Two gravid specimens and the posterior half of another gravid specimen of Bucephalus longicornutus (Manter, 1954) were recovered from experimentally infected Scorpaena cardinalis Richardson. The definitive host was found to be Kathetostoma giganteum Haast, the mcnkfish, and examination of several specimens from different localities combined with the experimental material provided numbers of B. longicornutus for study as follows: from the intestine of Scorpaena cardinalis used as an experimental host, two complete specimens in one host, and the posterior half of a specimen in another host; from the intestine and pyloric caeca of Kathetostoma giganteum from Foveaux Strait, 74 specimens from 10 of 13 hosts; from K. giganteum from Cook Strait, one specimen from one of four hosts.

K. giganteum from Foveaux Strait showed a 77% incidence of infection, and in 38% of the infected specimens, 5 or more adult worms were recovered.

K. giganteum from Cook Strait showed a 25% incidence of infection and only one adult worm was recovered. This is a similar incidence of infection to that obtained by Manter (1954), who examined monkfish from Cook Strait.

A number of fish species were obtained from Foveaux Strait in order to determine whether the range of host species for B. longicornutus could be extended. These included three specimens of Physiculus bachus (Bloch and Schneider); two Trigla kumu (Lesson and Garnot); three Neophrinichthys latus (Hutton); one Genypterus blacodes (Bloch and Schneider); two Parapercias colias (Forster); and two Arnoglossus scapha (Forster). However, no bucephalid infections were found. It was not possible to obtain a large number of each host species and thus the zero infection found may not be significant.

Bucephalus longicornutus (Manter, 1954)
(Text-fig. 9, A-J.)

1954. Alcicornis longicornutus Manter, p. 482.

Host: Kathetostoma giganteum Haast, monkfish; family Uranoscopidae.

Location : Pyloric caeca and intestine.

Locality: Cook Strait (type locality); Foveaux Strait.

Description (24 gravid specimens were studied and 12 were measured; 3 specimens were sectioned; measurements in mm) : Body elongate, truncate anteriorly tapering posteriorly. Total length varies between 0.73 and 2.86 (average approximately 1.6) and greatest width varies between 0.3 and 0.66 at approximately ovary level. Cuticle spinose, apart from anterior sucker concavity, tentacles and ventral to prominent radial muscles of anterior sucker. Spines more sparse over posterior third of body. Anterior sucker 0.2 to 0.3 long by 0.23 to 0.26 wide at its anterior margin. Seven tentacles surmount anterior sucker; three dorsal, two lateral, two ventral. Each approximately 0.09 to 0.11 long by 0.02 wide, having one thorn-like process, approximately 0.03 long, near base (Text-fig. 9, B). Tentacles retracted in most specimens but a complete series from almost fully extended to fully retracted obtained. Each tentacle, with muscular core which extends into the thorn-like process, bears a slight depression at its truncate or occasionally rounded distal end. Sucker musculature essentially scoop-shaped and three, occasionally five, tentacular ducts, continuous with free ends of tentacles, prominent in dorsal musculature. Prominent gaps between groups of oblique muscles along anterior margin of sucker coincide with positions of emergence of free ends of tentacles. Ducts for ventral pair of tentacles not observed. When ventral tentacles are completely retracted their points of emergence from musculature are marked by small, but conspicuous, ventral depressions. Prominent band of radial muscles, 0.05 to 0.06 wide, U-shaped or semicircular, around posterior margin of sucker concavity. Cuticle overhangs these muscles and demarcates posterior limit of the sucker concavity. Cuticle does not completely close off open end of musculature and spines on this part of cuticle are not always seen. Musculature U-shaped in transverse section and seven gaps between muscle fibres seen corresponding to seven tentacular ducts.

Mouth generally anterior to mid-body level, varying between 0.33 and 0.56 from anterior extremity. Pharynx, ovoid to spherical, 0.07 to 0.12 long by 0.07 to 0.12 wide. Eggs obscure oesophagus in material examined. Intestine ovoid, 0.2 to 0.3 long by 0.13 to 0.19 wide, dorsal in position and directed posteriorly, often obscured by eggs.

