Neoechinorhynchus golvani, Salgado-Maldonado 1978

Guillermo Salgado-Maldonado, 2013, Redescription of Neoechinorhynchus (Neoechinorhynchus) golvani Salgado-Maldonado, 1978 (Acanthocephala: Neoechinorhynchidae) and description of a new species from freshwater cichlids (Teleostei: Cichlidae) in Mexico, Parasitological Research 112, pp. 1891-1901 : 1892-1895

N. (N.) golvani Salgado-Maldonado 1978

Hosts: P. fenestratus (Günther, 1860) (Teleostei, Cichlidae )

Site: Intestine.

Locality: Lago de Catemaco, Veracruz, Mexico (18°21′– 18°27′N, 95°01′–95°07′W).

Voucher specimens: Holotype CNHE 601, paratypes CNHE 603, vouchers CNHE 604, 606, 631, 632

Redescription ( Figs. 1–6)

General (Based on 46 specimens, 18 mature and 3 juvenile males; 12 gravid, 10 mature plus 3 juvenile females).

Neoechinorhynchidae, Neoechinorhynchinae with characters of the genus as diagnosed by Amin (2002). Robust, medium size acanthocephalans. Trunk of mature males medium sized, ovoid long gradually tapering to both ends. Posterior end blunt in males ( Fig. 1). Trunk of ripen females of maximum size, ovoid long, tapering gradually to both ends; posterior end rounded in females ( Fig. 2). Giant hypodermal nuclei are not readily marked in mature specimens. In juvenile smaller specimens, body wall contains five dorsal and one ventral giant hypodermal vesicular nuclei. Sexual dimorphism in size is very evident in mature specimens; trunk of largest female is 15, 463 long, 3.6 times than largest male 4, 275 long ( Fig. 2). Proboscis and hooks similar sized in both sexes. Proboscis small in size compared to trunk. Proboscis short cylindrical, rather wider than long ( Fig. 3) with three circles of six hooks each. Anterior hooks notably larger. Anterior hooks equal in length, conspicuously long, stout, heavily curved, at least two times larger than other hooks in proboscis. Lateral anterior proboscis hooks placed little below level of the others in same circle. The hooks in middle and basal circles are smaller than those of the terminal series, about equal in length ( Fig. 3). Hooks of the first and second circles are wider apart than hooks of second and third circles ( Fig. 3). Only hooks of anterior circle evidently rooted; roots of anterior circle spoon-shaped, roots of other hooks mainly orbicular, discoid, but some hooks with long roots. Neck very short, rather wider than long. The entire presoma of the specimens, including the proboscis, neck and anterior portion of the body can retract in a telescoping manner into the anterior trunk region. In many cases, the proboscis does not invaginate but only retracts completely inside the receptacle and this retracts within the trunk; proboscis maintains shape and hook position. In other specimens, true proboscis invagination observed as in most acanthocephalan species. Proboscis receptacle with single muscular wall, with large more or less triangular ganglion at posterior end. Parareceptacle glandular structure present, difficult to see in many specimens but clearly visible in others (holotype CNHE 601 with parareceptacle structure). Parareceptacle structure along ventral side of proboscis receptacle, connecting anteriorly to body wall with duct, adheres to ventral side almost reaching posterior end of proboscis receptacle ( Fig. 4). Two lemnisci sacciform similar in length with giant nuclei not easily observed in several mounted specimens, widest posteriorly, longer than proboscis receptacle; one lemniscus with two giant nuclei, the other with one. Eggs ovoid, slender, without polar prolongation of fertilization membrane ( Fig. 6), with a delicate continuous outer membrane difficult to observe even amongst the eggs of a same specimen.

Measurements

Male (measures of seven mature specimens). Trunk 1,175– 4, 275 (2, 890)×417–907 (768). Proboscis 55–65 (61.2)× 63–72 (67). Anterior proboscis hooks 40–47 (42.4) long by 5–9 (6.6) wide at base; middle hooks 18–22 (19.6)×3–4 (3); basal hooks 18–21 (18.8)× 3–4 (3). Neck 25–35 (27)×65– 80 (71). Proboscis receptacle 250–336 (280) ×72–99 (84). Lemnisci 257–495 (392) × 37–128 (66) wide posteriorly, and 257–544 (408)×47–128 (71). In fully developed adults, the male reproductive system ( Fig. 1) occupies posterior half the length of the trunk 1,138–2,574 (1,979) (n =3 specimens measured), in diameter do not fill the cavity. Testes in broad contact with each other. Anterior testis ovoid, posterior testis ovoid to oblong, tandem, contiguous, posterior testis overlaping with cement gland. Anterior testis 376–821 (495)× 336–445 (385); posterior testis 250–544 (436)× 346–514 (428) (n =3). Cement gland voluminous, nearly the same diameter as the testes, slightly larger than broad, in broad contact with posterior testis, 643–643 (643)×415– 495 (455) (n =2); seven giant nuclei evident only in juvenile specimens. Cement reservoir conspicuous, ovoid, 227–247 (237)×148–198 (173) (n =2). Saefftingen’s pouch small, elongate, 396–396 (396) ×99–118 (108) (n =2). Sperm ducts on ventral side of testis, join posteriorly to form common sperm duct. Common sperm duct posteriorly opening on a seminal vesicle large and ovoid. This seminal vesicle empties in muscular pennis at the interior of bursa. Copulatory bursa opens terminally.

