Odiliacletodes secundus, Gomez, Samuel, 2018

Gomez, Samuel, 2018, New species of Eurycletodes Sars, 1909 and Odiliacletodes Soyer, 1964 from the deep Gulf of California (Copepoda, Harpacticoida, Argestidae), ZooKeys 764, pp. 1-25 : 2

Odiliacletodes secundus sp. n.

Material examined.

One female holotype (ICML-EMUCOP-130207-02) dissected on seven slides; collected on February 13, 2007.

Type locality.

Southern Trough of Guaymas Basin, Gulf of California, Mexico, 27°07'N, 110°53.4'W, depth 1642 m.

Description of female.

Habitus (Figs 8A, 9A) cylindrical, without clear distinction between prosome and urosome. Total body length, 545 µm, measured from tip of rostrum to posterior margin of caudal rami.

Rostrum poorly-developed (Fig. 8A), fused to cephalothorax. I was unable to observe the two sensilla typically associated to the rostrum; the latter was probably folded downwards making the sensilla hard to see. The cephalothorax and free thoracic somites with smooth posterior margin (Figs 8A, 9A); with sensilla as shown, dorsal sensilla of P3-P4-bearing somites broken off in Fig. 8A; cephalothoracic integument with posterior rudimentary pleurotergite of fused P1-bearing somite.

Urosomites with smooth posterior margin (Figs 8A, 9A). P5-bearing somite with spinules along posterior margin dorsally, with some spinules laterally. Second and third urosomites fused dorsally and ventrally forming genital-double somite (Figs 8A, 10A), former division between both halves of genital-double somite indicated by dorsal transverse row of spinules close to posterior margin of anterior half (Fig. 8A) and by lateral chitinous rib (Fig. 9A); anterior half without spinules ventrally, posterior half with spinules along posterior margin dorsally and laterally (Figs 8A, 9A), ventrally with median spinular row flanked by two pores (Fig. 10A). Fourth and fifth urosomites (Figs 8A, 9A, 10A) covered with minute spinules dorsally, laterally and ventrally, with row of spinules close to posterior margin, of which, ventral spinules longer and stronger (Fig. 10A).

Anal somite as long as two preceding somites combined, square from dorsal and lateral view (Figs 8A, 9A), dorsal and lateral surface covered with minute spinules, ventral spinules less abundant and comparatively stronger (Fig. 10A), ventrally cleft medially, with spinules close to joint with caudal rami; anal operculum rounded, with small spinules along posterior margin (Fig. 8A, B), associated surface ornamentation, two pores (seemingly without sensilla).

Caudal rami oval from dorsal (Fig. 8A, B) and ventral view (Fig. 10A), about 1.3 times as long as wide, rectangular from lateral view (Fig. 9B); with spinular ornamentation as shown; with seven setae as follows (Figs 8B, 9B): seta I ventral to seta II, aligned, subequal in length; seta III situated ventrally close to outer margin; setae IV and V longest; seta VI arising at inner distal corner; dorsal seta VII tri-articulated at base, issuing from median dorsal process.

Antennule (Fig. 11A). Hepta-segmented; surface of segments smooth except for two rows of spinules on first segment; second and last segments longest; sixth segment with two bipinnate elements and one slender, seemingly bare, short seta; last segment with eleven elements, five of which bi-articulated, three pinnate elements and acrothek, the latter consisting of one aesthetasc and two setae fused basally. Armature formula as follows: 1(0); 2(8); 3(3); 4(2+[1+ae]); 5(1); 6(3); 7(8+[acro]).

Antenna (Fig. 11B). Allobasis with two sets of inner spinules as shown; without abexopodal seta. Exopod represented by single seta. Inner margin of free endopodal segment with longitudinal spinular rows; with two lateral inner spines subequal in length, and five distal elements (two spines, and two geniculate elements, of which outermost fused to one seta basally).

Mandible (Fig. 12A). Coxa without spinular ornamentation. Gnathobase with three serrated teeth and a single spine, and with a lateral seta. Palp bi-segmented; first (basal) segment with few subdistal spinules, with two basal setae, with one outer (exopodal) seta; second (endopodal) segment without surface ornamentation, with one lateral seta, and two pairs of distal setae fused basally.

Maxillule (Fig. 12B). Arthrite of praecoxa armed with six apical spines, one lateral element, and two surface setae. Other parts lost during dissection.

Maxilla (Fig. 12C). Syncoxa with outer spinules, and with two endites; proximal endite small, with one slender seta; distal endite with two slender setae and one strong spinulose element. Allobasis without spinular ornamentation, drawn out into strong pinnate claw, with one slender bare seta and a strong spinulose spine. Endopod represented by two setae.

Maxilliped (Fig. 12D). Subchelate. Syncoxa with several rows of spinules as shown, with two setae. Basis with longitudinal outer spinules, unarmed. Endopod uni-segmented, fused to claw, the latter with subapical spinules.

P1 (Fig. 13A). Coxa ornamented with spinules as shown. Basis with outer and inner seta, with spinules at base of outer and inner seta and between rami. Exopod and endopod subequal in length. Exopod tri-segmented; segments with outer and apical spinules as shown; first segment longest, second and third segments subequal in length; first segment without, second segment with one inner seta, third segment with two outer spines and two apical setae. Endopod bi-segmented; first segment about 1.3 times as long as wide, with outer and distal spinules on anterior face, and with some spinules on posterior face, with one inner seta; second segment elongate, 4 times as long as wide, and 1.7 times as long as first segment, with one inner element, two distal setae, and one outer spine.

P2-P4 (Figs 13B, 14A, B). Praecoxa with row of distal spinules. Coxa of P2 and P3 with one median row of spinules on anterior face, some spinules close to inner distal corner, and longitudinal row of spinules on anterior and posterior face, of P4 presumably as in P2 and P3. Basis with slender, long spinules along inner margin, with spinules between rami and at base of outer seta, the latter spine-like in P2, lost during dissection in P3 and P4. Exopod tri-segmented; first and third segment elongate, third segment slightly longer than first; second segment small; first segment with inner slender, and outer strong spinules; second and third segments with outer spinules only; first and second segments with one inner seta; third segment of P2 and P4 with two inner setae, two apical elements, and three outer spines, of P3 with three inner elements, two apical elements, and three outer spines, outermost apical element on third exopodal segment of P2-P4 spine-like. Endopod tri-segmented; of P2 and P3 as long as exopod, of P4 reaching insertion of subdistal inner seta; first and second segments subequal in length; second segment elongate, longest, with one inner and two apical setae, and one outer spine.

Armature formula of P1-P4 as follows:

P5 (Fig. 10B). Baseoendopod and exopod distinct. Baseoendopod with spinules at base of outer basal seta on short setophore, along inner and outer margin of endopodal lobe, and between innermost and adjacent endopodal seta; endopodal lobe reaching almost to middle of exopod, with three setae, of which outermost slightly longer, innermost and median seta subequal in length. Exopod elongated, triangular, 3 times as long as wide, with two outer, two apical and one inner seta, with inner and outer spinules as depicted, seemingly without tube-pores.

P6 (Fig. 10A) very reduced, each leg represented by one small seta; genital field situated proximally on first half of genital-double somite, with one aperture.

Male unknown.

Etymology.

The specific epithet from the Latin secundus , second, refers to the second species of Odiliacletodes reported to date. The name is an adjective in the nominative singular, gender masculine.