Leucochloridium paradoxum

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Leucochloridium paradoxum
Leucochloridium paradoxum, parasite in Succinea putris
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Platyhelminthes
Class: Trematoda
Order: Diplostomida
Family: Leucochloridiidae
Genus: Leucochloridium
Species:
L. paradoxum
Binomial name
Leucochloridium paradoxum
(Carus, 1835)[1]

Leucochloridium paradoxum, the green-banded broodsac, is a parasitic

faeces
.

Life cycle

The species in Leucochloridium share a similar life cycle.[3][4] They are parasites of snails and birds. This is a truncated life cycle compared with typical trematodes, because the snail acts as both the first and second intermediate host.[5]

  • Sporocyst. The stalk of the largest broodsac is drawn shortened. A metacercaria is passing along the lowest stalk.
    Sporocyst. The stalk of the largest broodsac is drawn shortened. A metacercaria is passing along the lowest stalk.
  • Mature metacercaria ready to be transferred to the bird host; note the thick coat.
    Mature metacercaria ready to be transferred to the bird host; note the thick coat.
  • Adult found in the cloaca of the host bird; note the two prominent suckers.
    Adult found in the cloaca of the host bird; note the two prominent suckers.

Eggs ingested by the snail hatch into

insectivorous birds. Observations in captivity indicated that birds tore the broodsac out of the snail before eating it,[8] so the snail may survive this. Birds may also become infected by eating broodsacs that have spontaneously burst from the tentacle, surviving for an hour whilst they continue to pulsate.[7][9][10]

At their base,

distomes, c. 1.5 mm long. This form has two suckers on the ventral side, which anchor it to the cloacal wall, and a smooth dorsal surface. The adults are hermaphroditic and release eggs into the bird's faeces. Some will be eaten by a snail, thus completing the life cycle.[9][10]

In a study in Russia, snails became infected in spring and summer. The resultant sporocysts were producing infective metacercariae in the following spring but then died in late summer.[7] The lifetime of the adult stage in its bird host is believed to be of the order of weeks or months.[12]

Behaviour of the broodsacs and infected snails

Sporocyst of congener Leucochloridium variae within a snail. (video clip, 1m 30s)

The pulsations of the broodsacs typically vary from 40 to 75 times a minute depending on temperature, but they cease in the dark.[6]

The parasite manipulates the snail host's behaviour in a way likely to make it more conspicuous to birds. In one study of Succinea putris hosts, infected snails stayed in better lit places for longer, sat on higher vegetation, and were more mobile. Whereas 53% of infected snails remained fully exposed for the 45 minutes of the observation period, the figure was only 28% for the controls (nearby snails without Leucochloridium broodsacs).[2] Infected snails may survive for at least a year and continue to be able to use the eyes on the ends of their tentacles.[6] Although snails infected by other Leucochloridium species are reported to continue to reproduce,[3] snails infected by L. paradoxum often show a reduction of the sexual organs.[6]

The appearance and behaviour of the sporocysts is a case of aggressive mimicry, where the parasite vaguely resembles the food of the host, thereby gaining the parasite entry into the host's body by being eaten. This is unlike most other cases of aggressive mimicry, in which the mimic eats the duped animal.[13]

Taxonomy

In older literature, L. paradoxum may be referred to as L. macrostomum, derived from Rudolphi's 1803 description of Fasciola macrostoma, which he later (1809) renamed Distomum macrostomum. Zeller (1874) misidentified specimens of L. paradoxum as D. macrostomum. Rudolphi's species is now in the genus Urogonimus.[14] Leucochloridium heckerti Kagan, 1951 is also considered a synonym of L. paradoxum.[9]

The snail Succinea putris with broodsac inside its left tentacle

Identification

The easiest way to differentiate between Leucochloridium species is from the appearance of the broodsacs in the tentacle of the host snail. Leucochloridium paradoxum exhibits broodsacs that have green bands with dark brown and black spots, and with a dark-brown or reddish-brown tip.[9][6] Nowadays this method of identification may be supported with ribosomal DNA sequences.[12] A snail may be simultaneously infected by more than one species of Leucochloridium.[15]

The adults, found in the cloaca of birds, are less well known, so that distinguishing the species is less straightforward.[12]

Habitat

Leucochlordium paradoxum is found in moist areas, such as marshes, where the usual intermediate host Succinea snails are found.

