Chaunoplectella megapora, Wang & Zhang & Lu & Wang, 2018

Wang, Chunsheng, Zhang, Yuan, Lu, Bo & Wang, Dexiang, 2018, New Hexactinellid Sponge Chaunoplectella megapora sp. nov. (Lyssacinosida: Leucopsacidae) from Clarion-Clipperton Fracture Zone, Eastern Pacific Ocean, Zootaxa 4375 (1), pp. 136-142 : 137-140

Chaunoplectella megapora sp. nov.

( Figs. 1A–S , Table 1)

Material examined. Holotype: DY31-II-JL-Dive 64 sponge 0 1, SRSIO. (9°59.825'N; 154°17.803'W), depth 5258 m, 9th August, 2013. Collected by Chunsheng Wang using Jiaolong submersible mechanic arm. Fragments of tissues were studied in Xiamen University with a voucher number of XMU02000701. Spicules and fragments were deposited in XMU.

Description. Ovoid body shape, basiphytose, with a clear stalk-like base. The holotype is a 3/4 remnant of the original in situ sample, which appears to be 37 mm long with a tuft of 13 mm long basalia. The specimen was all white when observed in situ ( Fig. 1A ). The brick red color of the collected specimen was from deposits of the adjacent substrate when collected ( Fig. 1B ). A large opening on the top with a diameter approximately 18 mm was apparent from the in situ images, but the upper portion of the sample was lost during collection due to the fragility of the specimen. Approximately 15 prominent and thick-walled lateral oscula were observed on the surface. The oscula varied from 6.5 to 8.0 mm in diameter with a thickness of 1.5 to 2.0 mm. The surface of the body consists of loose tissues. The specimen’s root tuft was firmly embedded into a manganese nodule.

Spicules. Skeleton of oscula parts includes megascleres such as diactins, large hexactins, pentactins and a few stauractins ( Fig. 1C –H’). Basalia skeletons are typical lyssacine type. Basalia are mostly diactins of the same type as those observed in the choanosome. Some pentactins and few hexactins may be the supporting spicules connecting the body and basal part. Dermalia are pentactins.

Megascleres. Choanosomal skeleton mainly consists of hexactins ( Fig. 1C and C’) with asymmetrical rays. The shortest ray always ends in a swollen pointed tip, and short, dense spines are concentrated near the tip ( Fig. 1 C’). The longest ray is 231.56–607.34 µm, while the shortest ray is 60.52–380.08 µm with a diameter of 9.08 to 14.64 µm. Diactins ( Fig. 1D, E ) are common in sustaining the body by supplementing hexactins and pentactins. Diactins are 996.28–3508.58 µm long and 7.49–24.25 µm wide with an expansion in the middle. The diactin tip ( Fig. 1D ) is slightly inflated and covered with numerous short spines that are considerably denser near the tip. The rays of dermal pentactins ( Fig. 1F ) are all conical pointed tips with slight spines. The tangential rays are 258.35– 643.20 µm long, 10.91–14.45 µm wide, and the vertical ray is 319.14–518.28 µm long and 15.81–17.25 µm wide. Stauractins ( Fig. 1G ) are sometimes symmetrical with four equal length rays, but occasionally, the rays are not exactly the same length. We counted the symmetrical stauractins with equal length rays, the length is 260.00– 424.17 µm, and the ray width is 7.18–13.11 µm. Hexactins ( Fig. 1H ) are smaller than choanosomal hexactins but decrease in length and width ranges of the latter category. The length of each ray is 271.31–314.74 µm, and the width is 7.81–11.63 µm.

