Sciurella dolichotheca ( Allman, 1883 ) Galea & Maggioni & Di Camillo, 2021

Galea, Horia R., Maggioni, Davide & Di Camillo, Cristina G., 2021, Towards a better understanding of the genus Sciurella Allman, 1883 (Cnidaria: Hydrozoa: Plumulariidae): evidence from an integrative study, Zootaxa 5040 (1), pp. 1-32 : 24-26

publication ID	https://doi.org/ 10.11646/zootaxa.5040.1.1
publication LSID	lsid:zoobank.org:pub:519AA954-9B8F-4903-8379-E30704ABC375
persistent identifier	https://treatment.plazi.org/id/0393994D-FFCF-0D1A-7A90-05C1FAA4FD22
treatment provided by	Plazi
scientific name	Sciurella dolichotheca ( Allman, 1883 )
status	comb. nov.

Treatment

Sciurella dolichotheca ( Allman, 1883) View in CoL , comb. nov.

Figs 17–19 View FIGURE 17 View FIGURE 18 View FIGURE 19 ; Table 2

Plumularia dolichotheca Allman, 1883: 20 View in CoL , pl. 1 figs 7–8.— Allman, 1888: lxvi, lxix.— Billard, 1908: 760.— Billard, 1910: 38, fig. 17.— Bedot, 1916: 181.— Van Praët, 1979: 922, fig. 93.

Nemertesia cylindrica View in CoL — Nutting, 1927: 227 (non Antennularia cylindrica Bale, 1884 ).

Material examined. MNHN H.L. 1233, Philippines, Mindanao , off Zamboanga, 6.900000°, 122.300000°, 18 m, 30 Jan. 1875: three unstained cladia, as part of the holotype, mounted by Billard on a slide labeled in his handwriting: « Plumularia dolichotheca Allman type / 8.X.1908 / Provenance Coll. du British Mus » .

Diagnosis. Colony 7.6 cm high arising from a profuse mass of tangled stolonal fibers; stems likely simple ( Allman 1883: pl. 1 fig. 7), monosiphonic, though adjacent for a varied length above origin from hydrorhiza ( Allman 1883: 20, «stem irregularly branched»); cladia unbranched, alternate along the stem, about 1 cm long, divided into irregular internodes carrying 1–3 hydrothecae; the latter deep, thimble-shaped, fully adnate to the corresponding internode, always bearing a pair of lateral nematothecae, while a mesial nematotheca is to be found only below the proximal most hydrotheca of an internode. Gonotheca unknown.

Description. Since there are no matching records of P. dolichotheca in the zoological specimens database of the Natural History Museum, London, UK, only the material mounted by Billard on slide MNHN H.L. 1233 ( Van Praët 1979: 922), containing three (fragments of) cladia removed from the type of P. dolichotheca , is described herein, while the diagnosis given above is taken from the original account by Allman (1883).

Two cladia in the preparation bear remains of their corresponding stem apophyses. One apophysis displays one of its lateral sides: a conical mamelon can be seen, as well as the insertion sites for two nematothecae, the latter having been lost ( Fig. 17B View FIGURE 17 ); the cladium itself begins with three internodes, each bearing two hydrothecae ( Fig. 18C, D View FIGURE 18 ), while the fourth and last internode was broken off after its first hydrotheca; only the proximal most hydrotheca of the first internode bears a mesial nematotheca ( Fig. 18C View FIGURE 18 ), while the subsequent ones do not show any apparent sign proving that nematothecae were originally present and subsequently lost. The second apophysis displays, conversely, its adaxial side: the mamelon is seen from above and, on each side, the insertion site of a nematotheca could be noted, the apophysis having been detached from the stem shortly after ( Fig. 17A View FIGURE 17 ); the cladium proper starts with an internode bearing but a single hydrotheca with its full complement of three nematothecae ( Fig. 18A View FIGURE 18 ); the subsequent four internodes bear two hydrothecae each ( Fig. 18B View FIGURE 18 ), none being provided with mesial nematothecae. The third cladium was detached after its corresponding stem apophysis, and is composed of a sequence of four internodes, each bearing two hydrothecae ( Figs 17C View FIGURE 17 ; 18E View FIGURE 18 ), while a fifth and last internode bears three hydrothecae ( Fig. 18F View FIGURE 18 ); no mesial nematothecae are present on these internodes.

