Leuceruthrus ksepkai n., 2022

Bullard, Matthew R. Womble and Stephen A., 2022, Azygiid Parasites Of North American Endemic Pleurocerids And Centrarchids: Revision Of Leuceruthrus Marshall And Gilbert, 1905 (Digenea: Azygiidae), Description Of Two New Species, And Phylogenetic Analysis, Journal of Parasitology 108 (4), pp. 374-394 : 385-386

Leuceruthrus ksepkai n. sp.

( Figs. 9 13 ; Table II)

Diagnosis of cercaria (based on light microscopy of 12 stained, whole-mounted, naturally shed cercariae having a withdrawn distome) ( Figs. 9 13 ): Cercaria 3,600 4,140 (3,944, 5) long. Tail stem 2,980 3,460 (3,228, 5) long or 77 84% (82%, 5) of cercariae length, maximum width 560 740 (652, 2) or 4.3 5.7 (6, 2) X longer than wide, comprised of an anterior and posterior region ( Fig. 9 ); anterior tail stem region (ATS) 1,480 1,800 (1,668, 5) long or 39 46% (42%, 5) of cercariae length, with anterior ridge, and posterior collar, maximum width same as reported for tail stem, primarily cylindrical, tapering anteriorly, containing distome; ATS ridge near anterior end of tail stem ( Figs. 9, 10 ), preceding tail cavity opening, 320 490 (446, 5) wide, 120 220 (168, 5) of cercaria length from anterior end of cercaria; ATS collar 620 740 (675, 4) wide or 1.3 2.2 (1.6, 4) X wider than anterior tail stem ridge, appearing as a laterally expanded ‘‘flange like’’ tegumental ring, at confluence of anterior and posterior tail stems ( Figs. 9, 10 ); posterior tail stem region (PTS) dorsoventrally compressed, 1,400 1,820 (1,560, 5) long or 35 44% (39%, 5) of cercariae length, anterior width 520 600 (548, 4), medial width 380 580 (473, 4) posterior width 320 540 (408), nearly uniform in width anteriorly to posteriorly ( Fig. 9 ), bearing many minute protuberances ( Figs. 9, 11, 12 ); PTS protuberances, minute, marginally distributed throughout entire length of PTS, also encircling anterior third of PTS ( Figs. 9, 11, 13 ). Furcae with conspicuous black markings along margins when alive, oblong, dorsoventrally compressed, bearing many minute pored protuberances; furcal protuberances, minute, distributed marginally, and occasionally submarginally ( Fig. 9 ); dorsal furca, 690 790 (724, 5) or 17 19% (18%, 5) of cercariae length, 600 760 (678, 5) wide or 85 98% (94%, 5) of furca length, ventral furca, 680 860 (752, 5) or 17 20% (19%, 5) of cercariae length, 600 790 (684, 5) or 80 97% (91%, 5) of furca length. Tail cavity opening at anteromedial end of cercaria, directing anteriad. Tail stem spines not evident. Excretory system with 1 primary excretory canal, extending posteriad along medial axis of the posterior tail stem, bifurcating at synthesis of furcae, extending independently through each furcae, opening via excretory pore at distal end of each furcae ( Fig. 9 ).

Body of distome (¼cercarial body) ( Fig. 9 ) 1,540 1,630 (1,592, 5) long or 37 45% (41%, 5) of cercaria length, 490 550 (510, 5) wide or 2.8 3.3 (3.1, 5) X longer than wider, anterior margin 30 155 (88, 5) from tail cavity opening; forebody 880 980 (918, 5) long or 54 60% (57%, 5) of overall body length; hindbody 330 360 (350, 5) long or 21 22% (22%, 5) of overall body length, 37 40% (38%, 5) of forebody length, posterior end in-curled; tegument unarmed. Excretory system not evident. Nervous system not evident. Oral sucker 420 500 (467, 5) long or 26 32% (29%, 5) of body length, 310 365 (341, 5) wide or 64 75% (67%, 5) of body width, 50 100 (75, 5) or 3 6% (4%, 5) of body length from anterior body end, 840 1,040 (976, 5) or 52 66% (61%, 5) of body length from posterior body end, posterior margin 325 440 (373, 5) from anterior margin of ventral sucker ( Fig. 9 ). Ventral sucker in posterior half of body, 260 330 (296, 5) or 16 21% (18%, 5) of body length, 270 320 (294, 5) or 51 63% (58%, 5) of body width, 55 71% (64%, 5) of oral sucker length, 79 94% (86%, 5) of oral sucker width ( Fig. 9 ). Pharynx ovoid, 100 150 (125, 5) long or 6 9 % (8%, 5) of body length, 110 125 (112, 5) wide ( Fig. 9 ). Esophagus extending posteriad from mouth before bifurcating posterior to pharynx, esophageal branches arching posterolaterad before joining with intestinal ceca; dextral cecum 1,005 1,290 (1,173, 5) or 62 84% (74%, 5) of body length, laterad cecum length 245 360 (288, 5), descending cecum length 740 960 (885, 5), prececal space, 450 650 (526, 5) or 28 40% (33%, 5) of body length from anterior end of body, postcecal space, 55 120 (74, 4) or 3 7% (5%, 4) of body length from posterior end of body; sinistral cecum 1,050 1,330 (1,190, 5) or 64 82% (75%, 5) of body length, laterad cecum length 230 340 (266, 5), descending cecum length 775 1,000 (924, 5), prececal space 430 710 (532, 5) or 27 44% (33%, 5) of body length from anterior end of body, postcecal space, 50 100 (74, 4) or 3 6% (5%, 4) of body length from posterior end of body ( Fig. 9 ).

