Sphaeromicolinae, Hart, 1962

Williams, Bronwyn W. & Weaver, Patricia G., 2018, A historical review of the taxonomy and classification of Entocytheridae (Crustacea: Ostracoda: Podocopida), Zootaxa 4448 (1), pp. 1-129 : 16

C. Sphaeromicolinae and the Establishment of Hobbsiella

Hart (1962) established the subfamily Sphaeromicolinae to encompass all seven species in the genus Sphaeromicola recognized at that time, both Old World and New (i.e., S. topsenti , S. stammeri , S. dudichi , S. sphaeromidicola , S. hamigera , S. cebennica , and S. cirolanae ). The diagnosis for Sphaeromicolinae in Hart (1962) included: 1) spatulate-shaped distal podomere of mandibular palp, 2) absence of respiratory plate of the maxilla, 3) masticatory lobes of the maxilla vestigal, i.e., reduced or absent, and 4) a shortened peniferum, typically with a highly convex posterior margin. This diagnosis was repeated in Hart & Hart (1974), and is still valid at the present time.

Danielopol (1977b) proposed two groups within the genus Sphaeromicola , the cirolanae group in North America and the topsenti group in Europe. Distinction between the groups was based on antennal and antennule characters, and number of teeth on the the terminal claws of the thoracic legs. Unaware of the description of S. coahuiltecae in 1973 by Hobbs & Hobbs, Danielopol’s cirolanae group was represented by a single species, S. cirolanae .

Hart (1978) re-evaluated the criteria established by Danielopol (1977b), accounting for all three North American Sphaeromicola ; the description of S. moria occurred in the same paper. Hart confirmed that the antennal and antennule characters proposed by Danielopol to separate the cirolanae and topsenti groups held true, but contested Danielopol’s assessment of the terminal claw teeth. Upon close examination, the North American Sphaeromicola were shown to possess six claw teeth, not four, as suggested by Danielopol (1977b). As the teeth on the terminal claws of the thoracic legs of the European Sphaeromicola species range in number from five to eight, this character could not be used to consistently distinguish between the cirolanae group and topsenti group.

Danielopol & Hart (1985) erected a new genus, Hobbsiella , to encompass the three species in the revised cirolanae group, based on the original antennal and antennule characters identified by Danielopol (1977b). In Hobbsiella segments 4 and 5 of the antennule are fused, with segment 5 bearing five terminal setae, and segments 2 and 3 of antennal endopodite are also fused. In contrast, Sphaeromicola , now restricted to five European species, possesses an antennule of which segments 4 and 5 are not fused, with segment 5 bearing four terminal setae, and segments 2 and 3 of the antennal endopodite are similarly not fused ( Danielopol, 1977b; Hart, 1978; Danielopol & Hart, 1985).

Hart (1978: 730) remarked in a footnote that the strategy used by Danielopol to refer to antennal segments differed from that used by other entocytherid workers. Segments 1, 2 and 3 of the antenna, as reported by Danielopol (1977b) in the description of S. cebennica juberthiei and the designation of the topsenti and cirolanae groups, were equivalent to what were typically considered antennal segments 2, 3, and 4 (e.g., Hart et al. 1967; Rioja 1951). The same numbering scheme was used by Danielopol (1971a) for Hartiella , and Danielopol & Hart (1985) for Hobbsiella . This discrepancy serves as an important cautionary note for comparative work based primarily or entirely from written descriptions, and without a thorough understanding of the morphology of the group, or a homogenized and consistent terminology for all parts of podocopid ostracod limbs (see e.g. Smith & Tsukagoshi 2005 for the antennulae).

Sphaeromicolinae currently includes two genera and eight species, all exclusively associated with cavernicolous isopod hosts. Sphaeromicola is known from hosts in the families Cirolanidae and Sphaeromatidae in subterranean waters of Europe, and Hobbsiella inhabits hosts in the family Cirolanidae in subterranean waters of Central and North America.