Ontogeny of the jaws of monogonont rotifers: the malleate trophi of Rhinoglena and Proalides (Ploima, Epiphanidae)

Abstract

Information on the embryonic development of the malleate trophi in Epiphanidae (Rotifera, Monogononta, Ploima) is presented, based on scanning electron microscopy observations in Rhinoglena fertoeensis, R. frontalis, R. kutikovae, R. tokioensis, and Proalides tentaculatus, to contribute to the understanding of this structure of high evolutionary and functional relevance in Rotifera. The first observable and distinctly sclerotized structures were a double row of median transversal sclerites along the longitudinal axis, wherein the future unci, rostellar scleropili, cristae rami, and basal apophyses became recognizable. Fulcrum and manubria arose subsequently; the fulcrum sclerites were longitudinally ordered in a double layer. The rami chambers developed last as lamellar structures. Unci appeared as separate thin, elongate elements, the primary uncini, developing to uncus plates by transversal growth and apposition of sclerite material on the shafts of the uncini. The heads of the uncini showed their greatest development after fusion of their shafts into uncus plates. The interjacent spaces between the heads functioned as a mold, organizing bundles of sclerites which developed into the uniseriate, zigzag‐shaped cristae rami. The fulcrum attained its definite shape by elongation of the double layer of rod‐shaped sclerites into appressed sclerofibrillae. Manubria became visible as a proximal ridge of sclerites, whereupon a triangular lamella composed of crisscross‐oriented sclerites developed distally, growing out to the manubrial chambers. Ramus chambers originated from two longitudinal amorphous lamellae incorporating the median rami sclerites and closing from distal to proximal; subbasal chambers were formed before the basal chambers.

A data set on the distribution of Rotifera in Antarctica

“…Literature list: Nine additional papers were found to update the data set for the period 2015 to 2018: De Smet (2015), Iakovenko et al (2015), Sharov et al (2015), Zawierucha et al (2015), De Smet and Segers (2017), Gantait and Chandra (2017), Rochera et al (2017), Smykla et al (2018), andVelasco-Castrillón et al (2018). In addition, other 20 papers published before 2015 but reporting unidentified rotifers were included in the current data set: Steele et al (1994), Miller et al (1996, 2001, Vincent andJames (1996), McInnes et al (2001), Sinclair (2001), Sinclair andSjursen (2001), McInnes (2003), Sohlenius et al (2004), McInnes and Convey (2005), Barrett et al (2006), Cromer et al (2006), Newsham et al (2006), Nkem et al (2006), Ayres et al (2007), Sohlenius and Boström (2008), Simmons et al (2009), Yeates et al (2009), Hodgson et al (2010), Smyckla et al (2012.…”