7rElVa;

FISHERIES RESEARCH BOARD OF CANADA

Translation Series No. 1324

Life history of nematode of the genus Anisakis.

By Noboru Kagei

Original title: Anisakis-zoku senchu no seikatsu-shi.

From: Saishin-Igaku (Advances in Medical Sciences) 24 (2): 389-400, 1969.

Translated by the Translation Bureau( MG) Foreign Languages Division

Department of the Secretary of State of Canada

Fisheries Research Board of Canada Biological Station

Nanaimo, B.C.

1969

27 pages typescript

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The life hiatert of Jill:Sateen o4' the genus Anieakis.

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LIFE.B.ISTORY OF NEMATODES OF THE GENUS ANISAKIS

by

KAGEI, Noboru*

1. Preface

On the life history of nematodes of the subfamily Anisakis, many re-

ports have been made in recent years (Walton, 1937; Thomas, 1937, 1940; Scott,

1954, 1955; Myers, 1960; Berland, 1961; Hutton et al, 1962; and Huizinger,

1966, 1967). However, no report is known yet on details of the life cycle of

nematodes of the genus Anisakis which represents the subfamily Anisakis. It

is so far assumed that their definitive hosts are sea mammals, and that they -390-

begin their life cycle as eggs or larvae to bè eaten by microacopic crusta-

ceans, then infecting fishes which eat the crustaceans, and complete it by

c: reaching the definitive hosts whiàh eat the infected fishes. Their infection • *---4 m also occurs in man when he eats such infected fishes raw, thus causing acute

c7 abdominal syndrome in him. Suàh abdominal syndrome is called "Anisakiasie • n .

:C.() because its causes in most cases were . found to be nematodes of the genus O ›

'GU Anisakis. Nevertheless, few studies have ever been done on the life cycle of 2 0 • z

el s O rri n

tft

rn

such nematodes, mainly because of the difficulty in conducting experiments of

5; their infection. Therefore, the foregoing description of their life cycle is -1

*Department of Parasitology of the National Institute of Public Health.

Japanese M. G. 6. 9. 69

50$-200- 10-s>

(S-e4

2

largely based on mere assumptions. Without knowing the complete life history

of the nematodes, it is then impossible to discuss parasitologyof "Anise-

kiasis" and to find out agy preventive measures for it. Thus, the present

writer and his associates have been attempting to bring light or vit for sev-

eral years. On the basis of the results so far obtained together with various

related data reported elsewhere, the present paper will discuss the life cycle

of nematodes of the genus Anisakis.

Before entering the discussion, the present writer wishes to express

his profound gratitude to those who have helped this study, especially TOM°

(5-shima (of the Department of Medicine of Shinshii University), Akio Kobayashi,

Mitsuyoshi Kumada, Chikara Koyama, and Yoshitaka Komiya (of the Department

of Parasitology of the National Institute of Health), Masaaki Machida (of the

National Science Museum), Toshio Ishii (of the Japan Institute of Biological

Studies), Muneaki Abe (of the TUkai Sea-Region Fisheries Research Institute),

Hideo -Cmura (of the Institute of Cetacean Studies), Takahisa Nemoto (of the

Oceanographic Research Institute of Tiiky3 University), and Shigeru Motoda

(of the Department of Fisheries of Hokkaido- University).

2. Species of Nematodes of the Genus Anisakis and their Definitive Hosts

From the bibliographical point of view, 18 species of nematodes of

the genus Anisakis have so far been reported as shown in Table 1 (Mosgovoy,

1951), but all of them cannot be regarded as independent species. For in-

stance, A. kükenthali and A. dussumieri are apparently synonyms of A. simplex

(Lyster, 1940), and A. kogiane was corrected later to be a synonym of A.

simplex by its first reporters, Johnston and Mawson (1942). Also, there are

not a few species on each of which report was made only once, so that doubts

can be raised on such species whether they are really separate species.

Table 1: Species of the genus Anisakis reported up to date (iiio;i7Zy, 1951) and proble-matical names as independent species.

Single asterisks (*) indicate those apparently regarded as synonyms of other species. Double asterisks (**) indicate those reported only once.

Anisakis (Dujardin, 1945) * A. (Anisakis) dussumieri (Beneden, 1870)

** A. (A.) akrandri Mu et Hoeppli, 1933 * A. (A.) eatodonlis Bayas, 1929 * A. (A.) diomsdeat (Linstow, 1888) * A. (A.) kükenthali (Cobb, 1889)

** A. (A.) insignis (Diesing, 1851) ** A. (A.) ivaniskii Motgovoy, 1949 ** A. (A.) patagonica (Linztow, 1880)

A. (A.) rasmari (Baylls, 1918) A. (A.) similis (Baird, 1858) A. (A.) simplex (Rndolphi, 1809)

** A. (A.) tridsntata Kreis, 1988 A. (A.) typica (Diesing, 1860)

* A. (Skrjabinisskis) skrjabitti Mosgovoy, 1949 A. (S.) pkyseteris (Baylis, 1928)

*g' A. (S.) schupakovi Mosgovoy, 1951 * A. (?) kogians Johnston and Mawson, 1939

** A.(9) tursionis Oraux, 1946

3

However, since the present writer

could not examine their original de-

scriptions or type species, it is not

easy here to clear such problematical

cases. Yet, actual independent species

seem to be much fewer than 18.

