Larval study revealed diversity and life‐history traits of crypto‐benthic eel gobies

Abstract

Because adult and juvenile eel gobies usually hide within the burrows of muddy substrates, their diversity and life history have not yet been fully elucidated. We investigated larval specimens of the eel gobies collected on Okinawa Island in southern Japan. The genus Trypauchenopsis was previously thought to consist of only one species, but our larval collection identified two species, Trypauchenopsis limicola and Trypauchenopsis intermedia, distinguished by their species-specific melanophore arrangements and differences in their fin-ray counts. Taenioides kentalleni were previously known from only two specimens worldwide. A third specimen of this species has now been added from the larval collection. In addition to the three species above, Taenioides gracilis and Caragobius urolepis were identified and the larval morphologies of the five species were described for the first time. All the larvae collected in the present study were at late postflexion stage. T. limicola, T. intermedia and T. gracilis were presumably collected in the estuaries and beaches when approaching their adult habitats at the end of pelagic life. They were 8.5-10.3 mm in standard length, and otolith analysis suggests that their pelagic larval durations are a little longer than 1 month (average 34-37 days). The larval occurrence suggested that the spawning season of T. limicola is May-December, when the water temperature is warmer than approximately 20 C. Our work reveals that studying the larval stage can provide new information on the taxonomy and life history of the elusive cryptobenthic fish.

Genome Sequencing Provides Novel Insights into Mudflat Burrowing Adaptations in Eel Goby Taenioides sp. (Teleost: Amblyopinae)

“…One group of the bony fishes that show such seemly passive strategy of land conquest by living in mudflat burrow is Amblyopinae (Gobiiformes: Gobionellidae) [ 2 , 8 ], a portion of small elongate, mud-dwelling fishes of the Indo-West Pacific region that are commonly referred to as “eel gobies” [ 9 ]. They are usually found in deep burrows of tidal mudflats, muddy bottoms of estuaries, as well as substrates from the adjacent shallow waters [ 10 ]. Some species, including taxa in genus Odontamblyopus and Taenioides , are also frequently observed in intertidal zones in the exposed burrows filled with hypoxia waters during the low tide.…”

“…The burrows can usually reach to a maximum depth of ~1 m [ 11 ]. To better cope with the challenges of deep burrowing environments, Amblyopinae have evolved many morphological and physiological innovations which include small vestigial eyes covered with skin [ 10 , 12 ] that show their adaptations to turbid waters [ 9 ], richly vascularized inner epithelia in the buccal-opercular cavity that enable direct air breathing to cope with the hypoxia in their poorly oxygenated burrows [ 11 , 13 ], and improved starvation resistance that ensures survival during long period of embedment in burrows at the time of low tide or cold seasons [ 11 ]. However, the genetic basis of such morphological and physiological adaptations in Amblyopinae has remained largely unknown, to date.…”