Echinoderes ohtsukai, Yamasaki & Kajihara, 2012

Yamasaki, Hiroshi & Kajihara, Hiroshi, 2012, A New Brackish-water Species of Echinoderes (Kinorhyncha: Cyclorhagida) from the Seto Inland Sea, Japan, Species Diversity 17 (1), pp. 109-118 : 110-115

Echinoderes ohtsukai sp. nov.

[New Japanese name: Ohtsuka togekawa] (Figs 2–8)

Material examined.H olotype, ZIHU 3976, adult male, mounted in Hoyer’s-125; collected by H. Yamasaki from an

intertidal at (34°19′32.16̎N, 132°53′49.45̎E), Seto Inland Sea , Japan, on 10 October 2008 . Allotype, ZIHU 3977 , adult female, mounted in Hoyer’s-125; collection data as for the holotype . Paratypes: one male ( ZIHU 3978 ) and three females ( ZIHU 3979–3981 ), adults, each mounted on separate slide in Hoyer’s-125; one male ( ZIHU 3982 ) and four females ( ZIHU 3983–3986 ), adults, each mounted on separate SEM stub; collection data as for the holotype .

Diagnosis. Ec hinoderes with trunk 315–395 µ m long; short middorsal spine present on segment 4; lateroventral tubules present on segments 5 and 8; short laterodorsal tubules present on segment 10; both sexes without lateral terminal accessory spines; lateral terminal spines about 50% of trunk length; modi ed type-II glandular cell outlets located in various positions on segments 2–8; large sieve plates present sublaterally on segment 9.

Description.A dults consisting of head, neck, and 11 trunk segments (Fig 2A, B, 3A). Table 1 summarizes measurements; Table 2 summarizes arrangement of spines, tubules, and cuticular structures on each segment.

Head consisting of mouth cone and introvert (Figs 3A, 4A, B). Inner armature of mouth cone not observed. Outer armature consisting of nine outer oral styles covered with sets of spinous structures at their bases (Fig. 4A). Introvert comprising one ring of spinoscalids, six rings of regular scalids, and one ring of trichoscalids (Fig. 4B); spinoscalids, scalids, and trichoscalids not counted.

Neck consisting of 16 placids (Fig. 2A, B), all narrowing anteriorly. Midventral placid broadest, 14–16 µ m wide at posterior margin; other placids 7–10 µ m wide at posterior margin (Fig. 2A, B). Every second placid, i.e., eight placids in all, with trichoscalid plates, these lacking on middorsal, laterodorsal, lateral, lateroventral, and midventral placids (Fig. 2A, B).

Segment 1 consisting of complete cuticular ring. Pachycyclus thick along anterior margin (Figs 2A, B, 5A, 6A). Pairs of rounded sensory spots in subdorsal, laterodorsal, and ventrolateral positions (Figs 2A, B, 3B, 5A, 6A). Pairs of type-I glandular cell outlets in paradorsal and lateroventral positions (Figs 2A, B, 5A, 6A). Posterior edge with pectinate fringe composed of ne fringe tips (Figs 2A, B, 3B). Anterior part of ventral side without hairs but posterior part of both ventral and dorsal sides with acicular bracteate cuticular hairs arising from densely distributed perforation sites (Figs 2A, B, 3B).

Position

Segment MD PD SD LD ML SL LA LV VL VM 1 — gco1 rss rss — — — gco1 — rss 2 dss — gco2 dss, dss, gco2 — — — — gco2 dss 3 — — dss — dss — — gco2 — — 4 sp — gco2 — — — — gco2 — — 5 — — dss dss gco2 — — tu — dss 6 — — dss gco2 dss — — — — dss 7 — — dss — dss gco2 — — — dss 8 gco2 — dss — gco2 gco2 — tu — — 9 — — dss — dss si — — dss — 10 — — rss tu — — — — dss — 11 — — rss — — — — lts — —

Segment 2 consisting of complete cuticular ring. Pachycyclus thick along anterior margin of segment (Figs 2A, B, 5A, 6A). Droplet-shaped sensory spot in middorsal position. Two pairs of laterodorsal droplet-shaped sensory spots and one pair of ventromedial droplet-shaped sensory spots (Fig. 3B). Pairs of modi ed type-II glandular cell outlets (sensu Lundbye et al. 2011) in subdorsal, laterodorsal, and ventrolateral positions (Figs 2A, B, 3B, C, 5A, 6A). Acicular bracteate cuticular hairs arising from perforation sites which distribute throughout segment. Pectinate fringe as on pre- ceding segment.