According to the descriptions

and other reports known today, the

definitive hosts for such nematodes of

the genus Anisakis, as mentioned earlier

are mainly sea mammals, including such

various cetaceans and pinnipeds as

shown in Table 2, except the case of

A. diomedeae whose definitive hosts

reported are birds. Between cetaceans and pinnipeds, however, certain dif-

ferences are observable in their characteristics as hosts. For instance, A.

simplex, A. tvpica, and A. phvseteris are reported to be parasitic mostly on

cetaceans while A. similis and A. rosmari on pinnipeds (Kagei, et al, 1967,

and thereafter). Also, Scott and his associates, who previously reported the

parasitism of Terranova in many Canadian cod, investigated dolphins (Nezumi-

iruka, Phocaena phocaena, and Shiroiruka, Delphinapterus leucas)and seals

(Gomafuazarashi, Phoca vitulina, Haiiroazarashi, Halichoerus impus, and

Tategotoazarashi, Laephilus groenlandicus)*as definitive hosts for Terranova,

*Translator's note: Except certain names of nematodes and crustaceans, all zoological names in this paper are given in Japanese common names in the original. In this translation, therefore, each of these common names is trans-literated and its scientific name is supplemented next to the transliteration by the translator.

4

and reported that the dolphins were more infected with A. simplex while the

seals with Terranova decipiens (Scott and Martin, 1967; and Scott and Fisher,

1958 a, b).

Such differences were also found among sea mammals in Japanese waters.

In the investigations by the present writer and his associates (1967), as

shown in Table 3, most of the samples of pujiiruka (Stenella caeruleoalbus),

Nezumiiruka (Phocaena phocaena), Ishiiruka (Phocaenoides dahu), and Makkii-

kujira (Physeter catodon) were found highly infected with nematodes, both

Table 2: Species of the genus Anisakis found parasitic on sea mammals. -391- (Kagei, et al, 1967, and thereafter).

.r „ .e 'm :z.. § ee a r e Host u .. .u. .e :., ..E :

Cetacea

Semiku'ira (Balaena mysticetus) Shironagasukujira (Sibbaldus

musculus) KoiwashikuJira (BalaenoPetera +

acutorostrata) Iwashikujira (Balaenopetera

borealis) Zatoku'ira (Meeeptere +

novaeanglie) . NagasukuJira (Balaenopetera +

‘evsalus) Makkokujira (Physeter catodon) Komakkc (Kogia brevice;;) ---- + Akabokujira (Ziphius cavirostriz Kitatokkurikujira (Hyperoodon

ampullatus) Yoroppaooeihskujira (Mesoplodon .

bidens) Tsuchikujira (Berardius bairdi) Ikkaku (Monodon monocerOZ---- + Shiroitukt—tT5—elphinapterus -M.lelcas Ganjisueawairuka (Platanista +

gangetica) Amazoilkawairuka (Inia

geoffrensis)

5

Table 2 continued. - • . ,

Mairuka (Del nus delphis) + + ' '+ Haseiruka Delphinus capensis) + Harajirokamairuka (Lagenorhynchus + +

acutus) Hanajirokamairuka (Laenorhynchus + +

albirostris) Taiseiyobandoiruka (Tursiops +

truncatus) SujE7.117(itenella caeruleo- + +

albus) Shiwahairuka (Steno bredanensis) + + Bandoiruka (Tursiops gui) + Hashinagairuka (Stenella longiro- +

strie kunito) ---- Shinausui771.727a7sousa sinensis) + Kamairuka (Lagenorhynchus obli- +

quidens) . Nezumiiruka (Phocaena phocaena) + + Ishiiruka (Phocaenoides dallii) + + iii;7127:77kobicephala mel;;;IT + Okigondo (Pseudorca crassidens) + + Sakamata or(erliusorca) + Stinto -(=bicephala scammoni) + Hanagondo (Grampus grisét7) ----- +

Pinnipedia

Todo (Eumetopias) + + + Ashika (Zalophus) + + Minamiamericaottosei (Arctoce- +

phalus australis) Otaria (Otaria flauescens) + Seiuchi (aTi1enus) + + Hyoazarashrurga leptonYx) + Gomafuazarashi (Phoca vitulina) + Kasupianazarashi7P7s7a,caspica) . , + + Minamizoazarashi (Mirounga + +

leonina) Kitazoazarashi Miro +

angustirostris Haiiroazarashi (Halichoerus + - +

2M21.1â) Wamonazarashi (Pusa hispida) +

Birds

Ahodori (Diomedea albatrus) + +

6

Table 3: Infections of sea mammals in Japanese waters with nematodes of the subfamily Anisakis.

Aesakis Terranova . ‘ Number Rate Number of nema- Rate Number of

Species of of todes per sample of nematodes Reporter amples infec- infec- per sample

tion aim- Type I physe- tion (%) jakm.larvae teris (%) a dult larva

Su'iiruka - Stenell 411 61.8 47 53 0 0 0 0 N

caeruleoalbus) Nezumiiruka '

28 32.1 59 35 0 0 0 0

ere , agei, e Ishifruka al, 1967 (Phocaenoides 132 8.7 72 28 0 0 0 0 dahu)

MakkokuJira

(Physeter ' 3 100.0 10 23 30 0 0 0 e catodon TUTOTemeto-

3 100.0 1 110 0 66.7 167 1 Yamashit pies) et al, Filiriazarashi

1 0 0 0 0 100.0 5 0 1967 (Phoca hispida) Ottoaei

0( a1lorüus 305 99.5 4 55 0 11.2 1 0.5 Machida, urs 1967 , .