Distribution

Type locality
: island in the Elbe at Pillnitz

Leucochloridium paradoxum was originally described based on its sporocyst stage, collected from an island in the river Elbe at Pillnitz, near Dresden, Germany.[1] Other known locations are Poland, Belarus, the Saint Petersburg area of Russia, Denmark, Sweden, Norway, the Netherlands, the United Kingdom and Japan.[12][15][9][16] It is believed to be the species of Leuchochloridium infecting an endemic species of semi-slug on Robinson Crusoe Island in the Pacific, the only record from the Southern Hemisphere.[17]

Hosts

Intermediate hosts:

Hosts:

References

  1. ^ a b Carus, C.G. (1835). "Beobachtung über einen merkwürdigen schöngefärbten Eingeweidewurm, Leucochloridium paradoxum mihi, und dessen parasitische Erzeugung in einer Landschnecke, Succinea amphibia Drap. Helix putris Linn". Nova Acta Physico-Medica. Academiae Caesareae Leopoldino Carolinae Naturae Curiosorum. 17 (2. s., v. 7, pt. 1): 85-100 + Pl. VII.
  2. ^
    doi:10.1111/jzo.12094
    .
  3. ^
    doi:10.2307/3223567
    .
  4. doi:10.2307/3278459
    .
  5. doi:10.1016/S1471-4922(02)02262-6
    .
  6. ^ a b c d e Wesenberg-Lund, C. (1931). "Contributions to the development of the Trematoda Digenea. I. The biology of Leucochloridium paradoxum". Det Kongelike Danske Videnskakbernes Selskab, Naturvidenskabelig-mathematisk Afdeling. 4: 90–142.
  7. ^ a b c Tokmakova, A.S.; Ataev, G.L. (2015). "Сезонные изменения в биологии Leucochloridium paradoxum (Trematoda, Leucochlomorphidae)" [Seasonal changes in the biology of Leucochloridium paradoxum (Trematoda, Leucochlomorphidae)] (PDF). Parazitologiya (in Russian). 49 (3): 200–207.
  8. ^ Zeller, E. (1874). "Über Leucochloridium paradoxum Carus und die weitere Entwickung seiner Distomenbrut". Zeitschrift für wissenschaftliche Zoologie. 24: 564–578 + Pl. XLVIII.
  9. ^
    doi:10.1007/BF00009845
    .
  10. ^ a b Heckert, G.A. (1889). "Leucochloridium paradoxam. Monographische darstellung der entwicklungs- und Lebensgeschichte des Distomum macmstomum". Bibliotheca Zoologica. 4: 1-66 + Pls I-IV.
  11. ^ a b Ataev, G.L.; Dobrovolskij, A.A.; Tokmakova, A.S. (2014). "Размножение партенит трематод Leucochloridium paradoxum (Trematoda: Leucochloridiidae)" [Reproduction of trematode Leucochloridium paradoxum sporocysts (Trematoda: Leucochloridiidae)] (PDF). Parazitologiya (in Russian). 47 (2): 178–182.
  12. ^
    doi:10.1023/B:SYPA.0000003809.15982.ca
    .
  13. PMC 3748996
    .
  14. doi:10.2307/2422256
    .
  15. ^
    doi:10.1007/s00436-016-5082-6
    .
  16. ^
    doi:10.1016/j.parint.2019.101936
    .
  17. ^ a b Castillo, V.M.; González, H. (2021). "Evidence of parasitism in the semi-slug Omalonyx gayana d'Orbigny, 1835 with Leucochloridium paradoxum (Carus, 1835) sporocysts on Robinson Crusoe Island" (PDF). Tentacle. 29: 34–35.

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