Year-round high abundances of the world’s smallest marine vertebrate (Schindleria) in the Red Sea and worldwide associations with lunar phases

Abstract

Very little is known about the ecology and biology of the smallest marine vertebrates, fishes in the genus Schindleria. Even though over half of named Schindleria species have been identified in the Red Sea, the collection of only very few specimens has been documented. Here, we assessed abundance patterns of nearly two thousand Red Sea long dorsal fin (LDF) adults and found evidence for putative seasonal and spatial differences, likely related to differing habitat and environmental conditions. The highest abundances were outside local seasonal temperature extremes and decoupled from peaks of coral reef fish recruitment. We also found evidence for global trends in abundances related to lunar cycles using our Red Sea data and that from a recently published large collection of specimens from the DANA Expedition (1928–1930). The abundance of adult LDF Schindleria in relation to lunar phases differed significantly, with most Schindleria caught outside the full moon, and mostly during the new moon in the Red Sea and the 3rd quarter moon in the DANA collection. We further suggest that the abundances of Schindleria at coral reefs may be related to reproductive cycles and that these cycles may be timed with the moon as back-calculations of hatch dates from otoliths from the Red Sea significantly resulted after the new moon, making Schindleria the fastest-lived coral reef fish with the shortest generation times. Schindleria could be the most numerous coral reef fish in the world, for which we encourage increased research.

A new species of Schindleria (Teleostei: Gobiiformes: Gobiidae) from the Red Sea (Saudi Arabia) with a specialized caudal-fin complex

“…Kon et al (2007) describe 10 different morphotypes of such papillae. Seemingly less variable are the urogenital papillae of female Schindleria (e.g., Robitzch et al 2021a). Just two general types have so far been reported: (i) a plain urogenital opening (Ahnelt and Sauberer 2018;Ahnelt 2020) and (ii) a roundish, bulbous papilla with two short horn-like projections lateral to the urogenital opening (e.g., Bruun 1940;Sardou 1974;Johnson and Borthers 1993;Ahnelt 2019) (Fig.…”

“…Although some recent studies investigated sexual dimorphism (Robitzch et al 2021a), lunar migration cycles (Robitzch et al 2021b), and swimming mode (Robitzch et al 2022) of Schindleria, the entire lifecycle, habitat, and basic biology and ecology of these enigmatic fishes are virtually unknown and still need detailed exploration. Nonetheless, the collection in which this new species was found may allow for the inference of a few more details on the habitat or distribution of S. qizma.…”

A new species of toothless, short dorsal-fin Schindleria (Gobiiformes: Gobiidae) from the Red Sea (Egypt)

“…The genus Schindleria (Giltay, 1934) (Schindler's fishes or infant fishes) has a large biogeographic range spanning the entire Indo-Pacific from remote South American islands to East and South African coasts, and from the Red Sea to Japan (summarized in Ahnelt and Sauberer 2020). Often found in and close to coral reef lagoons (Leis 1994;Watson 2000; Robitzch et al 2021a), also offshore and deep-water records have been documented (Belyanina 1989;Parin 1991;Ahnelt and Sauberer 2020). Schindleria are not only among the smallest vertebrates (8 mm-22 mm, average ca.…”

“…Although individuals of Schindleria are likely among the most numerous fishes associated with coral reefs (Gosline and Brock 1960;Whittle 2003;Robitzch et al 2021) these tiny gobioids are easily overlooked and frequently mistaken for larval fishes (Bogorodsky and Randall 2019;Robitzch et al 2021a). Numerous records are based on a few specimens only Sauberer 2019, 2020;Robitzch et al 2021b) and these were often collected as by-catch of other research surveys.…”

“…Numerous records are based on a few specimens only Sauberer 2019, 2020;Robitzch et al 2021b) and these were often collected as by-catch of other research surveys. Therefore, almost nothing is known about the biology and ecology of Schindleria (Robitzch et al 2021a). To date, the sister group of Schindleria is still unknown and its position among gobioid fishes is still under debate (e.g., Ahnelt 2020;Abu El-Regal et al, 2021).…”