Gobiodon citrinus (Rüppel, 1838)

Gobiodon citrinus (Rüppel, 1838) View in CoL : Lemon Coralgoby

Synonyms or described as: Gobius citrinus (Rüppel, 1838) and Gobiodon hypselopterus ( Bleeker, 1875) .

Description: As one of the most easily distinguishable species in the genus, G. citrinus is differentiated by a larger size and distinctive colour. Adults frequently exceed 60mm in total length, making it one of the largest members in the genus ( Munday, Harold and Winterbottom, 1999). The body colouration of this species is most commonly a bright or dusky yellow but can be brown or even black in colouration ( Figure 11 View FIGURE 11 ). Groups are often observed exhibiting only one of the colour forms, e.g. all individuals bright yellow, or dusky/brown (Hildebrandt, pers. obs.). A black dot is visible on the upper opercular margin. Four iridescent blue stripes are visible on the face, passing either side of the eye and either side of the opercular margin spot, as well as an additional line along the base of the dorsal and anal fins.

Distribution: Gobiodon citrinus is a common sight on coral reefs throughout the Indo-Pacific ( Munday, Harold and Winterbottom, 1999; GBIF.Org, 2024).

Habitat: Often observed in calmer lagoon areas on the branches of arborescent acroporids such as Acropora intermedia ( Munday, Harold and Winterbottom, 1999) .

Status: This species is listed as of ‘Least Concern’ by the IUCN ( Larson, 2019c).

Sociality: They are typically observed in groups (mean group size: 4.11, SI: 0.63–0.64) ( Hing et al., 2018; Hing, 2019; Froehlich et al., 2024).

Genetics: Gobiodon citrinus has been observed to exist as two main populations, one residing in the Pacific Ocean and the other in the Red Sea ( Duchene et al., 2013). Sometimes analysed separately in genetic analysis, the two populations consistently appear as sister taxa however there is a noticeable divergence between the populations ( Duchene et al., 2013; Herler, Bogorodsky and Suzuki, 2013). Both populations appear frequently within the same clade alongside G. acicularis , G. ceramensis and G. okinawae ( Harold et al., 2008; Duchene et al., 2013; Herler, Bogorodsky and Suzuki, 2013; Hing et al., 2019).

Notes: Gobiodon citrinus is one of the more social members of the genus, frequently being easily photographed and identified sitting on the outer branches of more open Acropora corals (Hildebrandt, pers. obs.).