Rotifera of the Gulf of Mexico

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Sørensen, M. V. 2009. Rotifera of the Gulf of Mexico, Pp. 533 537 in Felder, D.L. and D.K. Camp (eds.), Gulf of Mexico Origins, Waters, and Biota. Biodiversity.

2 Sørensen, M. V Rotifera of the Gulf of Mexico, Pp in Felder, D.L. and D.K. Camp (eds.), Gulf of Mexico Origins, Waters, and Biota. Biodiversity. Texas A&M University Press, College Station, Texas. 27 Rotifera of the Gulf of Mexico Martin V. Sørensen Rotifera is a phylum of microscopic metazoans, characterized by the presence of cephalic ciliary bands, called the corona or wheel organ, and a complex pharyngeal apparatus, referred to as the mastax. The general appearance of a rotifer varies greatly, but typically the body can be divided into a head, a trunk, and a foot region. The head carries the ciliary wheel organ that is used for feeding and locomotion. A ventral mouth leads to the pharynx with the mastax that consists of chitinous jaws, called the trophi, and surrounding musculature. A short esophagus connects the pharynx with the stomach and the gut. The latter terminates into a dorsal cloaca posteriorly on the trunk. A flexible foot is often present posteriorly or ventrally on the trunk, and in most species it terminates into 2 toes with adhesive glands. Unlike in most other metazoans, the rotifer integument lacks an outer protective cuticle. Instead, their syncytial epidermal cells have an intracellular protein lamina located in the cytoplasm close to the apical membrane. This special feature is shared with their close relatives, the endoparasitic acanthocephalans. All rotifers are dioecious, but in many species the reproduction is solely based on parthenogenesis (in subclass Bdelloidea) or on a cyclic switch between parthenogenesis and gamogenesis. During the latter, short- lived and strongly reduced haploid males are present in a short period (Ruttner- Kolisko 1974, Nogrady, Wallace, and Snell 1993, Wallace 2002). Rotifers mostly inhabit freshwater, but some taxa are present in marine and brackish habitats as well. Only Rotifera. After Jennings about species are known as exclusively marine. Marine rotifers may be planktonic, periphytic, epibenthic, or interstitial, but they are never found in soft sediments, and they have only rarely been recorded from depths below 30 m. Rotifers do not have any commercial importance, and as they often occur in relatively low numbers, their ecological importance must be considered as minor. The rotifers have been studied by scientists since the first microscopes were invented, but in the beginning they were grouped among the protozoans. More recently, they have been assigned to the obviously polyphyletic Aschelminthes, together with other pseudocoelomate taxa such as Gastrotricha, Nematoda, and Priapulida. However, today most studies support a close relationship between 533

