Acanthochondria alleni, Tang, Danny, Kalman, Julianne E. & Ho, Ju-Shey, 2010

Tang, Danny, Kalman, Julianne E. & Ho, Ju-Shey, 2010, Acanthochondria cyclopsetta Pearse, 1952 and A. alleni n. sp. (Copepoda; Cyclopoida; Chondracanthidae) from flatfish hosts of the U. S. A., with comments on the taxonomic position of A. zebriae Ho, Kim & Kumar, 2000 and A. bicornis Shiino, 1955 and the validity of Pterochondria Ho, 1973, Zootaxa 2657, pp. 18-32 : 24-29

Acanthochondria alleni n. sp.

( Figs 5–7 )

Type material. Holotype Ψ ( LACM CR2003-0490), allotype ɗ ( LACM CR2003-0490.1), and 4 paratypes [1 Ψ with attached ɗ ( LACM CR2003-0490.2); another Ψ with attached ɗ ( CMA 2010.04.0010)], ex branchial cavity wall of 1 Xystreurys liolepis Jordan & Gilbert (269.6 mm SL), from 61 m depth at Station 4006 (33°51΄N, 118°26΄E), Santa Monica Bay, Southern California Bight, eastern Pacific Ocean, U.S.A., 11 August, 2003.

Other material examined. Santa Monica Bay, Southern California Bight, eastern Pacific Ocean, U.S.A.: 5 Ψ, ex branchial cavity wall of 2 X. liolepis (140 and 180 mm SL), from 25 m depth at Station 2385 (33°54΄N, 118°27΄E), 4 August, 1998; 1 Ψ, ex branchial cavity wall of X. liolepis (190 mm SL), from 13 m depth at Station 2306 (33°56΄N, 118°27΄E), 4 August, 1998; 1 Ψ, ex branchial cavity wall of X. liolepis (130 mm SL), from 58 m depth at Station Z2 (33°54΄N, 118°31΄E), 18 November, 1998; 2 Ψ, ex branchial cavity wall of 1 X. liolepis (320 mm SL), from 60 m depth at Station C9a (33°51΄N, 118°26΄E), 18 November, 1998; 3 Ψ, ex branchial cavity wall of 2 X. liolepis (150 and 220 mm SL), from 56 m depth at Station C6 (33°55΄N, 118°32΄E), 23 November, 1998; 8 Ψ [6 are deposited ( LACM CR 1999-052.1)], ex branchial cavity wall of 2 X. liolepis (130 and 150 mm SL), from 58 m depth at Station Z2 (33°54΄N, 118°31΄E), 11 May, 1999; 16 Ψ (15 with attached ɗ) [15 Ψ and 14 ɗ are deposited: 2 Ψ each with attached ɗ ( LACM CR2003-0490.3 and CR2003-0490.5); 13 Ψ (12 with attached ɗ) ( CMA 2010.04.0 0 11‒2010.04.0015)], ex branchial cavity wall of 7 X. liolepis (173.9–218.5 mm SL), from 61 m depth at Station 4006 (33°51΄N, 118°26΄E), 11 August, 2003; 2 Ψ each with attached ɗ ( CMA 2010.04.0018), ex branchial cavity wall of 1 X. liolepis (170.8 mm SL), from 61 m depth at Station 4150 (33°52΄N, 118°28΄E), 11 August, 2003; 1 Ψ, ex branchial cavity wall of X. liolepis (166.7 mm SL), from 44 m depth at Station 4185 (33°59΄N, 118°48΄E), 21 August, 2003; 2 Ψ each with attached ɗ, ex branchial cavity wall of 1 X. liolepis (166.7 mm SL), from 45 m depth at Station 4185 (33°59΄N, 118°48΄E), 21 August, 2003; 1 Ψ with attached ɗ, ex branchial cavity wall of X. liolepis (190.7 mm SL), from 53 m depth at Station 4230 (33°53΄N, 118°29΄E), 4 September, 2003.

Oceanside Shelf, Southern California Bight, eastern Pacific Ocean, U.S.A.: 2 Ψ each with attached ɗ ( CMA 2010.04.0011), ex branchial cavity wall of 1 X. liolepis (209.3 mm SL), from 32 m depth at Station A- 14-S (32°57΄N, 117°17΄E), 4 September, 2003.

San Pedro Shelf, Southern California Bight, eastern Pacific Ocean, U.S.A.: 3 Ψ each with attached ɗ [all deposited: 1 Ψ with attached ɗ ( LACM CR2003-0490.4); 2 Ψ each with attached ɗ ( CMA 2010.04.0016)], ex branchial cavity wall of 1 X. liolepis (164.3 mm SL), from 34 m depth at Station 4154 (33°37΄N, 118°04΄E), 26 August, 2003; 1 Ψ with attached ɗ ( LACM CR2003-022.1), ex branchial cavity wall of X. liolepis (208.6 mm SL), from 41 m depth at Station 4113 (33°35΄N, 117°58΄E), 27 August, 2003; 1 Ψ ( CMA 2010.04.0017), ex branchial cavity wall of X. liolepis (207.1 mm SL), from 33 m depth at Station 4241 (33°36΄N, 118°02΄E), 27 August, 2003.

