Anomalohalacarus Newell, 1949

Type species: Anomalohalacarus anomalus (Trouessart, 1894)

Female (holotype)

Idiosoma (Fig. 2A) elongate, 364 µm long (360–372 µm, mean = 365 µm, n = 4), 103 µm wide (103–107 µm, mean = 105 µm, n = 4), length-to-width ratio about 3.52 (3.43–3.52, mean = 3.48, n = 4). Dorsal plates (AD and PD) with smooth surface, each plate clearly separated by membranous cuticle; OC absent. Membranous cuticle between AD and PD 71% of idiosoma, covered with parallel wavy striae transversely; ornamented with 1 pair of glp (glp-2) and three pairs of ds (ds-2–ds-4); glp-2 located at anterior third of idiosoma dorsolaterally.

AD (Fig. 2A, C) 84 µm long (82–87 µm, mean = 84 µm, n = 4), about 0.23 times as long as idiosoma, 42 µm wide (40–44 µm, mean = 42 µm, n = 4), length-to-width ratio 1.98; rectangular-shaped with truncated anterior margin and slightly convex posterior margin; with 1 pair of glp-1 and ds-1; glp-1 located at anterior 15% of AD laterally.

PD (Fig. 2A and D) undivided, smaller than AD, 0.74 times as long as AD, 0.52 times as wide as AD; 62 µm long (60–68 µm, mean = 63 µm, n = 4), about 0.17 times as long as idiosoma, 22 µm wide (22–26 µm, mean = 24 µm, n = 4), length-to-width ratio 2.79; elongate rectangular-shaped with convex anterior and blunt posterior margins; with a pair of ds-6 and 2 pairs of glp (glp-3 and glp-4), each glp placed at anterior 14% and 91% of PD, respectively.

Five pairs of dorsal setae (Fig. 2A): ds-1 located at anterior 29% of AD; 3 pairs of ds (ds-2–ds-4) situated on membranous cuticle dorsolaterally, at anterior 16%, 31%, and 65% of idiosoma, respectively; ds-2 at level of posterior margin of AD; ds-2 and ds-4 slightly longer than others, similar to length of AD; ds-5 absent; ds-6 at posterior margin of PD.

All ventral plates (Fig. 2B) small and separated by membranous cuticle with striae similar to those on dorsal surface of idiosoma, except between left and right plates of AE covered with smooth membranous cuticle. AE (Fig. 2B and Fig. 4A) 58 µm long (58–64 µm, mean = 60 µm, n = 4), about 0.16 times as long as idiosoma, 26 µm wide (26–29 µm, mean = 27 µm, n = 4), length-to-width ratio 2.20; divided into left and right plates by membranous cuticle without striae; distance between plates widest at 21 μm near insertion of leg I, narrowest at 12 μm near posterior ventral seta; each plate bearing 2 ventral, 1 lateral setae, and 1 epimeral pore; posterior ventral seta (0.5 times as long as AE) shorter than others (0.8 times as long as AE); epimeral pore inserted at anterior 61% of AE.

PE (Fig. 2B) 49 µm long (46–53 µm, mean = 50 µm, n = 4), about 0.13 times as long as idiosoma, 18 µm wide (17–20 µm, mean = 18 µm, n = 4), length-to-width ratio 2.76; located at anterior 68–81% of idiosoma; divided into two plates, with 1 pair of dorsolateral setae and 2 pairs of ventral setae; foremost ventral seta located at anterior corner of PE and another seta at anterior 37% of PE, respectively.