Table 4: Major morphological differences among Anisakis species found in various sea mammals.

- , Shape of Number of Proportion in

Species Size Body the ven- papillae the lengths of Location of color triculus behind copulatory of the

adult anus mucrones on vulva (Pairs) both sides

Yellowish Rectan- A. simplex 65mm white gu1sr 7* 1 : 1.5 60%

Yellowish Rectan- A. typica 90mm 10 1 : 2.9 40% while gular

Light Almost Short and A. physeteris 100mm brown or square 6* almost even 30%

brown in length

*A pair of double papillae are included.

a,

-392-

young and adult, of the genus Anisakis. It is reported by Yamaahita and

others (1967) and Machida (1966, 1967), however, that young nematodes of the

genus Anisakis were found parasitic on Todo (Eumetopias), Fuiriazaraehi

(Phocahispida), and Ottosei (Callorhinus -ursinus ), but rarely the adults,

while both young and adult nematodes of the genus Terranova were found highly

parasitic on them. These findings indicate that nematodes of the genus Ani-

sakis in Japanese waters are more parasitic on cetaceans, especially dolphins,

than on the other sea mammals. Thus, Sujiirtika (Stenella caeruleoalbus)

whose ordinary population in the North Pacific is estimated to be two hundred

thousand may be considered to be not only a major group of definitive hosts

for nematodes of the genus Anisakis but also a most important group of infec-

tive agents of the "Anisakiasis° in man, because of their high rate of infec-

tion and the large quantity of nematOdes parasitic on them.

In the investigations by the present writer and his associates, as

in various other reports mentioned earlier, nematodes of the genus Anisakis

parasitic on such definitive hosts as mentioned above have so far been found

mainly in A. simplex and only rarely in A. tvpica and A. làyseteris, but in

none of the other species.

3. Major Characteristics of Nematodes of the Genus Anisakis Found in Sea

Mammals of Japanese Waters

Main morphological characteristics of adult nematodes of the three

species, A. simplex, A. tvpica, and A. phvseteris, of the genus Anisakis

which were found by the present writer in sea mammals of Japanese waters are

as follows:

(1) A. simplei (Rudolphi, 1809) Baylis, 1920.

The body is somewhat stocky, being narrower at the head and somewhat

7

8

wider toward the tail, and its color is yellowish white. The size measures

65mm in length and 2mm in width. As Shown in Table 4 and Figure 1, the main

morphological characteristics are: The male has 7 pairs of papillae behind

the anus (including 1 pair of double papillae), and the copulatory mucrones

are seen uneven in length in the proportion of 1 : 1.5. The female has the

vulva in the rear of the body at about 6g% of its length from the end of the

head. Striations measuring about 30).1 are seen on the cuticle.

(2) A. tvpica (Diesing, 1861) Baylis, 1920..

This species resembles A. simplex, but the body is generally a little

thinner and longer,. measuring 90mm in length and 1.5mm in width. The male has

10 pairs of long papillae behind the anus, all of which are single. Like A.

siMplex, its copulatory mucrones are uneven in length in the proportion of

1 : 2.9. The female has the vulva in the front of the body at about 40% of

its length from the end of the head. The dentigerous ridges in the front

edge of the head are deeper in the cut than those of A. simplex. The number

of individuals of this species found as being parasitic is much smaller than

that of A. simplex.

(3) A. phvseteris Baylis,:1923.

This species is larger in size than the foregoing two species. The

body is 10mm long and 4.5mm wide, and its color is browniàh in comparison

With the other two. The male has 6 pairs of papillae behind the anus (includ-

ing 1 pair of double papillae).. The copulatory mucrones are Short and almost

even in length on both sides. The female has the vulva at the place closer -393-

to the head (at about 34 of its length from the end of the head) than those

of the other two. The Shape of the lips on the head is triangular, being

quite - different from those of the other two, and small dentigerous ridges are

9

A...siiorptex A. typica A. physete ris

Figure 1: Shapes of the head and the male's tail of 3 species of nematodes of the genus Anisakis (drawn by Kagei).

seen along the front edge. A striking difference between this species and

the other two is seen in the shape of the ventriculus, which is almost square

in this species and rectanEular and considerably long (often S-shaped due to

the contraction at the time of fixation) in the other two. Because of this

difference, A. Phvseteris is claSsified as a subgenus of Skriabinisakis.

The striations on the cuticle are much finer than those of the other two spe-

cies.

Of the foregoing three species, A. simplex has been most frequently

used for research materials by the present writer and his associates, so that

the data on this species are most available. For this reason, the life his-

tory of A. simplex will be discussed mainly in the following pages.

4. EWE' and Their Growth

As shown in Picture 1, each of the eggs in the uterus of A. simplex

is almost spherical, measuring 50.7g x 53.Qn in size (average of 20 eggs).

10

The eggs of this species are supposed to have cleavage several times by the

time they are discharged, after spawned, into the water of the sea together

with excrements of their hosts. Thereafter, under certain conditions, they

grow rapidly into larvae within the egg-shell. It was observed that water

temperature is an important factor for their growth in this stage, as àhown

in Table 5. Such influence of water temperature on the growth of eggs was

also observed in case of other species of the subfamily Anisakis. Although

the growth of eggs of A. simplex at the water temperatures between 6° C and

26 ° C was not investigated in the present study as yet, the observation that

the eggs of Terranova, parasites to seals in the northern waters, grow more

normally'at the water temperature.13 °- 14° C than otherwise suggests that the

water temperature around 10. 0 may be most suitable for the growth of eggs of

A. simplex. However, since the eggs were still able to grow at the water

temperature as low as 2°C when they were cultivated in the sea-water for a

considerably long period, it is no doubt that the eggs of A. simplex grow

gradually even in winter in the northern waters (where water temperatures

in the south of the latitude 60°N never go down below 0°C even at the water

surface in winter, according to Muromtsjeb, 1963).

