Family Atractidae

                                 Revised 01/12/26

Classification:

Phylum Nematoda

  Class Chromadorea
    Subclass Chromadoria

     Order Rhabditida

Suborder Spirurina

        Superfamily Cosmocercoidea

Atractidae (Railliet, 1917) Travassos, 1919

A family of nematodes that are mainly parasites of amphibians, reptiles and also of fish.

Members of the Atractidae are unusual in that eggs hatch and larvae develop to third stage in utero to autoinfect the current host (Anderson 2000, Bursey ey al., 2014).

Their transmission from host to host is not understood. The life cycles of Orientatractis and Rondonia have not been determined, however Costa (1962) believed that larvae of Rondonia (previously known only from fish) pass from the host to infect other fish directly. Petter (1966) claimed that tortoises became infected only after attaining sexual maturity and wondered if transmission occurred during mating.

Some species are monodelphic, others didelphic. In monodelphic atractids, the vagina may open into the rectum, forming a cloaca, or into the vulva located near the anus (Moravec et al., 2025)

Characteristics:

Key to most of the Genera of the Family Atractidae (from Mondal and Manna, 2013)

1 Didelphic 2
  Monodelphic 4
2 Oral opening elongated in lateral axis. Pharyngeal part of esophagus forming small buccal cavity. Parasites of intestine of Hyracoidea Nouvelnema
  Oral opening not elongated . Pharyngeal part of esophagus not forming buccal cavity. 3
3 Tail of male rather short. Parasites of reptiles Fitzsimmonsnema
  Tail of male terminated by long filament. Parasites of intestine of Equidae and Primates Probstmayria
4 Parasites of mammals 5
  Parasites of reptiles , fishes and amphibians 9
5 Mouth simple 6
Mouth with cuticular formations 7
  Mouth with two rudimentary lips, with cup- shaped buccal capsule. Parasites of Rhinoceros Diceronema
  Mouth with 6 lips , cup- shaped buccal cavity with a pair of sub ventral teeth Rhinoceronema
  Mouth with more than 6 lips , without buccal capsule. Parasites of elephant Leiperenia
7 Pharynx without pectinated laminae. Parasites of intestine of Hyracoidea Grassinema
  Pharynx with pectinated laminae 8
8 Mouth with 3 pairs of pectinated laminae. Parasites of equides and Rhinoceros Crossocephalus
  Mouth with two large lateral pointed elevations and no lamina. Parasites of intestine of Hippopotamus Cobboldina
9 Cuticle without spines 10
  Cuticle with spines 19
10 Vulva opening into rectum forming cloaca Rondonia
  Vulva separate from rectum and anus 11
11 Mouth without lips. Parasites of fish and reptiles Monhysterides
  Mouth with 3 to 6 lips 12
12 Oral opening apical in position 13
  Oral opening ventrally displaced. Subventral lip with a fringe. Parasites of intestine of tortoise Labiduris
13 Mouth with cuticular formations 14
  Mouth without cuticular formations 15
14 Lips with small tongue-like cuticular expansions surrounding oral opening. Parasites of intestine of fish Klossinemella
  Lips without small tongue-like cuticular expansions surrounding oral opening. Parasites of intestine of tortoise Orientatractis
15 Mouth with three lips 16
  Mouth with four lips Paraorientatractis
  Mouth with six lips 17
16 Vulva close to anus . Lung parasites of turtles Pneumoatractis
  Vulva pre or post-equatorial. Lung parasites of turtles Pseudocyrtosomum
17 Tail short. Parasites of turtle Cyrtosomum
  Tail long 18
18 Buccal capsule present. Excretory-pore anterior to esophageal bulb. Parasites of turtle Rhinoclemmysnema
  Buccal capsule absent. Excretory-pore posterior to esophageal bulb. Parasites of reptiles, amphibians and fishes Atractis
19 Cuticle covered with many spines alternating in diagonal rows 20
  Only posterior dorsal surface of the body with or without spines. Parasites of intestine of reptiles Podocnematractis
20 Spines extend along entire length of body. in diagonal rows. Parasites of intestine of turtle Paratractis
  Spines vary in arrangement and differing in shape and size. Parasites of intestine of reptiles Buckleyatractis

 

Body size range for the species of this Family in the database - Click:

References:

Anderson R.C. 2000. Nematode Parasites of Vertebrates: Their development and transmission. 2nd Ed. CABI Publishing, Wallingford, Oxon, UK, 650 pp

Anderson, R.C., Chabaud, A.G., Willmott, S.  1978. CIH Keys to the Nematode Parasites of Vertebrates. Eds Anderson, R.C., Chabaud, A.G., Willmott, S. CAB

Bursey, C.R., Flanagan, J.P. 2002. Atractis marquezi n. sp. (Nematoda: Atractidae) and a Revision of Atractis Dujardin, 1845, Sensu Baker, 1987. J. Parasitol., 88:320-324.

Bursey, C.R., Goldberg, S.R., Kraus, F. 2014. New species of Rondonia (Nematoda: Atractidae), new species of Rondonia (Nematoda: Atractidae) and other helminths in Austrochaperina basipalmata (Anura: Microhylidae) from Papua New Guinea. Acta Parasitologica 59:115-121..

Bursey, C.R., Reavill, D., Greiner, E. 2009. Pneumoatractis podocnemis n. gen., n. sp. (Nematoda: Atractidae) from the Yellow-Spotted Amazon River Turtle, Podocnemis unifilis (Testudines: Pelomedusidae). Comp. Parasitol. 76(2):149-153

Mondal, S., Manna, B. 2013 Rhinoceronema unicornensis gen. n., sp. n. (Cosmocercoidea: Atractidae) from Indian one horned Rhinoceros (Rhinoceros unicornis Linnaeus, 1758) captivated at the Alipore Zoological Garden, Kolkata, India. J Parasit Dis 37134-141 https://doi.org/10.1007/s12639-012-0147-7.

Moravec, F., Salgado-Maldonado, G., Gonzalez-Solis, D. 2025. Some nematodes from fishes of the Lacantan River in the Lacandon rain forest of Chiapas State, southern Mexico, including Cucullanus potamarii sp. n. (Cucullanidae) from the endemic catfish Potamarius usumacintae (Ariidae). Folia Parasitologica 2025, 72: 020 doi: 10.14411/fp.2025.020

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