segment, segment bearing two setae, one inserted in middle of outer margin, the other distally. Segment 21 with two distal setae. Terminal segment relatively short, with two large apical setae plus two subapical. Setation of left antennule, mouthparts and swimming legs as for female.

Left leg 5 (®gure 38) reaching middle portion of inner margin of right second exopod segment. Coxa with large, basally wide spiniform anterior process on outer margin. Basis with short, subterminal lateral outer seta, barely reaching distal end of bearing segment. First exopod segment longer and wider than second, with low pad on middle portion, covered with stout setules. Second exopod segment with two pad-like processes, one a basal rounded structure covered by short, stout setules, the other rounded, covered with low tooth-like spines arranged in a semicircular pattern; on top of these, a spine-like projection with curved end, with a distal comblike structure. Endopod short, one-segmented, barely reaching second third of ®rst exopodal segment, tip covered with a crown of stout setules.

Right leg 5 (®gure 38): coxa with large spinous process on distal portion of external margin, inner margin smooth. Basis about 2.5±3 times as long as ®rst exopod segment, with semicircular cuticular ridge on distal margin of anterior surface, with strong subrectangula r protuberance on proximal third of inner margin, plus two hyaline processes, one rounded, with heavily chitinized central core on proximal third, and the other subquadrate, on the middle portion. Outer margin with short socketed seta on middle portion. First exopod segment short, with outer margin straight, slender, with subtriangular distal protuberance; inner margin with low subtriangular lateral process. Second exopodal segment more than three times as long as ®rst, with a chitinous semicircular process on anterior surface in proximal third. Lateral spine straight, with small spinules along inner margin, almost as long as bearing segment, borne slightly beyond distal third of segment. Terminal claw relatively slender, curved, tapering gradually from enlarged base, about 2.5 times longer than the second exopod segment, with row of low teeth along most inner margin. Right endopod reduced to a single lobe, short, one-segmented, barely reaching distal margin of ®rst exopod segment, without suture on posterior surface, with a crown of stout setules on tip.

Colour. Light blue in live and recently preserved specimens.

Etymology. Named after Dr Janet W. Reid, National Museum of Natural History at Washington, DC, in recognition of her abundant and relevant contributions to the knowledge of the Neotropical freshwater copepod fauna, and of her continuous interest in helping and guiding Latin American copepodologists.

Remarks

The distinguishing characters of M. reidae include a strong spine on segment 16 of the right male antennule (absent in M. montezumae , M. purpureus and relatively underdeveloped in M. albuquerquensis , M. amatitlanensis , M. nesus , M. texensis , and M. maya ). The new species has two well-de®ned internal hyaline processes on the inner margin of the basipod: other species have only one. The proximalmost process is clearly rounded, but it is subquadrate in M. nesus and M. albuquerquensis , oval in M. purpureus and M. maya , acute, triangular in M. texensis , and absent in M. montezumae and in M. amatitlanensis . In M. reidae , the second is subquadrate and located on the distal third of the segment. No other known species of this genus bears a second process. Another character is the chitinous process on the posterior surface of the second exopod segment of the right ®fth leg. Other appendages are similar to those of M. montezumae (Dos Santos et al., 1996) .

The occurrence of a dorsal keel on the female fourth pediger in Mastigodiaptomus has been recognized as variable, not present in all individuals ( Bowman, 1986; SuaÂrez-Morales et al., 1999). Therefore, in some species of the genus, the presence/ absence of this character has no taxonomic value. In M. reidae this process is absent, but that does not eliminate the possibility that some individuals have a dorsal keel.