The larva grown up within the egg-shell hatches out, keeping the

exouvium of the first larval stage as shown in the lower part of Picture 1.

Then, active movements of subh larvae can be observed in the water. Such

hatching of the second-stage larvae frbm the eggs into the water was also

observed in case of other nematodes of the subfamily Anisàkis. This Shows an

interesting phylogenic, and taxonomical, difference between these nematodes

and other.ascarides found in land animals. In addition, the larva of A.

àimplei is wide at the head and narrower toward the tail. Also, it is

BicdluMr

• v .-

Multicellular Tadpole Larval Molular -394-

50 g

- I ,

I \ ;

\,

e

' 50

11

characteristic of the larva in this stage in which the growth of each organ

inside the body is hardly observable, that the boring tooth can be observed

on the head.

5. First Intermediate Host--Experiment to Find Such Existence

There are many questions to be solved in regard to the life cycle of

the second-stage larvae hatched out of the egg-shell into the water. In fact,

Picture 1: Growth of the egg (top) and the second -stage .larva hatched out of the egg (bottom left, the whole body;' bottom center, the head; bottom right, the tail). (Drawn by Koyama and others).

13*,

12

Table 5: Time (number of days) spent for the growth of eggs of the nema-todes of each genus of the subfamily Anisàkis under various water

• temperatures.

Species Tempera- Morula. Gastrula Larval Hatching Reporter

ture stage stage stage

Terranova 2-4° C 4 days (no further growth in the ob- decidens servation until the 18th day)

13-14 3 7 13-14 Scott, . 17-25 2 3 4 ' 8-9 - 1955

(died 2 to 3 hours after

Contracaecum 7 (not grown) spiculigerum 13 - - - 25-30 Huizinger,

21 1-2 3 3-4 5-7 1966

Anisekis 2 - - 30 60 sil--11.21--e2S. 2-5 - - - 40 Kobayashi,

27 1-2 2-3 3-4 (no hatch- Kagei, et ing, dege- ai, 1966

nerated)

37 (not grown, degenerated)

in the life history of nematodes of the genus Anisakis, it is in this part -395-

that the present writer and his associates have been most interested.

As mentioned earlier, nematodes of the genus Anisàkis are generally

assumed to have two kinds of interMediate hosts, i.e., microscopic crusta-

• ceans in the sea and fishes feeding on such crustaceans. On the existence

of the first intermediate hosts, the report by Paljansky (1955) seems so far

to be only reliable . one, but its description of the case is so short that

Many questions can be raised about it. The present writer and his associates

• have assumed the existence of the first intermediate host, whatever its form

might be, on the basis of their own observations showing such a marked gap

in size between the second-stage larvae just hatched out of the eggs and the

third-stage larvae found in fishes which will be discussed later, as to imply

the existence of certain intermediate host in the process of growth between

13

the two, i.e., the former ranging from 262.2n to 342.4u in length (with the

average being 286.1u) and from 12.5u to 15.3u in width (with the average be-

ing 13.7u) (not including the encysting exuvium in each measurement with 20

individuals) and the latter being over 6mmi.n leneh.

There are two kinds of research into the question whether such first

intermediate h-osts exist. . One of them is to find out the larvae in question.

in various crustaceans and other organisms living in Japanese waters. How-

ever, because of the quantity of euphausiaceans eaten by fishes in a year

(for instance, a Saba, Scomber japonicus, eats 1,550g of floating crustaceans

during the first 9 Month after its birth and 3,660g in the following one year,

according to Hatanaka and Takahashi, 1960) and also the number of the third-

stage larvae parasitic on those fishes mentioned below, it is very difficult

to find out the larvae in euphausiaceans. In fact, as shown in Table 6, the

investigation made for the present study resulted in finding only one larval

nematode about 3mm long in a sample Thvssanoessa inermis, a species of the

Table 6: Results of investigation of the larval infections in various crus-taceans and other organisms.

_ Number of Number of infec- Place of sample

Species samples ted samples (%) collection

Euphausia similis 212 0 Pacific coast

Euphausia pacifica 139 0 Northern sea

Thyssanoessa inermis 282 1(0.4) Northern sea

Euphausiaceans in the . stomach of Tara (Gadus 529 0 Northern sea macrocephaiZ-

Northern sea and Caranus cristatus 1,441 0 Pacific coast

Sagiata elegans 6 0 Northern sea (Yamushi)

Medusas 107 0 Northern sea

Yamatoebi (Pandalus) 15 0 Hokkaid; ,

14

Euphausiacea in the northern waters. This larva was considered to be most

probably one of the Anisakis because of its boring tooth on the head and its

mucro on the tail, though it is not entirely certain as its ventriculus was

not observable. Here, Poljansky's report (1955), so far the only report on

the finding of larvae in euphausiaceans, is very interesting, especially

because it waein Thyssanoessa Au. that the larvae were found in his investi-

gation.

