Neotachidius parvus, Huys & Ohtsuka & Conroy-Dalton & Kikuchi, 2005
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publication ID |
0024-4082 |
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persistent identifier |
https://treatment.plazi.org/id/03978792-FFC0-1B38-FF5E-185DFBA186AF |
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treatment provided by |
Diego |
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scientific name |
Neotachidius parvus |
| status |
sp. nov. |
NEOTACHIDIUS PARVUS SP. NOV.
Synonym: Tachidius (Neotachidius) triangularis Shen & Tai, 1963 sensu Song & Chang (1995) [partim].
Type material: Holotype ♀ ( NMNH reg. no. 251942) dissected and mounted on slides . Paratypes deposited in NMNH are 2 ♀♀ (reg. no. 251943–944) and 3 ♂ (reg. nos. 251945–947) dissected and mounted on slides; 20 ♀♀ and 20 ♂♂ in alcohol (reg. no. 251973). Paratypes deposited in NHM are 1 ♀ dissected on ten slides (reg. no. 2003.808), 1 ♂ dissected on seven slides (reg. no. 2003.809); 24 ♀♀ and 13 ♂♂ in alcohol (reg nos. 2003.771–807)
Type locality: Stn five in a small river discharging into Kwangyang Bay, South Korea (34∞57.1¢N, 127∞36.4¢E), salinity 11.10‰ (see Ohtsuka et al., 1992) .
Additional material: (1) Taehwa River estuary, Ulsan, South Korea; leg. C.Y. Chang, 31 January 1987; 1 ♀ and 1 ♂ in alcohol ( NHM reg. nos. 2003.812–813). (2) Jochean, Cheju Island, South Korea; leg. C.Y. Chang and S. J. Song, 27 October 1993; 2 ♀♀ in alcohol ( NHM reg. nos. 2003.810–811) .
Body length: ♀: 500 ± 30 Mm (N = 53); ♂: 450 ± 30 Mm (N = 53; based on paratypes).
Neotachidius parvus is closely related to N. coreanus and the description below is consequently restricted to differences only.
Description
Based on NHM paratypes (reg. nos. 2003.771–809).
Female: Spinules around posterior margin of cephalosome and somites bearing P2–P3 shorter than in N. coreanus ( Fig. 11A). Slight differences in fine surface spinulation of pedigerous somites as illustrated in Figure 11A. Rudimentary tergite of P1-bearing somite less well defined. Posterior margin of P4-bearing somite denticulate laterodorsally but smooth dorsally; dorsolateral spinules shorter than in N. coreanus . P5- bearing somite with spinules around lateroventral corner of pleurotergite; lateral surface spinules distinctly shorter and more blunt than in N. coreanus ( Fig. 11C).
Dorsal posterior margins of genital double-somite and free abdominal somites 2–3 denticulate instead of with long spinules ( Fig. 11A, C); spinules along ventral posterior margin of these somites shorter than in N. coreanus ( Fig. 11B). Paired spinule rows posterior to genital slit absent (compare with N. coreanus : Figs 1B, 2C); remaining two rows consisting of smaller spinules ( Fig. 11B, C). Genital field area less raised in lateral aspect ( Fig. 11C). Lateral surface ornamentation of genital double-somite less elaborate than in N. coreanus ( Fig. 11C). Anal somite with paired laterodorsal spinule rows but without spinules dorsally ( Fig. 13D). Anal operculum spinulose but spinules markedly shorter than in N. coreanus .
Caudal rami ( Figs 11B, 13D) slightly longer than wide but shorter than in N. coreanus ; armature and ornamentation essentially as in N. coreanus , except dorsolateral spinule row (arrowed in Fig. 10D) absent.
Antennule ( Fig. 12A) with short apical segment, only slightly longer than segment 6. Armature as in N. coreanus .