GP (Fig. 2B and Fig. 4B) divided into 3 plates, consisting of 1 pair of anterior genital plates and 1 posterior genital plate; anterior genital plates sub-rectangular, situated lateral to genital foramen, 17 µm long (16–19 µm, mean = 17 µm, n = 4), 9 µm wide (8–10 µm, mean = 9 µm, n = 4), length-to-width ratio of 1.96; posterior genital plate inverted triangular, between genital and anal foramina, 7 µm long (6–9 µm, mean = 7 µm, n = 4), 16 µm wide (13–20 µm, mean = 17 µm, n = 4), length-to-width ratio of 0.46; 3 pairs of pgs in genital area; foremost pgs situated on membranous cuticle anterior to genital foramen; 2 pairs of pgs on anterior genital plates. Genital foramen (Fig. 4B) 19 µm long (17–21 µm, mean = 19 µm, n = 4), 4 µm wide (4–5 µm, mean = 4 µm, n = 4); slender, matchstick-shaped, pointed at anterior tip, widest at anterior 14%; 1 pair of sgs at widest genital foramen; genital groove placed between posterior genital plate and anal sclerites. Ovipositor (Fig. 2B) tube-shaped, its anterior tip not reaching anterior margin of PE.

Gnathosoma (Fig. 2A and E) slender, 117 µm long (114–124 µm, mean = 118 µm, n = 4), about 0.32 times as long as idiosoma, 31 µm wide (30–33 µm, mean = 31 µm, n = 4), length-to-width ratio of 3.73; without areolae and costae on surface. Rostrum (Fig. 2E) 62 µm long, as long as gnathosomal base, its tip not reaching to distal end of P-2; 4 pairs of rostral setae, consisting of 2 pairs of short rostral setae (proto- and deutorostral setae) on distal tip of rostrum and 2 pairs of long rostral setae (trito- and basirostral setae) located at anterior 26% and 59% of ventral surface of rostrum, respectively. Palp (Fig. 2F) with 4 segments, 11, 63, 8 and 16 µm, respectively; P-1 trapezoid, without setae and spines; P-2 longest, with 1 short proximal and 1 plumose distal setae dorsally, and distal seta slightly longer than proximal one; P-3 shortest, with 1 cuticle spine dorsomedially; P-4 conical, with 3 proximal and 1 tiny distal setae, and terminal tip bifurcated. Chelicera (Fig. 2G) long, 113 µm long, consisting of basal segment and movable digit; basal segment, 99 µm long, with slender distal part (36%) and broadened proximal part; movable digit, 16 µm long, with about 20 fine denticles along dorsal surface. Tectum (Fig. 2A) very small, slightly protruding at middle of anterior margin.

All legs (Fig. 3A–D) slender, legs I–IV 270, 168, 169, and 190 µm long, respectively; leg I longest and legs II–IV 0.62, 0.63, and 0.70 times as long as leg I, respectively. Chaetotaxy of legs as follows: trochanters 1-1-1-0; basifemora 2-2-1-0; telofemora 3-3-2-2; genua 5-5-3-3; tibiae 10-6-5-5; tarsi (excluding pas and famulus) 8-5-3-3; number of bipectinate setae on telofemora to tibiae I–IV (none in other segments): telofemora 0-0-0-1; genua 2-0-0-1; tibiae 2-2-2-3. Trochanters shortest in legs I–II. Basifemora shortest in legs III–IV; basifemur III with 1 long lateral seta, more than twice as long as corresponding segment. All genua shorter than preceding segment (telofemur), except for genu I similar in length to telofemur I. All tibiae longer than preceding segment (genu), except for tibiae I and II as long as preceding segment; tibia I with 2 bipectinate setae and 1 small spine ventromedially. All tarsi slightly shorter than preceding segment (tibia); tarsus I (Fig. 3E) with 1 pair of fossary lamellae protruded distally; with 1 solenidion, 1 famulus, 3 dorsal, 4 ventral setae, and 1 pair of doublet eupathid pas; tarsus II (Fig. 3F) with 1 slender claviform solenidion, 3 dorsal and 1 ventral setae, and 1 pair of singlet eupathid pas; tarsus III (Fig. 3C) with 3 dorsal setae and 1 pair of pas consisting of 1 medial eupathid and 1 lateral filiform pas; tarsus IV (Fig. 3D) with 3 dorsal setae and 1 pair of filiform pas; all tarsi with a pair of lateral claws bearing 1 dorsal accessory process and with single median claw; lateral claws of tarsus I shorter than others.

