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Zooid Morphology and Molecular Phylogeny of the Graptolite Rhabdopleura Annulata (Hemichordata, Pterobranchia) from Heron Island, Australia

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Zooid Morphology and Molecular Phylogeny of the Graptolite Rhabdopleura Annulata (Hemichordata, Pterobranchia) from Heron Island, Australia Canadian Journal of Zoology Zooid morphology and molecular phylogeny of the graptolite Rhabdopleura annulata (Hemichordata, Pterobranchia) from Heron Island, Australia Journal: Canadian Journal of Zoology Manuscript ID cjz-2020-0049.R2 Manuscript Type: Article Date Submitted by the 16-Oct-2020 Author: Complete List of Authors: Ramirez Guerrero, Greta; Université de Montréal, Sciences biologiques Kocot, Kevin; The University of Alabama System Cameron, DraftChristopher; Université de Montréal, Sciences biologiques Is your manuscript invited for consideration in a Special Zoological Endeavors Inspired by A. Richard Palmer Issue?: Rhabdopleura annulata, Pterobranchia, graptolite, rhabdopleurid, Keyword: Australia, PHYLOGENY < Discipline, HEMICHORDATA < Taxon © The Author(s) or their Institution(s) Page 1 of 21 Canadian Journal of Zoology Zooid morphology and molecular phylogeny of the graptolite Rhabdopleura annulata (Hemichordata, Pterobranchia) from Heron Island, Australia1 Greta M. Ramírez-Guerrero*, Kevin M. Kocot+, and Christopher B. Cameron* * Université de Montréal, Département de sciences biologiques, C.P. 6128, Succ. Centre-ville, Montréal, QC, H3C 3J7, Canada. [email protected]; [email protected] + The University of Alabama and Alabama Museum of Natural History, 500 Hackberry Lane, Tuscaloosa, AL 35487, USA. [email protected] Draft 1This article is one of a series of invited papers arising from the symposium “Zoological En- deavours Inspired by A. Richard Palmer” that was co-sponsored by the Canadian Society of Zo- ologists and the Canadian Journal of Zoology and held during the Annual Meeting of the Cana- dian Society of Zoologists at the University of Windsor, Windsor, Ontario, 14–16 May 2019. 1 © The Author(s) or their Institution(s) Canadian Journal of Zoology Page 2 of 21 Ramírez-Guerrero, G.M., Kocot, K., and Cameron, C.B. Zooid morphology and molecular phylogeny of Rhabdopleura annulata from Heron Island, Australia. ABSTRACT Rhabdopleura is one of the longest surviving animal genera. The five-known species are the only living Graptolithina, a group well known from their diverse Paleozoic fossil record. Here we add information on the soft bodied zooids and molecular phylogenetics of Rhabdopleura annulata Norman, 1921, which was previously only known from its tubes. Tubes and zooids were collected from Heron Island, Australia. Zooids have a single pair of tentaculated arms. Dark pigment granules are found throughout the body, and particularly dense in the pair of arms and the anterior lip of the cephalic shield. ColoniesDraft grow encrusted in and on coral debris. The tubes are either creeping or erect, but no stolon has been found. Inside of the coral matrix lacunae, the tube cortex formed a parchment-like wallpaper. Phylogenetic analysis based on combined 18S+16S rRNA sequences placed R. annulata as sister to the remaining rhabdopleurids, albeit with weak support. The biogeographic range of R. annulata extends from Indonesia to Tasmania, and New Zealand. Its occurrence on Heron Island does not extend this range, but highlights that rhabdopleurids may be more common, and in shallower waters, than previously appreciated, permitting further studies that may shed light on graptolite paleobiology. Key words: Rhabdopleura annulata, pterobranch, graptolite, rhabdopleurid, Australia. 2 © The Author(s) or their Institution(s) Page 3 of 21 Canadian Journal of Zoology INTRODUCTION Pterobranchs represent one of the two clades that form the phylum Hemichordata. This class of tube-dwelling organisms includes all fossil forms known as graptolites, as well as living representatives from the genera Atubaria, Cephalodiscus and Rhabdopleura. The first report of Rhabdopleura was made in the description of the living species R. normani by Allman (1869), who collected it from dredging in an archipelago in Scotland. Originally considered a bryzoan, Rhabdopleura is now recognized as an extant member of the subclass Graptolithina (class Pterobranchia), and includes five known living species and several fossil forms. The most recently described living species include R. annulata Norman, 1921 and R. recondita Beli, Cameron and Piraino, 2018. The taxonomic description of R.Draft annulata is based on the tubarium structure. Nothing was previously known about its zooid morphology, or its molecular sequences, limiting our abil- ity to understand the evolution of the species and rhabdopleurids in general. Additional rhabdopleurid sequence data are particularly needed because the clade has long branch length in 18S, 16S, mitochondrial, and phylogenomic data sets (Halanych 1995; Cameron et al. 2000; Cannon et al. 2013; Beli et al. 2018; Li et al. 2019). To contribute to the knowledge of this ge- nus, here we describe the tubes and zooids of R. annulata from the Great Barrier Reef and in- clude a new sequence for this species to construct a phylogeny of the genus. MATERIALS AND METHODS Samples were collected by snorkeling at ~50 m from shore in less than 1 m of water off Heron Island, Queensland, Australia (approximately 23° 26.43' S, 151° 54.70' W) in February 2014. Colonies were found growing in a calcareous matrix where the algae Amphiroa was dominant, 3 © The Author(s) or their Institution(s) Canadian Journal of Zoology Page 4 of 21 some colonies were possible to isolate from the substratum. Specimens containing tubes and zo- oids were fixed in 95% ethanol and 2.5% glutaraldehyde in filtered sea water (with the latter transfer to 70% ethanol) and stored at room temperature. Other zooids were preserved in RNAlater or placed directly into Ambion RNAqueous lysis buffer for RNA extraction and stored at -80°C. RNA extraction, transcriptome library preparation and sequencing, and mining of se- quence regions of interest from the transcriptomes was performed as described in Li et al. (2018). The raw transcriptome reads are available on NCBI SRA under accession number SRR11101525. Rhabdopleura sequences from other species were obtained from GenBank (Table 1). These sequences include R. normani from Bermuda (Halanych 1995; Worsaae et al. 2012), R. compacta Hincks, 1880 from the UnitedDraft Kingdom (Perseke et al. 2011), R. recondita from Italy (Beli et al. 2018), and two Rhabdopleura sp. collected from Florida and Iceland (Cannon et al. 2013). Other hemichordates were sampled including Cephalodiscus fumosus John, 1931 from Antarctica, and Saccoglossus pusillus Ritter, 1902 and Harrimania planktophilus Cameron, 2002 from British Columbia, Tergivelum cinnabarinum Priede, Osborn, Gebruk, Jones, Shale, Rogacheva and Holland, 2012 and Yoda purpurata Priede, Osborn, Gebruk, Jones, Shale, Rogacheva and Holland, 2012 from the Mid-Atlantic Ridge, Balanoglossus carnosus Müller in Spengel, 1893 from Japan, and Ptychodera flava Eschscholtz, 1825 from French Polynesia. An echinoderm (Odontaster validus Koehler, 1906) was also sampled and the cephalochordate (Branchiostoma lanceolatum (Pallas, 1774)) was used to root the tree. Sequences for 16S and 18S from all those species were aligned with MAFFT 7.407 using the default settings. Ambiguously aligned regions were trimmed with Gblocks 0.91b (b1 = half the number of sequences plus one, b2 = b1, b3 = 8, b4 = 2, b5 = a). Phylogenetic analyses were 4 © The Author(s) or their Institution(s) Page 5 of 21 Canadian Journal of Zoology conducted in RAxML 8.2.4 with the “-f a” flag, which specifies a search for best scoring ML tree and a rapid bootstrap analysis in one program run. Each matrix was partitioned by gene and analyzed with the GTRGAMMA model. Nodal support was assessed with the appropriate number of rapid bootstraps (-N autoMRE). For the combined analysis of 16S+18S, the matrix was partitioned by gene. TAXONOMY Class Pterobranchia Lankester, 1877 Subclass Graptolithina Bronn, 1849 Family Rhabdopleuridae Harmer, 1905 Genus Rhabdopleura Allman, 1869 Draft Type species: Rhabdopleura normani Allman, 1869 Diagnosis: Tubarium consist of basal creeping tubes with regular zigzag sutures, and parallel erect tubes with irregular fusellar rings that slightly widen in length. A black stolon system connects the tripartite zooids allowing movement along the erect tubes. Zooids possess a single pair of arms bearing ciliated tentacles and a U-shaped gut. Rhabdopleura annulata Norman, 1921 Fig. 1. 5 © The Author(s) or their Institution(s) Canadian Journal of Zoology Page 6 of 21 Neotypes. Field numbers KK254.2G, KK254.3G and KK254.5E from Heron Island, Australia, deposited in the Alabama Museum of Natural History. Diagnosis. Encrusting colonies with isolated erect tubes with irregular fuselli and zigzag patterned creeping tubes. Pronounced external projections of fusellar rings frequently show a T- shape. Zooids with brown pigments, especially abundant in the pair of tentacled arms. Description. Colony consists of isolated tubes and tubes of varying length embedded within a calcium carbonate coral matrix. Erect tubes with up to 45 irregular full fusellar rings with an average distance of 40 μm (ranging from 30 to 50 μm). Creeping tubes with regularly spaced fuselli forming a zig-zag pattern. Tubes Draftslightly conical with internal diameter from 150-140 μm at the base and 170-190 μm distally. Erect tube lengths and the corresponding number of fusellar rings varies considerably. Erect tubes grow at right angles from the creeping tube and do not branch. Rough external projections of the fusellar rings very clearly marked measuring up to 35 μm in thickness from the smooth internal surface, resulting in a maximal external
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