Another approach to the question of the first intermediate hosts is -

infection experiment. Oshima, one of the present writer's associates, did

this experiment with euphausiaceans in the Tansei-maru, ship of the Tokyo

University's Oceanographic Research Institute. In this experiment, as shown

in Table 7, the samples of larvae and euphausiaceans were made in contact with

each other for two hours, during which the larvae were apparently eaten by the

Table 7: Experiment of infection in euphausiaceans* and morphological changes in the larval parasites.

Number Number Number Number of days- of eupha- of in- of lar-after usiacean fected vae infec- samples samples found tion examined (Ratio per

to the sample total)

5

0

2. 3

Number of larvae which molted the encysting exuvium (Ratio to the total)

0 %

85.7

Length of larval body

;

286. 1 p. (262. 2-342. 6)

237. 6 (245. 5-318. 0)

259. 7 (254. 4-265. 0)

•

281.4 (187. 6-266. 9)

just hatched

dev:

2

6

1

4.5 I 22,2

2.0 I 50.0

Widtlk Method of of fixa- larval tion for body measure-

ments

13. 7 » (12. 9-15. 3)

18. 7 (13. 1-14. 8)

14. 5 (13. 6-15.8)

17. 8 (12. 9-20.6)

heat

formalin

alcohol

alcohol

*300-400 larval samples/ml. Two hours contact.

15

euphausiaceans. Then, about one week after their infection, those larvae were

observed to get rid of the encysting exuvae, but it was impossible to conti-

nue this experiment beyond the period of one week because of the difficulty

to breed the sample euphausiaceans. Therefore, although it is plausible to

assume that euphausiaceans can be the intermediate hosts in question, it is

not certain as yet that they actually play the role of such intermediate

hosts for the larval nematodes.

6. Second Intermediate Hosts

Those fishes and mollusks which are supposed to be second intermediate

hosts for parasites interest many people because they are directly related -396-

to the infection in man, so that Many studies have been made on them.

Most fishes and mollusks feed on zooplankton or phytoplankton. In

case that zooplankton in the sea can be the first intermediate hosts for the

larvae in question, as discussed in the preceding chapter, it is natural for

fishes to be infected with the larvae by eating such hosts. After entering

fishes in this way, then, the second-stage larvae are supposed to molt with-

in such fiéhes, so as to be the third-stage larvae.

Despite,the ._18. species of adult nematodes of the genus Anisakis

reported up to date, however, only two species in the third larval stage

have so far been observed to be parasitic on such fishes. These two species

are called by Berland (1961) as Type I and Type II larvae, respectively.

Their morphological differences are observed clearly in the ventriculus and

the tail end as éhown in Figure 2. Especially, the difference in the ventri-

culus.seems to correspond to that between the adult nematodes of the sub-

family Anisékis and the subfamily Skriabinisakis, in which the àhape of

(A) (B )

16

Type I larva can be considered to be

similar to that of the former and the

àhape of Type II larva to that of the

latter.

Fishes on which these two types

of larvae of the genus Anisakis are

parasitic may be listed up according

to various reports on them. As such

host fiahes in Japanese waters for

Type I larvae of the Anisakis, 104 spe-

cies under 59 families are reported

along with Surumeika (Ommastrephes

sloani pacificus). Including those

reported abroad, then, far more than

150 species of fishes and molluaks may

be considered to be possible second intermediate hosts for the Type I larvae.

As the hosts for Type II larvae of the Anisakis, on the other hand, only

AkamanbU (Lampris regia), Kitsunegatsuo (Sarda orientalis), Küroshibikamasu

(Prometheichthvs prometheus), and a few other fishes of the temperate zone

are seen in the past reports (and this is in fact an interesting point in con-

nection with the habitat of definitive hosts which will be mentioned later),

and, furthermore, the larvae parasitidon these fishes except AkamanbCi are

very small in quantity. Accordingly, the Type I larvae are considered to be

more important than those of Type II in the studies of.their infection in the

definitive hosts as the infective agents of Anisakiasis.

Thus, the distribution of such Type I larvae in Japanese waters was

Figure 2: Major morphological differences between two types of larvae of the sakis,

(A) (A) Type I larva; (B) Type II larva.

17

investigated by the present writer and his associates with a group of re-

search workers. The results may be summarized as shown in Table 8, which

shows that the larvae are parasitic mostly on fishes living around the north

Japan Sea and those migrating to this sea region from the south for the sea-

son. Such a pattern of distribution is seen typically in the case of annual

Sureeika (Omdastrephes sloani pacificus) which are caught mostly in Japanese

waters and used for food. As àhown in Figure 3 according to Soeda (1956),

the Surumeika grow up in autumn around Hokkaid -C, , when they begin to move

southward in two groups between October and December, one moving down along

the Pacific coast and the other along the coast of the Japan Sea. Then, they

reach the waters around southwest.Japan, where they spawn between February

and March. The young thus grown in the southwestern sea move northward again

along both sides of Japan between May and June. Here, almost no Anisakis

larvae were found in such young Surumeika caught on the way to the north or

when they just reached the sea around Hokkaidci, whereas those caught around

Hokkaid3 between autumn and winter were found highly infected with the larvae.

Therefore, it is clear that the infective agents live in the northern sea.

