Gobiodon, Hildebrandt & Froehlich & Klanten & Wong, 2025

Hildebrandt, Courtney A., Froehlich, Catheline Y. M., Klanten, O. Selma & Wong, Marian Y. L., 2025, Goby spotting: An updated guide to coral gobies (Genus: Gobiodon) in the Indo-Pacific Region, Zootaxa 5723 (2), pp. 151-188 : 158-159

Gobiodon bicalvolineatus Hildebrandt, Froehlich, Brodenicke, Klanten, Møller & Wong, 2024 : Speckle- Lined Coralgoby and previously recorded as Gobiodon sp. B

Synonyms or described as: Gobiodon sp. B ( Munday, Harold and Winterbottom, 1999) and Gobiodon new sp. ( Munday et al., 2004).

Description: Gobiodon bicalvolineatus , originally referred to as G. sp. B ( Munday, Harold and Winterbottom, 1999) prior to the official description, shares many visual similarities with G. brochus , G. erythrospilus and G. histrio , however is typically much smaller than these species ( Hildebrandt et al., 2024). The oblique pale patch on the cheek and recurved lower lip are shared with G. brochus , whilst the red body markings on a blue-green base colouration are shared with G. erythrospilus and G. histrio ( Figure 7 ). Unlike G. histrio and G. erythrospilus , the horizontal red-orange lines appear unbroken and much thinner on G. bicalvolineatus , and there is no distinct black spot on the upper opercular margin ( Munday, Harold and Winterbottom, 1999; Hildebrandt et al., 2024). The pectoral fin is angled more upward towards the dorsal surface than seen in congeners ( Hildebrandt et al., 2024). The caudal fin appears to be more elongated than in other species, with a less defined ‘blunt’ end ( Hildebrandt et al., 2024).

Distribution: Gobiodon bicalvolineatus is believed to be restricted to Papua New Guinea, namely Bootless Bay and Kranket Lagoon ( Munday, Harold and Winterbottom, 1999; Munday et al., 2004).

Habitat: Observed in the host coral Acropora caroliniana, Nemenzo, 1976 , a coral with a plate like growth form with prostrate branches ( Munday, Harold and Winterbottom, 1999; Munday et al., 2004).

Status: Due to the recent formal description, there is no current IUCN population status for G. bicalvolineatus .

Sociality: Gobiodon bicalvolineatus has not been included in any sociality studies at this stage owing to its restricted range and small population size. Whilst the species was not included in the study of sociality of this genus by Hing et al. (2018), it was noted that social groups comprising up to ten adult and juvenile individuals could be observed in the same coral ( Munday, Van Herwerden and Dudgeon, 2004), indicating the occurrence of groupforming behaviours.

Genetics: Gobiodon bicalvolineatus is another species where the phylogenetic position varies depending on the genetic markers that are used. Nevertheless, the species is typically always paired with their sister species G. aoyagii , and more often shares a clade with G. cobenjaminsis and the sister species G. brochus ( Harold et al., 2008; Duchene et al., 2013). However, it has also been seen to be located on an early diverging branch in isolation ( Herler, Bogorodsky and Suzuki, 2013). The species was also the focus of a haplotype analysis where it was compared to G. aoyagii , G. brochus , G. erythrospilus and G. histrio ( Munday, Van Herwerden and Dudgeon, 2004) . Gobiodon bicalvolineatus only displayed two different haplotypes, compared to the five seen in G. aoyagii and even greater numbers in the other species. It was hypothesised that this lack of diversity could have been the result of a genetic bottleneck occurring as a result of a founder effect due to a coral host shift ( Munday, Van Herwerden and Dudgeon, 2004).

Figures

FIGURE 7. LEFT: Illustration of Gobiodon bicalvolineatus by C. Hildebrandt. RIGHT: Underwater photograph of Gobiodon bicalvolineatus by P. Munday at Motupore Island, PNG.