Gobiodon ceramensis (Bleeker, 1852)

Gobiodon ceramensis (Bleeker, 1852) View in CoL : Ceram Coralgoby

Synonyms or described as: Gobius ceramensis ( Bleeker, 1853) .

Description: Gobiodon ceramensis has a uniform black colouration, like that seen in G. ater and the darker colour variation of G. acicularis . The defining feature of this species is the more angular first dorsal that is no greater in height than the second dorsal ( Figure 10 View FIGURE 10 ). This can be compared to G. acicularis which has a triangular ‘sail’ shape first dorsal that is significantly greater in height than the second dorsal. Juveniles of this species have been observed being white/clear with bifurcate black stripes down the body below the dorsal surface and along the lateral line, with spots or dots on the head and caudal peduncle regions of the body, similar to the description for G. spilophthalmus ( Hing et al., 2019) .

Distribution: Gobiodon ceramensis is commonly found in sheltered reef areas, such as lagoons, throughout the GBR, PNG and north Pacific Ocean ( Munday, Harold and Winterbottom, 1999; GBIF.Org, 2024).

Habitat: Unlike the majority of the genus, G. ceramensis displays a strong preference for corals from the family Pocilloporidae , most frequently Stylophora pistillata (Esper, 1792) , a densely branching coral with blunt branch ends ( Munday, Harold and Winterbottom, 1999; Veron et al., 2024). The species has also been observed inhabiting members of Acropora with corymbose growth forms, such as A. nasuta , at lower frequencies (Hildebrandt, pers. obs.).

Status: The species is listed as ‘Near Threatened’ on the IUCN Red List ( Larson, 2020e).

Sociality: Gobiodon ceramensis displays a lower level of sociality for the genus Gobiodon , primarily occurring in pairs (mean group size: 1.80, SI: 0.36) ( Hing et al., 2018; Hing, 2019).

Genetics: Gobiodon ceramensis is often observed as a sister group to G. acicularis in phylogenetic analyses ( Harold et al., 2008; Herler, Bogorodsky and Suzuki, 2013; Hing et al., 2019). An exception to this is seen in Duchene et al. (2013) where G. spilophthalmus was included in the analysis and was more closely related to G. ceramensis . In all recent genetic studies, the clade consists of G. ceramensis , G. acicularis , G. okinawae and G. citrinus ( Harold et al., 2008; Duchene et al., 2013; Herler, Bogorodsky and Suzuki, 2013; Hing et al., 2019).

Notes: The descriptions of G. ceramensis have many similarities with the descriptions of G. albofasciatus , a species often described in Japanese field guides (Sawada and Arai, 1972; Akihito, Ikeda and Sugiyama, 2002 ). It is not known whether these species are genetically differentiable or may be the same species, as the species description for G. albofasciatus did not include a comparison and no comparative or genetic analyses have been conducted. An extension of this confusion exists surrounding the appearance of juveniles of G. ceramensis , as juveniles of this species and individuals known as Gobiodon spilophthalmus share a striking resemblance (See Gobiodon spilophthalmus Fowler 1944 below).