Pseudacanthocanthopsis secunda ( Yamaguti and Yamasu, 1960 )

Maran, B. A. Venmathi, Tang, Danny, Madinabeitia, Ione, Izawa, Kunihiko, Ohtsuka, Susumu, Jang, Duck Jong & Nagasawa, Kazuya, 2013, Redescription of Pseudacanthocanthopsis secunda (Yamaguti and Yamasu, 1960) (Copepoda: Chondracanthidae) parasitic on marine fishes from the Seto Inland Sea, Japan and the East China Sea off Japan and Korea, Journal of Natural History 47 (5 - 12), pp. 553-562 : 555-558

Pseudacanthocanthopsis secunda ( Yamaguti and Yamasu, 1960)

( Figures 1–4 )

Pseudacanthopsis secunda Yamaguti and Yamasu, 1960: 137 .

Pseudacanthocanthopsis secunda: Yamaguti, 1963: 293 ; Ho, 1970: 192; Ho and Kim, 1995: 42; Østergaard, 2003: 144.

Material examined

Thirty adult females and two adult males (each male attached to the egg sac of a separate female) [only 20 females deposited from this collection (NSMT-Cr 21844)], ex gill filaments of 10 A. lineatus, Seto Inland Sea , off Osakikami-jima Island , Hiroshima Prefecture, Japan, 16 September 2010 ; 103 adult females (75 mature, 28 immature) and 25 adult males (19 males each attached to genito-abdomen of a mature adult female; two males each attached to genito-abdomen of an immature adult female; two males each attached to the egg sac of a separate female; two detached males stored in a separate vial) (NSMT-Cr 21845), ex branchial cavity wall of six A. lineatus , northern East China Sea, off Kyushu, Japan, 23–24 August 1982 ; six adult females (NIBRIV0000244191), ex gill filaments of three A. lineatus , northern East China Sea, off Yeosu Dolsan, Jeollanam Province, Korea, 30 August 2011 ; two adult females (NSMT-Cr 21846), ex gill filaments of two T. poecilonotus, Seto Inland Sea , off Osakikami-jima Island , Hiroshima Prefecture, Japan, 16 September 2010 ; one adult female (NSMT-Cr 21847), ex gill filament of P. major, Seto Inland Sea , Hiroshima Bay , Hiroshima Prefecture, Japan, 15 July 2008 .

Description

Adult female. Body ( Figure 1A,B ) 1.28 (1.17–1.36) mm long (from anterior margin of head to distal end of posterior processes on trunk) (n = 4), divided into head, neck and trunk. Head composed of cephalothorax (incorporating first pediger), wider than long [379 (350–400) × 729 (687–750) µm], with two pairs of rounded processes along anterior margin and another pair lateral to oral appendages. Neck region short, composed of second pediger. Trunk large, reniform, wider than long [0.86 (0.80–0.92) × 1.13 (1.05–1.18) mm], with pair of posterolateral processes. Genito-abdomen ( Figure 1C ) divisible as two tagmata; anterior tagma (genital somite) longer than posterior tagma (abdominal somite), with ventral pair of genital apertures; posterior tagma wider than long, with pair of caudal rami; latter wider proximally, bearing four setae (usual inner knob not observed).

Antennule ( Figure 1D ) unsegmented, elongated, with basal group of minute setae, four setae at distal two-thirds, three subapical setae and eight apical setae. Antenna ( Figure 2A ) three-segmented, composed of coxobasis and two-segmented endopod; coxobasis short, unarmed but ornamented with surface pits along medial margin; proximal endopodal segment forming powerful uncinate claw and ornamented with surface pits along two-thirds of claw and fine striations near tip; atrophied tip (distal endopodal segment) with four unequal apical setae. Labrum ( Figure 2B ) wider than long, naked. Mandible ( Figure 2C ) one-segmented, with apical falcate blade armed with 13–17 teeth along convex margin and double row of teeth (four to six inner teeth and three to six outer teeth) along concave margin (n = 5). Paragnath not observed. Maxillule ( Figure 2D ) unilobate, sigmoid, with one inner and two apical elements. Maxilla ( Figure 2E ) two-segmented, composed of syncoxa and basis; syncoxa robust, unarmed; basis forming claw-like process, armed with two unequal basal setae. Maxilliped ( Figure 2F ) three-segmented, composed of short syncoxa, elongate basis and short terminal claw (endopod); all three segments unarmed.

