Hamacantha (Vomerula) umisachii, Ise & Woo & Tan & Fujita, 2019

Ise, Yuji, Woo, Sau Pinn, Tan, Shau Hwai & Fujita, Toshihiko, 2019, First record of Hamacantha (Porifera, Demospongiae, Merliida, Hamacanthidae) from Japan, with description of two new species, Zootaxa 4657 (3), pp. 474-482 : 478-481

Hamacantha (Vomerula) umisachii sp. nov.

Figs. 4–5

Materials examined. Holotype NSMT–Po–2488. Off Hachijo-jima , Tokyo, Japan, 33º11.387′N – 139º38.623′E to 33º10.921′N – 139º39.114′E ( Fig. 1 ), 778– 682 m depth, collected by R / V ‘Tansei-maru’, chain bag dredge, 26 November 2007, in ethanol.

Description of holotype. External morphology. Very thinly encrusting sponge, about 8 x 4 mm and less than 1 mm thick, attached on volcanic rock, consisting of easily detachable dermal membrane. ( Fig. 4A ). Color in life not recorded, white in ethanol. The specimen was carefully detached from the substrate, and preserved in ethanol.

Skeleton. Ectosomal skeleton consists of a loose tangential reticulation of styles ( Figs. 4B, C ). Styles also make bouquets with points outward in the ectosome ( Figs. 4B, C ). Microscleres sparsely distributed in between spicule tracts in ectosome. Choanosomal skeleton couldn’t be precisely observed because the sponge was very thin and fragile, but consists of all spicule types. Of these, diancistras mostly attach on style bundles ( Fig. 4D ).

Spicules. Skeleton consists of stylote megascleres, and two types of diancistras, and one type of sigmas as microscleres ( Fig. 5 ).

Styles ( Figs. 5A, B ), smooth, straight or slightly curved, subtly fusiform, sharply pointed at one extremity, 248.8–357.3 (310.8) x 7.5–11.5 (9.5) µm.

Diancistras I ( Fig. 5C ), smooth, contorted with the other apex in a perpendicular plane, having thin fimbriae bearing only at the bended inner part of apices and in between the notches except middle part of the shaft where it is rounded due to absence of fimbriae, notch relatively large. Dimensions, 157.7–206.8 (177.1) x 10.5–16.0 (12.5) µm in shaft width.

Diancistras II ( Figs. 5D, E ), with cyrtancistra-like shape, smooth, fimbriae bearing only at the bended inner part of apices ( Fig. 5E ), rest of the shaft rounded, 48.0–75.1 (58.5) x 4.4–8.6 (6.1) µm in shaft width.

Sigmas ( Fig. 5F ), smooth, elongated, 29.4–36.0 (32.3) x 1.5–1.8 (1.6) µm in shaft width.

Etymology. The specific epithet ( umisachii ) is derived from “Umisachi-hiko”, a god of the sea and fisherman in Japanese mythology. “Umisachi-hiko” was bequeathed a magic hook from his father but one day his younger brother lost it in the ocean. A magic hook of “Umisachi-hiko” is here associated to diancistra, characteristic hooklike microscleres of Hamacantha species because it contains the meaning of hook (Greek: ancistra).

Origin of Japanese name. New Japanese vernacular name: Umisachi-kaimen is proposed herein. Etymology of “Umisachi” is explained above, and “kaimen” is sponge in Japanese. The Japanese names “Umisachi-kaimenzoku” is proposed for the genus Hamacantha (“zoku” is genus in Japanese) and “Umisachi-kaimen-ka” for the family Hamacanthidae (“ka” is family in Japanese).

Remarks. Some spicules of Hamacantha (Vomerula) species might be regarded as diancistras with cyrtancistra-like shape, as observed in H. (V.) umisachii sp. nov. Additional species bearing such spicules are compared to the new species below.

The smaller “diancistras” of the two types of diancistras in H. (V.) carteri lack fimbriae on the bended inner side ( Hajdu, 1994), and seems like cyrtancistra shape. However H. (V.) carteri has much larger styles (700–800 µm vs 248.8–357.3 µm), smaller diancistras (110–150 vs 157.7–206.8 µm), smaller cyrtancistra-like diancistras (27 µm vs 48.0– 75.1 µm), and smaller sigmas (20 µm vs 32.3–36.0 µm).

