Asteropontoides acutirostris, Kim, 2016

Kim, Il-Hoi, 2016, Siphonostomatoid copepods (Crustacea) mainly associated with marine invertebrates from Korean waters, Journal of Species Research 5 (3), pp. 393-442 : 428-433

publication ID	https://doi.org/ 10.12651/JSR.2016.5.3.393
persistent identifier	https://treatment.plazi.org/id/96353C58-E747-FF8B-FF59-FAD0FB30FDBE
treatment provided by	Felipe
scientific name	Asteropontoides acutirostris
status	sp. nov.

Treatment

Asteropontoides acutirostris View in CoL n. sp. ( Figs. 24-26 View Fig View Fig View Fig )

Material examined. One $ and 2♂♂ from washings of invertebrates on the sandy bottom in the depth of 25 m, Dogdo Island, 24 August 2016, collected by J.M. Lee.

Holotype ($, NIBRIV0000681228 ) and allotype (♂, NIBRIV0000681229 ), both intact, will be deposited in NIBR, Incheon, Korea. Dissected paratype (1♂) is retained in the collection of the author.

Other material examined. One $ from washings of invertebrates from a soft bottom, in the depth of 82 m, East China Sea (32°00′N, 126°00′E), 02 June 2015, collected by J.M. Lee GoogleMaps ; 1$(dissected and figured), from washings of invertebrates from a soft bottom, in the depth of 30 m, South of Geoje Island , 34°25′N, 128°30′E, Korea Strait, 08 June 2015, collected by J.M. Lee. GoogleMaps Holotype has been deposited in NIBR, Incheon, Korea. Dissected paratype is retained in the collection of the author .

Female. Body ( Fig. 24A View Fig ) narrow, 1.03 mm long, with dorsal surface covered by numerous minute spinules ( Fig. 24C View Fig ). Prosome fusiform, 673 μm long. Cephalothorax 414 × 298 μm, slightly longer than wide, with acutely pointed posterolateral corners. Second and third pedigerous somites also with pointed posterolateral corners. Fourth pedigerous somite with deeply concave posterior margin, with rounded posterolateral corners. Urosome ( Fig. 24B View Fig ) 4segmented. Fifth pedigerous somite 118 μm wide. Genital doublesomite 136 × 104 μm, consisting of wider anterior half and narrower posterior half (69 μm wide in this region); genital aperutres located dorsally near anterior third of doublesomite. Two abdominal somites 64 × 64 and 49 × 61 μm, respectively. Anal somite with row of spinules along posterodorsal and posteroventral margins; anal region large ( Fig. 24C View Fig ). Caudal rami slightly divergent ( Fig. 24C View Fig ); each ramus 64 × 27 μm, 2.37 times as long as wide, with parallel lateral margins, and armed with 4 distal and 2 dorsal, subdistal setae; outer dorsal seta (seta II) naked, but other 5 setae plumose; distal margin of ramus finely spinulose and inner margin setulose on distal half.

Rostrum ( Fig. 24D View Fig ) tapering, longer than wide, with acutely pointed distal apex, and minute setule at proximal third of lateral margin. Antennule ( Fig. 24E View Fig ) 405 μm long and 20segmented; armature formula 1, 2, 2, 2, 2 / 2, 2, 2, 7, 2 / 2, 2, 2, 2, 2, / 2, 2, 1 + aesthetasc, 6, and 8; 2 setae on second segment plumose, other setae naked; aesthetasc on antepenultimate segment large, 235 μm long, more than half as long as antennule, and as broad as penultimate segment. Antenna ( Fig. 24F View Fig ) slender; coxa short and unarmed; basis also unarmed, but with fine spinules on margins. Exopod small, 16 × 8 μm, armed with 3 setae. Endopod 3-segmented; first segment 97 μm long, unarmed; small second segment with 1 seta; third segment with 3 small setae and terminated by thin, elongate, spiniform claw of 160 μm long.

Oral siphon ( Fig. 24G View Fig ) 329 μm long, styliform, and extending slightly beyond intercoxal plate of legs 1. Mandible ( Fig. 24H View Fig ) consisting of stylet and 1segment ed palp; stylet articulated at proximal third, with 10 fine teeth distally; palp 27 × 8 μm, with circle of setules near middle and tipped by 2 plumose setae of unequal length. Maxillule ( Fig. 24I View Fig ) bilobed; inner lobe slightly longer than outer lobe, with 4 apical setae, including 1 minute one; outer lobe also with 4 apical setae, smallest one of which being plumose. Maxilla ( Fig. 25A View Fig ) slender and 2-segmented; syncoxa unarmed, but with 1 flexible tube proximally and numerous, minute spinules on inner surface; basis arched, thin, and elongate, with 1 seta in middle and tipped by thin terminal claw. Maxilliped ( Fig. 25B View Fig ) also slender, 5segmented; syncoxa with 1 inner seta subdistally; basis 128 μm long, with parallel margins, setulose outer margin and fine spinules near middle of inner margin; endopod elongate, with 2, 2, and 1 setae on first to third segments, respectively; lengths of these segments 10, 110, and 37 μm, respectively; terminal claw 103 μm long, about 2.8 times as long as terminal segment, weakly curved, with fine spinules along concave margin.

