Helobdella bowermani, Moser, William E., Fend, Steven V., Richardson, Dennis J., Hammond, Charlotte I., Lazo-Wasem, Eric A., Govedich, Fredric R. & Gullo, Bettina S., 2013

Moser, William E., Fend, Steven V., Richardson, Dennis J., Hammond, Charlotte I., Lazo-Wasem, Eric A., Govedich, Fredric R. & Gullo, Bettina S., 2013, A new species of Helobdella (Hirudinida: Glossiphoniidae) from Oregon, USA, Zootaxa 3718 (3), pp. 287-294 : 288-293

Helobdella bowermani n. sp.

Figures 1–3

Material examined. Holotype (USNM 1213041) Ball Bay (42° 24’ 21”N 122° 01’ 01”W) Upper Klamath Lake, Klamath County, Oregon on 30 May 2012.

Paratypes (USNM 1213042) 8 specimens mid-trench (42° 23’ 05”N 121° 55’ 38’W), 6 November 2008, 4 whole mount slides (USNM 1225776–1225779); USNM 1213043 3 specimens Ball Bay (42° 24’ 21”N 122° 01’ 01”W) on 30 May 2012, 2 whole mount slides (USNM 1225780–1225781); USNM 1213044 9 specimens midtrench (42° 23’ 05”N 121° 55’ 38’W), 18 June 2008; USNM 1213045 2 specimens mid-trench (42° 23’ 05”N 121° 55’ 38’W), May 2008; USNM 1213046 8 specimens mid-north (42° 26’ 22”N 122° 00’ 40” W), 30 May 2012, 1 whole mount slide (USNM 1225782); USNM 1213047 3 specimens Modoc Rim (42° 24’ 37”N 121° 51’ 52”W), 18 June 2008; YPM IZ 67710 4 specimens mid-trench (42° 23’ 05”N 121° 55’ 38’W), 18 June 2008; Upper Klamath Lake, Klamath County, Oregon.

Description. External morphology. Body lanceolate; length of preserved specimens 5.2–9.7 mm, mean ± SE 7.2 ± 0.2 mm (n=38), width at widest point 1.7–4.5 mm, mean 3.0 ± 0.1 mm (n=38). Dorsum pale yellow/buff with scattered chromatophores throughout the dorsal surface ( Figs. 1 A–B). Pair of widely separated eye spots and pair of black longitudinal pigment lines extending posteriad from the eye spots for a few annuli. Small oval-shaped nuchal scute (occasionally triangular) on VIII, raised in preserved specimens ( Figs. 1 A–B). Dorsal medial row of papillae with papillae on the a1 (papilla small), a2 (papilla large) and a3 (papilla large) annulus ( Figs. 1 A–B). Medial dorsal papillae row extends posteriad below the nuchal scute to a couple of annuli anteriad of the anus. Additional row of papillae at the extreme lateral margins on the a2 (neural) annulus, giving the body a serrated or denticulate appearance ( Figs. 1–2 ). Lateral papillae row begins as 2 papillae below the anus and extends anteriad. Anus located 1 annulus anteriad of the caudal sucker. Caudal sucker small to moderate size (half the diameter of mid-body, 0.7–1.3 mm in diameter, mean ± SE, 1.0 ± 0.0 (n=38), with few black chromatophores and no papillae. Ventrum without papillae and unpigmented ( Fig. 2 ). Male gonopore on annulus and female gonopore in furrow (1 ½ annuli between gonopores).

Internal morphology. Digestive system: Proboscis pore at center of anterior sucker. Robust proboscis uniformly cylindrical and in membranous sheath. In the anterior third of body, salivary glands diffusely scattered on either side of the proboscis and salivary ductule bundles attaching at each side of the base of the proboscis ( Figs. 3 A–B). Short, simple esophagus. Six pair of short, simple unlobed and unbranched crop ceca with no post ceca and four pair of intestinal ceca with the last pair reduced ( Figs. 3 A–B). Rectum robust, pyriform and recurved in some specimens ( Figs. 3 A–B).

Reproductive system: Male atrium opening into paired falciform to luniform atrial cornuae that extend laterally and anteriorly into ejaculatory ducts without atrial loops ( Figs. 3 A–B). Six pair of testisacs ( Figs. 3 A–B). Female gonopore simple, opening to pair of simple, tubular ovisacs. Length of ovisacs dependent on the reproductive state of the leech.

Taxonomic summary. Type locality. Upper Klamath Lake, Klamath County, Oregon.

Type material. Holotype USNM 1213041, Paratypes USNM 1213042–1213048, USNM 1225776–1225782, and YPM IZ 67710.

Etymology. Named to honor scientist and naturalist Jay Bowerman of the Sunriver Nature Center, Sunriver, Oregon.

DNA analysis. Molecular characterization of 614 nucleotides of CO-I revealed differences of 0.0% to 0.2% (0–1 nucleotide) among three specimens of Helobdella bowermani n. sp. (GenBank KF683192 – KF683194 ). Differences of 10.6% to 10.8% (65 to 66 nuceotides) were found between H. bowermani n. sp. and a specimen of Helobdella californica (GenBank HQ686307 ) collected from San Francisco, California. Comparison of CO-I sequence data of three specimens of H. bowermani n. sp. revealed differences of 12.2% to 13.7% (75 to 84 nucleotides) among three specimens of Helobdella atli (GenBank HQ179850 – HQ179852 ), differences of 12.7% to 13.2% (78 to 81 nucleotides) among three specimens of Helobdella simplex (GenBank KF683195 – KF683197 ), differences of 14.5% to 14.7% (89 to 90 nucleotides) among two species of Helobdella modesta from Washington (GenBank HQ179853 – HQ179854 ), differences of 14.7% to 14.8% (90 to 91 nucleotides) from a specimen of H. modesta from Ohio (GenBank AF329040 ), and differences of 14.7% to 14.8% (90 to 91 nucleotides) from a specimen of Helobdella stagnalis from the United Kingdom (GenBank AF329041 ).

