Chauhanellus velum, Domingues, Marcus V., Soares, Geusivam B. & Watanabe, Alana, 2016

Domingues, Marcus V., Soares, Geusivam B. & Watanabe, Alana, 2016, Monogenoidea (Polyonchoinea: Dactylogyridae) parasitizing the gills of marine catfish (Siluriformes: Ariidae) inhabiting the Atlantic Amazon Coast of Brazil, Zootaxa 4127 (2), pp. 301-326 : 311-313

Chauhanellus velum n. sp.

( Figs. 22–29 )

Type-host: Sciades couma (Valenciennes)

Site of infection: Internal borders of the primary lamellae of the gills.

Type locality: Fish market, Municipality of Bragança, State of Pará, Brazil.

Other records: Sciades herzbergii, Furo da Ostra (0°38’ 59”S, 47°53’22,89917”W) municipality of Curuça, State of Pará, Brazil; Sciades passany, Fish market, Municipality of Bragança, State of Pará, Brazil.

Prevalence of infection: 2 of 14 (14%) of S. couma ; 1 of 79 (1%) of S. herzbergii ; 3 of 13 (23 %) of S. passany .

Specimens deposited: Holotype, CHIOC 38261; 1 paratype, INPA 679; 4 vouchers, CHIOC 38261 –38262a– b, MPEG 060.

Etymology: The specific name (a noun) is from the Latin velum (a veil) and refers to the shape of the haptor.

Comparative measurements: Table 4 .

Description: Based on 6 adult specimens; 3 mounted in Gomori’s trichrome, 3 mounted in GAP. Body fusiform ( Fig. 22 ), total length excluding haptor 1025 (950–1100; n=2) long, 215 (180–250; n=2) wide at level of germarium. Tegument smooth. Cephalic margin tapered; moderately developed terminal lobes; three bilateral pairs of head organs with rod-shaped secretion; cephalic glands unicellular, lateral to pharynx. Eyes 4, posterior pair larger than anterior pair; accessory granules absent or few in cephalic area, spherical. Mouth subterminal, midventral; pharynx subspherical, 119 (n=1) long, 113 (n=1) wide; oesophagus, intestinal caeca obscured by vitellaria. Genital pore, genital atrium not observed. Testis post-germarial; testis dorsal to germarium. Testis spherical, 129 (100–158; n=2) long, 91 (58–125; n=2) wide. Vas deferens, seminal vesicle obscured by vitellaria. One prostatic reservoir, spherical, lying ventral posterior to copulatory complex. Copulatory complex comprising male copulatory organ, accessory piece; male copulatory organ, sclerotized, a coiled tube with 1 counterclockwise ring, base with an expanded sclerotized cap, 110 (n=1) long, distal aperture acute. Accessory piece sclerotized, non-articulated with male copulatory organ comprising two portions, proximal portion with three small projections (one projection serrated on inner margin) and duct throughout the male copulatory organ pass, distal portion an elongated sheath ( Fig. 23 ). Germarium 158 (159–165; n=2) long, 90 (63–116; n=2) wide, spherical. Vagina comprising vaginal aperture with dextroventral opening, marginal; vaginal vestibule with soft tissue; vaginal canal short, sclerotized, knob shape. Seminal receptacle, Mehlis’ glands, ootype not observed. Vitellaria dense throughout trunk, except in region of reproductive organs. Eggs not observed. Peduncle short. Haptor subcircular, velum like, anchor/bar complex positioned at center of haptor in a small protuberance, margin of haptor delicate, armed with 12 evenly spaced marginal hooks. Anchors dissimilar. Ventral anchor ( Fig. 27 ) 62(n=1) long, base 40(n=1) long, robust, base with expanded medial, posterior; inconspicuous roots, shaft bent at midpoint, forming angle of approximately 100°, short recurved point. Dorsal anchor ( Fig. 28 ) robust, with inconspicuous roots, expanded margin, slightly curved shaft, short point; anchor spine blunt. Ventral bar ( Fig. 24 ) 11(n=1) long, 46 (n=1) wide, curved in posterior direction with longitudinal groove; small protuberances at each end for articulation with ventral anchor. Dorsal bar ( Fig. 25 ) 12 (n=1) long, 52(n=1) wide, open V-shaped, with longitudinal groove, rounded ends; short posteromedial process. Hooks similar in shape ( Fig. 26 ), pairs 1–4, 6–7 at margin of the haptor, pair 5 not observed, 16 (n = 2) long, shank without inflation, depressed thumb, evenly curved shaft point, filamentous hook loop about 2/3 of shank length.

Remarks: Chauhanellus velum n. sp. differs from its congeners by possessing a subcircular haptor, veil like, with anchor/bar complex positioned in a small protuberance in the center of the haptor, and hooks marginal. The shape of the haptor seems to be related to the site on the gills where this parasite attaches. While other species Chauhanellus occupy the secondary lamellae of the gills, Chauhanellus velum n. sp is able to attach itself to the internal borders of the primary lamellae by folding the haptor in its transverse axis ( Fig. 29 ).

Figures

FIGURES 29. Photomicrograph of specimen of Chauhanellus velum n. sp. Arrow indicates the attachment point of the haptor to the internal borders of the primary lamellae. Scale of 50 µm.

FIGURES 22 – 28. Chauhanellus velum n. sp. 22. Holotype, whole-mount (ventral). 23. Copulatory complex. 24. Ventral bar. 25. Dorsal bar. 26. Hook. 27. Ventral anchor. 28. Dorsal anchor. Fig. 22 scale of 200 µm; Figs. 23 – 28 scale of 25 µm.

Tables

TABLE 4. Comparative measurements (in µm) of specimens of Chauhanellus velum n. sp. from the gills of Sciades couma, S. herzbergii and S. passany. MCO = male copulatory organ.

	S. couma	N	S. herzbergii	N	S. passany	N
Body
Length	1025 (950–1100)	2	760	1	–	–
Width	215 (180–250)	2	210	1	–	–
Haptor
Length	420	1	390	1	–	–
Width	470	1	410	1	–	–
Pharynx
Length	119	1	71	1	–	–
Width	113	1	95	1	105 (88–122)	2
MCO length	110	1	104 (97–112)	2	85	1
Ventral Bar
Length	11	1	10 (9–11)	2	14 (12–15)	2
Width	46	1	49 (46–52)	2	55 (52–57)	2
Dorsal Bar
Length	12	1	14 (12–15)	2	15	2
Width	52	1	49 (41–57)	2	67 (64–69)	2
Ventral Anchor
Inner	–		28 (25–31)	2	37	1
Outer	62	1	43 (41–44)	2	37	1
Base	40	1	29 (27–31)	2	45	1
Dorsal Anchor
Inner	–	–	115	1	150	1
Outer	–	–	123	1	165	1
Base	–	–	75	1	63	1
Hooks	16	2	16 (15–17)	2	16	2
Germarium
Length	158 (159–165)	2	125	1	–	–
Width	90 (63–116)	2	68	1	–	–
Testis
Length	129(100–158)	2	–	–	–	–
Width	91(58–125)	2	–	–	–	–