Paradoxum (= Macrostomum) Was for the Put at My Disposal by Mr

52 BASTERIA, Vol. 24, No. 4 en 5, 1960

Some observations on Leucochloridum paradoxum

(= macrostomum) Rud. 1802, from the Snail

Succinea putris L.

M.R. Honer

(Institute for Veterinary Parasitology and Parasitic Diseases,

State University, Utrecht, The Netherlands)

An exceptionally well-preserved specimen of Succinea putris L., infected with Leucochloridium paradoxum (= macrostomum) was for The put at my disposal by Mr. L. J. M. BUTOT investigation. snail had been collected by him in the South-Holland Biesbosch in

1958 and forms the basis of the following observations.

BRIEF HISTORICAL SURVEY

Leucochloridium for has been known a long time and has usually been recorded from Succinea record from Plan- spp., although one is orbis WESENBERG-LUND confirm sp. (but (1931) was unable to this).

The most complete studies on the parasite are by HECKERT (1899),

MONNIG (1922) and WESENBERG-LUND (1931), to which the reader is referred for detailed descriptions and literature. A key to species known at that time was erected by MCINTOSH (1932). WESENBERG- able of but LUND was to examine some 150 specimens this parasite, unfortunately gave no detailed measurements of either sporocysts or described and cercariaea, although he the morphology ecology in some detail.

Records of this parasite were brought together by VENMANS (1951), list find to whose this by Mr. L. J. M. BUTOT must now be added.

MORPHOLOGICAL EXAMINATION OF SUCCINEA PUTRIS

The of shell and width snail, length 1.94 cm 1.02 cm, was char- acterised by swollen, ovoid tentacles which increased markedly in size

(and especially in diameter), when the side or sole of the foot was

lightly pressed. After the removal of the shell and dissection, three

the left large sporocysts were found, one on hand side of the body

and two the hand side. The entire visceral on right mass was per- meated finer of with the terminations the sporocysts, making it dif- Honer: Leucochloridium paradoxum 53

and tissues. 1 shows ficult at times to separate host parasite Figure of the three in the of the snail, the appearance sporocysts body cavity after the removal of surrounding tissue.

1. Three from the of S. The Figure sporocysts body cavity putris. numbering full of is followed in the text. Only sporocyst 1 shown with its complement

agamodistomes. Abbreviations: v.m., visceral mass; c.a., closing mechanism;

a, agamodistomes.

THE SPOROCYSTS

examined The three sporocysts were separately by detaching just below of itself. the closing mechanism the large sporocyst Mr. BUTOT

had observed that in the living state, the sporocysts were of the and confirmed and distri- ,,green-sac" variety this was by the type

bution of pigment which was „clumped" as shown in Figure 2. In of with the case „brown" sacs the pigment is more even distributed

occasional raised areas. 4 54 BASTERIA, Vol. 24, No. en 5, 1960

The followed the is round the pattern by pigment a spiral long of axis the sporocyst but mostly confined to the cap region and the number of in of 1 larger pigment clumps the case sporocyst no. was

47, with many smaller spots on the wall of the sac, overlapping the

1 Figure 2. Distribution of pigment clumping on the caps of sporocysts and be follows 3 (see Fig. 1). It will seen that the pigment a more or less

spiral pattern.

first and second segments. MONNIG (1922) first developed the idea

that light stimulus on the pigmentation stimulates muscular con-

tractions and causes the characteristic „pumping" of the sacs. This for of probably accounts the concentration the pigment on the cap of the sporocyst, and for its clumping for it is just the cap of the

sporocyst that protrudes under the edge of the snail in the natural

expanded condition. In addition, spirally running musculature can Honer: Leucochloridium paradoxum 55

be below the and these first acti- seen pigment groups are probably vated by the light stimulus.

Table 1

Sporocyst/Measurement Length Breadth Number of cercariaea 1 9.20 1.60 61 1 2 9.41 1.23 97 [ 270 3 12.03 0.98 112 J

all measurements in mm.

The sporocysts were opened individually in separate watchglasses, measured and released and where they were the cercariaea were also of counted. The results are shown in Table 1 above. Although a total found 270 cercariaea (or agamodistomes) is recorded, more were in the finer ramifications of the sporocysts, bringing the total to from something like 360. WESENBERG-LUND states that 100 to 200 could found would agamodistomes be per ripe sac, so this suggest that we have to deal here with sacs that are not fully ripe.

To gain an idea of the ripeness of the sacs, in a very approximate but divide of comparative manner, we can the volume V each sporo- the number of cyst by N agamodistomes present, when we have:

Table 2

Sporocyst 1. 2. 3.

