Subterranean Fishes of the World

Country

Types

Holotype: PNM 15353, ex ZRC 56329, 49 mm SL, male.

Paratypes: ZRC 56329 49 mm SL male, PNM 15354, 42mm SL female, AMS I.47860-001 39mm SL male.

Distribution

Known only from the type locality: Ugnop Cave, Mindanao Island, Phlippines. This cave is also the type locality of Barbodes pyrpholeos and the two species coexist (Larson and Husana 2018, Husana 2020).

Habitat

A vadose cave stream with water colder than average for area suggesting a large body of groundwater, confined for a long period, as habitat. Numerous epigean cyprinid fishes, troglobitic crabs and shrimps, and cave crickets are also found in the cave and probably form the food supply for the fishes. The cyprinid fish is larger than the cave goby and may prey on it.

This species, and the sympatric Barbodes pyrpholeos share their habitat with a very troglomorphic crab Sundathelphusa prosperidad Husana 2020  (Decapoda: Brachyura: Gecarcinucidae) (Husana 2020).

Systematics

How closely, or not, Caecogobius personatus is related to Caecogobius cryptophthalmus is not settled as too few specimens of either species (4 only for each) are known. Larson and Husana (2018) suggest that they may even be separate genera. Tissue samples for molecular studies of C. personatus were taken and may provide further data in due course. In a detailed morphological study of Mugilogobius and allied genera Larson (2001) placed Caecogobius in the subfamily Gobionellinae and the Mugilogobius clade. She also provided a revised diagnosis of the genus and a drawing of the head of paratype CMK 7249 (which is ZSM 27189 on loan to CMK) of Caecogobius cryptophthalmus. Caecogobius appears to be close to Tamanka siitensis,  a freshwater goby from two crater lakes on Jolo Island, Sulu Archipelago, Philippines, and the two may share a common ancestor. The Sulu Archipelago is directly south east of Mindanao Island and it is very likely that they formed a common landmass at lowered sea level.

Kuang et al. (2018) used molecular markers to study the internal structure of the Suborder Gobioidei which contains within it eleven Families. They demonstrated that Milyeringidae is sister Family to a group of four  Families: Oxudercidae+Gobiidae+Butidae+ Eleotridae and is only disttantly related to four others: Odontobutidae, Rhyacichthyidae, Apogonidae and Kurtidae (samples from Thalasseleotridae and Trichonotidae were not availabe for analysis).

Museum Holdings

As above only.