Hymedesmia (Hymedesmia) spinata, Calcinai, Barbara, Bavestrello, Giorgio, Bertolino, Marco, Pica, Daniela, Wagner, Daniel & Cerrano, Carlo, 2013

Calcinai, Barbara, Bavestrello, Giorgio, Bertolino, Marco, Pica, Daniela, Wagner, Daniel & Cerrano, Carlo, 2013, Sponges associated with octocorals in the Indo-Pacific, with the description of four new species, Zootaxa 3617 (1), pp. 1-61 : 21-25

Hymedesmia (Hymedesmia) spinata n. sp.

( Figs. 12 A–J; 13) ( Tabs. 5 ; 6)

Holotype material. MSNG 56262: sample Bugor 513: Indonesia, North Sulawesi, Siladen Island, Siladen Barat, 23 m, 11 September 2007.

Paratype material. MSNG 56263: sample Bugor 311: Indonesia, North Sulawesi, Siladen Island, Siladen Barat, 25 m, 18 January 2007.

Other examined material: sample Bugor 309: Indonesia, North Sulawesi, Siladen Island, Siladen Barat, depth not stated, 18 January 2007; sample Indo 23: Indonesia, North Sulawesi, Siladen Island, Siladen Barat, depth not stated, 8 October 2008; sample Bugor 410 (bis2): Indonesia, North Sulawesi, Siladen Island, 26 m, September 2007.

Comparative material ( Fig. 14 A –I): Hymedesmia (Hymedesmia) prostrata Thiele, 1903 holotype material ZMB Por 3160 (only two spicule slides available); Hymedesmia (Hymedesmia) dichela ( Hentschel, 1911) syntype material ZMB Por 4438.

Diagnosis. Hymedesmia (H.) spinata n. sp. is characterised by two types of chelae and acanthostyles in a single category, widely variable in length and in the density of spination; smaller chelae have a characteristic apical spine on each ala.

Description. Epibiotic on Carijoa riisei ( Fig. 12 A–C), which is completely encrusted by the sponge (1–2 mm thick), leaving only the polyp openings free ( Fig. 12 C). Elevated, scattered oscules are evident. The holotype consists of several ramified fragments of C. riisei up to 8 cm long ( Fig. 12 B); the paratype covers some branches of C. riisei , up to 10 cm long. Consistency is soft and the surface smooth; brown in situ ( Fig. 12 A), whitish or orange when preserved in ethanol ( Fig. 12 B, C).

Skeleton. Ectosomal skeleton as a thin dermal membrane with scattered tornotes and chelae tangentially disposed ( Fig. 12 D). Choanosomal skeleton hymedesmoid; acanthostyles erect with heads on the substrate; scattered isotornotes and chelae in between. Tracts of tornotes run towards the surface connecting to ectosome ( Fig. 12 E).

Spicules. Isotornotes straight with acerate extremities ( Fig. 12 F), 177.5 – 245 x 2 – 5 μm. Acanthostyles in a single category, very variable in size and in the distribution of spines, 52.5 – 237.5 x 2.5 – 10 μm. Smaller acanthostyles strongly spined and with the tips ending in verticils of small spines ( Fig. 12 G) are more frequent ( Fig. 13 ); larger acanthostyles with no evident head, few spines and smooth tip ( Fig. 12 H) are uncommon ( Fig. 13 ); numerous intermediate forms with spined and smooth tips occur. Bhattacharya analysis of the acanthostyle lengths shows the presence of three distinct size categories ( Fig. 13 and Tab. 5 ). Only the first and smallest category (with a mean of 81.15 μm) is, however, represented with a considerable number of spicules. Two other groups, both with fewer spicules, cannot be considered different size classes ( Fig. 13 and Tab. 5 ). Arcuate chelae in two shapes and sizes: isochelae I with typical shape ( Fig. 12 I), 22.5 – 27.5 μm; isochelae II, with a very thin curved shaft and inconspicuous alae (about 1/7 of the total length), 12.5 – 17.5 μm. A spine at the apex of each ala is visible under SEM ( Fig. 12 J). Refer to Tab. 6 for complete measurements.

Remarks. As pointed out by Goodwin et al. (2011) a range in skeletal organisations has been documented from Hymedesmia and Phorbas , the thinner specimens having a Hymedesmia -like skeleton and the thicker a Phorbas - like architecture. Given the presence of acanthostyles erect on the substrate and supporting tornotes, we believe this species should be assigned to Hymedesmia .

Sixteen species of Hymedesmia (Hymedesmia) have been reported from the Indo-Pacific area (van Soest et al. 2011), 15 of which are characterised by a single category of chelae. Among these, the following have chelae sizes overlapping with our specimens: H. (H.) lancifera ( Topsent, 1906) and H. (H.) prostrata Thiele, 1903 both of which have chelae ~ 18 μm long, H. (H.) microstrongylata Bergquist & Fromont, 1988 with chelae of 18–30 μm, and H. (H.) stylophora Thomas, 1970 with chelae of 16–25 μm. Hymedesmia (H.) lancifera differs in having centrotylote tornotes with mucronate extremities and smaller acanthostyles (70 – 170 x 4.2 μm); H. (H.) microstrongylata has strongyloxeas and two categories of acanthostyles, with acanthostyle I up to 470 μm; H. (H.) stylophora has smaller acanthostyles (84–117 μm) and styles or subtylostyles as dermal spicules. Hymedesmia (H.) prostrata is very close to the new species ( Fig. 14A–D ); the re-examination of the holotype (slides of the skeleton) confirmed that it differs mainly in having one type of chelae ( Fig. 14D ) in a large size range (10 – (15.9 ± 3.9) – 22.5 μm), two types of acanthostyles of similar shape (187–240 μm and 80–117.5 μm, respectively; Fig. 14B, C ) and anisotornotes ( Fig. 14A ) (about 187.5–205 μm).

