Echinoderes romanoi, Landers, Stephen C. & Sorensen, Martin V., 2016

Landers, Stephen C. & Sorensen, Martin V., 2016, Two new species of Echinoderes (Kinorhyncha, Cyclorhagida), E. romanoi sp. n. and E. joyceae sp. n., from the Gulf of Mexico, ZooKeys 594, pp. 51-71 : 54-56

Taxon classification Animalia Echinorhagata Echinoderidae

Echinoderes romanoi sp. n. Figs 2, 3, 4

Material.

Holotype: Adult male (ZMUC KIN-962), collected from sediment on November 13, 2014, at station 012-2014 (Fig. 1), at 90 m depth, <100 km east of the outlet of the Mississippi River, Louisiana (29°15'10"N, 88°18'23"W), mounted in Fluoromount G®, deposited at the Natural History Museum of Denmark. Paratypes include two females (ZMUC KIN-963 and KIN-964) from station 012-2014, two females (ZMUC KIN-965 and KIN-966) from station 19-2014, one male from station 154-2010 (ZMUC KIN-967) and one male from 050-2013 (ZMUC KIN-899). All paratypes are mounted in Fluoromount G® and deposited at the Natural History Museum of Denmark. Additional nontype material is listed in Table 1. See Figure 1 for localities and Table 1 for detailed station information.

Diagnosis.

Echinoderes with middorsal spines on segments 4-8, and spines in lateroventral positions on segments 6-9. Tubes present in lateroventral position on segment 5. Glandular cell outlets type 2 present in subdorsal, laterodorsal, sublateral, and ventrolateral positions on segment 2, in midlateral position on segment 5, and in sublateral position on segment 8.

Description.

Adults with head, neck and eleven trunk segments, ranging from 196-247 µm in trunk length (Figs 2-4). For complete overview of measures and dimensions, see Table 2. Distribution of cuticular structures, i.e., sensory spots, glandular cell outlets, spines and tubes, is summarized in Table 3.

The head (Fig. 3A, B, 4B) consists of a retractable mouth cone and an introvert. The mouth cone has nine outer oral styles. The introvert sectors are defined by 10 primary spinoscalids in ring 1. Each primary spinoscalid consists of a basal sheath with approximately 7 long extensions forming a fringed margin, and a distal end piece with a blunt tip. It was only possible to obtain information about the appearance and arrangement of scalids for introvert sectors 2, 3, and 4, which have the following characteristics: single central scalids of Rings 02 and 04, and paired scalids of Rings 03 and 05.

The neck (Figs 2A, B, 3A, B) has 16 placids, measuring 10 µm in length. The midventral placid is broadest, measuring 9 µm in width at its base, whereas all other are narrower, measuring 5-6 µm in width at their bases. The trichoscalid plates, each with a trichoscalid, are present in subdorsal, laterodorsal and ventromedial positions.

Segment 1 (Figs 2A, B, 3 A–C, 4A) consists of a complete cuticular ring. Sensory spots are located anteriorly in subdorsal, laterodorsal, and ventromedial positions; sensory spots minute and rounded with two anterior cuticular hairs. Glandular cell outlets type 1 present middorsally, sublaterally and lateroventrally. Cuticular hairs sparse on dorsal and ventral surface. A line of cuticular hairs is located below the intersegmental joint line. Pectinate fringe of posterior segment margin with typical fringe tips.

Segment 2 (Figs 2A, B, 3 A–D, 4A) consists of a complete cuticular ring. Pachycyclus of the anterior segment margin interrupted in middorsal and lateroventral positions. Sensory spots located in laterodorsal, midlateral, and paraventral positions; sensory spots on this and following segments minute and rounded. Glandular cell outlets type 2 located in subdorsal, laterodorsal, sublateral and ventrolateral positions. Glandular cell outlets type 1 located in paraventral positions. Secondary pectinate fringe present on this segment and on the following segments 3-10.

Segment 3 (Figs 2A, B, 3 A–C), and remaining segments, consisting of one tergal and two sternal plates. Pachycyclus of the anterior segment margin interrupted middorsally, midventrally, and at the tergosternal junctions. Sensory spots present in subdorsal and sublateral positions. Cuticular hairs evenly distributed over tergal and sternal plates, between the pectinate fringe and intersegmental joint line, with a line of cuticular hairs below the joint line. Glandular cell outlets type 1 in paradorsal and paraventral positions.

Segment 4 (Figs 2A,B, 3A, B, 4A) with acicular spine in middorsal position. Sensory spots not present. Glandular cell outlets type 1 slightly anterior to the spine insertion paradorsally and also present in paraventral positions. Pachycycli and cuticular hairs as on preceding segment.

Segment 5 (Figs 2A, B, 3A,B, 4A,C,E) with acicular spine in middorsal position and tubes in lateroventral positions. Sensory spots present in subdorsal and ventromedial positions. Glandular cell outlets type 2 in midlateral position. Pachycycli, glandular cell outlets type 1 and cuticular hairs as on preceding segment.

Segment 6 (Figs 2A, B, 3A, B, E, 4E) with middorsal and lateroventral acicular spines. Sensory spots present in paradorsal, subdorsal, midlateral, and ventromedial positions; ventromedial sensory spots slightly closer to midsternal junction than those on preceding segment. Pachycycli, glandular cell outlets type 1, and cuticular hairs as on preceding segment.

Segment 7 (Figs 2A, B, 3A, B, E, 4C,E) with middorsal and lateroventral acicular spines. Sensory spots present in paradorsal, midlateral, and ventromedial positions; ventromedial sensory spots aligned with those on segment 5. Pachycycli, glandular cell outlets type 1, and cuticular hairs as on preceding segment.

