Cliothosa hancocki ( Topsent, 1888 )

Marlow, Joseph, Bell, James J., Shaffer, Megan, Haris, Abdul & Schönberg, Christine Hanna Lydia, 2021, Bioeroding sponge species from the Wakatobi region of southeast Sulawesi Indonesia, Zootaxa 4996 (1), pp. 1-48 : 17-20

Cliothosa hancocki ( Topsent, 1888)

Synonymies. Thoosa hancocci Topsent (1888) (original description with mis-spelled species name). Cliothosa seurati Topsent (1905) (junior synonym).? Cliona quadrata Hancock (1849) (senior synonym? Presently listed as separate species, see van Soest et al. 2021). Not: Vioa hancoccii Schmidt (1862) .

Material examined. Cliothosa hancocki : R1 -OA-01, slide of discarded sponge kept at VUW, sponge from west of Hoga , Wakatobi, Banda Sea, sampled between March and August 2014, 3– 20 m, coll. J. Marlow. B1-OA-01, slide of discarded sponge kept at VUW, sponge from west of Hoga , Wakatobi, Banda Sea, sampled between March and August 2014, 3– 20 m, coll. J. Marlow. PK-OA-01, slide of discarded sponge kept at VUW, sponge from west of Hoga , Wakatobi, Banda Sea, sampled between March and August 2014, 3– 20 m, coll. J. Marlow.

Morphology and erosion. Exclusively in alpha-morphology ( Fig. 7A ). Papillae light orange to dark yellow, circular, 1–5 mm in diameter. Choanosomal tissue of living sponge of slightly darker yellow-orange colour than papillae. Colour of ethanol-preserved specimens dull brown. Inhalant and exhalant papillae noticeably different. Inhalant papillae flush to substrate surface, short-cylindrical, with central, meshed area covering papillar lumen slightly below substrate surface, and with villi-bearing microsculpture. Exhalant papillae rising as stubby, conical to cylindrical projections 2–5 mm above substrate, walls becoming more delicate towards minutely scalloped apical edge. Papillar canals leading to sub-ovoid, large, irregular erosion chambers (cross-sectional area 5.1 cm 2 ± 6.5 SD; Fig. 7B ), with multiple canals often merging into one chamber, creating a “bagpipe” appearance. Erosion occasionally extending to 5 cm substrate depth.

Skeletal characteristics and presence of Symbiodiniaceae . Papillae with tylostyles densely packed in palisade, without microscleres. Tylostyles and amphiasters irregularly diffused throughout choanosome. No evidence for photosymbionts, neither by surface fluorescence, nor through histological observations.

Spicules. Megascleres—Straight to slightly curved, stout tylostyles, predominantly with pronounced spherical tyles, occasionally subterminal ( Fig. 7C ). Dimensions (min – mean – max and standard deviation): length 300 – 383.7 – 481 µm ± 48.9 SD; shaft width 7 – 11.6 – 18 µm ± 2.3 SD; and tyle width 8 – 12.7 – 21 µm ± 2.3 SD (means across three Wakatobi specimens, with N = 25 spicules each). Microscleres – characteristic, very abundant, delicate amphiasters, with 3–4 branches at either end of smooth shaft ( Fig. 7D & E ). Branches terminating in groups of delicate, recurved spines. Amphiaster dimensions (min – mean – max and standard deviation): total length 18 –22.3 – 28 µm ± 3.2 SD; and shaft width 1.5 – 2.4 – 3.7 µm ± 0.6 SD (means across three Wakatobi specimens). Branches of similar length as shaft without branches. No reduced, nodulous amphiasters found.

Habitat and occurrence in the Wakatobi. In low abundances in shallow water at most sites (<7 m depth). Occuring on bare calcareous substrate, and often in skeletons of dead massive Porites coral.

Remarks. In the respective Wakatobi specimens, the shape and dimensions of the tylostyles, the presence of amphiasterose microscleres and the large erosion chambers readily led to the conclusion that the material belonged into the genus Cliothosa . Except for Cliothosa aurivillii and Cliothosa delitrix , all known species occur in papillate alpha form without papillar fusion. Cliothosa erosion chambers are often considerably larger than in Cliona , and where respective observations are available, the endolithic tissue in Cliothosa spp. is usually soft and fragile (Cruz- Barraza et al. 2011 for Cliothosa tylostrongylata ; Schönberg & Wisshak 2012 for Cliothosa aurivillii ). Compared to Cliona and Pione , Cliothosa species often have comparatively robust tylostyles that have occasionally been described as ensiform (e.g. Calcinai et al. 2000 for Cliothosa dichotoma ). Tyles are comparatively wide and spherical and usually clearly demarkated against the shaft by a sharp edge, however, they can be subterminal ( Hancock 1849; Annandale 1915; Rützler & Stone 1986; Cruz-Barraza et al. 2011). Importantly, finding amphiasters with spines or actines that have split and recurving terminations is a clear indicator for Cliothosa . These amphiasters can be modified and less characteristic in some species, but commonly a short central axis ends in terminal branches that can in some species branch again into spines that recurve in the typical form. In Cliothosa aurivillii long spirasters occur, but again with terminally split spines. Reduced, nodulous forms of amphiasters exist and are characteristic, but cannot be found in every specimen and are patchily distributed where they occur ( Lindgren 1897; Annandale 1915; Schönberg 2000; Rützler 2002b). Further, Cliothosa spp. are yellow or orange to red or even dull pink, and are not known to harbour photosymbionts. Overall, the Wakatobi material fell well into the scope of the genus Cliothosa .

