Leptotachidia apousia, Kim, Jong Guk, Yu, Ok Hwan & Lee, Jimin, 2019

Kim, Jong Guk, Yu, Ok Hwan & Lee, Jimin, 2019, Description of two deep-water copepods of the genus Leptotachidia Becker from the northwestern Pacific (Harpacticoida, Pseudotachidiidae), ZooKeys 873, pp. 133-153 : 137-140

Leptotachidia apousia sp. nov. Figs 5 , 6 , 7

Type locality.

Abyssal basin of the Northwest Pacific Ocean (31°58'42.9"N, 155°53'42.7"E), 5482 m depth ( Fig. 1 ).

Material examined.

Holotype (adult female) dissected and mounted on 11 slides (cat. no. MABIK CR00246485) collected from the type locality on 1 November 2017.

Etymology.

The species name is derived from the Greek απουσία, apousia , meaning absence, lacking, and alludes to the absence of an inner seta in P3 enp-3. It is in the nominative singular. Gender feminine.

Description of female.

Total body length about 608 μm, greatest width about 99 μm measured at the middle of cephalothorax. Habitus ( Fig. 5A, B ) slightly damaged (thoracic legs detached), as in L. senaria sp. nov., but slightly narrower; ornamentation of somites slightly different from L. senaria sp. nov. in number and position of both sensilla and pores.

Cephalothorax ( Fig. 5A, B ) about 1.2 times as long as wide in dorsal view, as long as 18 % of total body length. Pleural areas of free pedigerous somites more weakly developed than in L. senaria sp. nov. Hyaline frills of second to fourth pedigerous somites smooth.

Urosome ( Fig. 5 A–C ) about 1.1 times as long as prosome. With deeply incised hyaline frills as in L. senaria sp. nov. except for penultimate somite with weakly incised hyaline frill ventromedially. Genital double-somite divided by lateral and ventral ridges, but fused dorsally and ventrolaterally. Genital slit ( Fig. 5G ) covered by single plate with two minute setae, inner about twice as long as outer, and one row of minute spinules on both sides; copulatory pore posterior to genital slit; seminal receptacles smaller than in L. senaria sp. nov. Pseudoperculum ( Fig. 5A ) on penultimate somite slightly wider than in L. senaria sp. nov. Anal somite small, with one pair of sensilla, one large and two small lateral pores, and one large and one small ventral pores; anal opening fringed with three pairs of setular rows.

Caudal rami ( Fig. 5 A–C, E, F ) slightly shorter than in L. senaria sp. nov., about 1.4 times as long as greatest width, with one large pore anteriorly and posteriorly; ventral spinule rows present near base of seta III and seta V, and closed to inner distal corner; armature as in L. senaria sp. nov. except for seta V about 2.8 times as long as seta IV.

Rostrum ( Fig. 5D ) as in L. senaria sp. nov. except for a pair of aesthetasc-like sensilla on distal margin closer to each other than in L. senaria sp. nov.

Antennule ( Fig. 6A ) as in L. senaria sp. nov. except for arrangement of elements on segments II, IV and V; segment II 1.1 times as long as wide, with one plumose, one bare and seven pinnate setae; segment IV with two pinnate and four weakly pinnate setae, and one aesthetasc fused to adjacent long weakly pinnate seta; segment V with one weakly bipinnate, two plumose, five spinulose and six bare setae; with distal acrothek composed of one aesthetasc and adjacent two spinulose setae, and one densely opaque bulbous appendage (Brodskaya organ). Armature formula as follows: 1-[1], 2-[9], 3-[8], 4-[5 + (ae + 1)], 5-[12 + Brodskaya organ + acrothek].

Antenna ( Fig. 6B ) as in L. senaria sp. nov. except for exp-1 with only one plumose seta.

Mandible ( Fig. 6C ) as in L. senaria sp. nov. except for absence of a rudimentary seta on lateral margin.

Maxillule ( Fig. 6D ), maxilla ( Fig. 6E ), and maxilliped ( Fig. 6F ) as in L. senaria sp. nov.

General shape of P1-P4 ( Fig. 7 A–D ) as in L. senaria sp. nov. except for setal armatures of P3 exp-3 and P2-P4 enp-3; P3 exp-3 ( Fig. 7C ) with three outer spines; P2 enp-3 ( Fig. 7B ) with one small bipinnate outer spine, one long apical seta with outer spinules and inner setules, and one small plumose apical seta; P3-P4 enp-3 ( Fig. 7 C–D ) with one small pinnate outer spine and one long bipinnate apical seta; inner margin of P3 enp-3 modified and dented as in L. senaria sp. nov. (indicated by arrowhead in Fig. 7C ).

P1-P4 armature formulae:

General structure of P5 ( Fig. 5H ) as in L. senaria sp. nov. except for setal armature; distal margin with one finely serrate and four coarsely serrate spines.

Male.

Unknown.

Figures

Figure 1. Map showing the sampling station.

Figure 5. Leptotachidia apousia sp. nov., female A habitus, dorsal B habitus, lateral C urosome, ventral D rostrum, dorsal E caudal ramus, dorsal F caudal ramus, ventral G genital field, ventral H P 5, anterior.

Figure 6. Leptotachidia apousia sp. nov., female A antennule B antenna C mandible D maxillule E maxilla F maxilliped.

Figure 7. Leptotachidia apousia sp. nov., female A P 1, anterior B P 2, anterior C P 3, anterior (arrowhead showing the modified and dented inner margin) D P 4, anterior.