Testes, ovoid to spherical, 0.13 to 0.2 long by 0.1 to 0.2 wide, on right side of the body, generally between intestinal and mid cirrus sac levels, diagonal in most specimens but occasionally tandem. Anterior testis usually touches posterior margin of ovary but in one specimen it overlaps ovary ventrally by approximately page 34

Text-fig. 9.—Bucephalus longicornutus. Morphology and anatomy of adult specimens from Kathetostoma giganteum Haast: Fig. A, ventral view of a specimen with the tentacles partly retracted; Fig. B, left lateral view of a specimen with the tentacles extended; Fig. G, ventral view of the anterior sucker with the tentacles almost completely retracted; Fig. D, ventral view of the anterior sucker with the tentacles completely retracted; Fig. E, ventral view of an immature specimen; Fig. F, ventral view of the Mehlis's gland complex; Fig. G, detail of a tentacle; Fig. H, normal operculate egg; Figs. I, J, abnormal eggs. For abbreviations see p. 9.

page 35 0.08 and in two specimens it is separated from ovary by approximately 0.02. Posterior testis usually touches anterior testis but in two specimens, it slightly overlaps anterior testis dorsally and in two specimens it is separated from anterior testis by a narrow gap. Vasa deferentia not observed. Cirrus sac, 0.4 to 0.64 long by 0.09 to 0.15 wide, extends to about mid-body level. In one specimen, proximal third of its length is bent at right angles to distal two-thirds. In remaining specimens it varies from straight, to crescent-shaped to sigma-shaped (Text-figs. 9, A and B). Cirrus sac consists of ovoid seminal vesicle, 0.09 to 0.13 long by 0.08 to 0.1 wide, and long pars prostatica. Genital atrium, 0.19 to 0.3 long, contains a smooth or corrugated genital lobe, 0.1 to 0.17 long. Gland cells surround genital atrium. Genital pore varies between 0.08 and 0.11 from posterior extremity.

Ovary generally spherical (but in five specimens ovoid), varies between 0.1 and 0.13 in diameter or 0.1 to 0.11 long and 0.12 wide, on right side of body at approximately intestinal level. Oviduct emerges from right side of ovary, opens into ootype, 0.01 to 0.02 posterior to ovary and gives off Laurer's canal approximately one-third from its proximal end. Laurer's canal runs obliquely towards dorsal midline and opens to exterior at approximately anterior testis level. Uterus emerges from posterior margin of ootype and was traced posteriorly to intertesticular level. Remaining coils indistinct.

Vitellaria arranged in two lateral groups between sucker and pharynx. Individual follicles clumped or spread and this can be related to number of eggs in uterus. Most often, 16 follicles on each side but this number can vary between 14 and 18. Each follicle more or less spherical, between 0.04 and 0.06 in diameter. A difference of 0.005 generally exists between extremes in sizes of follicles in a given specimen. Left vitelline duct runs obliquely to posterior testis level then loops and runs anteriorly on right side of body to enter vitelline reservoir immediately median to ootype. Right vitelline duct runs slightly obliquely and enters vitelline reservoir. Short duct connects vitelline reservoir with ootype (Text-fig. 9, F).

Eggs occupy most of body in most specimens. Their anterior extent is variable. In two specimens they extend just beyond pharynx level but in most they reach to within 0.1 to 0.18 of posterior limit of sucker. Eggs extend posteriorly to level of genital pore. They are ovoid, distinctly operculate, 0.021 to 0.035 long by 0.015 to 0.022 wide (Text-fig. 9, H). Two specimens contained a few abnormal eggs (Text-fig. 9, I, J).

Excretory pore terminal and saccular excretory bladder extends just anterior to pharynx. Flame cell formula not determined.

Discussion of Adult

Compared with the metacercaria, adult B. longicornutus have tentacles surmounting the anterior sucker and show considerable development of the reproductive system. The development of elements of the latter in the hindbody has a considerable bearing on the position of the mouth and intestine, a feature which differs considerably between metacercaria and adult. Remaining differences are relatively minor. Spines are absent from the cuticle overlying the band of radial muscles of the adult sucker; and the flap of cuticle closing off the open end of the sucker musculature in the metacercaria, while still present in the adult, is not conspicuous. Both of these differences may possibly result from the effects of attachment to the intestinal wall of the definitive host.

