Diagnostic figures of Pseudanthessius tenuis, from Nicholls (1944).

Belongs within: Poecilostomatoida.

Pseudanthessius is a genus of marine parasitic copepods associated with a wide range of invertebrate hosts of numerous phyla.

Characters (from Humes & Stock 1973): Body cyclopiform. Urosome in female 5-segmented (occasionally 4-segmented), in male 6-segmented (occasionally 5-segmented). Caudal ramus with six setae. Rostrum not well developed. First antenna 7-segmented, in female with armature 4, 13, 6, 3, 4 + 1 aesthete, 2 + 1 aesthete, and 7 + 1 aesthete; in male with same armature or in some species with additional aesthete on second segment. Second antenna 4-segmented, with formula 1,1,3 and variable terminal armature (1-4 claws or clawlike spines and a few setae; or, in P. tortuosus, two lamelliform elements, one seta, and three spines; or, in P. mucronatus, all elements setiform). Labrum deeply incised medially. Mandible with basal region having its convex edge smooth or with a weak scalelike area or a process and on concave edge a row of spinules; lash long or short. Paragnath a small lobe. First maxilla with three or four elements. Second maxilla of usual lichomolgid type. Maxilliped in female 3-segmented, with pointed tip; in male 4-segmented (assuming that proximal part of the claw represents a fourth segment). Legs 1-4 with 3-segmented rami, except leg 4 endopod which is 1-segmented with two distal elements. Leg 1 endopod of male same armature as in female, or with same formula but with slight differences in form of processes or elements, or in P. deficiens 1,1,4 or in both P. tortuosus and P. aestheticus 1,1,1,4. Leg 5 represented by three elements (subterminal seta and terminal spine and seta); no free segment. Leg 6 represented by two setae near genital openings.

<==Pseudanthessius Claus 1889 [Pseudanthessiidae] N44
    |--P. assimilis Sars 1917 N44
    |--P. concinnus Thompson & Scott 1903 N44
    |--P. dubius Sars 1918 N44
    |--P. gracilis Claus 1889 N44
    |--P. liber (Brady & Robertson 1875) N44 [=Lichomolgus liber BK77]
    |--P. mucronatus Gurney 1927 N44
    |--P. nemertophilus Gallien 1935 N44
    |--P. obscurus Scott 1909 N44
    |--P. sauvagei Canu 1891 N44
    |--P. tenuis Nicholls 1944 N44
    |--P. thorelli (Brady & Robertson 1875) N44 [=Lichomolgus thorelli BK77]
    `--P. weberi Scott 1909 N44

*Type species of generic name indicated


[BK77] Barel, C. D. N., & P. G. N. Kramers. 1977. A survey of the echinoderm associates of the north-east Atlantic area. Zoologische Verhandelingen 156: 1-159.

Humes, A. G., & J. H. Stock. 1973. A revision of the family Lichomolgidae Kossmann, 1877, cyclopoid copepods mainly associated with marine invertebrates. Smithsonian Contributions to Zoology 127.

[N44] Nicholls, A. G. 1944. Littoral Copepoda from South Australia. (II) Calanoida, Cyclopoida, Notodelphyoida, Monstrilloida and Caligoida. Records of the South Australian Museum 8 (1): 1-62.

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