Armature formula for legs 14 as follows:

Coxa Basis Exopod Endopod Leg 1: 01 11 I1; I1; III, 2, 2 01; 02; 1, 2, 3 Leg 2: 01 10 I1; I1; III, I, 4 01; 02; 1, 2, 3 Leg 3: 01 10 I1; I1; III, I, 3 01; 02; 1, I, 3 Leg 4: 01 10 I1;?;? 01; 02; 1, I, 2

Legs 13 ( Fig. 25 View Fig CE) with 3segmented rami. Leg 4 ( Fig. 25F View Fig ) with 3segmented endopod and probably with 3segmented exopod (distal segments not observed due to their damage). Distal margin of intercoxal plate of leg 1 smooth, but that of legs 24 spinulose. Inner distal corner of basis of legs 14 with row of spinules. Inner distal seta on basis of leg 1 naked. Outer margin of second exopodal segment concave, with row of long setules. Legs 24 with membranes on distal margin of basis at place medial to base of endopod and between bases of rami. Inner seta on coxa of legs 14 welldeveloped and plumose.

Leg 5 represented by lateral seta on fifth pedigerous somite and free exopod; exopod ( Fig. 25G View Fig ) elongate, 76 × 18 μm, gradually broadened distally with scattered minute spinules on surfaces, and distally armed with 3 setae, one of which being plumose, and with tuft small spinules on distal margin. Leg 6 represented by 1 small naked seta and 1 longer, plumose seta in genital aperture ( Fig. 25H View Fig ).

Male. Body 0.79 mm long. Prosome similar to that of female. Urosome ( Fig. 26A View Fig ) 5segmented. Fifth pedigerous somite 93 μm wide, with small, spinules-tipped lamella at ventrolateral region, near base of leg 5 exopod ( Fig. 26D View Fig ). Genital somite 76 × 91 μm, nearly quad rangular, with fine spinules on lateral surface. Three abdominal somites 45 × 61, 38 × 56, and 36 × 58 μm, respectively. First and second abdominal somites with membranous fringe along ventrodistal margin. Anal somite with ( Fig. 26B View Fig ) with row of spinules along ventrodistal margin. Caidal ramus 34 × 25 μm, 1.36 times as long as wide, with tapering process and spinules on ventrodistal margin.

Rostrum as in female. Antennule ( Fig. 26C View Fig ) 18segmented, geniculate between antepenultimate and penultimate segments; armature formula I, 2, I + 1, I + 1, 2, 2, 2, I + 1, 7, 2, 2, 2, 2, 2, 2, 2, 2 + aesthetasc, and 11 + aesthetasc; first, third, fourth, eighth segments each armed with 1 compound spine (bilaterally membranous and tipped by setule) and 1 seta; aesthetasc on penultimate segment large; terminal segment slender and tapering, its distal aesthetasc setiform, Antenna as in female.

Mouthparts and legs 14 as in female. Leg 5 ( Fig. 26D View Fig ) consisting of 1 plumose lateral seta on fifth pedigerous somite and free exopod; exopod ( Fig. 26E View Fig ) rhomboidal, 24× 21 μm, slightly longer than wide, armed with 3 setae (inner one smallest and plumose; outer and distal one naked) and with spinules on distal margin. Leg 6 ( Fig. 26D View Fig ) represented by 3 similar plumose setae on distal margin of genital operculum.

Etymology. The specific name acutirostris is a combination of Latin words acut (= sharp point) and rostr (= snout). It alludes to the sharply pointed rostrum of the new species.

Remarks. At present, the genus Asteropontoides Stock, 1975 contains three known species: A. attenuatus ( Thompson and Scott, 1903) and A. nicobaricus ( Sewell, 1949) from the Indian Ocean and A. elephantinus Johnsson, 1998 from the Brazilian coast.

Asteropontoides acutirostris n. sp. can easily be distinguished from A. elephantinus and A. nicobaricus , because the caudal ramus of the latter two species is wider than long, 10 × 21 μm measured by Johnsson (1998) for A. elephantinus and 1.25 times as wide as long in A. nicobaricus (see Sewell, 1949). In A. attenuatus the antennule is 18segmented in the female, the exopod of leg 5 is about 6 times as long as wide, the expanded anterior part of the genital doublesomite of the female is roundly convex, seen from the illustration of Thompson and A. Scott (1903), and the outer lobe of the maxillule is armed distally with 3 setae. Therefore, A. attenuatus is not conspecific with A. acutirostris n. sp.

