Parasphaerasclera, McFadden, Catherine S. & Ofwegen, Leen P. van, 2013

McFadden, Catherine S. & Ofwegen, Leen P. van, 2013, Molecular phylogenetic evidence supports a new family of octocorals and a new genus of Alcyoniidae (Octocorallia, Alcyonacea), ZooKeys 346, pp. 59-83 : 66-68

Parasphaerasclera gen. n. Figs 4-9

Type species.

Alcyonium rotiferum Thomson, 1910, by original designation.

Diagnosis.

As for the family.

Etymology.

From the Greek root para-, meaning beside or alongside of Sphaerasclera gen. n. These two genera share similar sclerite complements and forms, and both were previously considered to belong to Eleutherobia . Gender: fem.

Remarks.

All species of Eleutherobia that have digitiform to digitate or lobate growth forms, lack polyp sclerites, and have radiates or spheroids in the colony surface and interior are hereby reassigned to Parasphaerasclera gen. n. These include Parasphaerasclera albiflora (Utinomi, 1957) comb. n., Parasphaerasclera aurea (Benayahu & Schleyer, 1995) comb. n., Parasphaerasclera grayi (Thomson & Dean, 1931) comb. n., Parasphaerasclera nezdoliyi (Dautova & Savinkin, 2009) comb. n., Parasphaerasclera rotifera (Thomson, 1910) comb. n., and Parasphaerasclera zanahoria (Williams, 2000) comb. n. Although molecular data to support their inclusion in this clade are only available for Parasphaerasclera aurea , Parasphaerasclera aff. grayi and Parasphaerasclera rotifera , the other three species all share the diagnostic morphological characters of the family ( Utinomi 1957, Imahara 1977, Williams 2000b, Dautova and Savinkin 2009). These six species are morphologically distinct from the type species of Eleutherobia , Eleutherobia rigida (= Eleutherobia japonica , Pütter, 1900), which has polyp sclerites arranged as a collaret and points of spindles; radiates, spindles and club-like sclerites in the colony surface; and spindles in the interior coenenchyme ( Verseveldt and Bayer 1988).

We also reassign two species of Alcyonium to Parasphaerasclera gen. n., Parasphaerasclera morifera (Tixier-Durivault, 1954) comb. n. and Parasphaerasclera valdiviae ( Kükenthal, 1906) comb. n. The inclusion of Parasphaerasclera valdiviae comb. n. in Parasphaerasclera gen. n. is supported by both molecular phylogenetic (Fig. 1) and morphological evidence. Parasphaerasclera valdiviae comb. n. lacks polyp sclerites, the sclerites found in the surface of the colony are compact radiates and spheroids (Figs 6-7), and it shares with Parasphaerasclera rotifera comb. n. a growth form in which a conspicuous stalk gives rise to either branched or digitate lobes ( Verseveldt and Williams 1988).

Parasphaerasclera morifera comb. n., another speciesfor which we lack molecular data,shares many morphological characters with other species of Parasphaerasclera gen. n. Verseveldt and Bayer (1988) synonymized Nidalia morifera Tixier-Durivault, 1954 with Eleutherobia rotifera , but Williams (1992) later maintained the distinction between them. He reassigned Nidalia morifera not to Eleutherobia but rather to Alcyonium , based on its lack of permanent calyces. Although Verseveldt and Bayer’s (1988) diagnosis of Eleutherobia stated "Anthocodiae retractile within calyces" (p. 27), Benayahu and Schleyer (1995) noted that some of the species included in the genus lacked permanent calyces. Williams and Little (2001) subsequently emended the diagnosis of Eleutherobia to "calyces absent, although retracted polyps often form low rounded to conspicuous protuberances" (p. 198). Parasphaerasclera morifera comb. n. is strikingly similar to Parasphaerasclera aurea comb. n.; both species have a digitiform to lobular growth form with a short, indistinct stalk, and the sclerites in the colony surface are compact radiates and spheroids (Figs 4A, 5A). The only difference between the two species is the presence of “double-deltoids” in the colony interior of Parasphaerasclera aurea comb. n. (Figs 4B, 5B) ( Benayahu and Schleyer 1995).

