Mastigodiaptomus maya, 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 : 694-699

Mastigodiaptomu s maya n. sp.

(®gures 1±22)

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 1998.2716 . ALLOTYPE: adult female, collected 3 October 1998, in same locality, deposited at The Natural History Museum, London, registered under number 1998.2717 .

PARATYPES: one adult male, and one adult female from the same locality, deposited at the MuseÂum National d’ Histoire Naturelle, Paris, catalogue numbers MNHN- Cp1686 and MNHN-Cp1687, respectively. One adult male, and one adult female from the same locality, deposited at the National Museum of Natural History , Smithsonian Institution, Washington DC, catalogue numbers USNM-26148 6 and 261487, respectively. One adult female , one male, same locality, deposited at El Colegio de la Frontera Sur ( ECO-CH-Z00411 ). Original samples and additional specimens are deposited at El Colegio de la Frontera Sur, Unidad Chetumal , Quintana Roo, Mexico .

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

Description

Female (®gure 1). Mean length excluding furcal rami: 2.38 Ô 0.09 mm, range = 2.30±2.47 mm. Body robust, prosome slightly narrower anteriorly, symmetrical. Rostral points strong, distally acute (®gure 21). Thoracic wings slightly asymmetrical, left shorter than right. Right wing with one posteriorly directed process ending in a relatively large spine-like process. Left wing with a small spine on posterior margin. Urosome of three somites, relative lengths: 66.6 5 11.6 5 21.7 = 100. Genital double-somite slightly asymmetrical, with a small spine on anterior third of each lateral margin (®gure 1). Genital double-somite expanded ventrally, with rounded protuberance on genital opening (®gure 3). Anal somite about twice as long as preanal somite. Caudal rami about as long as wide, slightly asymmetrical, both margins lightly setose (not shown in ®gure 1). Caudal rami with three terminal, one dorsal, and two lateral setae, all setae biserially plumose, and more than 2.5 times as long as caudal rami (®gure 1).

Antennules (®gure 2) short, 25-segmented, reaching proximal third of genital double somite. Setae on segments 3, 5, 7 and 14 long. Armature per segments as follows (Arabic numerals = segment, Arabic numerals in parentheses =number of setae, ae= aesthetasc, sp = spine): 1(1 +ae), 2(3 +ae), 3 (1 +ae), 4(1), 5 (1 +ae), 6 (1), 7(1), 8 (1 +sp), 9 (2 +ae), 10(ae), 11 (2), 12(1 +ae +sp), 13 (1), 14 (1 +ae), 15 (1), 16 (1), 17 (1), 18 (1), 19(1 +ae), 20 (1), 21(1), 22 (2), 23 (2), 24(3), 25 (4 +ae).

Antenna (®gure 8) with exopod longer than endopod. Coxa with one seta. Basis with two short setae on outer distal margin. Endopod reduced, of two segments. First segment with one outer seta and a cluster of setules on inner margin. Distal portion of terminal segment with two lobes, outer with one short posterior and six anterior setae; internal with two short and six long setae. Exopod seven-segmented, with one seta on ®rst segment, three on second, and one seta on segments 3±6. Distal segment with one short seta on proximal third of inner margin, and three long terminal setae subequal in length.

Mandible (®gure 9) with six teeth on gnathobase, at least three are bi-pointed; ventral outermost tooth longer and wider. Distal end of inner margin with short, slender spine-like projection. Basis with two setae; endopod two-segmented, proximal segment with four setae; distal segment longer, with seven setae. Exopod foursegmented, with normal 1,1,1,3 setation pattern.

Maxillule (®gure 10) with praecoxal arthrite bearing 13 spiniform setae. Coxal epipodite with eight setae, inner wider than the rest, coxal endite with ®ve setae. Basis with one wide and short internal lobe bearing a short, single seta. Proximal and distal basal endites each with four setae. Endopod reduced, two-segmented, distalmost segment with two apical and one subapical setae. Exopod with six setae.

Maxilla (®gure 11) indistinctly segmented, with two praecoxal and two coxal lobes, and a well developed basal lobe. Setation pattern of ®ve lobes: 4, 3 (®rst and second praecoxal endites), 2, 3 (®rst and second coxal endites), 3 (basal endite); endopod well developed, three-segmented, with setation pattern: 1,1,3.

Maxilliped (®gure 12) well developed. Coxa fused with praecoxa, with anterior protuberance projecting over next segment, and row of short spinules surrounding process. Coxa with three distinct lobes, proximalmost with one seta, second and third each with two. Basis with row of short spinules on middle portion of inner margin, and group of three setae on inner margin distal third. Endopod sixsegmented. First segment partially fused to basis, bearing two subequal setae. Second segment with three subequal setae, third, fourth, and ®fth each with two setae; terminal segment with four subequal setae.

First leg (®gure 13) with three-segmented exopod, and two-segmented endopod, coxa with plumose seta on internal margin, reaching proximal margin of ®rst endopod segment. Basis with a cluster of long, thin setae on outer margin. Second, third and fourth legs (®gures 14±16) with three-segmented 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;2,2,3 leg 3 0±1 0±0 I±1;I±1;I,3,3 0±1;0±2;2,2,3 leg 4 0±1 0±1 I±1;I±1;I,3,3 0±1;0±2;2,2,3

Leg 5 (®gure 17). Coxa with small spiniform lateral process. Basis with inner margin straight, with short, slender lateral seta barely reaching one-quarter length of ®rst exopod segment. Endopod two-segmented, 5.3 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 one short, subterminal seta. Spine 1.6 times as long as seta. Distal margin of endopodal tip rounded, covered by short, 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 small teeth on mid margin, those on inner margin are longer and more closely set. Third exopod segment reduced, barely distinct from second, represented by short, strong, spiniform process near usual spine of second segment.