Hydrothecae relatively long, tubular, thick-walled, imperceptibly flaring at rim; the latter even, sloping behind. Nematothecae bithalamic, rim of upper chamber distinctly scooped adaxially; mesial nematotheca comparatively longer than its lateral counterparts, and borne on a conspicuous, adaxial, rounded projection of the internode.

Remarks. The thick, cord-like, monosiphonic, unbranched, proximally adjacent stems arising from a large mass of stolonal fibers ( Allman 1883: pl. 1 fig. 7), recall, by far, hydroids of the genus Nemertesia , rather than of Plumularia . Although there are no statements as to the division of the stem into internodes, it seems that two cladia per side are delimited by two successive, transverse nodes ( Allman 1883: pl. 1 fig. 8), an argument that further points towards a hydroid not belonging to the genus Plumularia . The division of cladia into internodes is very distinct in the material examined herein, and each internode bears generally two hydrothecae ( Fig. 18B–E View FIGURE 18 ), although one ( Fig. 18A View FIGURE 18 ) or three ( Fig. 18F View FIGURE 18 ) occasionally occur. Unlike Allman’s statements (1883: 20), the presence of a mesial nematotheca could be confirmed only in the proximal most hydrotheca of the cladia ( Fig. 18A, C View FIGURE 18 ). The second and, when present, third hydrotheca do not possess the basal bulge on which the mesial nematotheca is normally seated upon ( Figs 17C View FIGURE 17 ; 18B, D–F View FIGURE 18 ). The mesial ( Fig. 17F View FIGURE 17 ) and lateral nematothecae ( Fig. 17D, E View FIGURE 17 ) are very similar to those of both S. indivisa and S. cylindrica ; the hydrothecae, however, appear comparatively shorter, and the cladial internodes distinctly thicker.

As noted in the introduction, uncertainties exist as to the taxonomic position of this hydroid. Allman himself bring it closer to P. cylindrica Kirchenpauer , 187622 than to his own S. indivisa . Billard (1908, 1910) was of the 22 “Under the name of Plumularia cylindrica, Kirchenpauer described a species –also from Zamboanga – which in the form of the hydrothecae and in the general habit of the colony closely approaches Plumularia dolichotheca . It differs from it,

however, in every internode of the hydrothecal pinnae carrying only one hydrotheca, and in the opposite instead of alternate disposition of the pinnae” ( Allman 1883: 20–21).

opinion that it could represent a mere variety of S. indivisa (see footnotes 3–4 herein), but we have shown above that he followed the erroneous opinion expressed earlier by Kirkpatrick (1890) and, consequently, his observation appears convergent to that of Allman. However, the peculiar division of cladia into internodes bearing up to three hydrothecae, the shorter hydrotheca and the absence of a regular mesial nematotheca suggest that both species are distinct. The pinnate arrangement of the cladia, also noted in some stems of S. cylindrica from Bali examined here, does not exclude, in our view, this species from belonging to the genus Sciurella , to which it is provisionally assigned here, pending the discovery of additional, ideally fertile, specimens suitable for both morphological and molecular studies.

The material assigned by Nutting (1927) to Bale’s (1884) species displays the same feature as that noted by the authors in specimen MNHN H.L. 1233, i.e. «the mesial nematophores are absent except those immediately below each proximal hydrotheca on the hydrocladium». In being sympatric with the type material of P. dolichotheca , their conspecificity is further supported.

Distribution. Zamboanga, Mindanao, Philippines [ Allman (1883), as Plumularia dolichotheca ; Nutting (1927), as Nemertesia cylindrica ( Bale, 1884) ] ( Fig. 19 View FIGURE 19 ). Depth range: 16–18 m [ Allman (1883); Nutting (1927)].