It is possible that another South African species of Alcyonium , Alcyonium distinctum Williams, 1988, may also belong to this genus. Like other species of Parasphaerasclera gen. n. it lacks sclerites in the polyps, and the sclerites in the stalk surface are tuberculate spheroids and radiates ( Williams 1988, 1992). The colony growth form is lobate, with lobes arising from a short, thick stalk, somewhat resembling Parasphaerasclera valdiviae comb. n. Unlike other species of Parasphaerasclera gen. n., however, in Alcyonium distinctum the sclerites are restricted to the stalk surface: there are no sclerites in the lobes (polypary) and interior of the colony ( Williams 1988). In addition, the sclerites are not colored, and the bright purple color of living colonies is the result of an alcohol-soluble pigment. Material is not currently available for molecular analysis, so we cannot yet confirm the placement of Alcyonium distinctum in Parasphaerasclera gen. n.

A number of specimens of Parasphaerasclera gen. n. are known that differ somewhat from the descriptions of any of the nominal species listed above, and may represent additional, undescribed species of the genus. For example, there is considerable variation among those specimens of Parasphaerasclera grayi comb. n. that have been described and illustrated in the literature. Thomson and Dean’s original description ( 1931: 37) is rather confusing and sclerites were not depicted. The lectotype of Parasphaerasclera grayi that was designated and described by Verseveldt and Bayer (1988, figs. 24, 25) has sclerites in the colony surface that consist of 8-radiates (0.06-0.08 mm in length), crosses, and rods with tuberculate processes. The sclerites of the colony interior include particularly distinctive rod-like forms with smooth waists and high processes, up to 0.18 mm in length. Williams (2001) subsequently re-described Parasphaerasclera grayi based on specimens from the Solomon Islands. His specimens include 7- and 8-radiates (0.06-0.08 mm long) and crosses similar to those of the lectotype, but the rod-like sclerites in the colony interior are considerably smaller (most 0.07-0.08 mm long) and lack smooth waists ( Williams 2001, figs 5-8). In contrast, specimens of Parasphaerasclera grayi from Vietnam that were later re-described and illustrated by Dautova and Savinkin (2009, figs. 5-7) include "rather smooth" (p. 10) rods that more closely resemble those depicted by Verseveldt and Bayer (1988), but are somewhat smaller, up to 0.14 mm long. The specimens from Palau that we have sequenced and identified here as Parasphaerasclera aff. grayi have tuberculate rods that lack a smooth waist (Figs 8-9), similar to those of Williams’s specimens. In our specimens, however, the rods are considerably larger (to 0.16 mm long). In addition, although the radiates in the colony surface of Parasphaerasclera aff. grayi from Palau are similar in size to those of other Parasphaerasclera grayi specimens, they are more compact and some approach ovals in form (Figs 8A, 9A). This range of variation in sclerite form and size observed among the different specimens attributed to Parasphaerasclera grayi suggests that more than one species may be involved. It remains to be determined if Parasphaerasclera aff. grayi from Palau is the same as Parasphaerasclera grayi sensu Williams (2001) from the Solomons, and if either of these forms is conspecific with Dautova and Savinkin’s (2009) material from Vietnam. The latter most closely matches the Parasphaerasclera grayi lectotype of Verseveldt and Bayer (1988).

Parasphaerasclera gen. n. is most similar morphologically to the alcyoniid genera Paraminabea and Sphaerasclera gen. n. All three genera lack sclerites in the polyps and have spheroids or radiates in the colony surface and interior. The polyps of Paraminabea , however, are dimorphic, while those of Parasphaerasclera gen. n. are monomorphic. The unique capitate growth form of Sphaerasclera gen. n. distinguishes it from all species of Parasphaerasclera gen. n., which are digitiform to digitate or lobate. Parasphaerasclera gen. n. is also easily distinguished from the alcyoniid genera Eleutherobia and Alcyonium sensu stricto, both of which have sclerites arranged to form a collaret and points in the polyps, and spindles or rods in the colony interior.