New observations on the Antarctic Asteromphalus darwinii/hookeri diatom species-complex (Asterolampraceae)

• Published in: Polar Biology
• Main Authors: Hallegraeff, Gustaaf, Leblanc, Karine
• Other Authors: Institute for Marine and Antarctic Studies Hobart (IMAS), University of Tasmania Hobart, Australia (UTAS), Institut méditerranéen d'océanologie (MIO), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Toulon (UTLN)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2023
• Subjects: [SDE.BE]Environmental Sciences/Biodiversity and Ecology; [SDE]Environmental Sciences; Antarc*; Antarctic; antarcticus; Polar Biology
• Online Access: https://hal.science/hal-04292684; https://hal.science/hal-04292684/document; https://hal.science/hal-04292684/file/s00300-023-03160-6.pdf; https://doi.org/10.1007/s00300-023-03160-6

Abstract Antarctic diatom populations of Asteromphalus hookeri and related species such as A. hyalinus and A. parvulus exhibit a highly variable number of hyaline rays ranging from 3 broad + 1 narrow (3 + 1) in the smallest valves, with 4 + 1 (27%) and 5 + 1 rays (35%) most common, and 6 + 1, 7 + 1, and rarely 8 + 1 rays only in larger cells. During December 1959 to April 1960 in the southern sector of the Atlantic Ocean, 6% of valves occurred as “double forms” with epitheca and hypotheca of the same cell exhibiting 4 + 1/3 + 1, 5 + 1/4 + 1, 6 + 1/5 + 1 and 7 + 1/6 + 1 ray combinations. Smaller cells (3 + 1, 4 + 1) always exhibited jagged separating lines in the central area, but larger cells (7 + 1, 8 + 1) had mostly smooth lines, and either jagged or smooth separating lines occurred in intermediate 5 + 1 and 6 + 1 forms, respectively. Epitheca and hypotheca of one and the same cell always exhibited jagged or smooth separating lines, but never mixtures. Observations of silica deposition during October to November 2011 around the Kerguelen Island plateau using the PDMPO fluorescent marker suggest that Asteromphalus separating lines play a key role in silica cell wall development. We discuss implications for taxonomy of what we designate as two highly variable and often confused and overlapping cold-water diatom taxa, A. darwinii (jagged separating lines; synonyms A. beaumontii, A. hyalinus, A. leboimei , A. parvulus, A. rossii ) and A. hookeri (smooth separating lines; synonyms A. antarcticus, A. buchii ).