V/N 303 110 81

in 3 ju

It will be shown in the section dealing with the agamodistomes of that they are all the same order of size, so that the decreasing value of of V/N above-is not an expression the decreasing volume used but is indication of of by any one cercariaeum, an the density of crowding the agamodistomes. Thus they are nearly three times

in 2 and forth. as tightly packed sporocyst as in sporocyst 1 so If we accept the figures given by WESENBERG-LUND (1931) as to the number of cercariaea a Table in fully ripe cyst, the results in 2 with this. In there the larvae agree sporocyst 3 are most present

and 3 (112), there is the least room for them (81 ). This an /< gives idea of the tension and of leads swelling the sacs which finally to their and distribution of bursting thus their contents. 1960 56 BASTERIA, Vol. 24, No. 4 en 5,

THE AGAMODISTOMES

The number of agamodistomes was given in Table 1, per sporo- of taken random from and series of cyst. Groups 30 were at these a

measurements made. These are tabulated below; all measurements

in » are fx.

Figure 3. Agamodistome (cercariaeum) seen in lateral view. The well-develop-

ed cuticle is both oral and ventral (c) seen to have finger-like projections into suckers. Abbreviations 4. as in Figure

Table 3

From Sporocyst 1 2 3 Length 813 779 806

Breadth 264 287 285

Oral sucker 186X165 204X184 200X178

Acetabulum 160 161 170

Pharynx (diam) 91 90 93 Length/Breadth 3.08 2.83 2.71

surrounded The agamodistomes are by a thick, very transparent cuticle and This (shown in Figures 3, 4, 5). acts as a protective membrane for the larva within the sac, and can become very hard and thickened older order finer in specimens. In to see details, chloral-lactophenol was used in this case to soften and clear the Honer: Leucochloridium paradoxum 57

parasites. Although this cuticle completely surrounds the agamodist- suckers and ome, there is a connecting channel between the the surface of larvae in fact feed the cuticle, suggesting that the may 4 on neighbouring larvae, as is the case with many rediae. In Figure small rounded bodies, three in number are indicated in the hind end of the These the A 1 of the body. are n a g e n reproductive organs of of the adult, for the larva, so-called, is really a small edition the adult trematode be found for further to in many birds, except the development of certain organ systems and their proportions to one another.

Figure 4. Agamodistome viewed ventrally. The cuticle has been damaged by the fixation and mounting of the specimen. Key to abbreviations: o., oral of sucker; a., acetabulum; ph., pharynx an., Anlagen gonads; ex., excretory branches. bladder; gb., gut

The problem still remains for the field biologist and for the laboratory worker, as to how the Leucochloridium gains entry into its final hosts, which include non-carnivorous, seed-eating birds. Al- though it is generally accepted that birds peck off the swollen tentacles and become of thus infected, none the many experiments that have been carried out to this been prove have positive. In any case, does this not explain how seed-eating birds become infected. There would seem to be two possibilities worth investigating both in the field and in the laboratory, first that agamodistomes which have been from „exploded" a ripe sac on to leaves, stems, and so forth,

in some that noncarnivorous birds encyst way so also have the chance of being infected, and secondly that some other intermediate host under can be involved certain circumstances, as was shown by KRULL MAPES in the of Dicrocoelium dendriticum & case (1952). 1960 58 BASTERIA, Vol. 24, No. 4 en 5,

of from Figure 5. Photomicrograph agamodistome sporocyst 2, showing elaborations of the enclosing cuticle and general appearance of the cercari- under Abbreviations 4. aeum the microscope. as in Figure

LITERATURE

Studies KRULL, W. H., & C. MAPES, 1952. on the biology of Dicro- coelium dendriticum (Rud. 1819) Looss, 1899 (Trematoda: Di-

croeliidae), including its relation to the intermediate host, Cionella

lubrica (Miiller). Part VII: The second intermediate host of Dicro- coelium dendriticum. The Cornell Vet., vol. 603-604. 42, pp. of trematode MCINTOSH, A. 1932. Some new species worms of the

genus Leucochloridium Carus, parasitic in birds from Northern Honer: Leucochloridium paradoxum 59

with and other of the Michigan, a key notes on species genus.

Journ. Parasit., vol. 19, pp. 32-53- Leucochloridum macrostomum MONNIG, H. O. 1922. Ober (L.) (para-

doxum Carus) ein Beitrag zur Histologie der Trematoden. Mono- 61 graph, Jena. pp. WF.SENBERG-LUND. C. 1931. Contributions to the development of Leucochloridiumthe Trematoda Digenea. Part I. The biology of

paradoxum. D. Klg. Dansk. Vidensk. Selsk. Skrifter., Naturw.

Math. Afd., Raekke 9, Vol. 4 (3) pp. 90-142.

For a full bibliography of the parasite, the reader is referred to the last mentioned publication.

Summary

An account is given of Leucochloridium paradoxum (= macro-

stomum) Rudolphi, 1802 from Succinea putris L., found in the South- Holland Biesbosch. of and A description is given the sporocysts

their contents and some speculations over the unsolved problem of of definitive the entry the parasite into its host.

Samenvatting

dit artikel worden enkele In morphologische gegevens besproken betreffende een exemplaar van Leucochloridium paradoxum (= made crostomum) Rudolphi, 1802 in slak Succinea putris L. van de Zuidhollandse Biesbosch.

De maten van sporocysten en agamodistomen (cercariaea) en het worden aantal agamodistomen per sporocyst gegeven. Een theoretische de besmet- beschouwing over het probleem van de ting van eindgastheer besluit het artikel.