Triconia denticula Wi, Shin & Soh, 2011

Cho, Kyuhee, Böttger-Schnack, Ruth, Kim, Woong-Seo & Lee, Wonchoel, 2019, Two new species of the similis-subgroup of Triconia Böttger- Schnack, 1999 (Copepoda, Oncaeidae) and a redescription of T. denticula Wi, Shin & Soh, 2011 from the northeastern equatorial Pacific, Zoosystema 41 (28), pp. 567-593 : 585-588

publication ID	https://doi.org/ 10.5252/zoosystema2019v41a28
publication LSID	urn:lsid:zoobank.org:pub:EB5117B3-49C3-4F42-B8A7-65C9F3841A5A
DOI	https://doi.org/10.5281/zenodo.4439445
persistent identifier	https://treatment.plazi.org/id/03FA87C0-FFE9-954A-FF1D-FB223979958F
treatment provided by	Felipe
scientific name	Triconia denticula Wi, Shin & Soh, 2011
status

Treatment

( Figs 10-12 View FIG View FIG View FIG ; Tables 2, 3)

Triconia denticula Wi, Shin & Soh, 2011: 590-595 , figs 2-4, 9A, B, F (♀).

TYPE LOCALITY. — East China Sea (south of Cheju Island)

MATERIAL EXAMINED. — East China Sea. 3 ♀; NIBRIV-0000838015-017; each dissected and mounted on 10 slides, respectively; all specimens collected from the northeastern equatorial Pacific Ocean; station BN09-02-01; 10°30’N, 131°20’W, 0-100 m; 21. VII.2009 by D. J. Ham.

DESCRIPTION

Female

Body length. 648-663 Μm, based on three specimens. Exoskeleton moderately chitinized. Prosome about 2.1 times length of urosome, excluding caudal rami 1.9 times urosome length including caudal rami.P2-bearing somite without conspicuous dorsoposterior projection in lateral aspect ( Fig. 10B View FIG ). Integumental pores on prosome as indicated in Fig. 10A View FIG . Pleural areas of P4-bearing somite with rounded posterolateral corners. One pair of secretory pores discernible on first postgenital somite ( Fig. 10D View FIG ).

Genital double-somite. 1.7 times as long as maximum width (measured in dorsal aspect) and about 2.1 times as long as postgenital somites combined; largest width measured just posterior to mid-level; lateral margins of genital double-somite sinuous anterior to level of maximum width, tapering posteriorly ( Fig. 10C View FIG ); dorsal and lateral surface ornamented with several rows of spinules ( Fig. 10C, D View FIG ); anterior part of genital double-somite protruding dorsally ( Fig. 10D View FIG ). Paired genital apertures located at about 2/5 of distance along genital doublesomite from anterior margin. Paired secretory pores on dorsal surface located at about 2/3 of distance along double-somite from anterior margin (arrowed in Fig. 10C View FIG ).

Anal somite. Slightly wider than long; slightly longer than caudal rami ( Fig. 10C View FIG ). Ornamentation as in T. komo n. sp. ( Fig. 10C, D View FIG ).

Caudal ramus. About 1.6 times as long as wide; with seta VII slightly longer than half the length of seta IV and shorter than seta VI ( Fig. 10C View FIG ).

Antennule. 6-segmented, armature formula as for T. komo n. sp. ( Fig. 11A View FIG ).

Antenna ( Fig. 11B View FIG ). 3-segmented. Distal endopod segment with distal armature consisting of five curved setae, long naked (E), entire unipinnate (A), sparsely pinnate (B-D), setae A-D of graduated length with seta D shortest, and two slender bare setae (F+G), seta G shortest.

Labrum ( Fig. 11G, H View FIG ). With medial concavity between lobes covered anteriorly by single long hyaline lamella, lobes with dentiform processes around outer ventral margin more slender than in T. komo n. sp. Anterior surface with paired row of long setules and free margin of integumental pockets either side of median swelling ornamented with minute denticles. Posterior wall of medial concavity ornamented with four long sclerotized “teeth”, posterior surface with group of four secretory pores located on proximal part of each lobe ( Fig. 11H View FIG ).

Mandible ( Fig. 11C View FIG ). Maxillule ( Fig. 11D View FIG ) and maxilla ( Fig. 11E View FIG ) as for T. komo n. sp., with slight differences in surface ornamentation of coxa on mandible, and on syncoxa on maxilla.

Maxilliped ( Fig. 11F View FIG ). With ornamentation of syncoxa as figured. Basis with two bipinnate spiniform elements, nearly equal in length; fringe of long pinnules between distal seta and articulation with endopod, row of long spinules between proximal and distal setae; short transverse row of long setules near distal seta on anterior surface and additional longitudinal row near outer margin. Distal endopod segment (claw) with row of pinnules along proximal 2/3 of concave margin. Other elements as in T. komo n. sp.

Swimming legs 1-4 biramous ( Fig. 12 View FIG A-D). With armature and ornamentation as in T. komo n. sp. Intercoxal sclerites well developed, without ornamentation. Bases with short (P1, P2, P4) or very long (P3) outer seta.

Exopods. With ornamentation similar to T. komo n. sp. Distal spine almost equal in length to (P4) or shorter (P1, P2, P3) than distal exopod segment. Length of exopodal spine on exp-1 and exp-2 of P3 and P4 shorter than in T. komo n. sp. ( Fig. 12C, D View FIG ). Length ratio of outer spine on exp-1 relative to outer spine on exp-2 of P3 and P4 similar to T. komo n. sp. ( Table 3).