Segment 3 and following eight segments consisting of one tergal and two sternal plates (Fig. 2A, B). Pachycycli thick along anterior margin and along tergosternal and midsternal junctions (Fig. 2A, B). Tergal plate with pairs of dropletshaped sensory spots in subdorsal and midlateral positions (Figs 2A, 3B). Pair of modi ed type-II glandular cell outlets in lateroventral position. Cuticular hairs and pectinate fringe as on preceding segment.

Segment 4 with short aciculate middorsal spine (17 µ m long in holotype, 12–15 µ m long in allo- and paratypes) nev- er reaching the segment edge (Figs 2A, 5B). Sensory spots absent. Pairs of modi ed type-II glandular cell outlets in subdorsal and lateroventral positions. Pachycycli, cuticular hairs, and pectinate fringes of this and following six segments as on segment 3 (Figs 5B, 6B).

Segment 5 with pair of lateroventral tubules (23 µ m long in holotype, broken in allotype, 22–25 µ m long in paratypes) (Figs 2B, 6B, 7A). Pairs of droplet-shaped sensory spots in subdorsal, laterodorsal, and ventromedial positions. Pair of modi ed type-II glandular cell outlets in midlateral position (Fig. 7A).

Segment 6 without spines or tubules. Pairs of dropletshaped sensory spots in subdorsal, midlateral, and ventromedial positions. Pair of modi ed type-II glandular cell outlets in laterodorsal position.

Segment 7 similar to segment 6 expect for presence of pair of modi ed type-II glandular cell outlets in sublateral position, and absence of laterodorsal modi ed type-II glandular cell outlets (Figs 2A, B, 3C).

Segment 8 with pair of lateroventral tubules (17 µ m long in holotype, broken in allotype, 15–21 µ m in paratypes) (Figs 2B, 7B). Pair of droplet-shaped sensory spots in subdorsal positions. Five modi ed type-II glandular cell outlets, one middorsally and two pairs in midlateral and sublateral positions.

Segment 9 with three pairs of droplet-shaped sensory spots in subdorsal, midlateral, and ventrolateral positions (Figs 2B, 3D, 7B). Pair of oval sieve plates (12 µ m long and 3 µ m width in all specimens examined) in sublateral position (Figs 2B, 3D, 7B). Single pore about 3 µ m posterior to each sieve plate (Fig. 3D).

Segment 10 with pair of rounded sensory spots in subdorsal position and pair of droplet-shaped sensory spots in ventrolateral position (Fig. 2A–D). Pair of horn-like laterodorsal tubules present (19 µ m long in holo- and allotypes, 20–22 µ m long in paratypes) (Figs 2A, C, 3E, 8A).

Segment 11 without perforation sites or acicular cuticular hairs. Pair of rounded sensory spots in subdorsal position (Fig. 2A, C). Pachycyclus thick along anterior margin. Pair of lateral terminal spines present, about 50% as long as trunk (163 µ m long, 45% of trunk length in holotype; 190 µ m, 60% in allotype; 171–190 µ m, 43–49% in paratypes). Lateral terminal accessory spines absent in both sexes (Fig. 2A–D). ffiree pairs of penile spines present only in males (Figs 2A, B, 3E, 8B). Penile spine 1 longest (ca. 40 µ m in both holotype and male paratype, ZIHU 3978 ); penile spine 2 second longest (ca. 30 µ m in both holotype and male paratype, ZIHU 3978 ); penile spine 3 shortest (ca. 10 µ m in both holotype and male paratype, ZIHU 3978 ) . Tergal plate terminating in pair of pointed tergal extensions (ca. 13 µ m from base of extension to tip in all specimens). Posterior margin between tergal extensions densely fringed.

Etymology.ffi e species is named in honor of Professor Susumu Ohtsuka of Hiroshima University for his generous help in this study.

Species associations. Ec hinoderes ohtsukai co-occurred with two other kinorhynchs, Kinorhynchus yushini and Pycnophyes tubuliferus .