Microscleres. Toothed discohexasters ( Fig. 1I, J ) are the largest microscleres in the specimen. These microscleres have extremely short primary rays, each of which carries 5–7 secondary rays with discoidal ends. The secondary rays ( Fig. 1J ) are elongate and uniform along the rays. Edges of each disc contain 12 teeth. The diameter of whole discohexasters fall in the range of 272.19–280.31 µm, the primary rays are 11.64–28.37 µm, whereas secondary rays are much longer, with lengths ranging from 107.94 to 130.07 µm. The umbels are 24.40–29.68 µm wide. Toothed hemidiscohexasters ( Fig. 1K, L ) are only half the size of discohexasters even though they appeared to be very similar. Hemidiscohexasters usually bear four rays on a single short primary ray, and secondary rays are much shorter and more slender, thereby making the broken secondary rays seem sharper ( Fig. 1L ). There are 14 teeth on the discoidal ends, rather than 12. Dimensions of toothed hemidiscohexasters are 126.76–147.89 µm in diameter with short primary rays that are 4.61–14.89 µm long and secondary rays that are 43.15–65.88 µm long. The umbels are 18.18–25.42 µm in width. Sigmatocome ( Fig. 1M, N and O ) looks nearly the same as the one possessed in Amphidiscella lecus Reiswig, 2014 . Their curved secondary rays are extremely delicate and could easily be broken from centra when dissociated. The primary ray ( Fig. 1N ) length is 9.91–13.95 µm. The secondary rays ( Fig. 1O ) are sharply pointed and completely covered with reclined thrones with a curve length of 229.83 to 305.35 µm. There are comparatively fewer anchorate discohexasters ( Fig. 1P ) in the whole holotype. The umbels of them resemble small bells with obvious teeth, similar to the umbels of amphidiscs. The diameters are 92.71– 104.52 µm with primary rays and secondary rays with lengths of 5.49 to 6.06 µm and 33.71 to 44.49 µm, respectively. The umbels are 10.37–11.84 µm in diameter. Codonhexasters ( Fig. 1Q ) are the smallest microsclere with a diameter of only 66.36 to 81.02 µm. They look quite spherical under a light microscope, and are similar to those found in A. lecus . Each straight primary ray carries five secondary rays bending towards center and terminated by thimblate umbels. The primary ray lengths of condonhexaster are in the range of 8.22 to 14.14 µm, and the secondary ray lengths are 21.73–27.18 µm. The thimblate umbels are 10.92–18.08 µm in diameter. Stellate discohexasters ( Fig. 1R ) are rare in the holotype. We could only find one comparatively complete spicule across all slides. This type of discohexaster ended with very slender discoidal terminals, which could be a slightly dispersed at the end of secondary rays but always fell off easily. According to the sole stellate discohexaster that we measured, its primary ray is only 8.62 µm long, and the secondary ray is 41.31 µm and tipped with 6.43 µm wide umbel. Finally, we came across a unique sigmatocome ( Fig. 1S ) with much shorter curved secondary rays. The primary ray is 9.23 µm long, and the secondary ray is 102.18 µm long.

Etymology. The species name megapora refers to the distinct oscula presented by the new species.

Remarks. Possession of a lyssacine ( Leys et al. 2007) type of skeleton, ovoid-shaped body, basiphytose, choanosomal megascleres that are mainly hexactins, and various microscleres devoid of discohexactins places the holotype into the monotypic genus Chaunoplectella . Compared to Chaunoplectella cavernosa Ijima, 1896 , the only other species in genus Chaunoplectella , the combined features of the new specimen are distinguished in the following ways: (a) there are 15 large, enlarged and thick-walled parietal oscula scattered on the lateral surface of body. No tissue could be observed packaging the basal part, except a tuft of spicules protruding into a manganese nodule. (b) Sigmatocome resembles that possessed by Amphidiscella lecus . Generally, the sigmatocome resembles that in A. lecus both in shape and size. However, there are 9 short bases on primary rays in C. megapora sp.nov. instead of 5 to 7 in A. lecus . Moreover, in the right middle of these 9 short bases, there appears to be a swollen center bulging outward in C. megapora sp. nov., whereas no such expansion is observed in A. lecus . (c) The size of anchorate discohexasters fall in the range of “small discohexasters” according to the measurements referred to in the genus Chaunoplectella ( Tabachnick 2002) . However, these discohexasters differ from C. cavernosa in two ways. Firstly, the teeth of umbels in C. megapora sp. nov. are not that sharp, nor are they outward radiated ( Burton 1928; Ijima 1903; Tabachnick 2002; Tabachnick & Levi 2004; Topsent et al. 1928). Secondly, the primary rays of the discohexasters in C. megapora sp. nov. are much shorter than that in C. cavernosa . (d) The form of stellate discohexaster resembles that described in Oopsacas spinera Ijima, 1903 . (e) The unique holotype was found in the eastern Pacific Ocean; no other species in this family have been discovered in this area.

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Figures

FIGURE 1. Chaunoplectella megapora sp. nov. A, holotype in situ. B, preserved holotype. C and C’, choanosomal hexactin and itsend. D, ray end of diactin.E, diactin.F,pentactin.G,stauractin.H and H’,hexactin and its end.I, toothed discohexaster. J, secondary ray of toothed discohexaster. K, toothed hemidiscohexaster. L, secondary ray of toothed hemidiscohexaster. M, sigmatocome with hemidiscohexaster. N, primary rosette of sigmatocome. O, broken secondary ray of sigmatocome. P, anchoratediscohexaster.Q, codonhexaster.R, stellate discohexaster (arrow). S,unique sigmatocome.