Hysterothylacium physiculi, Moravec & Nagasawa, 2000

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 : 1568-1571

Hysterothylacium physiculi sp. n.

( Figure 6 )

Type material

HOLOTYPE and PARATYPES: Institute of Parasitology , Academy of Sciences of the Czech Republic, C Ïeske BudeÏjovice (catalogue number N-738) .

PARATYPES: National Science Museum , Tokyo (catalogue number NSMT-As-285 1) .

Description

Medium sized nematodes, females somewhat longer than males. Cuticle slightly transversely striated, almost smooth. Lateral alae present, starting a short distance posterior to base of lips; anterior ends of alae rounded; alae rather wide in anterior part of body, gradually narrowing from level of nerve ring and extending posteriorly as narrow ridges ending a short distance anterior to tail tip in female. Lips provided with wide membranous ¯anges, these being broadest in middle of lips, forming there distinct small lateral spikes. Dorsal lip somewhat smaller than subventral lips. Dorsal lip with two lateral double papillae; subventral lips with amphid, adjacent mediolateral double papilla and single lateral papilla. Interlabia triangular, low and broad, with distinct cuticular margin. Oesophagus slightly broader posteriorly than anteriorly. Nerve ring encircling oesophagus approximately at border of ®rst and second ®fths of its length. Ventriculus almost spherical; ventricular appendix relatively short. Excretory pore at about level of nerve ring. Intestinal caecum short, only slightly exceeding ventriculus anteriorly. Rectum a hyaline tube surrounded by three small, unicellular rectal glands. Tail of both sexes conical, with tip covered by numerous minute spines.

Male (three specimens; measurements of holotype in parentheses). Length of body 11,886±16,192 (16,192), maximum width 309±474 (391). Length of lips 85±175 (90). Interlabia 20±24 (20) long. Length of oesophagu s 1566±2236 (2236), maximum width 148 (148). Nerve ring and excretory pore 352±531 (531) and 363±653 (653), respectively, from anterior extremity. Ventriculus 96±139 Ö 100±124 (139 Ö 122); ventricular appendix 660±1218 (1218) long and 64±87 (87) wide. Intestinal caecum 100±261 (261) long and 80±87 (87) wide. Length ratio of caecum and ventricular appendix 1:4.3±6.6 (1: 4.7). Testis reaching anteriorly to small distance posterior to posterior end of ventricular appendix. Spicules short, alate, with rounded tips, measuring 324±416 (324) and representing 2.0±3.2 (2.0)% of body length. Caudal papillae: 19±29 pairs of preanal papillae, one to two pairs of adanal papillae and six pairs of minute postanal papillae; last postanal pair situated close to tail tip; pair of small lateral phasmids present slightly anterior to level of last but one postanal pair of papillae. Tail relatively short, measuring 120±220 (220); tail tip 14±28 (14) long.

Female (four gravid specimens; measurements of allotype in parentheses). Length of body 26,553 ±47,421 (47,421), maximum width 515±783 (783). Maximum width of lateral alae 28 (±). Length of lips 108±160 (160). Interlabia 40±48 (40) long. Length of oesophagus 2828±3872 (3872), maximum width 261± 348 (348). Nerve ring and excretory pore 609±783 (783) and 653±809 (809), respectively, from anterior extremity. Ventriculus 139±235 Ö 174±313 (235 Ö 313); ventricular appendix 1288±2410 (2410) long and 96±131 (131) wide. Intestinal caecum 226±522 (383) long and 96±157 wide. Length ratio of caecum and ventricular appendix 1: 3.1±6.3 (1: 6.3). Vulva non-elevated or elevated, pre-equatorial, 8755±13,740 (13,740) from anterior end of body, at 23 ±38 (29)% of body length. Vagina directed posteriorly from vulva. Uterus opposed. Anterior ovary reaching anteriorly almost to vulva in smaller specimens and somewhat exceeding vulva anteriorly in larger specimens. Eggs oval to almost spherical, thick-walled, nonembryonated; mature eggs (n 5 10) measuring 42±60 Ö 38± 50 (60 Ö 46). Tail elongate, narrow, 870±1314 (1314) long; tail tip 36±76 (40) long. Pair of small lateral phasmids present approximately at border of second and third thirds of tail length.

