Lissoclinum bistratum (Sluiter, 1905)

Hirose, Euichi & Nozawa, Yoko, 2020, Fig. 6 in Bruggmanniella sanlianensis Lin, Yang & Tokuda, 2020, sp. nov., Zoological Studies 59 (19), pp. 1-11 : 4

Lissoclinum bistratum (Sluiter, 1905)

Specimens: NMNS-8141-007 (Maobitou), -008 (Gongzibi), -009 (Jialeshuei).

Colonies were flat, irregularly shaped sheets and usually green due to the Prochloron distributed in the common cloacal cavities ( Fig. 3A ). The peripheries and the substratum side of the colony sheets were white due to globular spicules densely distributed in the tunic ( Fig. 3B ).

The present species shares many morphological features with Lissoclinum timorense (Sluiter 1909) , and the absence of the stellate spicules distinguishes L. bistratum from L. timorense ( Kott, 2001) . Monniot and Monniot (2001), however, considered the variability in the spicule composition to be intraspecific and proposed that L. timorense be assigned as a junior synonym of L. bistratum . Because there were no stellate spicules, the present specimens were identified as L. bistratum sensu stricto. There were no records of L. timorense from Taiwan, although this species is widely distributed in the tropical west Pacific from the Ryukyu Archipelago to GBR. The coral reefs in the Ryukyus are usually barrier reefs, and L. bistratum and L. timorense are often found at the same site; L. bistratum inhabits the reef flat and reef edge, while L. timorense inhabits the back reef. The reefs in Taiwan are mainly fringing reefs and lack back reefs, and the difference in reef structure is probably why L. timorense has never been recorded from Taiwan.

Figures

Fig. 3. Lissoclinum and Trididemnum species. (A, B), Lissoclinum bistratum at Gonzibi (A, colony; B, tunic spicules). (C–E), Lissoclinum midui at Gonzibi (C, colony; D, thorax; E, tunic spicules). (F–H), Lissoclinum punctatum at Gonzibi (F, colony; G tunic phycocyte; H, tunic spicules). (I–L), Trididemnum clinides at Shimen (I, colony; J, tunic spicules; K, unicellular cyanobacteria in the tunic; L, filamentous, multicellular cyanobacteria in the tunic). (M–P), Trididemnum cyclops at Shimen (M, colony; N, tunic spicules; O, enlargement of colony surface showing a zooid; P, thorax). Arrows in O and P indicate pigmentation at the top of endostyle (pigment cap). an, anus; fp, fecal pellet; g, greenish cyanobacteria; n, nucleus of tunic phycocyte; r, reddish cyanobacterium; un, unknown organ. Scale bars: B, E, G, H, J–L, N, and O = 20 µm; D and P = 0.1 mm; O = 0.2 mm.