Calthropella Sollas, 1888

Van Soest, Rob W. M., Beglinger, Elly J. & De Voogd, Nicole J., 2010, Skeletons in confusion: a review of astrophorid sponges with (dicho-) calthrops as structural megascleres (Porifera, Demospongiae, Astrophorida), ZooKeys 68, pp. 1-88 : 43-46

Genus Calthropella Sollas, 1888

Calthropella Sollas 1888: 107.

Pachastrissa Lendenfeld 1903: 80.

Pachataxa de Laubenfels 1936: 179.

Corticellopsis Bergquist 1968: 62.

Emended definition:

Calthropellidae with calthrops or short-shafted triaenes and their dichotriaene modifications as megascleres, supplemented in some species with auxiliary thin oxeas. Microscleres euasters and in some members aster- or rhabd-derived microspined forms.

Type species:

Calthropella simplex Sollas, 1888.

Comments: Calthropella species are diverse in megasclere and microsclere composition reflected in several generic names currently in use or considered synonyms. We propose to reassign Calthropella species as here employed, to three subgenera, including Corticellopsis , formerly a synonym, but now revived to encompass those Calthropella species having only ‘normal’ euasters, Pachataxa , formerly a valid genus, to encompass species with deformed microspined polyangular microscleres ( ‘ataxasters’) along with normal oxyasters, and Calthropella s.s. for species having globular asters with characteristically tuberculated rays next to normal asters. Several new species of all three subgenera have been found in various parts of the world and will be described below.

The genus Pachastrissa is subsumed into the subgenus Calthropella (Calthropella) because the type species, Pachastrella geodioides (cf. below) differs only from the type of Calthropella , Calthropella simplex , in possessing an unstable complement of single oxeas, without structural position in the skeleton, often broken, and occasionally absent. Below, we maintain separate species Calthropella (Calthropella) simplex and Calthropella (Calthropella) geodioides , because we did not examine the type of the former, but Sollas’ description of it makes it clear that it differs from Calthropella (Calthropella) geodioides in two doubtful features, lack of dichocalthrops (rarely present in Calthropella (Calthropella) geodioides ) and oxeas (unstable presence in Calthropella (Calthropella) geodioides , see below). Especially the shape of the globular asters in both is so similar that conspecificity is likely. Likewise Pachastrissa pathologica (Schmidt, 1868), and Pachastrissa inopinata (Pulitzer-Finali, 1983) are returned to Calthropella (Calthropella) , close to Calthropella (Calthropella) geodioides .

The junior synonymy proposed for Pachastrissa as Calthropella does not extend to Pachastrissa hartmeyeri Uliczka (1929) and Pachastrissa nux (de Laubenfels, 1954) as Jasplakina , both of which fit better in the ancorinid genus Penares on account of the structural oxeas and the presence of ectosmal microxeas in these species.

The newly defined genus Calthropella is distinct from Dercitus s.l. in the possession of true euasters, the lack of sanidasters, the lack of large darkly pigmented cells with inclusions, and in the harder less organic texture of most species (except subgenus Corticellopsis ). Calthrops are the dominant megasclere type, varying widely in size and shape (cladi 40-800 µm), with dichocalthrops so far known only from Calthropella (Calthropella) geodioides and its Indonesian ‘variety’. Asters are basically oxyasters, but they are often variable in shape with a strikingly high frequency of spheroxyasters with irregular shapes culminating in peculiar globular silica balls ornamented with tuberculated protrusions in some species. The subgenus Pachataxa has asymmetrical, deformed microspined siliceous microscleres which are derivatives of asters or microrhabds (which of these is unclear, so far). Differentiation in two aster types is usual. Like with several Dercitus species, oxea megascleres are reported in several descriptions, with widely different sizes and usually in broken condition. The oxeas may be foreign, but the persistent reports of their presence in some species indicate otherwise. In any case they do not have a structural position in the skeleton and are here considered ‘auxiliary’.

Key to the subgenera of Calthropella (see Fig. 23)

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