Cancricepon Giard & Bonnier, 1887

An, Jianmei, Wang, Mingxiao, Boyko, Christopher B. & Williams, Jason D., 2019, New hosts and localities for species of Cancricepon Giard & Bonnier, 1887 (Isopoda: Epicaridea: Bopyridae) with description of two new species and comments on the relationship between Cancricepon and Trapezicepon Bonnier, 1900, Zootaxa 4559 (1), pp. 136-150 : 137-138

Genus Cancricepon Giard & Bonnier, 1887

Type species: Cepon elegans Giard & Bonnier, 1887 , by subsequent designation of Markham, 1975.

Synonym: Merocepon Richardson, 1910

Type species: Merocepon xanthi Richardson, 1910 , by original designation.

Remarks. The type species of Trapezicepon Bonnier, 1900 , T. amicorum ( Giard & Bonnier, 1888) , is quite similar in many characters to species of Cancricepon , especially to C. castroi n. sp. The most obvious difference is that T. amicorum , which has been reported infesting Trapezia cymodoce (Herbst, 1801) (Trapeziidae) ( Bonnier, 1900) and Actumnus tomentosus Dana, 1852 [= A. setifer (De Haan, 1835) ] ( Pilumnidae ) ( Stebbing, 1910), lacks middorsal projections on any pereomeres of the female. The barbula is similar in both species in that there are two falcate lateral projections on each side but differs in that T. amicorum has a broad, flat median region, whereas members of the genus Cancricepon have a median region with a pair of blunt triangular projections. The males of T. amicorum and Cancricepon spp. are nearly indistinguishable. It appears that these two genera are closely related and molecular data would be helpful in determining if their status as separate genera is warranted.

A second species of Trapezicepon , T. domeciae Danforth, 1972 , was incompletely described and figured but appears to be congeneric with T. amicorum and therefore also closely related to Cancricepon spp. However, the third described species in Trapezicepon , T. thalamitae Markham, 1985 , is clearly not congeneric with T. amicorum nor closely related to any species of Trapezicepon or Cancricepon . This conclusion is based on numerous characters of the female and male of T. thalamitae including: female with large middorsal projections on pereomeres 6 and 7 in T. thalamitae vs. none in T. amicorum , male with head much narrower than first pereomere in T. thalamitae vs. subequal in width in T. amicorum , and male with medial dorsal fusion of pleomeres in T. thalamitae vs. pleomeres completely separated in T. amicorum . In fact, these three characters show that T. thalamitae belongs to Scyracepon Tattersall, 1905 , a genus in which females of all species have large middorsal projections on at least pereomeres 6 and 7, males have a head much narrower than the first pereomere, and males have medial dorsal fusion of all pleomeres. We therefore formally transfer T. thalamitae to Scyracepon , as S. thalamitae ( Markham, 1985) n. comb.

An additional juvenile female found parasitizing an unidentified species of Lambrus Leach 1815 (= Parthenope Weber, 1795) was identified as Trapezicepon sp. by Nierstrasz & Brender à Brandis (1931). However, due to the specimen’s immaturity, its generic placement is unclear and it could belong to any one of a number of keponine genera, including Apocepon Nierstrasz & Brender à Brandis, 1931, whose type species, A. sibogae Nierstrasz & Brender à Brandis, 1931, contains the only other bopyrid specimen (also a female) known to parasitize a host in Parthenopidae .