1 Lindgren (1897), 2 after Topsent (1891), original account Topsent (1888; as Thoosa hancocci ), 3 calculated from Schönberg (2000) using the first 3 samples in her Appendix 5

Van Soest et al. (2021) presently accept seven Cliothosa species as valid. Six of which occur in the Indo- Pacific ( Schönberg et al. 2017a; van Soest et al. 2021), and five of these have short amphiasters and needed to be compared to the Wakatobi specimens: Cliothosa dichotoma ( Calcinai et al., 2000) , Cliothosa hancocki ( Topsent, 1888) , Cliothosa investigatoris ( Annandale, 1915 —but probably not a Cliothosa, Schönberg pers. obs.), Cliothosa quadrata ( Hancock, 1849) and Cliothosa tylostrongylata Cruz-Barraza et al., 2011 . A further, yet undescribed Cliothosa sp. was sampled from the Wakatobi that will be briefly discussed below, but will be fully described in a separate publication.

Tylostyles of a mean length near 200 µm were described for Cliothosa dichotoma and Cliothosa tylostrongylata , which appears too short for the Wakatobi material. The Wakatobi specimens can further be distinguished from these species by other morphologic characters. Cliothosa dichotoma has tylostyles with ensiform shafts, amphiasters with irregular branching and smaller, porous erosion traces unlike in the Wakatobi samples ( Calcinai et al. 2000). Cliothosa tylostrongylata is red in life, not yellow-orange like the Wakatobi sponges, and has smaller, somewhat more robust amphiasters ( Cruz-Barraza et al. 2011). Tylostyles of a mean length between 340 and 380 µm have been described for Cliothosa investigatoris , Cliothosa quadrata , and some descriptions for Cliothosa hancocki (including the holotype; see Table 1 in Cruz-Barraza et al. 2011) and provided the best fit with the tylostyle dimensions of the Wakatobi material (Table 2). Clean separation from these species was difficult, but we excluded Cliothosa investigatoris as a deep-sea species lacking the delicate amphiasters (sampled from> 1200 m water depth).

Choosing between Cliothosa hancocki and Cliothosa quadrata was difficult as they are morphologically very similar. Also, the original description of Cliothosa quadrata was insufficient and did not mention any microscleres ( Hancock 1849). The short re-description by Rützler & Stone (1986) pictured delicate amphiasters very similar to those in Cliothosa hancocki , and the question has been raised whether the two species should not be synonymised (e.g. Cruz-Barraza et al. 2011). Topsent’s (1888, p. 81) description of Cliothosa hancocki speaks of his sponge closely mingling (“entrelacée”) with Hancock’s (1849) Cliothosa quadrata in the same substrate, and he assumed that the former only has nodulous and finely branching amphiasters, the second one only tylostyles. However, Topsent’s (1888) holotype contains both, amphiasters and tylostyles (C. Schönberg pers. obs.), further supporting the likelihood that Cliothosa hancocki and Cliothosa quadrata are the same species, but a formal comparison is still lacking. Within the scope of this paper we were unable to assess this putative synonymy and tentativley rejected Cliothosa quadrata due to a published tylostyle width of ~ 25 µm, which is twice that of the Wakatobi material and Cliothosa hancocki .

By excluding the other species of Cliothosa , and based on the spicule characters we decided that our material represented Cliothosa hancocki . Its original type location is unknown ( Topsent 1888), but as this species is likely conspecific with and co-occurred with Cliothosa quadrata , which is an Indo-Pacific species that has first been found in a shell of Tridacna gigas ( Hancock 1849) , we assumed the same for Cliothosa hancocki . In prior publications Cliothosa hancocki has always been treated as an Indo-Pacific species, and it has also previously been located at Sulawesi (e.g. Hooper et al. 2000; Schönberg 2000; Barucca et al. 2007). While our decision thus seems justified, large differences in mean tylostyle lengths reported for Cliothosa hancocki (see Table 1 in Cruz-Barraza et al. 2011) suggest that the present use of this name might nevertheless represent a species complex or that spicule size variation in Cliothosa species should be assessed by detailed biometry in future studies.

Figures

FIGURE 7. Cliothosa hancocki. (A) Field image of exhalant (left and centre of photograph) and inhalant papillae; (B) field image of erosion chamber; (C) tylostyles; (D) amphiaster with terminally split branches; (E) cluster of amphiasters around tyle.