Diplocardia verrucosa Ude, 1895

Damoff, George A. & Carrera-Martínez, Roberto, 2025, A review of literature and a reevaluation of Diplocardia verrucosa Ude, 1895 resulted in the discovery of a new species in southern New Mexico and west Texas, USA, Zootaxa 5589 (1), pp. 363-381 : 370-373

Diplocardia verrucosa Ude, 1895

( Figure 2 A–C )

Material examined. Representative specimen: Clitellate, USNM 1742101, within the city limits of Bartlesville, Washington County, Oklahoma, USA (36˚43’35”N, 95˚58’15”W). Collector George A. Damoff on 24 May 2017, elevation 194 m, 0.5 km southwest of Caney River in a closed canopy of bottomland hardwoods in deep silty clay. Additional specimens: 21 clitellates and and subadults also collected at numerous sites in Oklahoma and Texas, USNM 1742102–1742105 . Additionally, 55 specimens are curated at the Canadian Museum of Nature , although recently reported as Diplocardia sp. nov. TN01 in Damoff and Reynolds (2019) for reasons explained above .

Diagnosis. Small-sized, quadrithecal earthworm, 123 mm length X 2.5 mm diameter (xxx). Segment count 141. Epilobous tongue 1/2 width of segment, open, with minimal slight crisscrossed rugosities that contrast with smooth surface of ii. Saddled-shaped clitellum with ventral margin slightly dorsad to b. Genital tumescences range from spherical to irregular margins present in pre-, intra- and post-clitellar segments. Male groove narrow and shallow in 1/2xix─1/3xxi, nearly straight with secondary indentations associated with segmentation. Single dorsal blood vessel throughout. Last hearts xii. Intestinal origin xvi. Calciferous lamellae absent. Acryptate spermathecae with oblong diverticulum attached by a short stalk near base of ovoid ampulla.

Description

EXTERNAL.—Small-sized earthworm. For all three states (OK, TN, and TX), mean length of intact adult specimens 94 mm (range 64–142; n = 47); mean segment count of intact subadult and adult specimens 125 (range 71–149; n = 95); mean clitellate width 2.1 mm (range 1.3–2.7).

Body shape cylindrical throughout. Triannulation begins at vi and strongly evident in clitellar and postclitellar segments, except last five. Other specimens from OK, TN, and TX most often display triannulation over majority of length, a few specimens do not.

No pigmentation. Body color of formalin-fixed, ethanol-stored specimens uniform throughout: pinkish white (7.5YR 8/2) clitellum pink (7.5YR 7/4). TN specimens color dark reddish brown (2.5 YR 5/4) from 50 years of storage in ethanol; distinctly different color from OK and TX specimens.

Epilobous tongue about 1/2 width of segment, open though some have crease at base that gives closed appearance. Slight crisscrossed rugosities that contrast with smooth surface of ii.

First dorsal pore varied widely for populations within and between OK, TN, and TX with a range of 5/6–26/27. Nephridiopores not obvious.

Saddle-shaped clitellum xiii─xviii. Specifically, dorsal extent variable where anteriorly all or a fraction of xiii then most often extending posteriorly through all of xviii, though a few all or part of xix. Ventral extent slightly less than anterior segments and margin varies from slightly lateral to b or to a. Setal pairs visible in all clitellar segments. If first dorsal pore anterior to 13/14 then dorsal pores visible in clitellum.

Setae begin ii, closely paired below mL line. Ambulatory setae conspicuous, somewhat dark, observed in most segments before periproct. Setal arrangement at x: aa: ab: bc: cd: dd = 5:1:2.7:1.3:16.3 and at xxx: 4.3:1:2.3:1:13.3. Presence of copulatory setae variable, absent to present; if present, two in viii and two in ix. Penial setae also variable regardless of lifestage, either absent or present. If present, internally observed in xix and xxi; infrequently visible externally at one to all tips of male grooves. The penial setae of the TN specimens easily seen (red) in xix and xxi, length 0.5 mm, width about 0.05 mm. Setae a and b less conspicuous in viii and ix than in vii and x. Setae a and b missing in xix, xx, and xxi.

Spermathecal pores near anterior margin of viii, ix, all 0.1 mm in diameter, slightly raised (about 0.1 mm) on conical papillae (about 0.2 mm diameter). Pores of viii 0.3 mm from anterior margin, 0.25 mm from setae, and <0.05 mm lateral to a; pores of ix 0.5 mm from anterior margin, 0.3 mm from setae and <0.05 mm lateral to a.