Antenna ( Fig. 12B) with spinule rows on abexopodal margin of basis and proximal endopod segment. Exopod distinctly 2-segmented; exp-1 shortest, with one long slender plumose seta; exp-2 with short smooth seta fused to lateral margin and two unequal plumose setae apically; spinular ornamentation around outer distal corner of exp-2 more elaborate than in N. coreanus . Distal endopod segment laterally with one unipinnate spine in proximal third and one smooth seta plus one unipinnate spine in middle third. Apical armature of enp-2 consisting of one unipinnate spine and four geniculate setae; longest geniculate seta with few spinules and fused at base to short naked seta; segment with various spinule rows and surface frills as figured.
Mandible. Palp with similar armature as in N. coreanus . Endopod with spinule row on anterior surface (arrowed in Fig. 5D).
Maxillule, maxilla and maxilliped as in N. coreanus .
P1 ( Fig. 12C). Most spinules on anterior surface of praecoxa and coxa and around distal margin of basis distinctly shorter than in N. coreanus . Inner basal seta more slender and longer, reaching beyond distal margin of enp-2. Rami as in N. coreanus except for inner distal element of enp-3 (arrowed in Fig. 12C) being long, plumose and setiform instead of pinnate and spiniform.
P2–P4 ( Figs 12D, 13A) as in N. coreanus except for (a) intercoxal sclerites with spinules anteriorly but not posteriorly; (b) long spinules on anterior surface of coxa absent; (c) spinules around distal margin of basis uniform in size; (d) posterior spinules on P4 coxa absent, and (e) P4 exp-3 with only one spinule row on posterior surface.
P5 ( Fig. 13C) longer and with outer concavity less pronounced than in N. coreanus ; about 1.40 times as long as maximum width; spinule pattern on anterior surface and along inner margin different (as illustrated in Fig. 13C); apical seta smooth instead of plumose; spines more slender than in N. coreanus .
Male. Sexually dimorphic in size, urosome ornamentation, antennule, P2 endopod, P3 exopod, P5 and P6.
Antennule ( Figs 14A, 15A–D) as in N. coreanus except for two differences on segment 6: (a) multicuspidate process ( Figs 14A, 15B; b in Fig. 15D) less pronounced and typically with five cusps, and (b) cylindrical process adjacent to longitudinally ribbed element (a in Fig. 15D) with two spinulose elements (ventralmost smooth in N. coreanus ; arrowed in Fig. 14D). Armature formula: 1-[1 pinnate], 2-[1 pinnate], 3-[6 bare +5 pinnate], 4-[6 bare +2 pinnate + ae], 5-[2 pinnate], 6-[8 bare +4 pinnate +1 striated element + (1 + ae)], 7-[12 +2 modified + acrothek].
P2 endopod ( Figs 13B, 16B). Enp-1 comparatively longer than in N. coreanus with outer distal corner not spinous; spinules along outer margin longer, those of inner distal corner shorter than in N. coreanus . Middle segment transversally enlarged but markedly shorter than in N. coreanus ; outer margin distinctly convex; both inner setae markedly shorter than in N. coreanus . Enp-3 small ( Fig. 16B), with row of long setules on anterior surface covering spinous apophysis of enp-2; outer distal seta strongly reduced, represented by a short and blunt, basally fused element (arrowed in Fig. 13B).
P3 exopod ( Fig. 12E) more robust than in N. coreanus , with exp-2 being distinctly shorter; inner setae of exp-3 shorter. P3 endopod about as long as in N. coreanus but enp-3 proportionally longer.
P5 ( Fig. 14B, C) medially fused with medial incision more pronounced than in N. coreanus ; each with three serrate spines and two naked setae; middle and inner spines shorter than in N. coreanus ; anterior surface spinules absent; spinules around midventral distal margin coarser than in N. coreanus .
P6 ( Fig. 14B, C) symmetrical; each member with two serrate spines and naked outer basal seta; spinules around medial distal margin uniform in size and coarser than in N. coreanus .
Ornamentation of urosome essentially as in N. coreanus except for size of spinules ( Fig. 14B, C).
Variability: The females from Cheju Island were larger in size (575–579 Mm).
Etymology: The specific name is derived from the Latin parvus , meaning small, and alludes to the small size of the present species.
| NMNH |
Smithsonian Institution, National Museum of Natural History |
| NHM |
University of Nottingham |
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.