In addition to such geographical factor, feeding habits of fishes and

decapods were observed to affect their infection with Anisakis larvae. Accord-

ing to the observations Shown in Table 8, polyphagous fishes such as Suket3-

dara (Theragra chalcogramma), Sakuramasu (Oncorhynchus masou var. ishikawae),

and Madara (Gadus macrocephalus) in the group (A) are infected in higher

rates with larger numbers of parasites than Nishin (Clupea Pallasii) feeding

mainly on crustaceans. A similar pattern is seen in the group (B), in which

Maiwashi (Sardinops melanosticta) feeding only on phytoplankton are not infect-.

ed with Anisàkis larvae whereas Samma (Cololabis saira) feeding only on

,

d

on

'

18

zooplankton are infected in a low rate with a small number of parasites and

Maaji (Trachurus.japonicus), Hirasaba (Scomber Japonicus), and Surumeika

(OmmastrePhes sloani pacificus) all of which are piscivorous are infected in

higher rates with larger numbers of parasites than other species.

In order to examine further the relations between the feeding habit

Table 8: Results of investigation of fishes and decapods in the search of -397- the distribution of Anisakis larvae. (Kobayashi, Kagei, et al, 1966, and thereafter)7------

Distribution Name of Number Rate of Average The high- Feeding of samples sample of sam- parasit- number est num- habit

species pies ism of para- ber of sites para-

sites

(A)Species Suketodara distributed (Theragra 119 10 43.8 360 polypha- around the chalcoRra- gous north Japan mma) Sea region Sakuramasu

(Oncorhyn- 10 100 20.0 167 polypha- chus masou gous var. ishika- wae)

Madara (Gadus macrocepha- 48 96 32.6 24 polypha- lus) gous

. Nishin crustace- (Clupea 100 77 - 4.6 52 ans and Fallasii) fishes

(B)Species Maa i fishes an distributed Trachurus 285 51 31.1 676 crustace- along both a nicus ans sides of Hirasaba fishes an Japan (in (Scomber 573 81 9.4 109 crustace- . the Pacific japonicus) ans and the Surumeika Japan Sea) (Ommastre- 755 42 1.7 19 piscivoro migrating Plies sloani between the raciirc7:0— north and Samma south for (Cololabis 20 5 .1.0 1 zooplankt the season. saira)

,

19

Table 8 continued.

Maiwashi - (-SWII.Lops 20 0 0 0 phyto- melanosticta) plankton

(G) Species Akamanb-6* distributed Lam ris 2 100 76.5 100 ?

widely in X.2e1.11 the warm Katsuo water re- - -TWIwonus 10 90 6.1 20 piscivoroui gion having tia-17117--- long-range Gomasaba migration (ScOmber 20 55 2.5 5 fishes and habits. tapeinoce- crustacean,

phalus) Hagatsuo (Sarda 12 33 1.3 2 ? orientalis)

Maguro Thunnus

-ù7,7r7171Z7 20 0 0 0 piscivorou

(D) Species Ishi akidai distributed (Oplegnathus 13 0 0 0 grazer in the punctatus waters near Makogarei Japan being (Limanda 10 0 0 0 benthos- sedentary. vokohamae) eater

Hiika 23 0 0 0 ? 773-

Mongika ?

13 0 0 0 ?

Kiiika (cuttle- 20 0 0 0 ? fie,Sepia)

Yariika --(c.7jary, 24 0 0 0 ?

Dorvteuthis)

*Many larvae of Type II were included.

. February April June

5

.--• eke (4.) 0-0 ekYitt (B)

tEotealvat

7 a 9 10 II ix hiorrthi I 1 t

1 2 3 4 5 6

100r

so

20

(A)Rate of infection (B)Number of parasites

August October December

Monthly changes in the Surumeika distribution in Japanese waters (Soeda, 1956).

Figure 3: Seasonal migrations of Surumeika (Ommastrephes sloani pacificus) and monthly changes in the infection with Anisàkis larvae.

of host and the amount of parasites infected in it, variations in the infec-

tion of certain fiehes according to age were investigated as shown in Table 9.

Here, it was observed that the number of larval parasites per fish increased

with the increase in the age of fish in every sample species. Such a pattern

was previously observed in Nishin (Clupea Pallasii) by Bishop & Morgolis

(1955). However, interesting points in the present observations are that

Samma (Cololabis saira) samples, which feed only on zooplankton, were found

infected with the larval parasites for the first time in the fourth year after

birth, that Maaji (Trachurus japonicué) samples began to be infected in the

second year when'their feeding habit changed from plankton-eating to fish-

eating, and that polyphageus Tara (Gadus macrocephalus) and Sakuramasu (2n7

corhynchus masou var. ishikawae) samples &lowed rapid yearly increases in

the quantity of larval parasites. All of this seems to indicate as to the

21

second intermediate hosts involved in the life cycle of Anisakis that the

infection first occurs to the so-called first predators feeding on zooplankton

Table 9: Variations in the infection of various fishes by age with Type I -398- larvae of the Anisakis (average number of parasites per fish).

4 5 6 7 8 Feeding

Fishes habit

Samma (Cololabis 0 1.0 zooplankton saira)

Nishin (Clupea Pallasii) 1.8 2.4 3.4 mainly crus- taceans

Maaji (Trachurus 0 1.4 2.5 piscivorous japonicus) (after its

second year)

Masaba (Scomber 1.5 6.5 piscivorous jaroni7Z---

Tara (Gadus macrocepha- 13.3 35.9 94.1 polyphagous lus)

Suket&lara (Theragra chalcogramma 29.9 70.1 polyphagous

Sakuramasu (Oncorhyn- chus masou var. ishiljn=) 20.0 polyphagous

and then to the second predators, piscivorous or polyphagous, which eat the

infected first predators ("secondary infection," Miyazaki, 1954), thus causing

the rapid increase in the quantity of parasites in them.

