Acleotrema alejandroi, Santillan & Cruces & Mondragón-Martínez & Rojas & Chero, 2025

Acleotrema alejandroi sp. nov.

Figs 1A–H View FIGURE 1 , 6A View FIGURE 6

Type host. Kyphosus vaigiensis (Quoy & Gaimard) ( Centrarchiformes : Kyphosidae ), brassy chub.

Type locality. Off Puerto Santa Rosa (6°52’S, 79°55’W), Lambayeque, Peru, South America   GoogleMaps .

Deposited material. Holotype ( MUSM 5510 ); GoogleMaps 12 paratypes ( MUSM 5511 a–l).

Site in host. Gill filaments.

Etymology. The specific name is in honor of Dr.Alejandro Francisco Oceguera Figueroa (National Autonomous University of Mexico, Mexico) for his contributions to the field of parasitology.

Description. Based on 13 specimens: 8 mounted in Gomori’s trichrome and 5 mounted in Hoyer’s medium: Body elongate, fusiform, 0.75–1.24 (0.99; n = 13) mm long; greatest width 129–199 (160; n = 13) usually at level of testis. Tegument scaled in posterior area of trunk and peduncle ( Fig. 1A View FIGURE 1 ), scales effortlessly lost in fixed specimens. Cephalic region narrow, with one terminal and 2 bilateral poorly developed cephalic lobes; 3 bilateral pairs of conspicuous head organs; bilateral pair of unicellular cephalic glands lateral to pharynx. Two pairs of eye-spots present, equidistant; accessory chromatic granules absent ( Fig. 1A View FIGURE 1 ). Mouth subterminal; pharynx spherical, 38–52 (46; n = 12) in diameter; esophagus short; intestinal caeca unbranched, extending from anterior to near posterior end of trunk, not confluent posteriorly. Haptor differentiated from body proper, laterally expanded, 53–120 (80; n = 12) long, 208–330 (271; n = 12) wide. Anchors dissimilar, with fine conspicuous alae ( Fig. 1B–C View FIGURE 1 ). Ventral anchor 46–60 (56; n =11) long; elongate superficial root; well-elongate deep root twice as long as superficial root, medially expanded; curved shaft; and recurved point; point not surpassing level of tip of superficial root; base 3–4 (3; n = 11) wide. Dorsal anchor 19–26 (22; n = 8) long, with inconspicuous superficial root, short and subquadrangular deep root, evenly curved shaft, and short point; point surpassing level of tip of superficial root; base 6–10 (8; n = 8) wide. Ventral bar 159–234 (202; n = 13) long, elongate, with mid-ventral longitudinal groove, tapered ends ( Fig. 1D View FIGURE 1 ). Dorsal bars 68–101 (84; n = 13) long, almost bludgeon-shaped, with spatulate medial end ( Fig. 1E View FIGURE 1 ). Fourteen similar hooks, 9–11 (10; n = 12) long, each with depressed obtuse thumb, slender and slightly curved shank, and short point ( Fig. 1F View FIGURE 1 ); filamentous hook (FH) loop about shank length; hook pair 1 at level of ventral bar; hook pair 5 at level of dorsal bar; other submarginal pairs on lateral haptoral lobes. Genital atrium sclerotized, irregular in shape. Squamodiscs, similar, each 50–90 (72; n = 11) long; 132–194 (167; n = 12) wide, with 41–46 (44; n = 12) concentric rows; dumbbell-shaped rodlets ( Fig. 1G View FIGURE 1 ). Male copulatory organ (MCO) sclerotized, J-shaped, with spatulate distal end, 60–85 (74; n = 14) long. Middle portion of MCO surrounded by sclerotized sac; distal portion of sac with elongate sclerotized U-shaped process ( Figs 1H View FIGURE 1 , 6A View FIGURE 6 ). Testis ovate, 72–118 (95; n =5) long, 49–67 (59; n = 5) wide; vas deferens not looping left intestinal caeca, dilating to form C-shaped seminal vesicle in left side of trunk, posterior to genital atrium; prostatic reservoir, prostatic glands not observed. Ovary elongate, pyriform, 24–41 (29; n = 7) long, 50–90 (84; n = 7) wide, looping dorsoventrally right intestinal caeca; oviduct, oötype, uterus not observed. Vagina, seminal receptacle not observed. Vitelline follicles dense, extending from posterior level of pharynx to posterior end of trunk, absent in regions of reproductive organs. Eggs not observed.

Remarks. Based on the presence of a sclerotized genital atrium, a MCO lacking an accessory piece and a squamodisc with anterior rows of rodlets forming divergent rows ( Domingues & Boeger 2008), the newly collected specimens from K. vaigiensis are assigned to Acleotrema . Acleotrema alejandroi sp. nov. is mainly characterized by its MCO, which is J-shaped with a spatulate distal end. The middle portion of MCO is surrounded by a sclerotized sac; and the distal portion of the sac bears an elongated, sclerotized U-shaped process. The new species most closely resembles A. tamatavense ( Rakotofiringa, Oliver & Lambert, 1987) Domingues & Boeger, 2007 from Polyamblyodon gibbosum (Pellegrin, 1914) ( Sparidae ) in Madagascar and A. girellae Johnston & Tiegs, 1922 from Girella tricuspidata (Quoy & Gaimard, 1824) in Australia, due to its MCO which has a J-shaped internal tube. However, A. alejandroi sp. nov. differ from A. tamatavense by the morphology of the sclerotized sac that surround of the MCO (with elongated and sclerotized U-shaped process in the new species vs with a short C-shaped process in A. tamatavense ), and by dimensions of the ventral anchors (46–60 in the new species vs 25–30 in A. tamatavense ), ventral bar (156–188 in the new species vs 255–275 in A. tamatavense ), and dorsal bar (68–78 in the new species vs 105–110 in A. tamatavense ). Acleotrema alejandroi sp. nov. is easily differentiated from A. girellae by the sclerotised sac associated with the MCO (without radial musculature in the new species vs with radial musculature in A. girellae ) and by the morphology of ventral bar (more robust in the new species).