Among the species of Hymedesmia (Hymedesmia) from the Indo-Pacific area, only H. (H.) dichela ( Hentschel, 1911) possesses two categories of chelae; moreover it possesses acanthostyles and anisotornotes similar in shape and size to the new species ( Fig. 14 E–I). Nevertheless, the examination of the syntype reveals that in Hentschel’s species the tornotes have different extremities (anisotornotes, 150 – (189.3 ± 18.9) – 212.5 x 2 – (3 ± 1.2) – 5 μm) ( Fig. 14 E), acanthostyles (65 – (139.2 ± 62.3) – 230 x 5 – (6.1 ± 1.3) – 7.5 μm) always have smooth tips, not ending in verticils of spines ( Fig. 14 F), and chelae I (20 – (21.5 ± 1.8) – 25 μm) and II (10 – (12.5 ± 1.5) – 15 μm) are similar in shape ( Fig. 14 H, I); in particular chelae II, with SEM observations, do not have apical spines.

Etymology. Named after the presence of an apical spine on each ala of chelae II.

Figures

FIGURE 12. Hymedesmia (Hymedesmia) spinata n. sp. A, Sponge covering a colony of Carijoa riisei in situ (holotype); B, Holotype encrusting several fragments of C. riisei; C, Close up of the sponge showing the octocoral completely encrusted with only polyp openings free; D, Dermal membrane with scattered tornotes and chelae; E, Choanosomal skeleton hymedesmioid with acanthostyle heads on the substrate and scattered tornotes and chelae; F, Isotornote with close up of the acerate tip; G, Strongly spined acanthostyle and detail of the head and the spined tip; H, Acanthostyle with smooth extremity; I, Arcuate chela I; J, Arcuate chela II. (F – J, paratype).

FIGURE 13. Size / frequency distribution of acanthostyle lengths in Hymedesmia (Hymedesmia) spinata n. sp.

FIGURE 14. A – D, Hymedesmia (Hymedesmia) prostrata Thiele, 1903 holotype ZMB Por 3160. A, Anisotornotes and chelae; B – C, Small acanthostyles; D, Isochelae; E – I, Hymedesmia (Hymedesmia) dichela (Hentschel, 1911) syntype ZMB Por 4438. E, Anisotornote and close up of the extremities; F – G, Acanthostyles; H, Isochela I; I, Isochela II.

Tables

TABLE 5. Hymedesmia (Hymedesmia) spinata n. sp. Analysis with Bhattacharya’s method indicating the numbers of identified cohorts (groups) of acanthostyles, the mean length for each cohort and the number of spicules present in each cohort. S. d. Standard deviation; S. I. Separation index; separation of the groups is generally unreliable when the SI value is below 2. N. a. not applicable.

Group	Mean	s. d.	Population	S.I.
1	81.15	5.330	99	n.a.
2	129.29	4.190	11	2.890
3	217.50	4.770	4	3.190

TABLE 6. Spicule sizes in µm of Hymedesmia (Hymedesmia) spinata n. sp. and of the syntype of Hymedesmia (Hymedesmia) dichela (Henschel, 1911).

	Tornotes	Acanthostyles	Isochelae I II
H. (H.) spinata n. sp. MSNG 56262	185 – (205.5 ± 7.4) – 215 x 2.5	72.5 – (122.6 ± 49) – 215 x 2.5 – (4.1 ± 1) – 5	15 – (15.2 ± 0.8) – 25 17.5
H. (H.) spinata n. sp. MSNG 56263	192.5 – (206.5 ± 8.4) – 222.5 x 2 – (2.5 ± 0.2) – 2.5	52.5 – (120.4 ± 53.8) – 230 x 2.5 – (4.1 ± 1.1) – 5	25 – (25.5 ± 15 – (16.2 ± 1.3) – 1.1) – 27.5 17.5
H. (H.) spinata n. sp. Bugor 309	190 – (211.7 ± 16.2) – 245 x 2.5 – (3 ± 0.8) – 5	77.5 – (122.7 ± 49.9) – 237.5 x 3.7 – (4.7 ± 0.5) – 5	22.5 – (25.2 15 ± 1.4) – 27.5
H. (H.) spinata n. sp. Indo 23	180 – (199.4 ± 10.2) – 220 x 2.5	72.5 – (127.3 ± 46.8) – 212.5 x 5 – (5.8 ± 1.4) – 7.5	20 – (25.3 ± 12.5 – (14 ± 1.3) – 1.9) – 27.5 15
H. (H.) spinata n. sp. Bugor 410 (bis 2)	177.5 – (192.2 ± 9.2) – 205 x 2.5 – (3 ± 0.6) – 3.7	77.5 – (138.4 ± 59.3) – 237.5 x 5 – (6.7 ± 1.9) – 10	22.5 – (25.7 12.5 – (15.3 ± 1.4) ± 1.7) – 27.5 – 17.5
H. (H.) dichela Syntype ZMB Por 4438	150 – (189.3 ± 18.9) – 212.5 x 2 – (3 ± 1.2) – 5	65 – (139.2 ± 62.3) – 230 x 5 – (6.1 ± 1.3) – 7.5	20 – (21.5 ± 10 – (12.5 ± 1.5) – 1.8) – 25 15