Such increase in the quantity of parasites through "secondary infec-

tion" in the second intermediate hosts was demonstrated by an experiment in

which NiJimasu (SaImo Rairdnerii irideus) samples were injected through the

mouth with Type A larvae of the Anisakis collected from Suketeidara (Theragra

chalcogramma), so as to see the larvae molting in them (Kobayashi, Kagei, et

al, 1968, unpublished). •

A. simplex Cftifeeljeehale, 1/12.1244) A PhYselieris r,4 rel Ytheuge axttatC14à retezbateed )

•

1 - . ••• 4•$‘0, ,,,:".%%.•-• • • •

• 6 ; e •

c

_

(ia

▪ !Ilewn •: rykaLa

• -1742er■Guk _ •

fe4--einitz 50 10('

• • . r

22

7. Growth of Parasites Within Definitive Host—Relationship Between Larval

and Adult Stages

As mentioned earlier, there are considerably many species of adult

nematodes of the genus Anisakis, not including those called by synonyms of

other species. In order to elucidate the whole life cycle of such nematodes

and also to find out the species with which man may be infected, it is impor-

tant and necessary to find out which adult species those two types of larvae

so far found parasitic on fishes grow into. To this, infection experiment may

be the best method of approach, but it is very difficult, or hardly possible

at the present stage, because of certain problems concerning the definitive

(a) First molting; (h) Second molting; and (c) Oogenesis.

Figure 4: Measurements in the larvae (Type I and II) and the adults (simplex and phvseteris) of the Anisàkis. (A, B, and C indicate: tail-length/body-length x 100; ventriculus-length/body-length x 100; and esophagus-length/ventriculus-length x 100, respectively.)

23

hosts along with certain other obstacles. Consequently, attempts have been -399-

made in the present study by all possible methodsother than infection experi-

ment.

As one of such attempts, it was examined whether any continuity and

similarity exist in morphological measurements between the larvae and the

adults found in fiàhes and Sujiirtika (Stenella caeruleoalbus). As a result,

it was observed that there were almost no differences in the measurements of

various organs and other morphological characteristics between the samples of

Type I larvae found in fiees and those in the stomach of Sujiiruka when they

were of the same length. This supports the observation by Punt (1941) that

the two are of the same species. .Similar relations were also observed in

case of Type II larvae.

Such larvae infected in fishes were supposed to molt soon after their

entering the definitive hosts, as a large number of larvae found in the sto-

mach of hill:net were about as long as Type I larvae and had already lost

the boring tooth and the mucro of the tail end. Such molted larvae (in the

fourth stage of growth) were observed to have clearly shaped lips and con-

spicuous striations as long as about 301u on the cuticle covering the body

surface. Also, their reproductive organs were observed in the early process

of formation within the body, though the vulva was not yet open to the body

surface in the females and the papillae and copulatory mucrones were not

observable yet in the tail of the males. Their second molting within the

hosts occurred when they grew as long as 30mm, more or less. Then, the vulva

opened to the body surface, and the papillae and a pair of copulatory mucrones

became clearly observable, so that their specific identification could be

made unequivocably according to their morphological characteristics. The

6

Contmaccum acluneuni spietilissemm

Terranova Anisakis decipiens simplex

Contracaecum

eta Weber.

EGG

1-st. LARVA

2-st. LARVA

Planktin F;ish

3-st. LARVA

EGG

1-st. LARVA

2-st. li.ARVA

2-st. LARVA

. 1 Copepod*

lat. LARVA

FL(

1 3-st. LARVA

Er 1-st. LARVA

10

2-st. 'CAVA

2-st. I.A RVA

Invertebrate (Ntysids Shrimp)

I 2-st. LARVA

small Fi<N i 0 Fish

large Fish /

Ni. 3-st. LARVA

Er 1-st. LARVA

IC) 2-st. LARVA

2-st. LARVA

Invertebrate • (Euphauslid)

1 2-st. LARVA

srnall Fisti 1 0 Fiait

large Fish /

3-st. LARVA

Def. host.

e (Berland, 1961) (Huizinger, 1966) (Scott, 1954, '55, (Kagel, 1968) Myers, 1960)

4-st RVA

0 4-st. 1..ARVA 4-st. LARVA

IC) I-ARVA

I 0 5-st. (ADULT) 5-st. (ADULT) 5-st. (ADULT) 5-st. (ADULT)

3-st. LARVA 3-st. LARVA 3-st. LARVA 3-st. LARVA

Flair I( ) Seal 10 Dolp110

I. int. host.

2-st. LARVA

2-st. LAIltÇ'A

54h

24

&indicates n-th molting.

st = stage.

Figure 5: Models of the life history of nematodes of the subfamily Anisàkis. (Drawn by Kagei).

morphological measurements in each of suàh growth stages were found on a

straight line as àhown in Figure 4, so that the larvae of Type I could be

considered to grow into A. simplex within the stomach of Sujiiruka (Stenella

caeruleoalbus).

Between the larvae of Type I1. and the adults of A. ehyseteris, on the

other hand, continuities were observed for the most part in the morphological

measurements, and morphological similarities were also observable between the

two. The specific characteristics of this species after the second molting

were observable.only in the samples over 50mm in length.