Description of adult female. Body ( Figs 5 A–B) divided into head, neck, and large trunk. Average body length (from anterior margin of head to distal end of posterior processes on trunk) 6.95 mm (5.75–7.45 mm); average trunk width 1.85 mm (1.53–2.25 mm) (n = 7). Head composed of cephalosome only, about 1.4 times longer than wide. Neck region composed of first and second pedigers, about as long as head. Trunk composed of pedigers 3 and 4, indistinguishably fused to neck, flask-shaped, with pair of posterolateral processes; latter about 3 times as long as genito-abdomen. Genito-abdomen ( Figs 5 A–C) divisible as 2 tagmata by transverse constriction; genital somite with ventral pair of genital apertures and mid-ventral pair of spiniform setae; abdominal somite short, considerably narrower than genital somite, with dorsal pair of sensilla and apical pair of caudal rami. Caudal ramus ( Fig. 5 C) spiniform, armed with 2 ventral setae and 1 dorsal seta (usual inner knob not observed).

Antennule ( Figs 5 D–E) distinctly separated into large fleshy base and narrow tip (Type B-V); latter armed with 12 elements in total. Antenna ( Fig. 5 F) 2-segmented, composed of coxobasis and 1-segmented endopod; coxobasis short, unarmed; endopod forming powerful uncinate claw bearing proximal pore. Labrum ( Fig. 6 A) naked. Mandible ( Fig. 6 B) 1-segmented, with apical falcate blade armed with 106 teeth along convex margin and 41 teeth along concave margin (n = 1). Paragnath ( Fig. 6 C) lobate, with 2 proximal groups of spinules. Maxillule ( Fig. 6 D) unilobate, with 2 unequal apical elements and small outer knob. Maxilla ( Fig. 6 E) 2- segmented, composed of syncoxa and basis; syncoxa robust, unarmed; basis forming claw-like process, armed with 2 unequal basal setae and 14 marginal teeth (n = 1). Maxilliped ( Fig. 6 F) 3-segmented, composed of stout syncoxa, relatively thinner basis and short terminal claw (endopod); syncoxa naked; basis with 2 groups of denticles along inner margin; claw with 1 accessory tooth. Leg 1 ( Fig. 6 G) with elongate rami and several spiniform setules; exopod with 2 rudimentary apical elements. Leg 2 ( Fig. 6 H) similar to leg 1, except exopod with only 1 reduced apical seta.

Description of adult male. Body ( Fig. 7 A) composed of large cephalothorax and narrower genitoabdomen; latter with pair of unarmed opercula, each covering genital aperture ( Fig. 7 B); average body length 0.39 mm (0.36–0.42 mm) (n = 3). Caudal rami ( Fig. 7 B) spiniform, each with 3 basal setae and minute spinules apically (usual small inner knob not observed).

Antennule ( Fig. 7 C) unmodified, with multiple surface annulations and armature of 1-1-2-2-7. Antenna ( Fig. 7 D) stout, with unarmed coxobasis and uncinate claw (tip broken off in illustration) bearing 1 minute seta. Mandibular blade ( Fig. 7 E) with 42 teeth on convex side and 12 teeth on concave side (n = 1). Maxillule ( Fig. 7 F) lobate, with 2 apical elements (1 pointed and 1 with globose base and setiform tip) and inner rounded knob. Maxilla ( Fig. 7 G) as in female, except without teeth on basis. Maxilliped (not figured) as in female. Legs 1 and 2 ( Figs 7 H–I) rudimentary, each with 1 naked mid-lateral seta, distal lobe armed with 1 apical seta (apically bifurcate in leg 2), and rounded inner process.

Variability. One adult female (LACM CR2003-0490.5) from Santa Monica Bay, Station 4006, 11 August, 2003 sample with endopod on left leg 2 reduced to a rounded lobe. Another adult female from same collection (but not deposited) lacking exopod on left leg 1. Adult male (not deposited) from Santa Monica Bay, Station 4230, 4 September, 2003 sample with 2 teeth along outer distal margin of left maxillary basis.

Etymology. This species is named in honor of Dr. M. James Allen, an expert on the taxonomy and ecology of southern California marine fishes, particularly those of the order Pleuronectiformes .