Segment 8 (Figs 2A, B, 3A, B, E, 4D, E) with middorsal and lateroventral acicular spines. Sensory spots present in paradorsal position. Glandular cell outlets type 2 in sublateral position. Pachycycli, glandular cell outlets type 1, and cuticular hairs as on preceding segment.

Segment 9 (Figs 2A, B, 3A, B, 4D,F) with acicular spines in lateroventral position. Sensory spots present in paradorsal, subdorsal, laterodorsal and ventrolateral positions. Glandular cell outlets type 1 are present in paradorsal and paraventral positions. Minute sieve plates present in sublateral position. Cuticular hairs and pachycycli as on preceding segment.

Segment 10 (Figs 2 A–D, 3A, B, F, G, 4D, F) with sensory spots in subdorsal and laterodorsal positions. Glandular cell outlets type 1 in tandem at the middorsal position, and in paraventral position. Posterior margin of pectinate fringe curved slightly anteriorly at the middorsal location. Posterior margins of sternal plates slightly rounded. Cuticular hairs sparse.

Segment 11 (Figs 2 A–D, 3A, B, F, G, 4D, F) with lateral terminal spines. Sensory spots not observed. Females with thin lateral terminal accessory spines. Female gonopores near anterolateral margins of sternal plates of segment 11; gonopores with rounded, intracuticular thickenings, and externally covered by fringed flap. Males with three pairs of penile spines. The dorsal- and ventral-most penile spines are thin and flexible; medial ones are more stout and rigid, tapering towards the tip. Glandular cell outlets type 1 present in tandem at the middorsal position, with the anterior outlet positioned horizontally and the posterior outlet positioned vertically. Tergal extensions elongated and curved on the lateral surface, with margin of medial sides decorated with hair-like extensions. Sternal extensions are rounded.

Etymology.

This species is named after the late Dr. Frank A. Romano III, Jacksonville State University, Alabama, for his contributions to the study of meiofauna and for his initiation of our ongoing meiofauna survey.

Remarks.

Echinoderes romanoi sp. n. is characterized by the presence of middorsal spines on segments 4 to 8, lateroventral tubes on segment 5, lateroventral spines on segments 6 to 9, and glandular cell outlets type 2 on segments 2 (4 pairs), 5, and 8. This combination of spines, tubes, and glandular cell outlets is unique among all species in the genus. The spine/tube arrangement is not unusual among congeners: 36 additional species share the presence of middorsal spines on segments 4 to 8 and lateroventral tubes/spines on segments 5 to 9, and out of these, ten also lack tubes on segment 2 as does Echinoderes romanoi sp. n.: Echinoderes angustus Higgins and Kristensen 1988, Echinoderes aquilonius Higgins and Kristensen 1988, Echinoderes tubilak Higgins and Kristensen 1988, Echinoderes remanei ( Blake 1930), Echinoderes brevicaudatus Higgins 1977, Echinoderes cernunnos Sørensen et al. 2012, Echinoderes koreanus Adrianov, 1999, Echinoderes stockmani Adrianov, 1999, Echinoderes obtuspinosus Sørensen et al. 2012, and Echinoderes bookhouti Higgins, 1964 ( Blake 1930, Higgins 1964a, 1964b, Higgins 1977, Higgins and Kristensen 1988, Adrianov and Malakhov 1999, Sørensen et al. 2012, 2016). Many of the descriptions of these ten species do not include glandular cell outlet type 2 information, though there are a variety of characteristics that distinguish Echinoderes romanoi n. sp. from each of the 10 other taxa. The first three species, Echinoderes angustus , Echinoderes aquilonius , and Echinoderes tubilak , all described from Disko Island, Greenland, can be distinguished from Echinoderes romanoi n. sp. by size alone. The three Greenland species all have a trunk length and placid length much larger than the trunk length (196-247 µm) and placid length (10 µm) of Echinoderes romanoi n. sp. ( Echinoderes angustus 320-475 µm, 16-20 µm; Echinoderes aquilonius 363-465 µm, 15-20 µm; Echinoderes tubilak 333-415 µm, 14-18 µm). The same distinction is true for Echinoderes remanei , redescribed by Higgins (1964a), which has a trunk length of 282-358 µm. Echinoderes brevicaudatus has lateral dorsal tubes on segment 10, and short stubby lateral terminal spines, distinct from the new species. Echinoderes cernunnos has glandular cell outlets type 2 located similarly to Echinoderes romanoi on segments 2, 5 and 8, though Echinoderes cernunnos also has glandular cell outlets type 2 in the midlateral position on segment 7 and additionally has elongated spinous tergal extensions. Echinoderes koreanus has spines in the lateral dorsal positions on segments 7 and 8, and tubes in the laterodorsal position on segment 10, unlike the new species. Echinoderes stockmani is distinguished by having the lateral spines on segment 8 distinctly longer than those on segment 9, unlike Echinoderes romanoi n. sp. Echinoderes obtuspinosus has glandular cell outlets type 2 similarly to Echinoderes romanoi on segments 2 and 8. However, Echinoderes obtuspinosus has glandular cell outlets type 2 in the subdorsal position on segment 4 and none on segment 5. Further, Echinoderes obtuspinosus has short stubby lateral terminal spines. Finally, Echinoderes bookhouti has lateral accessory spines on segment 8, and lacks glandular cell outlets type two on segment 5 and in the laterodorsal and sublateral position on segment 2.