Stock (1975) established the genus Asteropontoides on the basis of two incompletely described species, A. attenuatus and A. nicobaricus . With the addition of A. elephantinus and the new species, this genus may be characterized anew as follows, based on the female: (1) the body is narrow, with 4segmented urosome; (2) the antennule is 1520segmented; (3) antenna, maxilla, and maxilliped are slender; (4) the oral siphon is elongate, extending over insertions of legs; (5) the mandibular stylet is thin and 2segmented and the palp is 1segment ed, with 2 distal setae; (6) the outer lobe of maxillule is more than half as long as the inner lobe; (7) the second exopodal segment of leg 1 with concave outer margin; (8) the armature formulae of the third exopodal and endopodal segments of leg 4 are III, I, 3 and 1, I, 2, respectively; (9) leg 4 with a welldeveloped inner seta on the coxa; and (10) the exopod of leg 5 is elongated, more than 4 times as long as wide.

Callomyzon n. gen.

Diagnosis. Body with thick exoskeleton, swollen cephalothorax and small urosome. Urosome 4segmented in female and 5segmented in male. Caudal ramus with 6 setae. Rostrum absent. Antennule of female 21segment ed; first segment with 1 seta; eighteenth segment with aesthetasc. Antennule of male 18segmented, with geniculation between antepenultimate and penultimate segments. Antenna with small exopod bearing 3 setae; endopod 3segmented, terminal segment with stout claw. Oral cone extending to insertions of maxilliped. Mandibular stylet with denticles distally. Mandibular palp 2 segmented, with 2 unequal distal setae; palp plus longer distal seta longer than stylet. Maxillule with 5 setae on inner lobe and 4 setae on outer lobe. Maxilla comprising syncoxa and clawlike basis. Maxilliped 6segmented. Legs 14 with 3segmented exopod and endopod; coxa of these legs without inner seta. Basis with 1 outer and 1 inner distal setae in leg 1, but only with outer setae in legs 24. First and second exopodal segments of legs 14 with 1 outer spine and 1 inner seta each. First and second endopodal segments of legs 14 with 1 and 2 inner setae, respectively. Armature formula for third exopodal segment in legs 14: III, 2, 2; III, I, 4; III, I, 4; and III, I, 3, respectively. Armature formula being 1, 2, 3 for third endopodal segment in legs 13, that of leg 4 being 0, 2, 1. No sexual dimorphism in legs 14. Leg 5 exopod small, with 3 setae.

Type species. Callomyzon macrocephalus View in CoL n. sp.

Etymology. The generic name Callomyzon is a combination of Greek Callo (= thickskinned) and myzo (to suck in), alluding to the thick exoskeleton of the new genus. Gender is neuter.

Remarks. In the genera of the Asterocheridae having 3 segmented rami in legs 14, the basic number of armature elements on the third endopodal segment is 6 in legs 13 and 5 in leg 4. The compositions of armature elements on these terminal endopodal segments are 6 setae (formula 1, 2, 3) in legs 1 and 2, 5 setae plus 1 spine (formula 1, 1 + I, 3) in leg 3, and 4 setae plus 1 spine (formula 1, 1 + I, 2) in leg 4. This armature condition is displayed by the type genus Asterocheres and many other genera in the family. In the case of leg 3 armature, very few genera deviate from this generality. Having six setae (formula 1, 2, 3) without a spine, as in Callomyzon n. gen., on the third endopodal segment is displayed only by two known genera: Tychomyzon Humes, 1991 and Asterocheroides Malt, 1991 .

Callomyzon n. gen. cannot be united with any of these two genera due to the significant differences from them, as follows. In Tychomyzon the antennule is 18segmented in the female (vs. 21segmented in Callomyzon n. gen), the mandible is Asteropontius type with 1segmented palp tipped by 1 seta (vs. 2segmented palp tipped by 2 setae in Callomyzon n. gen.), the third exopodal segment of leg 4 is armed with 4 spines and 4 setae (formula III, I, 4; vs. III, I, 3 in Callomyzon ), and the second endopodal segment of leg 1 is armed only with 1 inner seta ( Humes, 1991; vs. armed with 2 setae in Callomyzon ). In Asterocheroides the mandibular palp is 1segmented, the third exopodal segment of leg 1 is armed with 2 spines and 4 setae (formula II, 4; not III, 4 as in Callomyzon ), the third exopodal segments of legs 24 are armed with 3 spines and 4 setae (formula II, I, 4; not III, I, 4 or III, I, 3 as in Callomyzon ), the first exopodal segment of leg 1 lacks an inner seta, and the first endopodal segment of leg 4 lacks an outer spine ( Malt, 1991).