A neighbor joining tree of Helobdella spp. based on CO-I sequence data is presented in Figure 4 . Helobdella bowermani n. sp. formed a clade with H. californica , and a sister clade with Helobdella atli had modest support. The sister clade relationship of Helobdella simplex and Helobdella sorojchi had robust support.

Figure legends: atrial cornuae (AC), crop ceca (CC), ejaculatory duct (ED), intestinal ceca (IC), proboscis (Pr), rectum (R), salivary cells (Sc), testisac (T1–T6).

Natural history. Helobdella bowermani n. sp. occurs abundantly in the fine sediment and was collected in the open water benthos with an Ekman grab and a 0.5 mm sieve bucket throughout Upper Klamath Lake.

The reproductive period for Helobdella bowermani n. sp. was during spring with specimens brooding eggs and hatchlings in May and June, and a second reproductive period was observed in August and September.

Remarks. Three nominal species of Helobdella with a nuchal scute occur in the United States: Helobdella modesta (Verrill 1872) , Helobdella californica Kutschera 1988 , and Helobdella bowermani n. sp. Whether a fourth species of Helobdella with a nuchal scute, Helobdella stagnalis (Linneaus 1758) , occurs in the United States is in doubt. At one time, every specimen of Helobdella with a nuchal scute was identified as H. stagnalis , but differences in genetic distance prompted Siddall et al. (2005) to resurrect Helobdella modesta (Verrill 1872) . In a molecular characterization of H. modesta from the type locality (New Haven, Connecticut), Moser et al. (2011) suggested H. stagnalis is a complex of cryptic species and additional species similar to H. stagnalis likely exist in the United States. Although H. bowermani n. sp. has a nuchal scute, its dorsal medial row of papillae and a2 papillae on the lateral margins easily distinguish it from the non-papillated H. modesta and H. stagnalis .

Helobdella californica , which formed a clade with H. bowermani n. sp., exhibited a 10.6% to 10.8% difference among COI sequence data. Both nuchal scute species occur in the western United States, but H. californica has a pair of longitudinal stripes, diverticulated crop ceca at the lateral ends and no papillae which differentiate it from H. bowermani n. sp. Helobdella californica is also only known from Golden Gate Park [Stow Lake (type locality), San Francisco Botanical Garden Gunnera Creek and Mallard Lake], San Francisco, California (Kutschera 1988; 2011).

Helobdella bowermani n. sp. is morphologically similar to H. atli and H. simplex . All three species have a nuchal scute on VIII and dorsal-medial row of papillae. Comparison of H. bowermani COI sequence data with the other two species, revealed differences of 12.2% to 13.7% with H. atli and differences of 12.7% to 13.2% with H. simplex . There are also morphological differences between H. bowermani n. sp., H. atli and H. simplex . Helobdella simplex has a pale brownish coloration, a dorsal medial black line, 24 fine longitudinal lines, lateral extensions on every annulus, dorsal medial row of papillae with papillae of the same size on every annulus and it has a nuchal gland, but rarely nuchal scute (Moore 1911; Siddall & Borda 2004). Helobdella atli has a white or yellowish base color without any pigmentation, lateral extensions only on the a2 and a3 annuli, dorsal medial row of papillae with papillae only on the a2 and a3 annuli and a small triangular scute (Oceguera-Figueroa & Leon-Regagnon 2005). Helobdella bowermani n. sp. is differentiated from H. atli and H. simplex by its pale yellow/buff coloration with scattered chromatophore blotches throughout the dorsal surface, lateral extensions or papillae only on the a2 annulus, dorsal medial row of papillae with small papilla on a1 and larger papillae on a2 and a3, and a small oval scute (rarely triangular).

Helobdella bowermani n. sp. is also ecologically distinct, occurring in the fine sediment of open water benthos of an eutrophic lake. Whereas, H. atli is attached underneath submerged rocks and on plants in a lake (Oceguera- Figueroa & Leon-Regagnon 2005) and H. simplex is attached on submerged substrata and aquatic vegetation in rivers, streams and lakes (Moore 1911; Siddall & Borda 2004; Gullo 1998; 2007; César et al. 2009).

Figures

FIGURE 1. Holotype (USNM 1213041) of Helobdella bowermani n. sp. A. Dorsal surface B. Dorsal surface with shadow to highlight dorsal medial row of papillae. Scale bar equals 2 mm (A, B).

FIGURE 2. Ventral surface of Helobdella bowermani n. sp., Holotype USNM 1213041. Scale bar equals 2 mm.

FIGURE 3. Internal morphology of Helobdella bowermani n. sp. Paratype USNM 1225776, ventral view. A. Cleared and stained specimen, scale bar equals 1 mm B. Schematic drawing.

FIGURE 4. Neighbor joining (NJ) tree based on the Jukes-Cantor (JC) model and bootstrap analysis with 1000 replicates of CO-I sequence data of Helobdella spp.