Demidospermus bifurcatus, 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 : 552

Demidospermus bifurcatus sp. nov.

( Figs. 2 A–G )

Type-host: Ageneiosus inermis (Linnaeus)

Site of infestation: Gills

Type-locality: Moa River , Acre, Brazil (7º35’28.3’’ S, 73º55’17.4” W).

Parasitological indexes: Total number of hosts: 1; number of infested hosts: 1; total number of parasites: 10.

Specimens deposited: Holotype ( CHIOC 40448 a ), Paratypes ( CHIOC: 40448 b–g )

Etymology: The specific name is a Latin adjective (bifurcatus = forked), due to the bifurcation in the distal portion of the MCO.

Description (Based on 9 specimens mounted in Hoyer’s medium). Body elongated, fusiform, 355–650 (537; n=8) long by 78–175 (126; n=8) wide at the level of the ovary. Cephalic region broad; cephalic lobes weakly developed, 3 bilateral pairs of head organs; cephalic glands indistinct. Subspherical eyespot granules scattered throughout cephalic region. Pharynx subspherical to spherical 40–62 (54; n=8) long by 28–57 (49; n=8); esophagus short, intestinal ceca confluent posterior to gonads. Male copulatory organ robust tube, inverted C-shaped, with a bisected tip at its distal end, irregular base, 69–111 (88; n=8); accessory piece robust, embracing the MCO in its full extension, 63–105 (79; n=8), proximal portion expanded forming two arms, one wider than the other, with a tendency to wrap around the base of the MCO ( Fig. 2A ). Gonads in tandem; testis 187 (n=1) long; vas deferens looping left intestinal cecum. Seminal vesicle long, fusiform. Germarium pretesticular 75 (n=1) long. Slightly sclerotized vagina with bifurcated canal and ornate opening ( Fig. 2B ). Oviduct, ootype, and uterus not observed. Vitelline follicles densely distributed in trunk, not overlapping the reproductive organs. Peduncle inconspicuous. Haptor width similar to the body. Haptor sub-hexagonal, 71–215 (116; n= 8) wide. Ventral bar slightly curved 42–59 (50; n=8) long ( Fig. 2C ); dorsal bar open V-shaped 44–59 (52; n=8) long ( Figs. 2D ). Ventral anchor with elongated superficial root; deep root rounded; straight shank, straight and long point, extending slightly beyond superficial root 28–35 (32; n=16), base 17–24 (19; n=16) ( Fig. 2E ). Dorsal anchor with well-developed superficial root, deep root rounded, short, straight point extending slightly beyond superficial root, 22–35 (31; n=16), base 16–22 (19; n=16) ( Fig. 2F ). Hooks similar in shape and size, pair 1, 15–21 (18; n=8), pair 2, 15–21 (19; n=8), pair 3, 15–22 (19; n=7), pair 4, 16–19 (18; n=5), pair 5, 17–22 (20; n=5), pair 6, 17–20 (19; n=4), pair 7, 17–19 (19; n=4), with curved point and delicate shaft, protruding thumb, expanded shank proximally; FH loop approximately ⅔ shank length ( Fig. 2G ).

Remarks: Demidospermus bifurcatus is characterized by a MCO formed by a robust tube, inverted C-shaped, with a distal end presenting a bisected tip and a robust accessory piece, embracing the MCO in its full extension, proximal portion to the base of the MCO expanded forming two arms; this morphology of the copulatory complex distinguishes the new species from all congeners.

Figures

FIGURE 2. Demidospermus bifurcatus sp. nov. from Ageneiosus inermis. A. Copulatory complex, ventral view; B. Vagina; C. Ventral bar; D. Dorsal bar; E. Ventral anchor; F. Dorsal anchor; G. Hook. Scale bars: A, C, D = 30 µm; B, 10 µm; E, F = 20 µm; B, G =10 µm.