Endopods. Distal margin of P2-P4 produced into conical process ( Fig. 12 View FIG B-D), process with apical pore. Length data of spines on P2-P4 enp-3 of three specimens as shown in Table 2; length ranges of outer subdistal spine (OSDS) and outer distal spine (ODS) relative to distal spine (DS) given in Table 3.

P5 ( Fig. 10E View FIG ). Comprising long plumose outer basal seta and free unornamented exopod segment. Exopod longer than wide, bearing long slender seta (outer seta) ornamented with fine spinules along outer margin and a stout curved seta (inner seta), swollen at base and naked; outer seta about twice longer than inner seta.

P6 ( Fig. 10C View FIG ). Represented by operculum closing off each genital aperture, ornamented with spine and minute spinule (visible under light microscope).

Male.

Unknown

REMARKS

The original description of T. denticula by Wi et al. (2011) was based on female specimens from the south of Cheju Island of Korea (the East China Sea). As mentioned by Wi et al. (2011), this species closely resembles T. rufa in the form of the genital double-somite and the relative length of the outer basal seta and exopodal setae on P5, but differs: 1) in the absence of the dorsoposterior projection on the P2-bearing somite, which is present in T. rufa , a species of the conifera -subgroup; and 2) in the length to width ratio of P5 exopod, being 1.5 times longer than wide, whereas the length is 2.8 times longer than wide in T. rufa (Böttger-Schnack 1999) .

Specimens of T. denticula from the northeastern equatorial Pacific Ocean agree in almost all morphological characters with the original description of the species from Korean waters, based on the figures published by Wi et al. (2011). But they exhibited some variability in the length ratio of the prosome to urosome (including CR), with the Pacific specimens being larger (1.9:1) than those in the Korean waters (1.7:1); in the length to width ratio of the genital double-somite, being somewhat more elongate (1.7:1) than in the Korean waters specimens (1.5:1); in the length ratio of the caudal ramus to anal somite, which is shorter (0.6:1) in the Pacific specimens, compared to those in the Korean waters (about same length); and in body size, being somewhat smaller (648-663 Μm) in our study area than in the Korean specimens (660-710 Μm) (cf. Table 3).

Wi et al. (2011) mentioned that the exopodal spines on the first exopod segment in P3 and P4 of T. denticula are shortest among the species examined. However, in that study the definition of the proportional lengths of the exopodal spines is not sufficiently clear, as it can be misinterpreted where e.g. “[…] the tip of exopodal spine is reaching […]”. In order to provide more precise information, we calculated the length of the spine on exp-1 relative to the spine on exp-2 of P3 and P 4 in T. denticula from the Korean waters (paratype) in NIBR and from the Pacific Ocean. We also measured the lengths of the endopodal spines on P2-P 4 in specimens of the two areas. The resulting length ratios are given in Table 3. The recalculated ratio values for Korean specimens are largely overlapping with the range of values reported for specimens from the equatorial Pacific Ocean; only the ratio values for spines on P2 enp-3 are not completely overlapping and are tentatively higher for Korean specimens than for the open Pacific specimens.

T. denticula from the Korean waters described by Wi et al. (2011) exhibited numerous small scales on the surfaces of the genital double-somite, the anal somite and the caudal ramus, which were discerned by a using scanning electron microscope. Actually, these structures are hardly discernible with a light microscope due to their small size. In the Pacific specimens, the surface ornamentation of the genital double-somite was probably not fully discerned, but just on the dorsolateral part at half length of the genital double-somite. Also, T. denticula specimens from the two areas seemed to differ in the position of paired integumental pores on the dorsal surface of the genital double-somite, which are located at approximately 2/3 of distance along genital double-somite from anterior margin in the Pacific specimen and in the same vertical line with the genital apertures (cf. Fig. 9A, C View FIG ), while in the specimen from the Korean waters they were figured as being situated at about half the distance along the genital double-somite from anterior margin and much closer to the lateral margin of the double-somite ( Wi et al. 2011: fig. 3C). However, upon reexamination of the undissected female paratype of T. denticula (NIBRIV0000214678) during the present study, it was found that the position of paired integumental pores was similar to their position in the Pacific specimens.

The type material of T. denticula from the Korean waters which was loaned from the collections of NIBR and reexamined by the senior author of the present study turned out to be insufficient for taxonomic comparisons due to the following reasons:

1) The holotype sample (NIBRIV0000214676) nominated as: “ Holotype female dissected and mounted on 1 glass slide” ( Wi et al. 2011: 590) was found to contain an undissected female specimen of the dentipes -subgroup of Triconia on this slide.

2) The first paratype sample (NIBRIV0000214677) nominated as: “ 2 females dissected and mounted on 3 slides”, was in very poor condition and it was difficult to make out the contents on the slides. Recognizable contents were present in only one of the three slides.

3) The second paratype sample (NIBRIV0000214678) nominated as: “[…] 2 undissected females in 1 vial […]” ( Wi et al. 2011: 590) included one female of T. denticula and one female of a species of the dentipes -subgroup of Triconia .

In conclusion, a fundamental revision of the type material of T. denticula is required.