Huridostomum formionis Mamaev, 1970

Lakshmi, Triveni & Madhavi, Rokkam, 2008, Redescription of Huridostomum formionis Mamaev, 1970 (Digenea: Monorchiidae) from the black pomfret, Apolectus niger (Carangidae), from the coast of Visakhapatnam, Bay of Bengal with a discussion on related genera and the proposal of Pseudametrodaptes n. gen., Zootaxa 1734, pp. 59-64 : 60-61

Huridostomum formionis Mamaev, 1970

( Figs. 1 –8)

Host: Apolectus niger Bloch (Carangidae) , black pomfret (Syn: Formio niger Bloch ; Parastromateus niger Bloch ; Stromateus niger Bloch ; Citula halli Evermann & Seale ).

Locality: Visakhapatnam Coast, Bay of Bengal (17°44’N, 83°23’E)

Site: Intestine

Specimens deposited: BMNH 2008.1.29.1

Prevalence and mean intensity: A total of 118 flukes were obtained from 20 of 164 black pomfrets examined during 2004-2006. Each infected fish carried 1–25 flukes and the infection was fairly common during the months November–January. The prevalence and mean intensity were respectively 12.2% and 5.9.

Description: (Based on 20 flukes, measurements on 8 flukes) ( Figs 1– 4 )

Body elliptical, broadest at midbody, anterior part extensile, appears as narrow neck, terminating in expanded funnel-like oral sucker region; posterior region cylindrical, terminal part muscular appearing as finger like knob; total length 1248–2320, maximum width 336–480. Entire body spinose; spines triangular, prominent, arranged in regular rows over forebody, becoming sparse posteriorly. Eye-spot pigment lacking. Oral sucker cup-shaped, expanded anteriorly, rounded posteriorly, 128–224 by 192–256 in size with vertical slit-like opening. Anterior dorsal margin of oral sucker with group of 36–40 enlarged spines; spines rhomboidal, of uniform size measuring 16 by 8, arranged in two alternating rows. Ventral sucker in second quarter of body, poorly developed, much smaller than oral sucker, 66–72 in diameter, protrusible. Sucker ratio 1: 0.35– 0.38. Forebody 560–992 long, size varies with degree of contraction. Mouth subterminal, prepharynx small, 16–20 long; pharynx globular, 60–88 by 44-80 in size; esophagus 192–416 long, narrow, bifurcates well anterior to ventral sucker, ceca long, narrow, terminate just short of posterior extremity.

Genital pore median, anterior to ventral sucker. Testis single, elliptical with irregular outline, 640–960 by 64–112, occupies major part of intercaecal region of posterior half of hindbody. Post-testicular space 320–650 long with numerous circular muscles. Cirrus sac long, narrow, sinuous, 640–920 long, 80–128 wide, extends well posterior to ventral sucker to almost midlevel of testis. Seminal vesicle elliptical, occupies major part of cirrus sac; prostate cells few; cirrus very long, eversible, armed with numerous triangular spines, everted in most specimens.

Ovary entire or lobed, anterolateral to testis, overlapping anterior part of testis. Receptaculam seminis uterine. Laurer’s canal not visible. Uterine coils quite extensive, occupy entire hindbody except for muscular knob-like part at posterior region, overlapping all organs obscuring testis, terminal organ, ovary; consist mainly of three vertical loops, one on left and two on right side. Distal part of uterus modified into short thick-walled muscular metraterm. Eggs numerous, nearly rounded, thick-shelled, operculate, 14–16 by 10–12 in size. Terminal organ lies dorsal to anterior part of cirrus sac, small, oval to elliptical, thick-walled, spined along its entire length; spines triangular, similar in size and shape to cirrus spines. Metraterm joins distal part of terminal organ. Vitelline follicles in two lateral groups in front of ventral sucker, each group with numerous small follicles, commence from bifurcation point or a little anteriorly; extend slightly posterior to ventral sucker, confluent at level of bifurcation. Vitelline ducts originate from vitelline follicles as wide ducts, converge towards ovary. Excretory pore terminal, vesicle not observed.

Morphological variations: ( Figs 6 –8). Our specimens exhibited considerable morphological variations especially in the body shape, and the size of neck and posterior knob-like region. The body shape varied from the typical form described above to a cylindrical shape without a distinct neck (Fig. 8). In some flukes, the knob-like structure at posterior end had contracted totally appearing indistinct and the uterus extended almost to the posterior end of the body. The neck region was highly extensile and variable in size. Some of the flukes had a peculiar shape, with a bloated middle part, narrow anterior region and the knob-like posterior part appearing as an appendage ( Fig. 6 ). Further, the body spines and anterior group of spines were lost in most individuals probably due to post mortem effects and the tegument appeared smooth and the anterior part naked. The posterior extent of cirrus sac also varied from near the anterior margin of testis to its mid-level.

Figures

FIGURES 1 – 7. Huridostomum formionis. 1. Whole adult parasite, ventral view. 2. Anterior portion showing pattern of spination. 3. Rhomboidal spine of anterior region. 4. Terminal genitalia. 5. Terminal organ. 6, 7, 8. Morphotypes, note morphological variations in body shape and extent of cirrus sac. Abbreviations: AS, anterior spine; C, cirrus; CS, cirrus sac; GP, genital pore; MT, metraterm; OS, oral sucker; OV, ovary; SV, seminal vesicle; T, testis; TO, terminal organ; UT, uterus; VS, ventral sucker; VT, vitellarium. Scale-bars: 1,4, 5 = 200 μm; 3 = 15 μm; 2,6, 7,8 = 100 μm.