Ovipores in xiv, presetal, slightly mesad or in line with a, less than 0.1 mm diameter. Commonly observed pinkish white papillae (“halo”) surrounding the single pair of ovipores, oval to slight dumbbell-shaped boundary that extends slightly lateral to b ─ b. Strong brown color of papillae in TN specimens same as clitellum.

Male groove, in line with a, extends from 1/2xix–1/3xxi, nearly straight to slightly sigmoid with secondary indentations associated with intersegmental grooves and secondary annulations. Shallow, narrow (greatest width about 0.1 mm), and flush with surrounding adjacent ventral surface. Prostatic pores inconspicuous in tips of male groove. Male pore xx, at anterior-most margin of 19/20 within male groove, occasionally conspicuous. Associated with numerous genital tumescences (GT).

GT are frequently in ix to xxiv, in intersegmental furrows frequently in 12/13 to 16/17, 18/19; these segments can have up to 7 GTs, some are occasionally unpaired mV. All are slightly raised above the external body wall. Paired GT vary in width apart, from slightly merged within a ─ a, to widely separated each between a ─ b. GT not spanning an intersegmental groove are postsetal. As with dorsal pores, GT distribution varied for populations within and between states. OK and TX specimens typically had a similar range of segments with GT, x to xxiv, and number of GT per segment, 1, 2, 4, and less frequent, 3. These differed from the TN specimens with range of GT segments, vii to xxii, and number of GT per segment, 1, 2, 4, 6 and less frequent, 3, 5, or 7. Most GT are circular though some have irregular margins that vary in diameter 0.2─ 0.9 mm. Color of GT for OK and TX specimens are a near white inner area contrasted by a narrow border of light brown; TN specimens are shades of reddish brown. Contrast with surrounding tissue is not sharp.

Spermatophores. None observed adhering to the exterior body wall.

INTERNAL.—Septa thickened 6/7─12/13 and slight musculature evident in 6/7─10/11, with greatest thickness 7/8─9/10. All septa posterior to 12/13 same thickness. All preclitellar septa drape anteriorly covering all internal organs in the adjacent anterior segment where septa attach to the body wall. Intersegmental bands extend posteriorly from the surface of the pharynx (ii–iv) and gizzards (v–vi). Transeptal muscles numerous in ii–xii, with greatest abundance associated with the pharynx, penetrate muscled septa at oblique angles. Most transeptal muscle bands confined to two adjacent segments, yet at least one penetrates through 6/7─8/9 septa. Anterior end attached to an organ of the alimentary canal and the posterior end attached to the body wall. Integument and body musculature (longitudinal and transverse muscle layers) each about 0.1 mm thick.

Coagulum (preserved coelomic fluids), abundant throughout, denser in segments anterior to intestine, especially in ix─xi. Same opaque white as seminal vesicle making it difficult to parse the two.

Alimentary canal. Pharynx in ii–iv covered in transeptal muscle bands, whitish in color, 0.1–0.2 mm width, in numerous distinct layers over dorsal and lateral surfaces of the pharynx, extending posteriorly, anchored in body wall. Two gizzards in v–vi without distinct demarcation also with numerous transeptal muscle bands extending posteriorly for one or two segments. Esophagus vii–xv, uniform in diameter from xiii–xv. Calciferous glands or lamellae absent. Intestinal origin xvi, fully expanded at junction with esophagus at septum 15/16. The intestine of a few specimens expands (tapers) gradually to full diameter in xvi, while a few others display an abrupt expansion somewhere well within xvi; only one of the 110 specimens had the intestinal origin in xvii and this may have been a result of obvious external trauma to the body wall during development. Simple lamelliform typhlosole most often begins in xviii, occasionally in xix, and extends about 0.5 mm into lumen or 1/4 to 1/3 of the inside lumen diameter. Remainder of gut lining generally smooth with few ridges.

Nephridia . Holoic, in iii to terminal segments near periproct. Tubules about 0.03 mm diameter, centered on d. Exoic duct exits coelom 0.2─ 0.3 mm anterior to d. Avesiculate.

Vascular system . Dorsal vessel single throughout; blood engorgement often observed but span of segments highly variable between specimens. Ventral vessel most easily observed in xvi; dorsal to and immediately adjacent to the ventral nerve cord; greatest diameter 0.4 mm. Paired latero-esophageal vessels (hearts) x–xii often engorged with blood. Extra-esophageal vessels vii–ix, about 1/4 less diameter than hearts and occupy same position in each segment as the hearts.

