Cumoechidae, Boyko & Williams, 2023

Boyko, Christopher B. & Williams, Jason D., 2023, Nomenclatural and taxonomic changes in parasitic isopods (Isopoda: Epicaridea) including two new families and note on the questionable association between monogeneans and bopyrids, Zootaxa 5258 (3), pp. 251-269 : 260-261

Family Cumoechidae n. fam.

( Fig 4J )

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Diagnosis: Epicaridium larva with antennules as long as body; setae on antennules and uropodal exopod and endopod as long as or longer than body. Cryptoniscus larva/male body elongate. Head longer than wide, conical, posterior margin no wider than pereomere 1; eyes absent. Antennule article 1 elongate with ca. 16 marginal acute teeth. Coxal plates with posterior margins toothed. Pereopods 1–3 gnathopodal, 4–7 ambulatory with propodi tapering distally, dactyli as long as propodi. Pleotelson margin with 10 teeth, distalmost pair longest. Mature female spheroid in dorsal view, dorsoventrally compressed, segmented, ventral surface with long median cleft and raised segmented pad surrounding cleft; anterior region with reduced antennae and pair of pereopods. Parasitizing cumaceans.

Included genus and species: Cumoechus Hansen, 1916 , type genus (type species = Cumoechus insignis Hansen, 1916 by monotypy).

Distribution: South of Jan Mayen, Norway (69°31’N, 07°06’W), 1309 fms (2394 m); northwest of the Faeroes, Denmark (63°26’N, 07°56’W and 61°08’N, 09°28’W), 436–471 fms (797–861 m); southwest of the Faeroes, Denmark (61°08’N, 09°28’W), 436 fms (797 m) ( Hansen 1916).

Hosts: Cumacea : Diastylis echinata Spence Bate, 1865 , D. polaris G. O. Sars, 1871 , Hemilamprops cristatus (G. O. Sars, 1870) ( Hansen 1916) .

Remarks: Nierstrasz & Brender à Brandis (1931) noted similarities between the females of the nebaliacean parasite Apocumoechus paranebaliae Nierstrasz & Brender à Brandis, 1931 and Cumoechus insignis Hansen, 1916 and placed both species in Cabiropidae , although with hesitation and noting that the cabiropids represented a heterogenous grouping. Danforth (1970) proposed a new subfamily of Cryptoniscidae , Apocumoechinae, to contain the nebaliacean parasite and another new subfamily, Cumoniscinae, to include Cumoniscus Bonnier, 1903 and Cumoechus ; this work was not published (i.e., not recognized by the ICZN) and there were no characters provided to differentiate these taxa. These subfamily names were also mentioned by Adkison (1990) in his unpublished dissertation. Trilles (1999) placed Cumoechus in Apocumoechinae without comment and, again, provided no characters to differentiate Apocumoechinae from other taxa. Trilles (1999) also mentioned Cumoniscinae but it appears that he considered it to be a synonym of Apocumoechinae. Although Apocumoechinae has never been made available, Cumoniscidae is an available name from Nierstrasz & Brender à Brandis (1923; see Boyko & Boxshall 2018) but the type genus Cumoniscus is a tantulocaridan, not an epicaridean, and Cumoechus does not belong to this family.

It is clear from the characters of the females, cryptoniscus larvae/males, and epicaridium larvae of Cumoechus insignis , that this genus and species does not belong in Cabiropidae (see Boyko 2013). We consider the characters of C. insignis , in particular those of the cryptoniscus larva, to indicate that this genus and species belongs in its own family, Cumoechidae n. fam.

The female of C. insignis is superficially similar to that seen in species of Clypeoniscus Giard & Bonnier, 1895 (Cabiropidae) , particularly in the structure of the appendages: compare Hansen (1916: pl. 16, fig 5b, herein Fig. 4J ) with Giard & Bonnier (1895: pl. 8, fig 22), but there are no lateral lobes in C. insignis ( Hansen 1916: pl. 16, fig 5a). The cryptoniscus larva of C. insignis (slender body, elongate antennule basal segment, antennule peduncular segment 2 with large distal teeth, pereopods 1–3 prehensile, uropodal exopod and endopod slender and elongate; see Hansen 1916: pl. 16, fig 5c, e, f, i) is very different from that seen in species of Clypeoniscus (short, tear-drop shaped body, short antennular basal segment, antennule peduncular segment 2 without large distal teeth, pereopods 1, 2 prehensile, uropodal exopod and endopod stout and short). Likewise, the epicaridium larvae are different, with those of Cumoechus insignis ( Hansen 1916: pl. 16, fig 5k) having the antennules as long as the body and setae on the antennules and uropods that are as long as or longer than the length of the body while the antennules, antennular setae, and uropodal setae of Clypeoniscus species are much shorter than the body.

The unusual epicaridium larva of Cumoechus insignis superficially resembles that of Scalpelloniscus vomicus Hosie, 2008 (Hemioniscidae) as both have antennules, antennular setae and uropodal setae that exceed the length of the body. However, the seta on the distolateral corner of the uropodal sympod is shorter than the exopod in C. insignis and the anal tube is much shorter than the exopod while the epicaridium larva of S. vomicus have setae on the sympod that are more than three times as long as the exopod and the anal tube is as long as the exopod.

The female of Apocumoechus paranebaliae is much less well described than that of C. insignis and no larval stages are known. From the limited data presented by Nierstrasz & Brender à Brandis (1931), it appears that Apocumoechus may be closer to Clypeoniscus than to Cumoechus but new collections and redescription of the type species are needed.

Hansen (1916) figured specimens from three different collections and two different host species. Nielsen & Str̂mberg (1965) indicated the specimens (all syntypes) of Cumoechus insignis from the three different hosts might not “all belong to the same species” but this was speculative as they examined no specimens.

Figures

FIGURE 4. Capitoniscus cumacei Bourdon, 1972.A, cryptoniscus larva, dorsal view. B, antennule. C, pereopod 1. D, pereopod 3. E, pereopod 7. I, female, ventral view. Capitoniscus peruvicus (Menzies & George, 1972) n. comb. F, cryptoniscus larva, dorsal view. Carocryptus laticephalus Schultz, 1977. G, cryptoniscus larva. Capitoniscus australis Bourdon, 1981. H, pleotelson, distal margin, dorsal view. Cumoechus insignis Hansen, 1916. J, female, dorsal view. “Leponiscus pollicipedis” Giard, 1887 (nomen nudum) (= Hemioniscus sp.). K, male, ventral view, in part. Figures not to scale. A–E, I from Bourdon (1972); F from Menzies & George (1972); G from Schultz (1977); H from Bourdon (1981a); J from Hansen (1916); K from Bocquet-Védrine & Bocquet (1972).