Male (®gure 4). Length excluding furcal rami: 2.18Ô 0.04, range = 2.1±2.22 mm. Body relatively slender, with typical diaptomid shape. Rostrum as in ®gure 22. Pediger 4 wider than succeeding somite; pediger 5 tapering posteriorly, asymmetrical, with reduced lateral wings, less developed than in female. Right wing (®gure 7) pointing outwards, posterior end reaching almost to distal third of ®rst urosomite, with terminal mamilliform spine. Left wing reduced, with small naked lobe, pointing posteriorly. Urosome symmetrical, ®ve-segmented. First urosomite with posterior spine on right margin, with rounded process on left margin. Relative lengths of urosomites: 15.4 5 26.3 5 20.3 5 21.4 5 16.6 = 100. Caudal rami as for female. Only inner margin setose.

Antennules (®gure 5) slightly longer than in female, last segment surpassing posterior margin of caudal rami. Right antennule geniculated between segments 18 and 19, with one seta on segments 3±7; large setae on segments 3, 7 and 14. Aesthetascs on segments 1, 5 and 12. 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 proximal third of next segment, that on latter reaching beyond middle of segment 12; segment 12 with one seta and a short spine; 13 with one seta and one large stout spine, its base almost as wide as bearing segment, spine reaching beyond middle of segment 14. Segment 14 with one spine, a short seta plus one long seta reaching middle of segment 16; segment 15 with one spine and two setae; 16 with broad-based spiniform process pointing distally on outer margin, with one spine borne near its base, and long seta on distal margin; 17 with one seta, and spine-like process closely adjacent to inner margin of segment; 18 and 19 with spiniform processes on inner margin. Segment 20 (®gure 20) with short, wide knoblike process on distal inner margin, almost reaching halfway along next segment (®gure 5), and bearing three setae, two inserted in middle and one distally. Segment 21 with one seta. Terminal segment relatively short, with three apical large setae plus two subapical. Setation of left antennule, mouthparts and swimming legs as for female.

Left leg 5 (®gures 18, 19) short, barely reaching middle portion of inner margin of right ®rst exopod segment. Coxa with large, basally wide spiniform anterior process on outer margin. With a strong cuticular, heavily chitinized process near inner anterior margin. Basis with short, subterminal lateral outer seta, not reaching distal end of bearing segment. First exopod segment longer and wider than second. Second with large basal, inner pad covered with long ®ne setules, plus two distal pad-like processes, one terminal, digitiform, with terminal row of low tooth-like spines arranged in a semicircular pattern, the other a rounded pad with tiny spines over its surface; between these, a spine-like projection with curved end, covered with spinules along its longitudinal axis. Endopod one-segmented, reaching beyond two-thirds of second exopod segment, tip covered with stiOE setules.

Right leg 5 (®gure 19). Coxa with usual spinous process on distal portion of external margin, with two cuticular processes on anterior surface. Basis about three times as long as ®rst exopod segment with faint cuticular ridge on anterior surface, and an additional rounded protuberance on proximal portion of inner margin. Outer margin of ®rst exopod segment straight and smooth, inner margin without lateral process; segment with tongue-like chitinous process on distal margin, projecting into succeeding segment. Second exopod segment more than three times as long as ®rst, with a low rounded protuberance on inner margin. Lateral spine slender, slightly curved, almost as long as bearing segment, with a row of low spinules along mid portion of inner margin, extending beyond distal third of segment. Terminal claw relatively slender, curved, tapering gradually from enlarged base, about 1.7 times longer than exopod segments 1 and 2 combined, without teeth on inner margin, but with very ®ne irregularities mainly along its middle portion. Right endopod reduced to a single lobe, short, one-segmented, barely reaching proximal margin of ®rst exopod segment, without suture on posterior surface, with a row of setules on tip.

Colour. Some individuals show an intense blue coloration; in others the cephalothorax has a light violet tone and the rest of the body is blue. Most specimens become discoloured after ethanol preservation.

Etymology. The species is named `maya ’ by apposition and refers to its occurrence at one of the main archaeological sites of the ancient Mayan culture in Campeche.

Remarks

Mastigodiaptomu s maya is distinguished by its large size and by diOEerences between the spiniform processes on segments 13 and 14 of the right male antennule. These spines are commonly subequal in length in the genus. Another distinguishing character is the spiniform sensilla of the basipodite of leg 5 of the female, which is very short, not spatulate as is typical in most species of Mastigodiaptomus . However, these diOEerences are not su cient to justify the erection of a new genus.

The new species can be distinguished from its congeners by a combination of distinctive characters: the right posterior corner of the female double-genital somite is slightly produced posteriorly, the female leg 5 endopodite is short, the basipodite of the male right leg lacks the hyaline process which is present in all the other species of Mastigodiaptomus . The spine on the male right antennule segment 13 is very large, and that of segment 14 is much reduced, whereas both tend to be subequal in other species of the genus. A similar condition is present in M. purpureus (see Wilson, in Wilson and Yeatman, 1959), but in this species the spine on segment 13 is shorter. Another distinctive feature is the rounded shape of the protrusion on the antepenultimate segment of the same antennule. This process is acute or fang-shaped in most of the other species of the genus. A striking feature of this species is its large size (2.4 mm). Most other species of Mastigodiaptomus range from 1±1.7 mm. The only exception is M. purpureus (2.5 mm).