The “strongly curved sigmancistras” of H. (V.) forcipulata Lévi, 1993 might be regarded as cyrtancistra-like diancistras. Spicules of H. (V.) forcipulata are styles, diancistras, “strongly curved sigmancistras”, and slender sigmas, according to its original description ( Lévi, 1993: Fig.13C). However, Lévi (1993) might have erroneously mentioned diancistras in etymology and remarks part. He explained etymology of this species as “Latin forceps, forceps. This is connected with the form of the diancistras” and remarks as “This sponge has distinctive sigmoid diancistras, unknown to the other Hamacantha ”. However, the description about diancistra is simple as “Diancistras: 120–170 µm / 35 µm: both ends are in different planes”, and thus doesn’t match the shape of forceps. We inferred that Lévi’s mention about diancistra in etymology and remarks is not about the diancistras, but clearly about the “strongly curved sigmancistra”. Lévi (1993) himself possibly had the impression that “strongly curved sigmancistra” is a kind of special diancistra. H. (V.) umisachii sp. nov. and H. (V.) forcipulata can be differentiated by the shape of their cyrtancistra-like diancistras, the dimensions of the styles (248.8–357.3 vs 370–460 µm), and of the sigmas (29.4–36.0 vs 25 µm).

The other cases of possession of cyrtancistra-like diancistra in Hamacantha have recently been reported from H. (V.) jeanvaceleti Castello-Branco & Hajdu, 2018 , H. (V.) klausruetzleri Castello-Branco & Hajdu, 2018 , and H. (Zygherpe) desmacelloides Hajdu, Hooker and Willenz, 2015 . Hamacantha (V.) jeanvaceleti totally differs from H. (V.) umisachii sp. nov. by having two types of cyrtancistra-like diancistras. H. (V.) klausruetzleri also totally differs from H. (V.) umisachii sp. nov. by having strongyles, two types of cyrtancistra-like diancistras, and two types of sigmas. Both species totally lack authentic diancistras, which are present in H. (V.) umisachii sp. nov. ( Fig. 5C ). Hamacantha (Z.) desmacelloides and H. (V.) umisachii sp. nov. are primarily separated by the shape of their megascleres, the diagnostic character of subgenera of Hamacantha : style for subgenus Vomerula , and tylostyle for sub- genus Zygherpe ( Hajdu et al., 2015) . Furthermore H. (Z.) desmacelloides can be separated from H. (V.) umisachii sp. nov. by having two types of sigmas with microspined apices, and for lacking authentic diancistras.

Lastly, H. (V.) mamoi sp. nov., described above, lacks cyrtancistra-like diancistras ( Fig. 5D ), and has larger styles (347.5–431.0 µm vs 248.8–357.3 µm) and larger sigmas (51.4–63.7 µm vs 29.4–36.0 µm) when contrasted to H. (V.) umisachii sp. nov.

Figures

FIGURE 1. Location of sampling sites. Open star indicates sampling site of Hamacantha (Vomerula) mamoi sp. nov., and solid star indicates that of Hamacantha (Vomerula) umisashii sp. nov..

FIGURE 4. Hamacantha (Vomerula) umisachii sp. nov., holotype (NSMT-Po-2488). A, external morphology. B, skeletal arrangement of surface of ectosome. Note darker parts are bouquets of upward styles (b). C, other magnified view of surface of ectosome. Sheet of styles gather to bouquets (b). D, diancistras attach on bundle of styles. Scale bars: A, 2 mm; B, C, 100 µm; D, 50 µm.

FIGURE 5. Spicules of Hamacantha (Vomerula) umisachii sp. nov., holotype (NSMT-Po-2488). A, styles. B, magnified view of both extremities of mycalosyle, left: blunt end or base, right: sharply pointed end or apex. C, diancistras I. D, diancistras II (cyrtancistra-like diancistras). E, magnified view of tip of diancistra II, note the hook-like structure. F, sigmas. Scale bars: A, 100 µm; B, F, 10 µm; C, 50 µm; D, 20 µm; E, 3 µm.