Nervous system . Dorsal bi-lobed cerebral ganglion on dorsal surface of pharynx in iii united with ventral nerve cord by circumpharyngeal connectives that pass over the lateral surface of the pharynx. Ventral nerve cord easily observed, sandwiched between the ventral blood vessel and body wall; opaque and about the same diameter as the ventral blood vessel.

Male sexual system . Testes holandric in x and xi, attached near mV posterior surface of septa 9/10 and 10/11, respectively. Series of strings branching from a single trunk attached to septum has a similar appearance, though smaller size, as ovaries of some diplocardians. Periesophageal testis sac not detected. Male funnels, conspicuous (about 0.5 mm diameter), attached to anterior surfaces of septa 10/11 and 11/12, near a–b. Iridescence observed on both testes and male funnels. Racemose seminal vesicles in ix typically smaller than those in xii which often fills the entire coelomic cavity; often absent in ix for the OK specimens, especially for those collected in Jackson County. Prostates paired in xix and xxi, in line with a. Sharp transition in diameter from duct to gland. Curved prostatic duct short (ca. 2 mm long) and narrow (<0.1 mm diameter). Gland with smooth margin and sharp folds—sometimes more than six 90° and 180° loops—with asymmetrical distribution of R/L, anterior/posterior prostates that span three or more pre- and post-segments adjacent to segment of duct; overall length can exceed 3 cm. Penisetal bundles about 0.5 mm in length and 0.05 mm diameter, in xix and xxi, penetrating body wall with prostatic duct. Transverse muscle bands observed only in TN specimens.

Female sexual system . Ovaries in xiii, conspicuous conical cluster (not distinct strings) attached to ventrad posterior surface of septum 12/13. Ovarian funnels conspicuous, attached to ventrad anterior surface of septum 13/14, irregular wavy rim about 0.3 mm diameter. Oviducts pass through 13/14 septum, short duct in xiv about 0.2 mm diameter, penetrates body wall adjacent to ventral nerve cord, near a.

Spermathecae. Quadrithecal, in viii and ix. Duct emerges near a, length about 1─ 2 mm long by <1 mm diameter. Acryptate. Diverticulum sessile or on a short stalk attached near ectal end (near ampulla); oblong single chamber; length at least double the width; with iridescence on some specimens. Ampulla ovoid, relatively large compared to overall size of clitellate specimens, 1─ 2 mm long by 1─ 2 mm wide, sometimes width slightly greater than length; iridescence not observed ( Fig. 2 ).

Remarks

Ude’s 1895 original description of Diplocardia verrucosa is based on three specimens that are supposed to be the type series. There are only two specimens presently curated in the Museum of Nature Hamburg, Germany that are designated syntypes (accession number: ZMH-ANN-OL-V382). While at the current time we are unable to study the specimens in person (due to the fragility of the material, shipping for examination was not an option), digital photographs provided by the museum curator of one of the two specimens shows that it has its male field in xix-xxi, consistent to D. verrucosa , but completely lacks the genital tumescence described by Ude and recognized as a major diagnostic feature for this species by multiple authorities (e.g., Murchie 1962, Gates 1967, 1977). Furthermore, this specimen lacks a clitellum, while Ude describes the presence of it. The second specimen in this lot lacks its anterior portion and therefore its identification is not possible. Given this and that Ude used three specimens, and that one of the specimens do not seem to fit Ude’s description, it is possible that these specimens might not be those used by Ude to describe D. verrucosa and were mislabeled at some point. Another possibility is that these specimens have been worn due to their age and these diagnostic characters have been damaged or lost. In any case, careful in person examination of the one full specimen should be carried out to confirm if it fits the original description by Ude (1895). If this specimen is indeed an inadequate representation of the species, a neotype could be proposed from its type locality at Omaha, Nebraska following the International Commission on Zoological Nomenclature Code (1999) Article 75. Such determination should be carried out in a future study.

The Tennessee specimens differ from the other specimens in numbers per segment and segment range of GT; other than slight variation in overall size (likely due to site quality), this single character is the only notable difference for all 110 specimens from all three states.

Gut content mostly fine sand (0.05 mm dia.) with low amount (<10%) of short dark fibers and scattered pieces of woody material (up to 1 X 2 mm); TX specimens had slightly larger sand grains.

Based on collection records that span over a century from multiple sites in more than a dozen states in the USA D. verrucosa clearly prefers hydric soils.

Figures

FIGURE 2. Diplocardia verrucosa: (A) ventral view, spermathecae from (B) viii, and (C) ix; Diplocardia farrishi sp. nov.: (D) ventral view, spermathecae from (E) viii, and (F) ix. SP, spermathecae pores; F, female pores; P, prostatic pores; and M, male pores.