Male

Idiosoma (Fig. 4C) 388 µm long (359–388 µm, mean = 372 µm, n = 5), 108 µm wide (102–137 µm, mean = 117 µm, n = 5), length-to-width ratio about 2.85–3.52; almost similar to female, except for length ratio of AD/PD and genital region. AD (Fig. 4C and E) 74 µm long (69–85 µm, mean = 76 µm, n = 5), about 0.19 times as long as idiosoma, 37 µm wide (35–43 µm, mean = 39 µm, n = 5), length-to-width ratio 1.97. PD (Fig. 4C and F) undivided, rectangular-shaped with both blunt anterior and posterior margins, almost similar to length of AD (0.96 times as long as AD), more slender 0.65 times as wide as AD; 72 µm long (68–83 µm, mean = 74 µm, n = 5), about 0.19 times as long as idiosoma, 18 µm wide (17–21 µm, mean = 19 µm, n = 5), length-to-width ratio 4.00.

GA (Fig. 4D and G) 58 µm long (52–58 µm, mean = 55 µm, n = 5), about 0.15 times as long as idiosoma, 40 µm wide (36–40 µm, mean = 38 µm, n = 5), length-to-width ratio 1.45; elliptical, with concave posterior region between GO and anal plate and gradually tapering to pointed ends at both sides posteriorly; with 7 pairs of pgs, each forming several branches towards distal part of seta. GO 19 µm long, (15–19 µm, mean = 17 µm, n = 5), 15 µm wide (12–15 µm, mean = 14 µm, n = 5), located in center of GA, about 0.33 times as long as GA; with 2 pairs of sgs, each located at anterior 45% and 74% of genital sclerites. Spermatocyte (Fig. 4D) distinct, extending beyond anterior end of PE.

Idiosoma sub-conical, 363–372 µm long in females and 359–388 µm long in males; membranous cuticle decorated with wavy striae, except between divided AE plates; PD undivided, much more slender than AD; 5 pairs of dorsal setae (lacking ds-5); AE divided into two plates by smooth membranous cuticle; PE with 1 dorsal and 2 ventral setae; P-2 with 1 short proximal and 1 plumose distal setae, dorsally; genua I and IV with 2 and 1 ventral bipectinate setae, respectively; tibia IV with 5 setae; tarsus I with 4 ventral setae; female's GP divided into three plates; female with 1 pair of sgs on genital foramen; male's GA with 7 pairs of branched pgs and 2 pairs of sgs.

The specific name is derived from the Latin ‘angustus’ (meaning narrow or slender), alluding to a slender posterior dorsal plate in the new species.

South Korea (this study).

Anomalohalacarus angustus sp. nov. was found among particles of various sizes, ranging from fine to coarse sandy beaches, at Pohang on the east coast and Geoje and Tongyeong on the south coast. On the fine sandy beach at Pohang, Actacarus ornatus and Actacarus pacificus co-occurred with the new species and on the coarse sandy beaches of Geoje and Tongyeong, Acarochelopodia sp., Actacarus ornatus, Actacarus pacificus, and Maracarus sp. also were present. Harpacticoids, nematodes, polychaetes, and ostracods were observed along with halacarids.

Anomalohalacarus biformis Abé 1996a: 8, figs. 1–4.

Female

Idiosoma (Fig. 5A) elongate, 298 µm long (284–298 µm, mean = 291 µm, n = 2), 103 µm wide (98–103 µm, mean = 101 µm, n = 2), length-to-width ratio about 2.89 (2.89–2.90, mean = 2.90, n = 2). AD and PD clearly separated by membranous cuticle with transversely parallel wavy striae. OC absent. Membranous cuticle between AD and PD occupying 59% of idiosoma; decorated with three pairs of ds (ds-2 to ds-4) and 1 pair of glp-2 situated at anterior 42% of idiosoma dorsolaterally.