Type host. Physiculus maximowiczi (Herzenstein) ( Moridae , Gadiformes ) (body length 15.7±25.5 cm).

Site of infection. Intestine.

Type locality. Kamaishi Bay , northern Honshu (Iwate Prefecture), Japan, in the western North Paci ®c Ocean (21 October 1982) .

Prevalence and intensity. Prevalence unknown, specimens collected from eight infected ®shes; one to six (mean two) nematodes per ®sh.

Etymology. The speci®c name of this nematode relates to the generic name of the ®sh host.

Comments

According to Bruce et al. (1994), the genus Hysterothylacium Ward et Magath, 1917 comprises 52 species parasitic as adults in marine, estuarine and freshwater ®shes. Five more species, H. cenotae (Pearse, 1936) , H. rhamdiae Brizzola et Tanzola, 1995 , H. japonicum Rajyalakshmi, 1996 , H. patagonense Moravec, Urawa et Coria, 1997 and H. nipponense Moravec et Nagasawa, 1998 , have been added to this genus since ( Brizzola and Tanzola, 1995, Moravec et al,. 1996, 1997, Moravec and Nagasawa, 1998a,b, Rajyalaksmi, 1996). Unfortunately, many Hysterothylacium species are poorly described, which makes for di culties in comparing them with recently described forms ( Bruce and Cannon, 1989).

Characteristic features of H. physiculi sp. n. are shape of the lips, with lateral ¯anges widest at middle of lips and forming there distinct points; presence of low interlabia; well developed lateral alae starting suddenly at some distance posterior to base of lips; a markedly short intestinal caecum; very short equal spicules; a spiny tail tip in both sexes; a long conical tail in the female, and the number and distribution of caudal papillae in the male. It diOEers from other adequately described species of the genus reported, for example, by DeardorOE and Overstreet (1978, 1981, 1982), Bruce and Cannon (1989), Bruce (1990a,b), Petter and Radujkovic (1989), Petter et al. (1995) in combinations of diOEerent morphological and biometrical characters. As far as the present authors know, this is the only known species with so sharply pointed lateral lip ¯anges.

Hysterothylacium physiculi diOEers from most congeners in having a markedly short caecum, resembling thus some other species possessing lateral alae, such as H. fabri (Rudolphi, 1819) , H. pelagicum DeardorOE et Overstreet, 1982 , H. reliquens (Norris et Overstreet, 1975) , H. scomberoidei Bruce et Cannon, 1989 and H. trichiuri (Thwaite, 1927) ; it diOEers from them, however, in conspicuously shorter spicules, character of the lateral alae, arrangement of caudal papillae and some other features. In the length of spicules it resembles H. ogcocephali (Olsen, 1952) , but this has a diOEerent shape to the lips and a very short female tail; very short spicules are present also in H. cenotae and H. rhamdiae , parasites of neotropical freshwater cat®shes, but their lateral alae are absent or poorly developed and they have diOEerent shapes to the lips.

According to Bruce et al. (1994), only one Hysterothylacium species , H. tasmaniense (Johnston et Mawson, 1945) has so far been reported from ®shes of the family Moridae ; it diOEers from H. physiculi in the shape of the lips and in much longer spicules ( Bruce, 1990a).

In 1985, Moravec and Nagasawa reported a third-stage larva of H. fabri (Rudolphi, 1819) from the intestine of P. maximowiczi (the type host of H. physiculi ) from Hokkaido, Japan, the identi®cation being based principally on the character of the caecum and the ventricular appendix. Now it is almost sure that this larva was conspeci®c with H. physiculi . Although adults of H. fabri have been reported from marine ®shes from the Far East ( Zhukov, 1960), this species has much longer (about 1 mm) spicules as compared to H. physiculi , in addition to other interspeci®c diOEerences.

Figures

FIG. 6. Hysterothylacium physiculi sp. n.: (A) cephalic end of young female; (B,C) cephalic end of female, dorsal and ventral views; (D) tail of male; (E) posterior end of male; (F) distal end of spicule; (G) tail tip of male; (H, I) tail tips of young females; (J) egg; (K) tail of female. Scale bars in mm.