Cymothoida Wägele, 1989

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Suggested Common Name: Fisheaters
Number of subordinate taxa: 1405 species in 9 families worldwide, 246 species in 7 families in our area
Etymology: after Cymothoa Fabricius, 1787, see that account for more information. Common name refers to this suborder's propensity to either predate on or parasitize fishes (and other vertebrates), something unique to it over other groups other than Gnathiidea. A name theming based on the Golden Age of Piracy is given to many subordinate taxa to allude to their ravenous carnivory.
Taxonomic History: Cymothooidea Leach, 1814; the superfamily Cirolanoidea is seperated in Bruce & Poore, 2003 and previous papers based on mandibular details but the few details seem to be more signifigant on a family basis rather than a superfamilial basis.
Size Range: up to +250mm
Description: Body ovate, compact ; sexual dimorphism obvious to absent, pleopod dimorphism restricted to presence or absence of appendix masculina. Antenna 1 well-developed or secondarily reduced, scale absent (present in Bathynomus). Antenna 2 without scale. Mandible incisor large, cutting, 1-few-cuspidate; lacinia present or fused with spine row; spine row present; palp present (very rarely absent). Maxilla 1 usually biramous. Maxilla 2 present, exopod with 2 endites. Maxilliped epipod present in at least a few groups; basis not dominating maxilliped size; endite small, rarely reaching past palp segment 1, usually tapering; palp present, generally well-developed. Pereopods 2-7 coxae formed into coxal plates, variously free to fused with tergites. Penes present, shape and separation various. Pleon all segments free or secondarily fused. Pleonite 1 similar to other pleonites. Pleopod 1 not modified, not sexually dimorphic. Pleopod 2 slightly modified, slightly dimorphic mainly in the presence or absence of the appendix masculina. Pleopod 3 endopod ovate to subrectangular, tip rounded. Telson ventrally flattened, lacking a branchial chamber. Uropods set ventrolaterally or ventrally on telson, forming a tailfan with telson.
Type taxon: Cymothoidae Leach, 1814
Notes: This taxonomically confused suborder until fairly recently included Anthuridea, Gnathiidea and Epicaridea until genetic analyses found that these taxa are all unrelated to each other. The currently circumscribed families are likely highly paraphyletic or even polyphyletic with each other, with Cirolanidae in particular appearing to have the rest of the families nestled in it according to genetic data.

Subordinate taxa: Aegidae, Anuropidae, Cirolanidae, Corallanidae, Cymothoidae, Tridentellidae

Key to families
1 a. Uropods identical to the pleopods, giving the animal the appearance of having no uropods; antenna 1 large and reduced to 2 segments with a distinct groove, making it appear scalloped; bizarre bathypelagic parasites of jelly animals, known species are usually a vivid red --> Anuropidae
b. Uropods sharply differentiated from the pleopods; antenna 1 not as above, with a distinct peduncle and flagellum; highly carnivorous to facultative parasites of vertebrates --> 2

2 (1) a. All pereopods prehensile; body moderately contorted in adults (♀'s); adults obligate parasites on the surface, in the gills or in the mouth of fish, immatures (incl. ♂'s) facultatively parasitic--> Cymothoidae
b. At least some pereopods ambulatory (all ambulatory in some Cirolanidae but then troglobitic); body not contorted in any life stage; free-living carnivorous, facultative vertebrate parasites or obligate jelly animal parasites --> 3

3 (2) a. Maxilliped and maxilla 1 with stout recurved apical spines; maxilla 2 lateral lobe formed into a slender stylet, medial lobe small, lacking stout circumplumose spines  --> Aegidae
b.  Maxilliped and maxilla lacking stout recurved apical spines; maxilla 2 lateral lobed not formed into a slender stylet, medial lobe large with or without stout circumplumose spines --> 4

4 (3) a. Mandible incsisor multicuspid, prosterior tooth prominent, lacinia well-developed, spine row set on fleshy lobe, molar large, spinose, blade-like; maxilla 1 biramous; maxilla 2 lateral lobe with 11-14 apical spines, medial lobe large with 3-4 circumplumose spines --> Cirolanidae
b. Mandible incisor weakly or not toothed, with lacinia weakly developed or absent, spine row not set on fleshy lobe, molar absent or small to moderately sized, sparsely spined; maxilla 1 uniramous; maxilla 2 lateral lobe with 1-5 stout apical spines, medial lobe small, lacking circumplumose spines --> 5

5 (4) a. Mandible lacinia absent, molar moderately large; maxilla 1 stout, 2-segmented, endite conical, often with tridentate scale-like spines; maxilla 2 lateral lobe slightly curved, tip with 3-5 stout hooked spines and smaller subapical spines; maxilliped with endite, palp 5-segmented; generally deepwater --> Tridentellidae
b. Mandible lacinia absent or small with a weak spine row, molar absent or small; maxilla 1 small, 1-4 segmented, endite rounded, bifid, trifid or sublinear, lacking tridentate scale-like spines; maxilla 2 lateral lobe sickle-shaped with 1-3 large hooked apical spine and 0-3 smaller subapical spines; maxilliped lacking endite, palp 3-5-segmented; shallow to deepwater --> Corallanidae

Sources

Sources

An, J., Yin, X., Chen, R., Boyko, C. B., & Liu, X. (2022). Integrative taxonomy of the subfamily Orbioninae Codreanu, 1967 (Crustacea: Isopoda) based on mitochondrial and nuclear data with evidence that supports Epicaridea Latreille, 1825 as a suborder. Molecular Phylogenetics and Evolution, 107681.

Brandt, A., & Poore, G. C. (2003). Higher classification of the flabelliferan and related Isopoda based on a reappraisal of relationships. Invertebrate Systematics, 17(6):893-923.

Delaney, P. M. (1988). Systematics, Phylogeny and Biogrography of the Marine Isopod Family Corallanidae Hansen, 1890. Contributions in Science, 409, 1-75.

Schultz, G. A. (1977). Bathypelagic isopod Crustacea from the Antarctic and southern seas. Biology of the Antarctic seas V, 23:69-128.

Thomas Thorpe, J. A. (2024). Phylogenomics supports a single origin of terrestriality in isopods.
Proceedings B, 291(2033):20241042.

Published: Jan 1, 2023
Updated: Dec 13, 2024