Remarks. Acanthochondria alleni n. sp. resembles A. soleae (Krøyer, 1838) , A. elongata (Bassett-Smith, 1898) and A. cyclopsetta Pearse, 1952 in having relatively slim and elongate rami on legs 1 and 2 of the adult female; all four species are also parasitic on flatfish hosts. The new species can be distinguished from those species, except A. cyclopsetta , by having a Type B-V antennule in the adult female. Acanthochondria alleni n.

sp. differs from A. cyclopsetta by having a head that is longer than wide ( Figs 5 A–B) (vs. head about as long as wide ( Figs 1 A–B)), a flask-shaped trunk lacking a mid-lateral constriction ( Figs 5 A–B) (vs. linguiform trunk with a prominent mid-lateral constriction ( Figs 1 A–B)), a relatively longer pair of posterolateral processes on the trunk (each process is about 3 times vs. slightly more than 1.5 times longer than the genitoabdomen (cf. Figs 5 A–B and 1A–B)), a considerably shorter abdominal somite relative to the genital somite ( Fig. 5 C) (vs. nearly as large as genital somite ( Fig. 1 C)), caudal rami inserted terminally on the abdominal somite ( Fig. 5 C) (vs. inserted proximally on the abdominal somite ( Fig. 1 C)), a relatively narrower tip on the antennule (cf. Figs 5 D–E and 1D–E), a naked antennal claw ( Fig. 5 F) (vs. surface striations present near the tip ( Fig. 2 A)), a naked labrum ( Fig. 6 A) (vs. spinular row present along posterior margin ( Fig. 2 B)), only 1 accessory tooth on the maxilliped claw ( Fig. 6 F) (vs. with multiple accessory teeth ( Fig. 2 F)), and relatively naked legs 1 and 2 ( Figs 6 G–H) (vs. numerous bullate patches present, each bearing minute spinules ( Fig. 2 G)) in the adult female.

Acanthochondria alleni n. sp. is, to the best of our knowledge, the only parasitic copepod reported from Xystreurys liolepis Jordan & Gilbert, a paralichthyid flatfish species distributed from Monterey Bay, California, U.S.A., to the Gulf of California, Mexico ( Miller & Lea 1972). Furthermore, this parasite species is probably host specific to X. liolepis as it has not been found on 14 other pleuronectiform species collected within the Southern California Bight (see Kalman 2006a, b). In contrast, A. cyclopsetta appears to be host specific to the paralichthyid flatfish genus Cyclopsetta , particularly those species, viz. C. chittendeni and C. fimbriata , occurring in the western central Atlantic Ocean (see Khidir et al. 2004). Sampling of the two Cyclopsetta species that are known to occur in the eastern central Pacific Ocean, namely C. panamaensis (Steindachner) and C. querna ( Jordan & Bollman), are needed to determine whether or not A. cyclopsetta also occurs in other geographic regions.

Figures

FIGURE 1. Acanthochondria cyclopsetta Pearse, 1952, adult female. (A) habitus, dorsal; (B) habitus, ventral; (C) genito-abdomen, lateral; (D) antennule, with enlarged view of distal end, dorsal; (E) antennule (armature elements omitted), anterior. Scale bars: A – B, 1.00 mm; C – E, 100 µm.

FIGURE 2. Acanthochondria cyclopsetta Pearse, 1952, adult female. (A) antenna, anterior; (B) labrum, ventral; (C) mandible, dorsal; (D) maxillule, dorsal; (E) maxilla, posterior; (F) maxilliped, posterior; (G) leg 1, with enlarged view of surface ornamentation and exopod tip, ventral. Scale bars: A – B, F, 100 µm; C – E, 50 µm; G, 200 µm.

FIGURE 5. Acanthochondria alleni n. sp., adult female. (A) habitus, dorsal; (B) habitus, ventral; (C) genito-abdomen, lateral; (D) antennule, with enlarged view of apical armature, ventral; (E) antennule (armature elements omitted), anterior; (F) antenna, posterior. Scale bars: A – B, 1.00 mm; C, F, 50 µm; D – E, 100 µm.

FIGURE 6. Acanthochondria alleni n. sp., adult female. (A) labrum, ventral; (B) mandible, dorsal; (C) paragnath; (D) maxillule, dorsal; (E) maxilla, anterior; (F) maxilliped, posterior; (G) leg 1, with enlarged view of exopod tip, ventral; (H) leg 2, with enlarged view of exopod tip, ventral. Scale bars: A, E – F, 50 µm; B, D, 25 µm; C, 10 µm; G – H, 200 µm.

FIGURE 7. Acanthochondria alleni n. sp., adult male. (A) habitus, lateral; (B) genito-abdomen, ventral; (C) antennule, anteroventral; (D) antenna, posterior; (E) mandible, dorsal; (F) maxillule, ventral; (G) maxilla, posterior; (H) leg 1, posterior; (I) leg 2, inner. Scale bars: A, 100 µm; B, G, 25 µm; C – F, H – I, 10 µm.