Spinitectus macrospinosus Choudhury & Perryman, 2003

Arai, Hisao P. & Smith, John W., 2016, Guide to the Parasites of Fishes of Canada Part V: Nematoda, Zootaxa 4185 (1), pp. 1-274 : 112-114

Spinitectus macrospinosus Choudhury & Perryman, 2003

Description (after Choudhury & Perryman 2003). With characteristics of the genus. “Head” region without spines, gradually widening posteriorly; transverse rows of cuticular spines prominent in the oesophageal region. Rows of spines divided into four sectors; prominent in the anterior third of body; sectors approximately on same level in anterior region of body; arrangement in sectors less well defined posterior to oesophageal region. First row with small spines; spines increasing in size posteriorly in oesophageal region before becoming narrower, then smaller; sectors of spine-rows becoming widely separated posteriorly in oesophageal region. Spines decreasing in number over first four rows ( Fig. 68 A). In oesophageal region mean length of spines is 0.0218 in males, and 0.0268 in females. Mouth terminal, ovoid, elongated along dorso-ventral axis, bordered by four low, submedian labia (two subdorsal, two subventral) bearing narrow, thickened sublabia, by two lateral pseudolabia, each sublabium bearing single papilla-like protuberance; inner margin of pseudolabia narrower; base widening inside oral cavity and continuous with inner wall of prostom. Short prostom followed by narrow cuticularized relatively long buccal cavity that extends beyond level of 1st row of spines; oesophagus with anterior muscular region, longer posterior glandular portion; intestine ending in short rectum surrounded by a few large gland cells; rectum leading to ventral slit-like anus. Anterior end with paired lateral amphids, and two pairs of lateral papillae. Small, simple lateral deirids between first two spine rows. Excretory pore between the 6th and 7th spine rows ( Fig. 68 A).

Males: 5.5–8.0 long, 0.070–0.085 maximum width. Spination begins 0.075–0.090 from anterior end; 56 to 67 rows of spines discerned in oesophageal region; spines extend to posterior 3rd of body, not discernible beyond region of seminal vesicle. Nerve ring 0.150–0.165 from anterior end. Prostom plus buccal cavity 0.120–0.132, muscular oesophagus 0.335–0.445, and glandular oesophagus 1.800–2.480 long. Testes originate in posterior 3rd of body; they extend anteriorly, loop posterior to oesophageal-intestinal junction before continuing posteriorly to form seminal vesicle occupying most of pseudocoelom width in posterior quarter of body, merging posteriorly with vas deferens. Posterior region of body often coiled, with an area rugosa in pre-cloacal region. Caudal region with alae flanking most of tail; four pairs of pre-cloacal papillae; six pairs of post-cloacal papillae, 6th pair (possibly phasmids) medial to 5th pair. Spicules unequal, left one 0.125–0.155 long, appearing ensheathed, with sclerotized and unsclerotized parts, bent near middle, blade portion narrowing to rounded end. Right spicule arcuate, 0.055– 0.070 long, with narrow sclerotized portion and broad unsclerotized membranous side, distal end pointed with conspicuous recurved ventral barb ( Fig. 68 B).

Females: 8.70–12.65 long, 0.085–0.115 maximum width. Spination begins 0.080–0.113 from anterior end, extending to posterior 3rd of body to within short distance of anus; 59 to 69 rows of spines discerned in oesophageal region. Nerve ring 0.155–0.180 from anterior end. Prostom plus buccal cavity 0.130–0.140, muscular oesophagus 0.405–0.555, and glandular oesophagus 2.350–2.880 long. Amphidelphic, each arm of reproductive system consisting of coiled, looped ovary, followed by looping oviduct, seminal receptacle, uterus, anterior arm of system looping near oesophago-intestinal junction, loops of posterior ovary reaching near anus ( Fig. 68 C). Uteri voluminous. Muscular vagina posteriorly directed, 0.225–0.290 long. Vulva inconspicuous, its opening transversely ovoid or slit-like, post-equatorial ( Fig. 68 D). Eggs 0.035–0.040 long, 0.018–0.025 wide, without surface ornamentation or filaments; terminal uterine eggs contain coiled larvae. Anus 0.117–0.142 from posterior end; tail apparently unspined, tapering to terminal heart-shaped mucron set off from body by narrow constriction. Phasmids ventro-lateral near tail tip ( Fig. 68 C).

Site: intestinal lumen

Hosts: Ictalurus punctatus ; Hiodon alosoides (immature worms only); Noturus flavus (immature worms only)

Distribution: Manitoba

Record: Choudhury & Perryman 2003

Comment: Moravec et al. (2009) claimed that Spinitectus macrospinosus Choudhury & Perryman, 2003 is a junior synonym of Spinitectus tabascoensis Moravec, García-Magaña & Salgado-Maldonado, 2002 . However, morphological, morphometric and geographical differences between the two species suggest that further morphological and molecular studies should be undertaken before the synonymy is accepted (A. Choudhury, pers. comm.).

Figures

FIGURE 68. Spinitectus macrospinosus Choudhury & Perryman, 2003. A. female, anterior region, lateral view; B. right spicule [top], left spicule [bottom]; C. female, posterior region showing ovary and oviduct; D. female, vaginal region. (Redrawn from Choudhury & Perryman 2003)