Leg 1 ( Figure 2G ) large, modified, biramous, with rami fused proximally to protopod; latter laterally inflated, with outer naked seta; exopod one-segmented, rounded, with five to six naked setae (n = 6); endopod one-segmented, subquadrate, with three or four naked apical setae (n = 6). Leg 2 ( Figure 2H ) minute, biramous; protopod with outer naked seta; exopod one-segmented, with four or five naked setae (n = 4); endopod one-segmented, with three or four naked setae (n = 4).

Adult male. Body ( Figure 3A,B ) 303 (280–330) µm long (excluding caudal setae) and 110 (105–115) µm wide (n = 3), divided into large cephalothorax (incorporating first pediger), short second pediger and long genito-abdomen; latter with pair of opercula, each covering genital aperture and bearing two minute lateral setae ( Figure 3B ). Caudal ramus ( Figure 3C ) subquadrate, bearing two outer, one apical and two inner setae (usual small inner knob not observed).

Antennule ( Figure 3D ) three-segmented; first segment longest, bearing 10 setae; second segment shortest, bearing four setae; third segment bearing eight setae and two aesthetascs (seta and aesthetasc on anterodistal corner shares common base). Antenna ( Figure 3E ) three-segmented, composed of coxobasis and two-segmented endopod; coxobasis short, with small digitiform element along inner margin; proximal endopodal segment forming powerful uncinate claw, bearing two spiniform setae and one digitiform element along inner margin; atrophied tip (distal endopodal segment) with one large claw, one small seta and one small claw apically. Labrum (not figured) similar to that of female. Mandible ( Figure 3F ) with 12–13 teeth on convex side and no teeth on concave side (n = 2) of blade. Maxillule ( Figure 3G ) lobate, with two apical elements. Maxilla ( Figure 3H ) as in female, except with larger setae and three or four apical teeth (n = 4) on basis. Maxilliped ( Figure 3I ) three-segmented; first two segments elongate and naked; third segment forming uncinate claw.

Leg 1 ( Figure 4A ) biramous, with unimerous exopod and bimerous endopod; protopod with outer naked seta; exopod with five spines (each with accessory flagellum at tip) and three naked setae; first endopodal segment unarmed; second endopodal segment with four apical naked setae. Leg 2 ( Figure 4B ) biramous, with one-segmented rami; protopod with one outer naked seta; exopod with three spines (each with accessory flagellum at tip) and four naked setae; endopod with four apical naked setae.

Figures

Figure 1. Pseudacanthocanthopsis secunda (Yamaguti and Yamasu, 1960), adult female. (A) Habitus, dorsal; (B) same, ventral; (C) genito-abdomen, ventral; (D) left antennule, including enlarged view of distal end, ventral. Scale bars: A, B = 300 µm; C = 50 µm; D = 100 µm.

Figure 2. Pseudacanthocanthopsis secunda (Yamaguti and Yamasu, 1960), adult female. (A) Left antenna, with enlarged view of distal end of atrophied tip and surface ornamentation on coxobasis and endopod, anterior; (B) labrum, ventral; (C) left mandible, dorsal; (D) right maxillule, dorsal; (E) right maxilla, posterior; (F) left maxilliped, posterior; (G) right leg 1, ventral; (H) left leg 2, ventral. Scale bars: A, B, E, F = 20 µm; C, D, H = 10 µm; G = 50 µm.

Figure 3. Pseudacanthocanthopsis secunda (Yamaguti and Yamasu, 1960), adult male. (A) Habitus, dorsal; (B) same, lateral; (C) genito-abdomen, ventral; (D) left antennule (arrowhead indicates aesthetasc), dorsal; (E) left antenna, posterior; (F) right mandible, ventral; (G) right maxillule, posterior; (H) right maxilla, posterior; (I) right maxilliped, lateral. Scale bars: A, B = 100 µm; C = 50 µm; D, I = 20 µm; E, H = 10 µm; F, G = 5 µm.

Figure 4. Pseudacanthocanthopsis secunda (Yamaguti and Yamasu, 1960), adult male. (A) Right leg 1, anterior; (B) left leg 2, anterior. Scale bars: A, B = 20 µm.