Murrayinella murrayi (Heron-Allen & Earland) and Schackoinella globosa (Millett) are two small (maximum diameter about 110-180 μm) benthic foraminifers, mainly observed in coastal Indo-Pacific waters (Loeblich & Tappan, 1994). They are common in the inner neritic assemblages of Phetchaburi (Thailand Gulf) (Melis & Violanti, 2006), and are also present in pelitic bottoms of the Khao Lak coastal area (Southwestern Thailand, Andaman Sea), affected by the December 26, 2004 tsunami. The two taxa are very similar, poorly described, reported in literature under different generic names and the family attribution of both is controversial. Both species have a perforate wall, trochospirally coiled tests with few globose to subangular chambers and a thickly tuberculate to spinose umbilical area. In order to define unambiguous criteria for the separation of the two taxa, a detailed morphological study has been carried out on well preserved tests, selected from Phetchaburi and Khao Lak assemblages. Quantitative analyses evidenced a different areal distribution of two specie in the Phetchaburi coastal area. M. murrayi is more frequent in the shallowest northern and central bottoms, near river mouths, and it appears to be tolerant of salinity variability. Instead, S. globosa characterizes the southern and deeper sites, is less affected by fluvial run-off (Melis & Violanti, 2006), and reaches its highest frequencies in diatoms-rich assemblages. This association and the morphology of the umbilical area suggest a herbivorous diet for S. globosa, in comparison with other species, cracking diatom frustules on umbilical tubercles (Austin et al., 2005). Studies in progress on the Khao Lak area, in normal marine waters, are supporting the ecologic interpretations of the two taxa made on the Phetchaburi assemblages.
Murrayinella murray (Heron-Allen & Earland) and Schackoinella globosa (Millett): morphology, taxonomy and inferred ecology
VIOLANTI, Donata;
2007-01-01
Abstract
Murrayinella murrayi (Heron-Allen & Earland) and Schackoinella globosa (Millett) are two small (maximum diameter about 110-180 μm) benthic foraminifers, mainly observed in coastal Indo-Pacific waters (Loeblich & Tappan, 1994). They are common in the inner neritic assemblages of Phetchaburi (Thailand Gulf) (Melis & Violanti, 2006), and are also present in pelitic bottoms of the Khao Lak coastal area (Southwestern Thailand, Andaman Sea), affected by the December 26, 2004 tsunami. The two taxa are very similar, poorly described, reported in literature under different generic names and the family attribution of both is controversial. Both species have a perforate wall, trochospirally coiled tests with few globose to subangular chambers and a thickly tuberculate to spinose umbilical area. In order to define unambiguous criteria for the separation of the two taxa, a detailed morphological study has been carried out on well preserved tests, selected from Phetchaburi and Khao Lak assemblages. Quantitative analyses evidenced a different areal distribution of two specie in the Phetchaburi coastal area. M. murrayi is more frequent in the shallowest northern and central bottoms, near river mouths, and it appears to be tolerant of salinity variability. Instead, S. globosa characterizes the southern and deeper sites, is less affected by fluvial run-off (Melis & Violanti, 2006), and reaches its highest frequencies in diatoms-rich assemblages. This association and the morphology of the umbilical area suggest a herbivorous diet for S. globosa, in comparison with other species, cracking diatom frustules on umbilical tubercles (Austin et al., 2005). Studies in progress on the Khao Lak area, in normal marine waters, are supporting the ecologic interpretations of the two taxa made on the Phetchaburi assemblages.
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