AD (Fig. 5A and C) 67 µm long (58–67 µm, mean = 63 µm, n = 2), about 0.22 times as long as idiosoma, 36 µm wide (32–36 µm, mean = 40 µm, n = 2), length-to-width ratio 1.86; rectangular in shape with truncated anterior margin and slightly convex posterior margin; ornamented with a longitudinally weakly split areolation in the middle to posterior third of AD, 1 pair of glp-1 at anterior 21% of AD laterally, followed by 1 pair of ds-1.

PD (Fig. 5A, D) undivided, 43 µm long (39–43 µm, mean = 41 µm, n = 2), about 0.14 times as long as idiosoma, 23 µm wide (21–23 µm, mean = 22 µm, n = 2), length-to-width ratio 1.87; smaller than AD, 0.64 times as long as AD, 0.64 times as wide as AD; convex anterior and lateral margins, and slightly blunt posterior margin; with 2 pairs of glp (glp-3 and glp-4) placed at anterior 12% and 87% of PD, respectively and 1 pair of ds-6 at posterior glp-4.

Five pairs of dorsal setae (Fig. 5A): ds-1 positioned at anterior 40% of AD laterally; 3 pairs of ds (ds-2 to ds-4) more and less evenly spaced on membranous cuticle at 20%, 38%, and 63% of idiosoma, respectively; ds-3 shorter than ds-2 and ds-4; ds-5 absent; ds-6 shortest, situated at posterior edge of PD.

All ventral plates (Fig. 5B) small and separated by membranous cuticle with striae, excluding between left and right plates of AE. AE (Fig. 5B) 69 µm long (58–69 µm, mean = 64 µm, n = 2), about 0.23 times as long as idiosoma, 32 µm wide (26–32 µm, mean = 29 µm, n = 2), length-to-width ratio 2.16; divided into left and right plates by smooth membranous cuticle (Fig. 5E), of which membranous cuticle with striae extending posterior ventral setae about 1/6 posterior part; distance between plates widest, 24 μm near insertion of leg I and narrowing gradually towards posterior part; each plate bearing 2 ventral, 1 lateral setae, and 1 epimeral pore; posterior ventral seta (41 µm long) shorter than others; epimeral pore inserted at border of epimera I and II, about anterior 66% of AE.

PE (Fig. 5B) 48 µm long (45–48 µm, mean = 47 µm, n = 2), about 0.16 times as long as idiosoma, 21 µm wide (20–21 µm, mean = 21 µm, n = 2), length-to-width ratio 2.29; situated at anterior 63–81% of idiosoma; each plate bearing 1 dorsolateral, 2 ventral setae and 1 vestigial scar of seta; ventral setae located at anterolateral corner and at half of PE, respectively.

GP (Fig. 6A) divided into 3 plates, consisting of 1 pair of anterior and 1 posterior genital plates; anterior genital plates sub-rectangular-shaped, located on either side of genital foramen, 18 µm long (12–18 µm, mean = 15 µm, n = 2), 11 µm wide (8–11 µm, mean = 10 µm, n = 2), length-to-width ratio of 1.64; posterior genital plate inverted triangular posterior to genital foramen, 7 µm long (n = 2), 22 µm wide (20–22 µm, mean = 21 µm, n = 2), length-to-width ratio of 0.32; 3 pairs of pgs, consisting of foremost one located on membranous cuticle anterior to genital foramen and the other 2 pairs on anterior genital plates. Genital foramen (Fig. 6A) 17 µm long (15–17 µm, mean = 16 µm, n = 2), 3 µm wide (n = 2); slender, pointed at both anterior and posterior tips, widest at anterior 15% of genital foramen; sgs absent; genital groove placed between posterior genital plate and anal foramen. Ovipositor (Fig. 5B) tube-shaped, anterior end not reaching anterior edge of PE.

