Higginsia fragilis Lévi, 1961

Morrow, Christine, Cárdenas, Paco, Boury-Esnault, Nicole, Picton, Bernard, Mccormack, Grace, Soest, Rob Van, Collins, Allen, Redmond, Niamh, Maggs, Christine, Sigwart, Julia & Allcock, Louise A., 2019, Integrating morphological and molecular taxonomy with the revised concept of Stelligeridae (Porifera: Demospongiae), Zoological Journal of the Linnean Society 187, pp. 31-81 : 73-74

Higginsia fragilis Lévi, 1961 (p. 14, fig. 16)

Material examined: Holotype MNHN DCL373 sv 99, Aldabra C. Lévi (microscope slide only).

Description: Choanosomal skeleton: Ascending sinuous columns composed of styles (rhabdostyles) and occasionally tylostyles, with interconnecting spicules ( Fig. 23F). Heads of principal spicules embedded in spongin. Secondary reticulation, with one to three spicules interconnecting.

E c t o s o m a l s k e l e t o n: S u r f a c e l ay e r o f s t r a i g h t acanthoxeas arranged tangentially.

M e g a s c l e r e s: R o b u s t s t y l e s t o t y l o s t y l e s, 3 0 8– 358– 422 (SD = 28) µm × 10–11 µm ( Fig. 23C); thin strongyles (tornotes) with basal ends rounded and slightly dilated, 178– 270– 317 (SD = 38) µm ( Fig. 23D).

Microscleres: Acanthoxeas 91– 102– 110 µm × 1–2 µm ( Fig. 23E).

Remarks: This species appears to be a poecilosclerid, and morphologically it is similar to Spanioplon armaturum ( Fig. 23A, B). Both species share style/tylostyle megascleres and tornotes with basal ends rounded and slightly dilated. The ‘acanthoxeas’ in Higginsia fragilis are also similar to those of Spanioplon armaturum (which vary from acanthoxeas to acanthostyles) and are unlike the acanthoxeas in other Higginsia and Halicnemia species. On the basis of the morphology, we propose the transfer of Higginsia fragilis to Spanioplon ( Hymedesmiidae : Poecilosclerida ).