Testes abreast, round to oval ( Fig. 9 ); dextral testis 55 65 (60, 4) or 3 4% (4%, 4) of body length, 50 70 (58, 4) or 0.85 1.2 (1, 4) X wider than long; sinistral testis 50 80 (61, 4) or 3 5% (4%, 4) of body length, 65 70 (66, 4) or 0.77 1.10 (0.92, 4) X wider than long; pretesticular space 1,000 1,160 (1,075, 4) from anterior end of body or 61 75% (67%, 4) of total body length; posttesticular space 300 420 (3,489, 4) from posterior end of body or 19 26% (22%, 4) of total body length. Prostatic sac 65 75 (71, 5) long, 60 85 (100, 5) or 0.85 1.3 (1, 5) X wider than long ( Fig. 9 ). Genital atrium circular in ventral view, 35 45 (28, 2) in diameter. Genital pore 835 960 (877, 5) of body length from anterior end of body or at 52 59% (55%, 5) of body length. Features of terminal male genitalia (i.e., seminal vesicle, pars prostatica, ejaculatory duct, sinus organ) appearing as anlagen, difficult to discern.

Ovary near posterior end of body or 160 310 (210, 5) of body length from posterior end of body, 50 75 (59, 5) long or 0.80 1.50 (1, 5) X longer than wide, 50 60 (55, 5) wide ( Fig. 9 ). Fine details of the female genitalia (i.e., oviduct, Laurer’s canal, ovovitelline duct, oötype, and Mehlis’ gland) difficult to discern. Uterus 430 655 (543, 2) long or 34 37% (35%, 2) of body length, 13 20 (17, 2) wide, extending in a straight line from anterior margin of ovary, passing between testes, difficult to discern distally; metraterm not evident. Vitellarium lacking in distome.

Taxonomic summary for Leuceruthrus ksepkai n. sp.

Type host: Elimia floridensis (Reeve, 1860) , rasp elimia.

Other hosts: Elimia sp. 1 and M. salmoides .

Type locality: Holmes Creek (30°36 ′ 25 ′′ N, 85°44 ′ 49 ′′ W), Florida .

Other locality: Chocktawhatchee River (30°30 ′ 51 ′′ N, 85°50 ′ 55 ′′ W), Florida .

Specimens and sequences deposited: Holotype (cercaria, USNM 1593586 ), paratypes (cercariae, USNM 1593587 , 1593588 ), ITS2 (cercaria from E. floridensis , GenBank ON877233 ).

Prevalence and intensity of infection: 5 of 134 (4%) E. floridensis and 12 of 210 (6%) of Elimia sp. 1 from Holmes Creek and Chocktawhatchee River, respectively, were infected.

ZooBank registration: urn:lsid:zoobank.org:act:C76AAE4F-1681-4D99-8086-E6C2F2E40C0B .

Etymology: The specific epithet ‘‘ ksepkai ’’ is for Steven P. Ksepka, Aquatic Parasitology Laboratory, Auburn University, and is in recognition of his work exploring the parasites of centrarchid fishes in the southeastern United States.

Taxonomic remarks on Leuceruthrus ksepkai n. sp.

We studied only naturally shed, actively swimming cercariae of L. ksepkai (Table II). Cercariae from both snail hosts ( E. floridensis and Elimia sp. 1 ) were morphologically identical and regarded as conspecific herein. Leuceruthrus ksepkai differs from all nominal congeners by the combination of having broadly rounded furcae (with slight pigmentation along margin in living specimens), no spines on the tail stem, distinct anterior and posterior ridges that flank the tail stem portion accommodating the withdrawn distome, minute protuberances occupying the lateral margin of the tail stem for its entire length, and protuberances that encircle the anterior third of the posterior tail stem (immediately posterior to the tail stem portion containing the withdrawn distome). Leuceruthrus ocalana is the only other species of Leuceruthrus that has broadly rounded furcae (which superficially resemble those of Proterometra spp. ; Fig. 18 ). As indicated above, we consider L. ocalana a species inquirendae because its original description is deficient and incomplete.

Figures

Figure 18.—Maximum likelihood phylogenetic tree based on the internal transcribed spacer 2 (ITS2). Support values aside each node. Cercariae accompany the end of each branch.

Figures 9–14. Leuceruthrus from Holmes Creek, Florida. (9–13) Naturally shed cercaria of Leuceruthrus ksepkai n. sp. from Elimia floridensis from Holmes Creek, Florida. (9) Cercaria (USNM 1593587) showing tail cavity opening (tco), position of anterior ridge (ar), and anterior collar (ac), anterior (ats) and posterior tail stem (pts) regions, location of the distome, showing pharynx (p), ceca (c), prostatic sac (ps), ventral sucker (vs), testes (t), ovary (o), and paired oblong furcae (f). Dorsal view. (10) Anterior portion of tail stem accommodating the withdrawn distome. (11) Illustration of posterior tail stem showing position of associated protuberances. (12) Posterior tail stem showing position of associated protuberances. SEM. (13) Highmagnification view of a posterior tail stem protuberance. SEM. (14) Adult of Leuceruthrus cf. ksepkai from stomach of largemouth bass, Micropterus salmoides from Holmes Creek, Florida (USNM 1593590) showing mouth (m), pharynx (p), ceca (c), prostatic sac (ps), genital pore (gp), ventral sucker (vs), testes (t), distal portion of uterus (ud), vitellarium (vi), origin of uterus (uo), ovary (o), vitelline reservoir (vr), excretory duct (ed), excretory bladder (eb), and excretory pore (ep). Ventral view.