Tarsocryptus laboriosa ( Tilbrook, 2006 ) Tilbrook, 2006

Tilbrook, Kevin J., 2011, New genus for a unique species of Indo-West Pacific bryozoan, Zootaxa 3134, pp. 63-67 : 64-66

Tarsocryptus laboriosa ( Tilbrook, 2006) comb. nov.

( Figure 1)

Biflustra reticulata Tilbrook, Hayward & Gordon, 2001: 38 , fig. 2E.

Aplousina laevigata (nomen nudem): Liu, Yin & Ma 2001: 448, pl. 17, figs 6, 7.

Biflustra reticulata: Hayward 2001: 997 , fig. 2A,B. Biflustra laboriosa Tilbrook, 2006: 20 .

Material. Holotype: NHMUK 1998.8.4.66, Port Vila Harbour, Efate, Vanuatu. Paratypes: NHMUK 1998.8.4.65, Port Vila Harbour, Efate, Vanuatu; NHMUK 1998.8.4.288, Erakor Lagoon, Efate, Vanuatu, collected by D. P. Gordon. Other material examined: MTQ G25162, NW of Palfrey Island, Lizard Island, 14.68976º S, 145.44014º E.

Description. Colony encrusting, up to 2–3 cm 2. Autozooids irregularly oval, 0.50–0.60 x 0.25–0.35 mm, separated by shallow grooves. Gymnocyst minimal, varying in width, prominent proximally, but surrounding entire cryptocyst. Cryptocyst one third to one half of frontal area, extending to a greater or lesser extent either side of opesia, negligible distally, extensive proximally, flattened, smooth apart from a raised reticulate pattern of tubercles. Opesia oval to triangular (0.25–0.35 x 0.23–0.28 mm). A pair of multiporous septula in each lateral wall, up to 10 uniporous septula in transverse wall. Basal wall generally entire but partially lacking in some autozooids. Cyphonautes larva transparent (0.30–0.40 x 0.25–0.30 mm). Lophophore with 10 tentacles. Ancestrula ca 0.35 mm long, identical in morphology to subsequent autozooids, giving rise to pair of a different-sized first-generation autozooids distolaterally.

Remarks. This unique species is extremely distinctive with its relatively large cryptocyst bearing a reticulate ornamentation, obvious even on the ancestrula. Hayward (2001) noted that Tarsocryptus laboriosa larvae were collected during mid-September at Lizard Island and that they had all settled and metamorphosed within a day or two. Four days later, juvenile colonies were recorded, consisting of the ancestrula and two first-generation autozooids with an additional two zooidal buds. It is worth noting that Liu et al. (2001) found that colonies growing on the seagrass Zostera japonica had autozooids with a far greater range in size than those encrusting other substrata.

The need to reassign Tarsocryptus laboriosa has been apparent almost from the time of its first documentation. It is ironic that this newly documented species should be figured twice within the first year of its discovery, and these occurrences highlighted the need for a re-evaluation.

As explained by Tilbrook (2006), Liu et al. (2001) recorded this species as ‘ Aplousina laevigata Liu & Ristedt, 2000 ’; however that epithet is a nomen nudem since the Liu & Ristedt paper recorded as ‘in press’ in the bibliography was never published.

Distribution. Originally described from Vanuatu, where it was often found encrusting species of the calcareous green alga Halimeda , Tarsocryptus laboriosa has subsequently been found as a fouling species in the South China Sea and as a coral-reef associate at Lizard Island on the northern Great Barrier Reef. This known distribution suggests that this species should also be found within the wider Indo-Philippine region.