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A Newly Described Butterfly Sea Slug
Cyerce blackburnae (Moreno, Gosliner, Wilson, Krug & Valdés, 2025) is one of the rarest butterfly sea slugs at our macro dive sites in Romblon, Philippines. Scientists formally described this species in 2025. It was previously unknown to science. It belongs to the order Sacoglossa, family Caliphyllidae. Furthermore, it is one of nine new Cyerce species scientists described in the same landmark 2025 paper. Its close relatives Cyerce nigra and Cyerce katiae are also in our Marine Life Encyclopedia.
Defence by Autotomy
Like all Cyerce species, Cyerce blackburnae has large, flat, leaf-like cerata. The animal feeds on green algae of the genus Udotea. When a predator attacks, it sheds its cerata. The cerata continue to writhe on the seafloor after separation. As a result, the predator targets the moving cerata instead. Meanwhile, the animal escapes. This strategy is called ceratal autotomy. In addition, the bold colouration on the cerata warns predators of chemical defence compounds.
Finding It at Sunset Cove
At Sunset Cove Beach & Dive Resort, our guides search sandy rubble substrate near Udotea algae patches. The animal reaches 10 to 20 mm in length. Therefore, diopters and high magnification give the best results. Approach very slowly — it sheds its cerata immediately when startled. For underwater macro photographers in Romblon, the leaf-like cerata pattern creates outstanding close-up images. Consequently, this species is one of the most exciting recent discoveries at our dive sites.
| Order | Sacoglossans (Sacoglossa) |
|---|---|
| Family | Caliphyllidae |
| Subfamily | Cyercinae |
| Genus | Cyerce |
| WoRMS AphiaID | 1814150 |
| iNaturalist | 1623585 |
| Size | 15–35 mm |
|---|---|
| Colour Variations | Body translucent with distinctive colouration on cerata. As a newly described species (2025), full colour variation data is still being documented. Closely related to Cyerce nigra and shares similar cerata morphology — large, flattened, leaf-like appendages. Exact colour pattern distinguishes it from other Cyerce species through molecular analysis. |
| Identifying Features | Distinguished from other Cyerce species primarily through molecular (COI, 16S, H3) and morphological (penial anatomy, radulae) analysis. Large flattened leaf-like cerata typical of genus. Bifurcate enrolled rhinophores. Transverse groove ventrally along foot. Best identified in the field by location, substrate association with Udotea algae, and comparison with known Cyerce species photographs from the same region. |
| Depth Range | 3–30 m (most common: 10 m) |
|---|---|
| Temperature | 22–28°C |
| Primary Prey / Host | Udotea spp. (green algae) |
| Seasonal Presence | Year-round — most frequently sighted December to April during calm season |
|---|---|
| Egg Ribbon | White, coiled ribbon |
| Spawning Season | Not yet documented — insufficient records as newly described species |
| Chemical Defence | Present |
| Aposematic Colouring | Present |
| Camouflage Strategy | Aposematic colouration — bold patterns signal chemical defence to predators. |
| Escape Response | Ceratal autotomy — voluntarily sheds cerata which continue to writhe, distracting the predator while the animal escapes. |
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Phylogenetic systematics of the genus Cyerce Bergh, 1870 (Sacoglossa, Caliphyllidae) with descriptions of nine new species
Moreno, K.; Medrano, S.; Gosliner, T.M.; Wilson, N.G.; Krug, P.J.; Valdés, Á. (2025)