Eubostrichopsis johnpearsei, Ott & Pröts, 2021

Ott, Jörg A. & Pröts, Philipp, 2021, Eubostrichopsis johnpearsei n. gen., n. sp., the first stilbonematid nematode (Nematoda, Desmodoridae) from the US West Coast, Zootaxa 4949 (2), pp. 353-362 : 355-357

Eubostrichopsis johnpearsei sp. n.

( Figs. 2–5 )

Type material: Holotype male, paratype female, other paratypes: male 2, females 2–3

Type specimens deposited in the collection of the Natural History Museum Vienna ( Austria) Numbers Invertebrata varia Collection 5855 (holotype), 5856 (paratype male 2), 5857/1–3 (paratypes female 1–3). Type locality: Beach south of Yaquina Head , Newport (Oregon) (holotype male, paratype male 2, paratype female 1–2). Sampling date: April 25, 1986 .

Other locality: beach in front of the Joseph M. Long Marine Laboratory, Santa Cruz (California) (paratype female 3). Sampling date: March 2, 1986 .

Etymology: The species is named in honor of the late John Pearse, 1940–2020, eminent invertebrate biologist and the first author’s friend and generous host during his sabbatical at the University of California Santa Cruz 1985–86, when the specimens were collected.

Measurements. Table 1.

With the characters of the genus. Slender worms with a short pharynx and short tail. There are two circles of subcephalic setae on the cephalic capsule. Both the cephalic and subcephalic setae slightly curved inward. No somatic setae except for the precloacal region and tail of males. Cephalic capsule without block layer, surface largely unstriated, striation starting a few µm before level of posterior end of cephalic capsule. Striae 0.7–1 µm wide, striation extending over whole body, tip of tail with an unstriated terminal part, 15 µm long. Precloacal region of males with a medioventral membranous ridge, 340 µm (holotype) and 250 µm (paratype) long, 4 µm high, bearing a row of short (4 µm long) setae, 10–20 µm apart. Male tail with two pairs of thorn-like hollow setae (porids) at 40–47 and 75–80 % of tail length. Pharynx with cylindrical anterior part, spherical bulbus occupying 20 % of pharynx length, no cardia. Prominent nerve ring encircling pharynx directly anterior to bulbus. No excretory system present. Males monorchic, testis starting at midbody; spicular apparatus with prominent musculature. Females didelphic, amphidelphic, ovaries reflexed, anterior ovary left, posterior right of gut. Female 3 with two ripe eggs in each uterus 80 x 30 µm. Vulva not specially cuticularized, slightly posterior to midbody. Symbiont coat ( Fig. 6 ) covers the whole striated part of the worms’ body. Bacteria are 7–10 µm long, in center of cell 0.7 µm wide, tapering towards poles. Bacteria appear to divide longitudinally. Thicker (1.4–1.6 µm) cells show a distinct longitudinal groove. Approximately 170 cells per 100 µm 2 of host surface. A 4 mm long worm therefore carries about 850 000 bacterial cells. Total volume of symbiotic coat is more than 90 % of host volume or almost half of holobiont volume.

Figures

FIGURE 2. Eubostrichopsis johnpearsei sp. n. A. Holotype, total view. B. Anterior body region of male paratype. C. Cloacal and tail region of male paratype. D. Spiculum and gubernaculum of holotype. E. Anterior body region of female paratype 1. F. Tail of female paratype 1. b—bulbus, bac—bacteria, cs—cephalic setae, de—ductus ejaculatorius, fa—fovea amphidialis, g—gut, gb—gubernaculum, gso—glandular sensory organ, nri—nerve ring, scs—subcephalic setae, sp—spiculum, spt—spin neret, t—testis, tg—tail gland, th—thorn-like setae, vd—vas deferens.

FIGURE 3. Eubostrichopsis johnpearsei sp. n. A. Head region of holotype. B. Pharynx bulbus of holotype. C. Testis region of paratype. D. Vas deferens of paratype. E Tail of holotype. F. Spiculum of holotype. DIC micrographs of preserved specimens. b—bulbus, bac—bacteria, cc—cephalic capsule, cg—caudal gland, gb—gubernaculum, gso—glandular sensory organ, i—isthmus, smu—muscles of the spicular apparatus, sp—spiculum, t—testis, th—thorn-like setae, vd—vas deferens. Scalebars A–E: 20 µm, F: 10 µm

FIGURE 4. Eubostrichopsis johnpearsei sp. n. A. Female paratype 3, total view. B. Female paratype 1, anterior body region. C. Female paratype 1, anterior ovary. D. Female paratype 1, vulva region. F. Female paratype 3, eggs in uterus. LM micrographs of preserved specimens. b—bulbus, cc—cephalic capsule, cs—cephalic setae, e—egg, scs—subcephalic setae, ov—ovary, vu— vulva. Scalebars A: 100 µm, B–D: 20 µm, E: 10 µm.

FIGURE 5. Eubostrichopsis johnpearsei sp. n. A. Head region of holotype. B. Head region of female paratype 1. Volume renderings based on image stacks of autofluorescence signal acquired with a confocal microscope. cs—cephalic setae, fa—fovea amphidialis, scs—subcephalic setae. Scalebars A–B: 15 µm.

FIGURE 6. Eubostrichopsis johnpearsei sp. n. Symbiotic bacteria. A. Sagittal optical section through region of junction between testis and vas deferens in holotype. B. Detached symbionts showing an optical cross section through the dense bacterial coat. DIC micrographs of preserved specimens. bac—bacteria, cut—cuticle, g—gut, t—testis, vd—vas deferens. Scalebars A: 20 µm, B: 15 µm.