3 534 ~ Rotifera Rotifera. After Jennings Rotifera. After Jennings Rotifera, Acanthocephala, Micrognathozoa, and Gnathostomulida, and the 4 taxa are usually united in a clade named Gnathifera (Ahlrichs 1995, Rieger and Tyler 1995, Giribet et al. 2000, Kristensen and Funch 2000, Sørensen et al. 2000). Rotifera consist of about 1900 described species, and the phylum can be divided into 2 classes: the Eurotatoria and the Pararotatoria. The latter contains only 3 species that are distributed between the 2 genera Seison and Paraseison. Common for all Seisonidae is that they are commensals or ectoparasites on the leptostracan Crustacea Nebalia (Ricci, Melone, and Sotgia 1993, Segers and Melone 1998, Sørensen, Funch, and Segers 2005). The Eurotatoria consist of the subclasses Bdelloidea and Monogononta. The Bdelloidea are characterized by reproduction based solely on parthenogenesis, and the group is only rarely present in marine environments. The Monogononta comprises more than 1500 species and display by far the greatest morphological disparity (Nogrady, Wallace, and Snell 1993, Melone et al. 1998, Sørensen 2002). The endoparasitic acanthocephalans have traditionally been considered a sister group to the Rotifera, but recent studies indicate that they could be a rotifer ingroup. This, however, still needs confirmation from further morphological as well as molecular studies (Ahlrichs 1995, Garey et al. 1998, Giribet et al. 2000, Sørensen et al. 2000). Information on rotifers from the Gulf of Mexico (GMx) is scarce and restricted to a few reports from the Texas coastline near Corpus Christi (Holland et al. 1975, Lee, Macko, and Clereszko 1981, Tunnell and Alvarado, 1996) and 2 more thorough studies from the north coast of Florida near Fort Walton (Turner 1990, 1993), resulting in a total of 23 rotifer species (see the taxonomic summary). None of the recorded species are endemic for the Gulf of Mexico, and endemism is generally uncommon for marine rotifers. When it apparently occurs, it is probably primarily due to our limited information about distributional ranges for marine rotifers, rather than examples of true endemism. Instead, there is a high fraction of cosmopolitan species. Several of the recorded species display a peculiar and apparently extremely patchy distribution. For example, Encentrum striatum has been recorded from the Black Sea and the Gulf of Mexico only. This is, however, not uncommon for marine rotifers and again, it is merely a reflection of our insufficient information about their distributional patterns. Many of the recorded species, such as Encentrum marinum, Notholca salina, and Trichocerca marina are common marine inhabitants, whereas others are euryhaline, brackish- water species. Typical euryhaline species are Brachionus plicatilis, Colurella adriatica, C. colurus, Lecane inermis, L. luna, and Notholca bipalium. A few of the recorded species, inclusive Brachionus plicatilis, Colurella salina, and Proales minima, have also been recorded from inland salt springs. The latter species is, however, probably synonymous with Proales halophila, which is a common brackish- water species (De Smet 1996). Abbreviations The following abbreviations are used in this chapter s checklist: ben = benthic; bsl = beach and shoreline; cep = coastal surface and epipelagic; ins = interstitial; plk = planktonic; sft = soft substrates (mud, sands, clays); svg = submergent vegetation. References 1. Ahlrichs, W. H Ultrastruktur und Phylogenie von Seison nebaliae (Grube 1859) und Seison annulatus (Claus 1876). Cuvillier Verlag, Göttingen, Germany.

