Raphidascaroides nipponensis, Yamaguti, 1941

Moravec, F. & Nagasawa, Kazuya, 2000, Some anisakid nematodes from marine ® shes of Japan and the North Paci ® c Ocean, Journal of Natural History 34 (8), pp. 1555-1574 : 1556-1560

Raphidascaroide s nipponensis Yamaguti, 1941

( Figures 1 , 2 )

Description

Large-sized, brownish nematodes with ®nely transversely striated cuticle. Oesophageal part of body narrow, elongate. Lips of approximately equal size, elongate, with membranous ¯anges, these being broadest at posterior half of lips; pulp with two anterior lobes, the anterior edges of which appear under the optical microscope to bear rows of minute formations reminiscent of dentigerous ridges (®gure 1A,C), but no dentigerous ridges were found with SEM (®gure 2); with the optical microscope, groups of similar minute papilliform structures are seen on either side near middle of pulp (®gure 1A,B,C), representing apparently hypodermal outgrowths into cuticle. Dorsal lip bearing two subdorsal double papillae near anterior end of pulp, each subventral lip with one double subventral papilla and small simple papilla and amphid situated laterally. Interlabia well developed, narrow, provided with distinct cuticular margin; interlabia diOEerentiated from underlying tissue (not coniform). Cervical alae absent. Oesophagus markedly long and narrow; ventriculus globular, ventricular appendix relatively short. Nerve ring encircling oesophagus approximately at border of ®rst and second fourteenths of its length; excretory pore slightly posterior to nerve ring level. Intestine straight. Rectum short, hyaline, surrounded by three unicellular rectal glands. Tail of both sexes conical, ending in small processes covered by ®ne rudimentary spines.

Male (ten specimens). Length of body 32,115 ±68,804, maximum width 659± 1483. Lips 196±244 long, length of interlabia 68±92. Length of oesophagus 4594±10,300, maximum width 247±350. Nerve ring and excretory pore 548±1035 and 592±1061, respectively, from anterior extremity. Size of ventriculus 131± 235 Ö 209±392, length of ventricular appendix 696±983, its width 87±174. Posterior end of body of older males ventrally curved. Spicules equal, alate, 1888±2513 long, representing 3.6±5.9% of body length. Total of 20±23 pairs of subventral papillae present, 13±16 being preanals, one to two adanals and four to six postanals; papillae of several most posterior preanal pairs and of adanal and postanal pairs very small. Tail 183±270 long.

Female (®ve gravid specimens). Length of body 67,609±73,480, maximum width 1339±1442. Lips 264±268 long, length of interlabia 104±108. Length of oesophagus 8940±9950, maximum width 330±412. Nerve ring and excretory pore 922±966 and 1088±1105, respectively, from anterior extremity. Size of ventriculus 235±244 Ö 287± 331, length of ventricular appendix 870±873, width 122±125. Vulva situated at anterior part of body, 20,229 ±21,651 from anterior extremity (at 29±30% of body length), vulvar lips not elevated; vagina directed posteriorly. Both undulating ovaries situated at anterior part of body, in region posterior to vulva and vagina. Uterus forming numerous coils at region posterior to vagina, but considerable part of posterior half of body without any genital organs. Eggs shortly oval to almost rounded, thin-walled, smooth, non-embryonated; size of eggs 56±68 Ö 40±48. Length of tail 278±505. Rectum a hyaline tube, surrounded by three unicellular rectal glands.

Host. Halieutaea stellata (Vahl) ( Ogcocephalidae , Lophiiformes ).

Site of infection. Stomach.

Locality. East China Sea (31 October 1987) .

Comments

Yamaguti (1941) established the genus Raphidascaroides for one species, R. nipponensis Yamaguti, 1941 , and its subspecies R. nipponensis lophii Yamaguti, 1941 , diOEerentiating it from Raphidascaris Railliet et Henry, 1915 by the presence of distinct interlabia; both forms were reported to have lips with dentigerous ridges. Later ( Yamaguti, 1961a) he described another species, not mentioning the presence of dentigerous ridges, and when rede®ning the genus ( Yamaguti, 1961b), the diagnosis was modi®ed in that the dentigerous ridges were said to be occasionally absent; in all other species later added to this genus dentigerous ridges are absent.

However, Bruce (1990a), considering the presence of dentigerous ridges to be a character consistent within genera, rediagnosed Raphidascaroides , retaining in it only the forms with dentigerous ridges, i.e. R. nipponensis and R. nipponensis lophii ; he noted that the generic concept of Raphidascaroides could be resolved only by a detailed redescription of the type species, R. nipponensis , and, for the time being, he retained current combinations of other species of this genus (see also Bruce et al., 1994).

Yamaguti (1941) described R. nipponensis from the intestine of Ateleopus japonicus Bleeker ( Ateleopodidae, Cetomimiformes ) (type host) and Zebrias zebrinus (Temminck et Schlegel) ( Soleidae , Pleuronectiformes ) from Tosa Bay (Paci®c Ocean), oOE Shikoku, and R. nipponensis lophii from the intestine of Lophius litulon ( Jordan) ( Lophiidae , Lophiiformes ) from the Paci®c Ocean near Japan; none of them has been recorded since. The author mentioned that both forms were so similar that he`felt some hesitancy in distinguishing the two’; nevertheless, he distinguished them on the basis of small diOEerences in the length of the oesophagus, number of preanal papillae and position of the vulva. However, these diOEerences are evidently associated with the body size (specimens of R. nipponensis lophii were larger) or an intraspeci®c variability in the number of preanal papillae. Consequently, we consider both forms identical, taking R. nipponensis lophii for the junior synonym of the nominotypica l subspecies R. nipponensi s nipponensi s.

The morphology of the present nematode material is almost identical with that of R. nipponensis and, therefore, we consider them to belong to this species. The only substantial diOEerence is the absence of dentigerous ridges on the lips; however, it is apparent that Yamaguti (1941) mistook minute formations below the cuticle for dentigerous ridges; such formations are also visible under the optical microscope in the present specimens, but SEM micrographs do not show any dentigerous ridges. We also examined the type specimens of R. nipponensis and R. nipponensis lophii , but these specimens mounted in lactophenol are now in poor condition and it is impossible to do any detailed study of them. Since R. nipponensis is the type species of the genus, it is necessary to change the diagnosis of Raphidascaroides given by Yamagut i (1961b) and Bruce (1990a) in that`the lips are without dentigerous ridges’.

The occurrence of R. nipponensis in H. stellata represents a new host record.

Figures

FIG. 1. Raphidascaroides nipponensis Yamaguti, 1941 from H. stellata: (A, B) cephalic end, dorsal and lateral views; (C) subventral lip; (D) region of oesophago±intestinal junction; (E) oesophageal part of body of gravid female; (F) egg; (G) distal end of spicule; (H) tail of male; (I) tip of male tail; (J) caudal end of female; (K) tail of male; (L) caudal end of male; (M) tip of female tail. Scale bars in mm.

FIG. 2. Raphidascaroides nipponensis Yamaguti, 1941 from H. stellata, SEM micrographs of cephalic end (female): (A) dorsal view; (B) apical view; (C) subventral lip; (D) lateral view. Abbreviations: dl5 dorsal lip; i 5 interlabium; p 5 double papilla; s 5 single papilla; vl 5 subventral lip.