Heth, Cobb, 1898

Phillips, Gary, Moulton, John K. & Bernard, Ernest C., 2020, Heth pivari n. sp. (Nematoda: Ransomnematoidea: Hethidae) from the indigenous North American millipede Narceus gordanus (Spirobolida: Spirobolidae), with keys for worldwide Heth spp., Zootaxa 4861 (4), pp. 486-514 : 507-508

Key to group 2 Heth spp.

1. Multiple cuticular knob–like papillae in anterior esophageal region............................................. 2

- Knob-like papillae absent near head region, rarely one or two close to the cervical collar............................ 9

2. Lateral cervical collar spines reaching or overlapping proximal base of anterior lateral spines........................ 3

- Lateral cervical collar spines not reaching anterior lateral spines................................................ 6

3. Anterior and posterior lateral spines about equal in length..................................................... 4

- Posterior lateral spines much longer than anterior spines ( Fig. 11G ); anterior anal lip normal, without large lobe; female 2,340 – 3,230 μm long............................................................................... H. initiensis

4. Anterior anal lip with large lobe extending over anus; female 2,610 –4,225 μm long ( Fig. 11E )............ H. impalutiensis

- Anterior anal lip not swollen into large lobe................................................................ 5

5. Shield length and width about equal ( Fig. 11M ); female 1,365 –2,075 μm long.......................... H. taynguyeni

- Shield longer than wide ( Fig. 12C ); females 2,550 –2,640 μm long................................. H. vietnamensis

6. Shield width twice that of its length; female 2,190 –4,483 µm long ( Figs. 2A, B, D , 6A )................. H. pivari n. sp.

- Shield length and width about equal, or length much longer than width.......................................... 7

7. Shield tapering, up to 3 times longer than wide ( Fig. 12A ); females 2,180 –2,370 μm long................ H. tonkinensis

- Shield width and length similar, rounded or trapezoidal in shape................................................ 8

8. Shield rounded or ovoid; lateral spines less than 20 µm long ( Fig. 11A ); female 1,105 –1,440 μm long.......... H. baudini

- Shield trapezoidal; lateral spines 28–30 μm long ( Fig. 11L ); female 1,905 –2,575 μm long.................... H. taybaci

9. Cervical collar overlapping proximal base of anterior lateral spines............................................ 10

- Lateral cervical spines not overlapping anterior lateral spines................................................. 12

10. Eight longitudinal ridges extending from base of posterior lateral spines to vulva ( Fig. 11B ); female 2,160 –2,600 μm long.............................................................................................. H. costata

- Longitudinal ridges absent............................................................................ 11

11. Anterior and posterior lateral spine pairs fused, 26–33 μm long; shield a semicircle, about twice as wide as long ( Fig. 11I ); females 2,700 –3,024 μm long................................................................. H. orthopori

- Anterior lateral spines widely separated, 50 μm long; posterior lateral spines 55 μm long, bases closer but not touching ( Fig. 11K ); females 2,010 –2,360 μm long........................................................... H. sutherlandi

12. Lappets continuous, not separated laterally................................................................ 13

- Lappets separated................................................................................... 15

13 Length of cervical spines along lappet edges irregular, some spines forked; anterior and posterior lateral spines with fused bases ( Fig. 12B ); females 1,700 –2,800 μm long........................................................ H. tuxtlensis

- Cervical spines along lappet edges about the same size...................................................... 14

14. Shield forming a W-shape, length and width equal ( Fig. 11H )............................................. H. juli

- Shield entire, not bilobed, well anterior to base of anterior lateral spines ( Fig. 11C )..................... H. dimorphum

15. Wing-like lateral alae present; each pseudolabial plate with three conspicuous spines; cuticular collar with more than 100 spines; shield tapering, ( Figs. 12D ); female length 2,400 –2,960 μm................................. H. xaniophora

- Lateral alae absent................................................................................... 16

16. Anterior lateral spines widely separated; shield of typical size ( Fig. 11J ); females 1,970 –2,630 μm long.. H. ortonwilliamsi

- Anterior lateral spines fused basally; shield trapezoidal, small ( Fig. 11F ); females 1,764 –1,962 μm long....... H. insularis

Figures

FIGURE 2. Heth pivari n. sp., female. A) Habitus, sublateral view, right side. B) Anterior end, sublateral view. C) Part of anterior region, lateral view showing neck retractor muscles; rp, ramified projection of the stoma entrance lumen (Spiridonov & Yushin 2000). D) Collar, lateral view; box shows dimensions of shield. E) Oviduct-uterus region with migrating sperm. Scale bars: A, 230 µm; B, C: 25 µm; D, 40 µm; E, 115 µm.

FIGURE 6. DIC micrographs of Heth pivari n. sp., female and male structures. A) Lateral ornamentation in anterior region of female. B) Male, lateral somal extensions of posterior arcade surrounding anterior esophagus. C) Female, secretory-excretory pore (arrow). D. Female, somatic papillae anterior to vulva. E) Fusiform to comet-shaped sperm in male. All scale bars 20 µm.

FIGURE 11. Worldwide Heth spp., continuous collar with cervical shield (Group 2). A) H. baudini (after Malysheva & Cribb 2012). B) H. costata (after Hunt 1994). C. H. dimorphum (after Chitwood 1935). D) H. hamatus (after Bowie 1985). E) H. impalutiensis (after Malysheva et al. 2012). F) H. insularis (after Kloss 1965). G) H. initiensis (after Malysheva & Sumaya 2017). H) H. juli (after Cobb 1898). I) H. orthopori (after Adamson 1987). J) H. ortonwilliamsi (after Hunt 1994). K) H. sutherlandi (after Hunt 1994). L) H. taybaci (after Malysheva & Spiridonov 2010). M) H. taynguyeni (after Malysheva & Spiridonov 2010).

FIGURE 12. Worldwide Heth spp. Group 2 (continued). A) H. tonkinensis (after Malysheva & Spiridonov 2010). B) H. tuxtlensis (after Mejía-Madrid 2014). C) H. vietnamensis (after Malysheva & Spiridonov 2010). D) H. xaniophora (after Hunt 1994), en face, lateral and dorso-ventral views.