Aquatic Botany 96 (2012) 63–66 Contents lists available at SciVerse ScienceDirect Aquatic Botany j ourna l ho me page: www.elsevier.com/locate/aquabot Short communication Starch grain morphology of the seagrasses Halodule wrightii, Ruppia maritima, Syringodium filiforme, and Thalassia testudinum Stephanie Peek ∗ , Mark T. Clementz Department of Geology and Geophysics, Dept. #3006, 1000 E. University Ave, University of Wyoming, Laramie, WY 82071, USA a r t i c l e i n f o Article history: Received 22 July 2011 Received in revised form 1 October 2011 Accepted 4 October 2011 Available online 12 October 2011 Keywords: Starch grain Morphology Seagrass Halodule wrightii Ruppia maritima Syringodium filiforme Thalassia testudinum a b s t r a c t Starch grains are a ubiquitous component of plants that have been used in tandem with phytoliths, pollen, and macrofossils to reconstruct past floral diversity. This tool has yet to be fully explored for aquatic plants, specifically seagrasses, which lack phytoliths and are rarely preserved as macrofossils or pollen. If starch grains in seagrasses are morphologically distinct, this method has the potential to improve seagrass identification in the fossil record in such cases where its starch is preserved (e.g. scratches and occlusal surfaces of tooth enamel from seagrass consumers). The goals of this study were twofold: (1) to determine if starch is present in seagrass material and (2) to assess how starch grain morphology differs between different seagrasses. This study focused on four abundant and ecologically distinct seagrasses from the Caribbean: Halodule wrightii, Ruppia maritima, Syringodium filiforme, and Thalassia testudinum. Starch grains were observed in all species except S. filiforme. Grains from H. wrightii are typically observed in side-on orientation, are sub- round to angular, and are fairly small (3-19 m, end-on). Grains of R. maritima are small spherical grains (4–8 m) that have a centric hilum and a straight extinction cross with a median angle between the arms of 90 ◦ . Grains from T. testudinum are large (9–31 m, end-on), conical in side-on and round/sub-round in end-on orientation, have a slightly eccentric hilum with an obvious particle, and prominent lamellae. Visual assessment and comparative statistics demonstrate that the morphology of starch grains from T. testudinum, R. maritima, and H. wrightii are significantly different. With more extensive research, there is potential for the positive identification of starch grains from an unknown seagrass. The ability to identify seagrass from starch grains could facilitate the identification of seagrasses in the fossil record and supply information on seagrass evolution and distribution, climate effects on seagrass distribution, and the diets of seagrass consumers. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Fossil evidence of seagrasses is known since the late Creta- ceous but fossil localities are limited to only a handful of sites (Brasier, 1975; Lumbert et al., 1984), as plant remains of seagrasses are rare and nearly impossible to identify without the preserva- tion of reproductive parts (Brasier, 1975). Additionally, seagrasses do not have phytoliths and their pollen is not preserved because it lacks exine (Brasier, 1975; Domning, 1982). For these reasons, the identification of fossil seagrasses primarily relies on associ- ated fauna (e.g. foraminifera, mollusks, echinoids, crustaceans, and sirenians) and distinctive sedimentary features of seagrass commu- nities (Brasier, 1975). However these identification methods have limitations, some of which could be overcome if starch grains from ∗ Corresponding author. Tel.: +1 307 766 6048; fax: +1 307 766 6679. E-mail addresses: speek@uwyo.edu (S. Peek), mclemen1@uwyo.edu (M.T. Clementz). different species of seagrasses are distinct and are preserved in the fossil record. Starch is the energy source of a plant and, while present in all plant parts, it is most heavily concentrated in storage organs (i.e. roots, tubers, rhizomes, fruits, and seeds) (Gott et al., 2006). Starch grains occur in a variety of characteristic forms that can be used to identify plants to family and genus level, sometimes even species (Reichert, 1913). Starch is also highly resistant to alteration, which has enabled it to be preserved in a variety of climate regions rang- ing from arid to tropical and recovered from several substrates, including fecal material (Barton and Matthews, 2006); cracks, pits, and crevices in pottery, millstones, or other grinding tools and associated soils recovered from archaeological sites (Samuel, 1996; Piperno and Holst, 1998; Lentfer et al., 2002; Piperno et al., 2004; Barton and Matthews, 2006; Perry et al., 2007); and pyritized starch grains have even been found in rocks of Eocene age (Wilkinson, 1983). Unaltered starch grains could be preserved in the fossil record if they are protected from destructive elements such as microorganisms, soil moisture, soil pH, and oxygen following rapid 0304-3770/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.aquabot.2011.10.001