Demidospermus juruaensis, Justo & Martins & Cohen, 2024

Justo, Marcia Cristina Nascimento, Martins, Williane Maria De Oliveira & Cohen, Simone Chinicz, 2024, Three new species of Demidospermus (Monopisthocotyla: Dactylogyridae) parasitizing Ageneiosus inermis (Siluriformes: Auchenipteridae) from western Amazon, Brazil, Zootaxa 5541 (4), pp. 549-562 : 550-552

Demidospermus juruaensis sp. nov.

( Figs. 1 A–I )

Type-host: Ageneiosus inermis (Linnaeus, 1766)

Site of infestation: Gills

Type-locality: Juruá River , Acre, Brazil (7º40’34.1’’S, 72º39’39.5W) .

Parasitological indexes: Total number of hosts: 5; number of infested hosts: 4; total number of parasites: 53.

Specimens deposited: Specimens deposited: Holotype ( CHIOC 40446 a), Paratypes ( CHIOC: 40446 b–f; 40447 a–d)

Etymology: The specific name refers to the river where the fish hosts were collected.

Description (Based on 20 specimens, 4 stained with Langeron's hydrochloric carmine and 2 specimens stained with Gomori’s trichrome and mounted in Canada balsam, and 14 mounted in Hoyer’s medium). Body elongated, fusiform, 550–1,300 (838; n=20) long by 200–500 (306; n=20) wide at the level of the ovary. Cephalic region rounded, with indistinct cephalic lobes and three bilateral pairs of head organs; cephalic glands not observed. Eyespots 2, dorsal to pharynx. Pharynx 52–100 (73; n=13) long by 55–100 (75; n=13); esophagus short, intestinal ceca confluent posterior to gonads ( Fig. 1A ). Male copulatory organ (MCO) a slender tube, slightly curved, with irregular base, 51–85 (70; n=14); accessory piece robust, following the same curvature as the MCO, ship anchor shape, forming two arms dissimilar in size at its distal portion, serving as guide for the MCO, 60–110 (87; n=14) long ( Fig. 1B ). Gonads in tandem; testis 40–70 (54; n=6) long; Vas deferens looping left intestinal cecum. Seminal vesicle elongated. Germarium pretesticular. Germarium 75–105 (91; n=7). Oviduct, ootype, uterus and vagina not observed. Vitelline follicles densely distributed in trunk, not overlapping the reproductive organs. Peduncle broader than haptor. Haptor subquadrate, 147–475 (311, n=20) wide ( Fig. 1A ). Ventral bar 80–112 (95; n=14) long, with enlarged ends and elongated posteromedial projection, 22–36 (28; n=14) ( Fig. 1C ); dorsal bar slightly U-shaped, with enlarged ends, 55–94 (73; n=15) long ( Fig. 1D, E ). Ventral and dorsal anchors similar in shape with well-developed superficial and deep roots, long, rectangular superficial root; rounded deep root; short shaft, and point short. Ventral anchor 52–67 (62; n=27), base 43–55 (51; n=27) ( Fig. 1F ); dorsal anchor 42–51 (48; n=27), base 30–45 (35; n=27) ( Fig 1G ). Hooks different in size and shape: hooks 1–4, 6, 7 with delicate shank, divided in two subequal units, proximally expanded, depressed thumb, slightly curved shaft and point; hook pair 5 with shank divided in two equal subunits, proximally expanded, round end, erected thumb, slightly curved shaft and point, hook pair 1, 42–56 (52; n=10); pair 2, 60–70 (65; n=10), pair 3, 51–67 (58; n=10), pair 4, 45–56 (52; n=9), pair 5, 21–25 (22; n=10), pair 6, 45–55 (51; n=9), pair 7, 47–56 (52; n=9) ( Figs 1H, I ); filamentous hook (FH) loop approximately ¼ shank length.

Remarks: Demidospermus juruaensis was allocated to the genus, based on the MCO, which comprises a counterclockwise tube, a sheath-like accessory piece, tandem gonads, and a sinistral vaginal aperture. The new species resembles Demidospermus majusculus Kritsky & Gutiérrez, 1998 by the projection of the ventral bar. The new species shares the diagnostic feature of the MCO formed by a slightly curved slender tube, without forming a ring, with Demidospermus araguaiaensis Cepeda & Luque, 2010 , Demidospermus armostus Kritsky & Gutiérrez, 1998 , Demidospermus bidiverticulatum ( Suriano & Incorvaia, 1995) Kritsky & Gutiérrez, 1998 , Demidospermus brevicirrus Mendoza-Palmero, Scholz, Mendoza-Franco & Kuchta, 2012 , and Demidospermus ichthyocercus Monteiro, Kritsky & Brasil-Sato, 2010 . However, D. juruaensis sp. nov. differs from all those species mainly by the morphology of accessory piece, that follows the same curvature as the MCO, the anchor shape at its distal portion (articulated, sinuous shaped in distal portion in D. araguaiaensis , bifurcating at mid-length in D. armostus , irregular-shaped, basally articulated with MCO in D. bidiverticulatum , boot-shaped with hooked process directed posteriorly in D. brevicirrus and articulated and with shape of homocercal fishtail in D. ichthyocercus ), and by the hooks which present a very different morphology of the distal end of the shank, with a spear-shaped ending.

Figures

FIGURE 1. Demidospermus juruaensis sp. nov. from Ageneiosus inermis. A. Total ventral view (composite); B. Copulatory complex ventral view; C. Ventral bar; D, E. Dorsal bar; F. Ventral anchor; G. Dorsal anchor; H. Hook pairs 1–4, 6–7; I. Hook pair 5. Scale bars: A = 300 µm; B = 50 µm; C–I = 30 µm.