Abstract
Abstract. Living Ammonia species and an inventory of dead assemblages from Adriatic subtidal, nearshore environments were investigated at four stations off Bellaria, Italy. Ammonia falsobeccarii, Ammonia parkinsoniana, Ammonia tepida, and Ammonia veneta were recognized in the living (rose-bengal-stained) fauna, and Ammonia bellaria n. sp. is described herein for the first time. Ammonia beccarii was only found in the dead assemblage. The biometry of 368 living individuals was analysed by using light microscopic and scanning electron microscopic images of three aspects. A total of 15 numerical and 8 qualitative parameters were measured and assessed, 5 of which were recognized to be prone to a certain subjectivity of the observer. The accuracy of numerical data as revealed by the mean residuals of parallel measurements by different observers ranged from 0.5 % to 5.5 %. The results indicated a high degree of intraspecific variability. The test sizes of the individual species were log-normally distributed and varied among the stations. Parameters not related to the growth of the individuals, i.e. flatness of the tests, dimensions of the second-youngest chamber, proloculus, umbilical and pore diameter, sinistral–dextral coiling, and umbilical boss size, were recognized as being species-distinctive in combination. They may well supplement qualitative criteria that were commonly used for species discrimination such as a lobate outline, a subacute or rounded peripheral margin, or the degree of ornamentation on the spiral and umbilical sides. The averages of the measured parameters were often lower than the range of previously published values, mainly because the latter were retrieved from a few adult specimens and not from the whole assemblage as in the present approach. We conclude that the unprecedented high proportions of Ammonia beccarii in the northern Adriatic may well be artificial. A robust species identification without genetic analyses is possible by considering designated biometric parameters. This approach is also applicable to earlier literature data, and their re-assessment is critical for a correct denomination of recent genotypes.
Highlights
Species of the genus Ammonia Brünnich (1772) are deemed important members of benthic foraminiferal assemblages in intertidal to outer shelf environments worldwide (Murray, 1991)
Ammonia parkinsoniana, Ammonia tepida, and Ammonia veneta were recognized in the living fauna, and Ammonia bellaria n. sp. is described for the first time
Ammonia beccarii was only found in the dead assemblage
Summary
Species of the genus Ammonia Brünnich (1772) are deemed important members of benthic foraminiferal assemblages in intertidal to outer shelf environments worldwide (Murray, 1991). They show significant proportions in both living faunas and dead assemblages Some Ammonia species show a high tolerance to salinity and temperature variations in laboratory experiments and natural environments (Bradshaw, 1961, 1968; Stouff et al, 1999a) They may stand only moderate levels of organic carbon enrichment, avoid hypoxia, or fall into dormancy under anoxic conditions (de Chanvalon et al, 2015; LeKieffre et al, 2017; Bouchet et al, 2021). Taxonomical, distributional, and ecological investigations prevailed but only a few Ammonia species names were
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