Only three immature worms were recovered from the material examined. Two of these had their tentacles partially extended and all three, apart from the absence of eggs, were very similar to sexually mature adults.

Manter (1954) placed the above species in the genus Alcicornis McCallum, 1917. The single specimen he recovered from one of four Kathetostoma giganteum from Cook Strait was mounted in lateral view and the sucker-like nature of the anterior end was not evident, appearing instead rhynchus-like, and this is diagnostic of the genus Alcicornis. Manter compared the species with other known species of Alcicornis. However, because of the change in generic status proposed here it is now necessary to compare Bucephalus longicornutus with related species of Bucephalus.

In the possession of one thorn-like process at the base of the tentacle, B. longicornutus resembles B. polymorphus von Baer, 1827, B. introversus Manter, 1940, and B. scorpaenae Manter, 1940. However, it differs from B. polymorphus in that the cirrus sac is much longer in relation to the total length, the tentacles do not taper to a point and the thorn-like process on the tentacle is situated nearer the base of the tentacle; from B. introversus in that the anterior sucker does not introvert into the anterior end of the body and the structure of the genital atrium is not as complex; and from B. scorpaenae in that the excretory vesicle is shorter, the pars prostatica is not subdivided and the genital lobe is simpler in structure.

B. longicornutus does show some resemblance to B. kathetostomae (Manter, 1934) (a species in which the structure of the tentacles is unknown), from a related host, Kathetostoma albigutta Bean. However, it differs from B. kathetostomae in the absence of the muscular sphincter surrounding the genital pore, shorter genital atrium, the absence of processes on the eggs and considerably shorter excretory vesicle.

There are two main differences between Manter's description of B. longicornutus and that given above. These are the bipartite rather than ovoid seminal vesicle, and the longer tentacles. Both of these characters are considered to be subject to variation. The shape of the seminal vesicle is probably dependent on the amount of sperm present and the length of the tentacles on their degree of contraction.

The variations noted for B. longicornutus are considerable. The position of the internal organs is apt to be governed by the degree of contraction of the body on fixation and by the number of eggs in the uterus. The arrangement of the vitelline follicles, which has been mentioned above, illustrates this latter point. Egg size is extremely variable between specimens from different hosts but is generally more or less constant within a group of specimens from the same host. A similar phenomenon has been noted by Manter (1940a) for B. varicus Manter, 1940 (synonym: B. polymorphus of Nagaty, 1937). Slight variations of from 0.002 to 0.004 exist between egg sizes in a given specimen as was also noted by Manter (1954) in the one specimen of B. longicornutus which he examined. Egg size cannot be correlated with the length of the specimen, e.g., a specimen of 1.718 long had eggs 0.021 by 0.016 while a specimen 1.818 long had eggs 0.032 by 0.020; but can, however, be correlated with the number of eggs present, e.g., a specimen 1.110 long had few eggs and these were large, being 0.035 by 0.022 while a specimen 1.496 long had many eggs and these were relatively small, being 0.024 by 0.016.

B. longicornutus parallels B. varicus in the range of variation exhibited. Such a range has not been noted for other species of the genus. However, many of these species are either insufficiently described (vide van Beneden, 1870) or known only from a few specimens (vide Velasquez, 1959). Characters such as total length, relative position of internal organs and minor differences of only 2μ to 3μ in egg size have, in some cases, been used to separate species (vide Velasquez, 1959). In view of the variations of these characters known for B. varicus and B. longicornutus, two species which have been collected from a number of different host species and the same host species respectively, these specific distinctions should be regarded as tentative and possibly subject to alteration after reference to further material.

The most constant features noted in those specimens of B. longicornutus examined were the nature of the genital atrium and genital lobe, and the floor of the anterior sucker. Unfortunately, descriptions of these features are absent from many systematic papers dealing with species of Bucephalus and they may, in future, prove more satisfactory criteria for differentiating between species than those used in the past.