Female (measures of four gravid specimens, two of them with proboscis retracted). Trunk 7, 355–15, 463 (10, 270),× 1,485–3,0 69 (2,002). Proboscis 60–75 (67)×70–92 (81). Anterior proboscis hooks 45–50 (47)×7–7(7) wide at base; middle hooks 18–20 (19)×3–4 (3); basal hooks 18–20 (19)× 3–4 (3). Proboscis receptacle 280–310 (295)×112–127 (119). Lemnisci 350– 462 (406)×85–95 (90), and 350–462 (406)× 87–100 (93). Gonopore subterminal ventral ( Fig. 5). Mature maximum size drawed at the same scale. 3 Proboscis. 4 Anterior end of a paratype (CNHE 634). 5 Reproductive system of a female. 6 Egg teased from the body cavity eggs inside body cavity 27–32 (29.8)×8–10 (9) (35 eggs measured).

Intraspecific morphological variability

Morphological study of specimens of N. golvani found in P. fenestratus from Lago de Catemaco lake showed that body shape and size, proboscis receptacle and lemnisci size, and male genital organ distribution are variable characteristics, while proboscis and hook dimensions are very stable from early stages of development.

Body shape changes in males and females as they grow. In smaller males, the medial anterior portion of the body appears distended, the neck and proboscis emerge as a conical projection towards the anterior end whereas the trunk tapers towards the posterior extreme, curving ventrally. Larger males are elongated and ovoid, tapering gradually towards both ends, the posterior extreme being curved ventrally. Females are ovoid, and gravid females are larger, very elongate ovoids, almost belted, tapering gradually towards the anterior end with a rounded posterior end ( Fig. 2). Body shape and internal organ position change according to degree of contraction and accumulation of genital products. Specimen handling during whole mount preparation can also modify general body shape and internal organ position and appearance.

Male N. (N.) golvani in P. fenestratus from Lago de Catemaco can reach sexual maturity at almost one quarter of maximum size while females reach at one thirteenth maximum size. The smallest male specimens with spermatozoids in the seminal vesicle and with a full cement reservoir measure 772–1,712 (1,167)×445–623 (504) (n =3) whereas the largest male measured 4,275×970. Females continue growing after fecundation and during embryo development, increasing size up to 15-fold. Smaller females with developing eggs measure 990–1,287 (1,155)×316–574 (418) (n =3), while the largest gravid female measures 15,463×3,069.

Proboscis and proboscis hook shape and size are very stable characteristics from very early development stages. In the smallest males (772–1,712 (1,167)×445–623 (504)), proboscis measures 57–68 (62)× 70–78 (74), apical hook length is 50–53 (51.6), medial hook length is 20–22 (21) and basal hook length is 15–17 (16) (n = 3). In the smallest nongravid females with a complete ovarium, body size is 505–1,197 (759)× 205–366 (279), proboscis measures 55– 67 (61) ×58–85 (71), apical hook length is 50× 6–10 (8.7), medial hook length is 16–20 (18)×3, and basal hook length is 16× 3 (n =3). The smallest gravid females with developing eggs measure 990–1,287 (1,155)×316–574 (418), proboscis measures 58–70 (65) ×68–85 (76.6), apical hook length is 48–50 (49.3), medial hook length is 22 (22), and basal hook length is 16–18 (17) (n =3). Hook dimensions can be measured even in specimens where the proboscis is retracted in the anterior body; in one very small (600×287) specimen, the invaginate apical hook measures 47× 8 and the medial and basal hooks measure 20×3.

Presence of N. golvani in other host fish species

Examination of museum specimens confirmed the presence of N. golvani , i.e., acanthocephalans with the morphological and meristic characteristics compatible with those described above, in the cichlid species (Teleostei: Cichlidae ) recorded from the localities and dates listed in Table 2.

Remarks

Taking into account the data presented here, N. (N.) golvani can be specifically identified using six criteria: (1) proboscis is small, subcylindrical, and rather wider than long (♂ 55– 65 (61.2)×63–72 (67), ♀ 60–75 (67)× 70–92 (81); (2) proboscis is reduced compared to overall body length, this disproportion between minimum proboscis size and total length is notably accentuated in adult specimens of maximum size; (3) in terms of proboscis hook shape and size, apical ring hooks are conspicuous, two lateral apical hooks are slightly below the four remaining hooks, apical hooks are three times longer (♂ 40–47 (42.4), ♀ 45–50 (47) than the medial and basal hooks, which are approximately the same size (♂ 18–22 (19.6), 18–21(18.8), ♀ 18–20 (19), 18– 20 (19); (4) apical hook length is 50 % greater than the proboscis length (♂♀ 61–81 %); (5) egg dimensions (27–32 (29.8)×8–10 (9)); and (6) lemnisci extend in the anterior fifth of the body and are larger (≈1.5 times) than the proboscis receptacle. Proboscis dimensions, hook length and egg size of N. golvani are useful taxonomical structures because their dimensions remain stable from early development stages (Salgado-Maldonado 1985 and data in the present work).

The species exhibits broad morphological variability, particularly in body shape and size; apparently, it also continues to grow throughout its lifespan. Specimen examination showed that body shape is modified by contraction of different series of musculature. Specimen shape depends on degree of maturity, while organ location and shape is influenced by degree of body extension or contraction, and by the accumulation of genital products. Males can reach sexual maturity at one quarter of full size and females at one thirteenth of full size. Examination of many N. (N.) golvani specimens during this study helped identify sexual dimorphism in terms of size; that is particularly accentuated in this species where gravid females are four to five times larger than males.

In addition to this considerable morphological variability, N. (N.) golvani can also be found in a wide range of cichlid fish hosts. The size, shape, and position of different organs and structures in helminths can be greatly modified in response to host influence (Stunkard 1957; Buckner and Nickol 1979).

The present data record the presence of N. golvani as a parasite in 19 cichlid species along both coasts of Mexico and Central America. It occurs from Nayarit to Oaxaca along the Pacific versant, and along the Atlantic coast it occurs from the Panuco River in Mexico to Nicaragua.