Remarks.A mong the 69 species of Echinoderes , four have been reported to have a single middorsal spine on segment 4 and to lack lateral terminal accessory spines in females, as in E. ohtsukai . ffiese are E. capitatus ( Zelinka, 1928) , E. isabelae GªOrdóñez et al., 2008, E. rex Lundbye et al., 2011 , and “ E. teretis ” ( Zelinka 1928; Brown 1985; Nebelsick 1992; Adrianov and Malakhov 1999; GªOrdóñez et al. 2008; Lundbye et al. 2011). ffie name “ Echinoderes teretis ”, which rst appeared in Brown’s (1985) unpublished PhD thesis, is an unavailable name, which we do not intend to describe although it has been frequently used with Brown (1985) as the naming authority (e.g., Adrianov and Malakhov 1999; WoRMS 2010; Lundbye et al. 2011). None of these latter works has made the name available and, despite our morphological characterization of this species below, we disclaim any intention of making it available herein and assuming its authorship. In addition, four other species have lateroventral tubules only on segments 5 and 8, as in E. ohtsukai : E. applicitus Ostmann et al., 2012 ; E. coulli Higgins, 1977 ; E. maxwelli ( Omer-Cooper, 1957) ; and E. lispinosus Adrianov, 1989 ( Omer-Cooper 1957; Higgins 1960, 1977; Adrianov 1989; Ostmann et al. 2012).

Echinoderes applicitus di ers from E. ohtsukai in the form of the tergal extensions (short and conical with liform tips in E. applicitus vs long with pointed tips in E. ohtsukai ) and in the absence of the middorsal spine on segment 4 (present in E. ohtsukai ).

Echinoderes capitatus and E. ohtsukai both have a pair of lateroventral spines on segments 5 and 8, but di er in the arrangement of tubules on segments 2, 6, 7, and 9: E. capitatus has four pairs of tubules on segment 2 and one pair each on segments 6, 7, and 9 ( Nebelsick 1992) whereas E. ohtsukai lacks tubules on segments 2, 6, 7, and 9.

Echinoderes coulli and E. maxwelli di er from E. ohtsukai in lacking a middorsal spine on segment 4 (present in E. ohtsukai ); furthermore, these two species lack laterodorsal tubules on segment 10 (present in E. ohtsukai ).

Echinoderes lispinosus di ers from E. ohtsukai in lacking a middorsal spine on segment 4 (present in E. ohtsukai ) and in having a pair of lateral terminal accessory spines (absent in E. ohtsukai ).

Echinoderes isabelae di ers from E. ohtsukai in having subdorsal, laterodorsal, sublateral, and ventrolateral tubules on segment 2 (no tubules in E. ohtsukai ); lateroventral spines on segments 6 and 7 (no spines in E. ohtsukai ); subdorsal tubules on segment 7 (no tubules in E. ohtsukai ); sublateral tubules and lateral accessory tubules on segment 8 (only lateroventral tubules in E. ohtsukai ); and lateroventral spines on segment 9 (no spines in E. ohtsukai ). Echinoderes isabelae lacks laterodorsal tubules on segment 10 (present in E. ohtsukai ).

Echinoderes rex resembles E. ohtsukai in having pairs of lateroventral tubules on segments 5 and 8, a pair of laterodorsal tubules on segment 10, and a pair of large sieve plates on segment 9 ( Lundbye et al. 2011). In this genus, only these two species have been reported to have modi ed type-II glandular cell outlets, although the position and ar- rangement of the outlets on each segment are not identical between them. Echinoderes rex di ers from E. ohtsukai in having a longer trunk (482–528 µ m vs 315–395 µ m in E. ohtsukai ), very much shorter lateral terminal spines (20–24 µ m vs 163–190 µ m in E. ohtsukai ), lateroventral spines on segments 6 and 7 (absent in E. ohtsukai ), and two pairs of penile spines in males (three pairs in E. ohtsukai ).

“ Echinoderes teretis ” di ers from E. ohtsukai in having lateral spines on segments 6 and 7 (absent in E. ohtsukai ). In addition, “ E. teretis ” has neither tubules nor spines on segment 10, while E. ohtsukai has a pair of laterodorsal tubules on this segment.