Rhyncholagena paraspinifer, Ma, Lin & Li, Xin-zheng, 2018

Ma, Lin & Li, Xin-zheng, 2018, First report of the genus Rhyncholagena Lang, 1944 from the South China Sea, with the description of a new species (Crustacea, Copepoda, Harpacticoida, Miraciidae), ZooKeys 805, pp. 15-31 : 17-22

Rhyncholagena paraspinifer sp. n. Figs 1, 2, 3, 4, 5, 6, 7, 8

Type locality.

South China Sea, sampling locality (18°35.81'N, 110°43.44'E), 30.1 m depth, soft mud, collected by JB Wang, LM Shuai, J Zhou, QX Han and L Ma, 19 October 2007.

Material examined.

Holotype 1♀ dissected on three slides (MBM189117). Paratypes: 1♀ on one slide (MBM189079), 1♂ (MBM189080) on one slide and 6 ♀♀, 4 ♂♂ (MBM189081) in 70 % ethanol. Allotype1 ♂ on two slides (MBM189118). All paratypes and allotype were collected from the type locality.

Description.

Female (based on holotype and one paratype).

Habitus (Figs 1A, 2A, B). Total length of holotype female (body plus caudal rami, excluding caudal setae): 710µm. Body long and cylindrical, widest at head, tapering posteriorly. Prosome four-segmented: cephalothorax (including two thoracic somites bearing maxilliped and P1) and three articulated somites bearing P2 to P4; all prosomites with row of spinules on posterior margins, respectively. Urosome five-segmented, comprising P5-bearing somite, genital double-somite, and three abdominal somites. Urosomites with rows of hyaline frills on dorsal edge respectively, excluding penultimate urosomite; urosomites ornamented with hyaline frills on ventral side. Genital field (Figure 2B) located rather proximally, genital apertures situated ventrally, covered by reduced P6 on both sides. Anal somite slightly cleft in posterior, unornamented, 0.4 times as long as wide; anal operculum narrow, unornamented. Caudal ramus almost as long as broad, carrying six setae: two outer setae, smooth; two medial setae, well developed; two inner setae, slender.

Rostrum (Figs 2A, 4A) demarcated from cephalothorax, elongated, almost triangular with pair of sensillae on each side of rostrum approx. 1/3 from acute tip.

Labrum (Figure 2C) somewhat hexagonal, with toothed fringe at tip.

Antennule (Figure 3A) with eight segments; first segment and second segment the longest; aesthetasc on fourth segment reaching beyond distal end of terminal segment. Armature formula: 1-[1], 2-[7], 3-[7], 4-[3+aes], 5-[1], 6-[1], 7-[3], 8-[5].

Antenna (Figure 3B) biramous, small coxa without ornamentation. Allobasis elongated, about three times as long as coxa, with spinules on lateral margin. Exopod two-segmented, with 1:1.2 setae; exp-1 long, almost two times as long as exp-2. Endopod one-segmented, with row of spines on inner and out edge, respectively; lateral armature consisting of three smooth setae; apical armature consisting of six elements: four geniculate setae, two slender and smooth setae.

Mandible (Figure 3C) gnathobase with eight large, smooth teeth and one seta, outmost teeth combined with seta on the base. Basis with four rows of spinules and three setae. Exopod one-segmented, with one lateral seta, two terminal setae. Endopod one-segmented, with two lateral setae, four terminal setae.

Maxillule (Figure. 4B). Praecoxa and coxa demarcated. Arthrite with nine apical spines, two juxtaposed setae on surface. Coxal endite with two setae. Basis with four naked setae. Endopod one-segmented, with four naked setae. Exopod one-segmented, with two setae.

Maxilla (Figure 4C). Syncoxa with spinules along outer margin; with three endites bearing three, two, two setae, respectively. Allobasis with one claw and one seta. Endopod one-segmented, with four setae, respectively.

Maxilliped (Figure 4D). Subchelate. Syncoxa with several spinules along inner and distal margins, two setae located at distal margin. Basis with row of spinules and one seta on inner margin. Endopod one-segmented; with two setae and one strong claw.

P 1 (Figure 5A). Coxa with row of spines on anterior surface, row of spinules along outer margin. Basis bearing one outer plumose seta and one strong inner spinulose spine, terminal margin with spinules, surface with setules. Exopod three-segmented, short, reaching to nearly 4/5 length of enp-1; outer margins of each segment ornamented with spinules; inner margins of exp-2 and exp-3 with setules; exp-2 with one plumose seta; exp-3 with two geniculate setae, two spinulose spines and one smooth spine. Endopod three-segmented, outer margins of each segment with spinules;enp-1 elongated, 1.8 times as long as enp-2 plus enp-3, inner margin with setules and one plumose seta; enp-2 short, with one inner seta; enp-3 longer than exp-2, approx. twice as long as enp-2.

P2-P3 (Figs 5B, 6A). Intercoxal sclerites approximately triangular, with two distal (or apical) projections. Coxae with row of spines on outer margins. Basis with rows of spines on anterior margins. Exopods and endopods three-segmented, outer margins of each segment ornamented with spinules; endopod nearly as long as exopod.

P4 (Figure 6B) Intercoxal sclerites almost quadrate, with two distal blunt projections. Coxa of almost rectangular shape with two rows of spinules on anterior surface. Basis with row of spines on anterior margin. Exopods and endopods three-segmented, endopod shorter than exopod. Setal formulae of female P1-P4 as follows:

Right and left P5 (Figure 7C) not fused medially, baseoendopod and exopod separated. Baseoendopod reaching nearly to 1/5 length of exopod; with two plumose and three spinulose setae, second innermost one longer than others. Exopod nearly rectangular, 1.3 times as long as greatest width, ornamented with one spinulose and four naked setae, distalmost one longest.

Male based on allotype and one paratype differs from female as follows:

Body (Figs 1B, 7A) slightly shorter than female holotype, total length of allotype male (body plus caudal rami, excluding caudal setae): 610 µm. Urosome (Figure 7B) six-segmented, genital somite and the first abdominal somite separate, urosomites with rows of small spinules except penultimate urosomite. Caudal ramus as long as broad, with six setae.

Antennule (Figure 8A) nine-segmented, haplocer. Armature formula: 1-[1], 2-[8], 3-[2], 4-[6+aes], 5-[1], 6-[3], 7-[1], 8-[2], 9-[4], geniculation between sixth and seventh segments.

Antenna, mandible, maxillule, maxilla, maxilliped, P3 and P4 similar to female.

P1 (Figure 8B). Coxa with four rows of spines on anterior surface and inner margin. Basis bearing one fingerlike spine and two spinous projections on inner margin; exp-1 without spines on outer margin. Other characters as in female.

P2 with protopod and exopod as in female holotype. Endopod (Figure 8C) two-segmented; enp-1 with one slender inner seta; enp-2 modified as common in genus, with two slender setae on inner margin; one seta and one spinous spine on distal margin; one stout spine on outer margin.

P5 (Figure 8D) baseoendopod unseparated, with two spinous spines, reaching beyond the end of the exopod; exopod with denticles and four unequal setae, two pinnate, two slender and naked.

P6 (Figure 7B) reduced each to three setae inserted on distal margin of somite.

Variability.

Most morphological features are conservative, except body length. Body length of female varies from 450µm to 710µm and male from 460 µm to 610 µm.

Etymology.

The species is named according to many spines on the body.