25

Because ho experiment of infection was made, thè period taken for the

sexial maturity in these nematodes was not clear at all. Also, the relation-

àhip between A. typica and Type I larvae remains as a question to be inves-

tigated.

8. Summary

The present paper has discussed the life cycle of nematodes of the

genus Anisakis, especially A. simplex, taking into consideration certain

ecological aspects of their hosts. The discussion may be summarized as shown

in Figure 5. Such life cycle is also observed commonly in other genera of

the subfamily Anisàkis, so that it may be quite interesting to see' the life

cycle of A. simplex as the one characteristic of the subfamily Anisàkis.

In Short, the life cycle of nematodes of the subfamily Anisàkis may

be described as follows: The eggs grow in the sea after spawned until the

second-stage larvae hatch out of the egg-Shell into the water. These larvae

molt the cuticle for the first time within their first intermediate hosts.

When they have grown to certain extent, they are taken by their second inter-

mediate hosts, within which they complete the second molting to be the third- .

stage larvae. Some of the third-stage larvae are taken further by another

hosts, so that the number of the second intermediate hosts increases through

such "secondary infection." By eating these second intermediate hosts, then,

the definitive hosts become infected with the larvae. Within the alimentary -340-

cana]. of their definitive hosts, the larvae grow up, molting twice, into ma-

tured nematodes to spawn the eggs there. In the life cycle thus described

very briefly, however, there are still many obscure points as have been men-

tioned in various places in the present paper, and hence many questions still

remain for future studies.

.«>

Main Literature Cited

IE X At

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marine fishes. Sanie. 11 : 1-50,1961.

2) Bishop, Y. M. and Margolis, L. : A statistical exami-

nation of Anisakis larvae (Nematoda) herring

(Clupea pallasi) of the British Columbia coast.

J. Fish. Ras. Bd. Canada. 12 (4) : 571-592,1955.

3) Hatanaka, M. and M. Takahashi : Studies on the

amounta of the anchovy rammed by the mackerel.

Tohoku Jour. Agr. Rea. 11 : 83-100,1960.

4) Hu izinger, H. W. : Studies an the life cycle and

development of Contracarcum spiculigerum (Rudol-

lphi, 1809) (Ascaroidee : Hetcrocheilidae) from

marine piscivorous birds.J. Elisha Michell Sci. Soc.

82 : 181-195,1966.

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375,1967.

6) Fiutton, R. F., T. Ball and Eldred, B. : Immature

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Henry, 1912, from shrimps. J. Parasit. 48 : 327-332,

1962.

• 7) Johnston, T. H. and Mawsoa, P. M. : Remarks on some

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'12) .e.1—p5:17inefit. ;t8t1,*., 4(2): 111-124,1955.

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344,1960.

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(In Russian). Trud. Zool. Inst. Akad. Nauk. SSSIt.

19,1955.

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parasites de poissons de la mer du Nord. Mem.

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with a larval marine nematode from smelt. J. Fish.

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sitic ascarid, Porrocaecum decipiens, in the common porpoise, Phocacna phocaena, from the Lower Bay of Fundy. J. Fish. Ras. Bd. Canada. 15 (1) : 1-4,1958 a.

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FirefAm,,- (14) : 1-24,1956. 24) Thomas, L. J. : On the life cycle of Contracaecum

spiculigerum (Rud.). J. Parasit. 23: 429-431,1937. 25) Thomas, L. J. : Life cycle studies on Contracaecunt

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96

(Translation of Japanese literature) .

8) Kagei, Noboru, Tomoo Oshima, Akio Kobayashi, Mitsuyoshi Kumada, Chikara Koyama, Yoshitaka Komiya, and Akira Takemura: Kakushu kaisan-honyii-dUbutsu ni kisei suru Anisakis-zoku senchii-rui no ch3sa-7171772-7.tigations of nema-todes of the genus Anisakis parasitic on various sea-mammals.) Kiseichii-shi(. Parasit.) 16 (6): 427-435, 1967.

9) Kobayashi, Akio, Chikara Koyama, Mitsuyoshi Kumada, Yoshitaka Komiya, Tomoo Oshima, Noboru Kagei, Toshio Ishii, and Masaaki Machida: Kaisan-gvorui ovobi ika-rui ni tsuite no Anisakinae yU-senchU no kansen-chosa

to Ottosei)(1), Inai-Kiseichu-shi (J.

Kiseichü-shi (J.

27

(Investigations of infection of sea-fishes and decapodes with larval nematodes of Anisakinae). Kiseichii-shi (J. Parssit.) 15: 348-349, 1966.

11)Machida, Masaaki: Ottesei no kiseichii (Parasites kiseichu ni tsuite (777J;Me in the ventriculus). Parasit.) 15 (7): 544-545, 1966.

12)Miyazaki ? IchirU: GahechU-shU (Guathostomasis). Parasit.) 4 (2): 111-124, 1955.

16)27...Ref.: Reports, Zool. Inst. Ac/Sc.

17)finvestigations regarding certain parasitic nematodes of North-Sea fiàhes. - Memoirs, Belgian Royal Museum of Nat. History.j.

24) Soeda, Kànsaike: Surumeika, Ommastrephes sloani pacificus (Steenstrup), no seitai narabini hanshoku ni kansuru Icx7;1711-TAn ecological study of Ommastrephes sloani eacificus and its reproduction). RokkaidC"-ku Suisan-Kenkviisho Kenkyu-Hokoku (Bull. Hokkaido Sea1121a- Fish. Res. Inst.) (14): 1-24, 1956.