Chauhanellus peruvianus, Cruces & Ñacari & Mondragón-Martínez & Simões & Luque & Chero, 2025

Chauhanellus peruvianus sp. nov. Cruces, Ñacari, Luque & Chero

( Figs. 1A–G View FIGURE 1 )

Type host. Galeichthys peruvianus Lütken ( Siluriformes , Ariidae ), Peruvian sea catfish.

Site in host. Gill filaments.

Type locality. Puerto Pizarro ( 3°29’S, 80°24’W), Tumbes, Peru, South America GoogleMaps .

Type material. Holotype: MUSM 5571 ; paratypes: MUSM 5572 a-d; hologenophore: MUSM 5573 .

Molecular sequence data. The 28S rDNA (844 bp) obtained from one specimen, were deposited in GenBank (accession numbers PV599984).

Etymology. The specific epithet refers to the country where the new species was found.

Description: Based on eight specimens, four mounted in Hoyer’s medium and four stained with Gomori’s trichrome. Body elongated ( Fig. 1A View FIGURE 1 ), slender to robust, 835–961 (882; n = 4) long; greatest width 86–94 (90;

with boldface type.

n = 4), usually at level of vaginal opening. Tegument thin, surface smooth. Cephalic margin narrow, tapered; cephalic lobes poorly developed; 3 bilateral pairs of conspicuous head organs; bilateral groups of cephalic glands at postpharyngeal level. Eyes four, equidistant, members of anterior pair smaller than those of posterior pair; chromatic granules absent. Pharynx oval, muscular, glandular, 62–72 (67; n = 4) long, 33–45 (37; n = 4) wide; esophagus short; intestinal bifurcation postpharyngeal; intestinal ceca not confluent posteriorly to gonads, lacking diverticula. Peduncle broad, elongate, with well-developed secretory gland. Haptor digitiform, differentiated from body proper, almost subspherical, 76–118 (97; n = 4) long; 83–105 (97; n = 4) wide, with two haptoral glands. Anchors dissimilar. Ventral anchor 30–32 (31; n = 4) long, with divergent roots; deeply expanded deep root resembling an alar extension, tapered elongate superficial root, evenly curved shaft, recurved point; point extending at level of tip of superficial root ( Fig. 1B View FIGURE 1 ). Dorsal anchor robust, 35–38 (37; n = 4) long, with conspicuous inner filament, with inconspicuous roots, slightly curved shaft, recurved point; point extending well past level of tip of inner base ( Fig. 1C View FIGURE 1 ). Ventral bar 59–62 (61; n = 4) long, slightly bent, elongated, with two well-developed posterolateral projections for articulation with ventral anchors ( Fig. 1D View FIGURE 1 ). Dorsal bar 81–84 (83; n = 4) long, V-shaped, with tapered anterolateral projections for articulation with dorsal anchors, expanded posteromedial projection with crenulated margin ( Fig. 1E View FIGURE 1 ). Seven pairs of similar hooks, 12–14 (13; n = 4) long, each with undilated shank composed of a single subunit, erect thumb, slightly curved shaft and delicate point; filamentous hook (FH) loop approximately equal in length to shank ( Fig. 1F View FIGURE 1 ). Male copulatory organ (MCO) 47–50 (49; n = 8) long, sclerotized, tubular, with shaft exhibiting proximal and distal curvatures, with spear-shaped distal end, base with sclerotized cap; accessory piece sclerotized, elongate, grooved, proximally expanded, distally hook-shaped ( Fig. 1G View FIGURE 1 ). Gonads tandem. Testis ovate, intercecal, dorsal to ovary, 114–122 (118; n = 4) long, 43–45 (44; n = 4) wide; vas deferens looping left intestinal cecum, dilating to form sigmoid seminal vesicle in left side of trunk, posterolateral to MCO; single elongate saculiform prostatic reservoir, lying posterior to the base of MCO. Ovary 102–119 (111; n = 4) long, 28–31 (29; n = 4) wide; ovate. Vaginal aperture dextrolateral; vaginal vestibule well-elongate, sclerotised, tubular, directed anteriorly; vaginal duct narrow, short, running anteriorly to join small subspherical seminal receptacle. Oviduct, oötype and uterus not observed. Vitelline follicles dense throughout trunk, lateral fields of follicles confluent anterior to MCO and posterior to testis. Egg not observed ( Fig. 1A View FIGURE 1 ).

Remarks: Chauhanellus peruvianus sp. nov. appears to be closely related to C. riograndinensis and C. susamlimae , both described from the Atlantic coastal region of the Amazon Basin, by having a digitate haptor and a similar pattern of the roots of the ventral anchor. However, the new species differ from C. riograndinensis by the morphology of the MCO (a tubular structure with proximal and distal curvatures in the new species vs a tube forming approximately one counterclockwise ring in C. riograndinensis ), the accessory piece (distally hook-shaped in the new species vs T-shaped in C. riograndinensis ), and the posteromedial projection of the dorsal bar (expanded with a crenulated margin in the new species vs elongated in C. riograndinensis ). The new species differ from C. susamlimae in the morphology of the accessory piece, which is hook-shaped in C. peruvianus sp. nov., but elongated in C. susamlimae . Additionally, the MCO of C. peruvianus sp. nov. presents proximal and distal curvatures, whereas it is sigmoid in C. susamlimae .