Geographic variation in otolith morphology among freshwater populations of Aphanius dispar (Teleostei, Cyprinodontiformes) from the southeastern Arabian Peninsula

Abstract

Aphanius Nardo is a large genus of teleost fishes in the Old World, with 19 described species. Several of these species have only recently been recognized and additional species can be expected from isolated populations in remote areas. We show here that otolith morphology and statistical analyses of otolith variables can contribute to the detection of genetic differentiation in Aphanius. We studied samples of eight Aphanius dispar populations from the southeastern part of the Arabian Peninsula. Two populations originate from freshwater habitats far inland and probably have been isolated since the late Holocene some 4,000 years ago, three populations come from freshwater habitats with occasional connections to the sea, one population originates from a coastal site, and two were artificially introduced populations. The coastal population is interpreted as possessing the basic otolith type of A. dispar. The basic otolith type also occurs in fishes from the freshwater habitat which is located closest to the coast. Otoliths from the two other freshwater populations with occasional connections to the coast differ slightly from the basic type. However, the two populations from the long-term isolated freshwater habitats far inland show distinct morphological changes. Our results are consistent with the hypotheses that i) otolith morphology is primarily genetically determined and is little influenced by physical parameters of the habitat, and ii) isolated A. dispar populations may be capable of evolving into new species within short periods of time.

Otolith shape variation provides a marker of stock origin for north Atlantic bluefin tuna (Thunnus thynnus)

“…The relationship between fish size and otolith shape reflects the combined effects of ontogeny and the environment on otolith shape (Vignon 2012). The overall species-specific shape of the otolith and the nature of its development during ontogeny from the circular larval otolith to the more complex morphology of the adult otolith is genetically determined (Hüssy 2008;Reichenbacher et al 2009;Vignon and Morat 2010), with exogenous factors having a modulating effect through, for example, the effects of feeding and growth on the nature of crystal formation (Gauldie and Nelson 1990) and the rate of protein accretion in the otolith (Hüssy 2008). The shape of the otolith may also reflect its physiological function in hearing and balance, and such variation can have an adaptive significance.…”

Late Pleistocene to Holocene diversification and historical zoogeography of the Arabian killifish (<i>Aphanius dispar</i>) inferred from otolith morphology

“…2; see Reichenbacher et al 2009a). In addition, a total of 60 specimens from southern Iran were studied, i.e.…”

“…According to the habitat descriptions for A. dispar from the United Arab Emirates and southern Iran (Reichenbacher et al 2009a, Teimori et al 2012a and own observations at the sites in Oman, the general environmental conditions of the sites are comparable, i.e. all are shallow pools, the water energy is low, temperature and pH are generally within the range of 25-28°C and pH 8.0-9.5, and salinity is about 0.05-3%.…”

“…The principal habitats of A. dispar are coastal lagoons, but also inland waters such as endorheic drainage systems and hot springs (Krupp 1983, Wildekamp 1993, Abdoli 2000. Pronounced intraspecific differences are known to exist in morphological characters of the individuals and otolith traits (Wildekamp 1993, Reichenbacher et al 2009a, Teimori et al 2012a). These differences suggest that some of the landlocked populations have been isolated since the last humid phase of the Holocene, approximately 5500 years ago (Preusser 2009), and perhaps represent species in statu nascendi.…”

Inter-population differences in otolith morphology are genetically encoded in the killifish <i>Aphanius fasciatus</i> (Cyprinodontiformes)

“…The results of this study shed new light on previous work on the differences in otolith morphology between populations of Aphanius iberus (Reichenbacher and Sienknecht 2001) and A. dispar (Reichenbacher et al 2009a, 2009b, Teimori et al 2012a, 2012b. In these studies, otolith differences have been interpreted as indicating allopatric genetic divergence, but a test of this interpretation by molecular data analyses has not been conducted.…”