Gnathosoma (Fig. 5A and B) 118 µm long (114–118 µm, mean = 116 µm, n = 2), about 0.36 times as long as idiosoma, 31 µm wide (29–31 µm, mean = 30 µm, n = 2), length-to-width ratio of 3.81; without ornamentation on surface. Rostrum (Fig. 5B) 59 µm long, slightly longer than gnathosomal base, its anterior tip not extending beyond distal end of P-2; 4 pairs of rostral setae, composing of 2 pairs of short proto- and deutorostral setae situated on distal end of rostrum and 2 pairs of long trito- and basirostral setae at anterior 29% and 59% of rostrum ventrally, respectively. Palp (Fig. 5F) 4-segmented, 11, 58, 9, and 15 µm long, respectively; P-1 without setae and spines; P-2 longest, with 1 short proximal and 1 plumose distal setae, dorsally; P-3 shortest, with 1 dorsomedial spine; P-4 conical, its terminal end bifurcated, with 3 proximal and 1 tiny distal setae. Chelicera (Fig. 5A and G) 119 µm long, consisting of basal and movable distal segments; basal segment 107 µm long, with wide proximal part and slender distal part (38%); movable segment 20 µm long, with about 25 fine denticles dorsally. Tectum (Fig. 5A) tiny, weakly convex at middle of anterior edge.

All legs (Fig. 6B–E) slender, leg I longest, 257 µm long, and legs II–IV 174 µm, 175 µm, and 186 µm long (0.67, 0.68, and 0.72 times as long as leg I), respectively. Chaetotaxy for legs I–IV as in Anomalohalacarus angustus sp. nov., except for tibiae 10-6-5-6(5); arrangement of legs I–IV similar to the new species. All legs with a pair of lateral claws bearing 1 accessory process dorsally and with single median claw; lateral claws of tarsus I shortest.

Male

Idiosoma (Fig. 5H), 294 µm long (294–311 µm, mean = 303 µm, n = 2), 102 µm wide (102–110 µm, mean = 106 µm, n = 2), length-to-width ratio about 2.83–2.88; almost similar to female, except for length ratio of AD/PD and genital region. AD (Fig. 5H and I) 62 µm long (62–76 µm, mean = 69 µm, n = 2), about 0.21 times as long as idiosoma, 35 µm wide (35–42 µm, mean = 39 µm, n = 2), length-to-width ratio 1.77. PD (Fig. 5H and J) 52 µm long (52–63 µm, mean = 58 µm, n = 2), about 0.18 times as long as idiosoma, 26 µm wide (26–32 µm, mean = 29 µm, n = 2), length-to-width ratio 2.00; undivided, rectangular with truncated anterior and posterior margins; smaller than AD, 0.84 times as long as AD and 0.74 times as wide as AD.

GA (Fig. 6H) 50 µm long (50–57 µm, mean = 54 µm, n = 2), about 0.17 times as long as idiosoma, 38 µm wide (38–43 µm, mean = 41 µm, n = 2), length-to-width ratio 1.32; elliptical, with a depressed posterior region behind GO and gradually tapering towards posterior ends at both sides; with 7 pairs of filiform pgs, foremost pgs at level of anterior sgs. GO (Fig. 6H) 20 µm long, (20–26 µm, mean = 23 µm, n = 2), about 0.40 times as long as GA, 12 µm wide (12–17 µm, mean = 15 µm, n = 2); with 2 pairs of sgs, each situated at anterior 26% and 58% of genital sclerites, respectively. Spermatocyte (Fig. 6H) extending beyond anterior end of PE.

Japan (Abé 1996a), Korea (this study).

Anomalohalacarus biformis occurred at a beach on the southern coast of Jeju Island, South Korea. Specimens were obtained by filtering sand with medium-sized grains, along with Actacarus pacificus, Acarochelopodia sp., Acaromantis sp., Copidognathus sp., Maracarus sp., Rhombognathus sp., Simognathus sp., and Scaptognathus sp. In addition to halacarids, harpacticoid copepods, nematodes, polychaetes, and ostracods were also present in the sand sediments.