Capitoniscidae, 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

Family Capitoniscidae n. fam.

( Fig 4A–D, I )

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Diagnosis: Cryptoniscus larva /male body elongate. Head wider than long, anteroposteriorly inflated, posterior margin wider than pereomere 1; eyes absent. Antennule article 1 short, rounded, without marginal teeth; dense setal brush present. Coxal plates with weak marginal crenulations but without teeth. Pereopods 1–3 gnathopodal, 1 and 2 with globular propodi and thick dactyli extending to distal margin of merus, pereopod 3 with ovate propodus and slender dactylus extending to distal margin of carpus; pereopods 4–7 ambulatory with propodi tapering distally; all pereopodal dactyli bearing a distal tooth. Pleotelson triangular, with or without distal row of few stout teeth. Mature female spheroid in dorsal view, unsegmented, possibly with two pairs of pereopods and two pairs of posterior tubercles. Parasitizing cumaceans.

Included genera and species: Capitoniscus Bourdon, 1972 , type genus (type species = Capitoniscus cumacei Bourdon, 1972 by monotypy); Capitoniscus australis Bourdon, 1981 ; Capitoniscus peruvicus ( Menzies & George, 1972) n. comb.; Carocryptus Schultz, 1977 (type species = Carocryptus laticephalus Schultz, 1977 by original designation).

Distribution: Off coast of South Africa (35°44’S, 34°16’E), 3800 m ( C. cumacei ) ( Bourdon 1972); South Pacific Ocean (50°06’S, 127°31’W – 50°12’S, 127°30’W), 3914 m ( C. australis ) ( Bourdon 1981a); off coast of Peru (09°05’S, 80°43’W), 5586–5648 m ( C. peruvicus n. comb.) ( Menzies and George 1972); Southern Ocean (64°58’S, 114°13’W – 65°19’S, 114°06’W), 3312 m ( C. laticephalus ) ( Schultz 1977).

Host: Cumacea : Bathylamprops natalensis Jones, 1969 ( Bourdon, 1972) for C. cumacei ; hosts of other species not known.

Remarks: The three species of Capitoniscus and one of Carocryptus are very similar in all known characters. Of these species, only C. cumacei was described based on a male associated with a female; all others are known only from the cryptoniscus larval stage collected in plankton samples. Cryptoniscus larvae/males of these species are characterized by their inflated heads ( Fig. 4A ), antennules ( Fig. 4B ), and pereopod morphologies ( Fig. 4C–E ), a unique combination of characters within Cryptoniscoidea ; thus, the new family Capitoniscidae is herein erected for these two genera that were previously placed as Cryptoniscoidea incertae sedis. Capitoniscus peruvicus n. comb. was very incompletely described and figured but is clearly congeneric with C. cumacei and C. australis , albeit that C. peruvicus n. comb. has the most inflated head of all these species ( Fig. 4F ).

The species of Capitoniscus and Carocryptus can be distinguished by the following characters of the cryptoniscus larvae: coxal plates not visible in dorsal view ( Capitoniscus ; Fig. 4A ) vs. visible in dorsal view ( Carocryptus ; Fig. 4G ) and pleotelson distal margin with few blunt teeth ( Capitoniscus ; Fig. 4H ) vs. smooth ( Carocryptus ; Fig. 4G ). The female of C. cumacei ( Fig. 4I ) was incompletely described and figured due to the specimen being lost after a preliminary sketch was made ( Bourdon 1972).

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).