4 Sørensen ~ De Smet, W. H The Proalidae (Monogononta). Pp in H. J. F. Dumont ed., Guides to the Identification of the Microinvertebrates of the Continental Waters of the World, Vol. 9, Rotifera, Vol. 4. SPB Academic Publishing, Amsterdam. 3. Garey, J. R., A. Schmidt- Rhaesa, T. J. Near, and S. A. Nadler The evolutionary relationships of rotifers and acanthocephalans. Hydrobiologia 387 / 388: Giribet, G., D. L. Distel, M. Polz, W. Sterrer, and W. C. Wheeler Triploblastic relationships with emphasis on the acoelomates and the position of Gnathostomulida, Cycliophora, Plathelminthes, and Chaetognatha: a combined approach of 18S rdna sequences and morphology. Systematic Biology 49: Holland, J. S., N. J. Maciolek, R. D. Kalke, and C. H. Oppenheimer A benthos and plankton study of the Corpus Christi, Copano, and Aransas Bay Systems. III. Final Report to Texas Water Development Board. Center for Coastal Studies, Corpus Christi, Texas. 6. Kristensen, R. M., and P. Funch Micrognathozoa: a new class with complicated jaws like those of Rotifera and Gnathostomulida. Journal of Morphology 246: Lee, W. Y., S. A. Macko, and L. S. Clereszko Toxic effects of cembranolides derived from octocorals on the rotifer Brachionus plicatilis. Journal of Experimental Marine Biology and Ecology 54: Melone, G., C. Ricci, H. Segers, and R. L. Wallace Phylogenetic relationships of phylum Rotifera with emphasis on the families of Bdelloidea. Hydrobiologia 387 / 388: Nogrady, T., R. L. Wallace, and T. W. Snell Rotifera: Biology, Ecology and Systematics. Pp in H. J. F. Dumont, ed. Guides to the Identification of the Microinvertebrates of the Continental Waters of the World, Vol. 4, Rotifera, Vol. 1. SPB Academic Publishing, Amsterdam. 10. Ricci, C., G. Melone, and C. Sotgia Old and new data on Seisonidea (Rotifera). Hydrobiologia 255 / 256: Rieger, R. M., and S. Tyler Sister- group relationship of Gnathostomulida and Rotifera Acanthocephala. Invertebrate Biology 114: Ruttner- Kolisko, A Plankton rotifers. Biology and Taxonomy. Die Binnengewässer (suppl.) 16: Segers, H., and G. Melone A comparative study of trophi morphology in Seisonidea (Rotifera). Journal of Zoology, London 244: Sørensen, M. V., P. Funch, E. Willerslev, A. J. Hansen, and J. Olesen On the phylogeny of the Metazoa in the light of Cycliophora and Micrognathozoa. Zoologischer Anzeiger 239: Sørensen, M. V On the evolution and morphology of the rotiferan trophi, with a cladistic analysis of Rotifera. Journal of Zoological Systematics and Evolutionary Research 40: Sørensen, M. V., P. Funch, and H. Segers On a new Seison Grube, 1861 from coastal waters of Kenya, with a reappraisal of the classification of Seisonida (Rotifera). Zoological Studies 44: Tunnell, J. W. Jr., and S. A. Alvarado Checklist of species within Corpus Christi Bay National Estuary Program Study Area: references, habitats, distribution, and abundance. Vol. 4. Texas A&M University, Corpus Christi, Texas. 18. Turner, P. N Some interstitial Rotifera from a Florida, USA, beach. Transactions of the American Microscopical Society 109: Turner, P. N Distribution of rotifers in a Floridian saltwater beach, with a note on rotifer dispersal. Hydrobiologia 255 / 256: Wallace, R. L Rotifers: exquisite metazoans. Integrated and Combined Biology 42: Submitted: August 2005 Accepted: December 2005

5 536 ~ Rotifera Taxonomic summary for Rotifera of the Gulf of Mexico. Component subgroups Total species Number endemic species Number cosmopolitan species Subclass Bdelloidea Subclass Monogononta Order Collothecacea 1 0 Order Flosculariacea Order Ploima Total species Checklist of Rotifera from the Gulf of Mexico. Taxon Habitat- Biology Depth (m) Overall geographic range GMx range References / Endnotes Class: Eurotatoria Subclass: Bdelloidea Family: Philodinidae Rotaria sp. ben, bsl, sft 0 ne 19 Subclass: Monogononta Order: Collothecacea Family: Collothecidae Collotheca sp. svg 0 ne 19 Order: Flosculariacea Family: Testudinellidae Testudinella obscura Althaus, 1957 ben, bsl, sft 0 Asov Sea, Black Sea, GMx ne 19 Order: Ploima Family: Brachionidae Brachionus angularis (Gosse, 1851) ben, bsl, sft 0 Cosmopolitan ne 19 Brachionus plicatilis (Müller, 1786) ben, bsl, sft 0 Cosmopolitan ne, nw 5, 7, 17,19 Keratella americana Carlin, 1939 ben, bsl, sft 0 North and South America ne 19 Notholca bipalium (Müller, 1786) ben, bsl, sft 0 Cosmopolitan ne 18 Notholca japonica kisselevi Kutikova, 1970 ben, bsl, sft 0 Sea of Othotsk, GMx ne 19 Notholca salina (Focke, 1961) ben, bsl, sft 0 Cosmopolitan ne 18 Family: Dicranophoridae Encentrum marinum (Dujardin, 1841) ben, bsl, sft 0 Cosmopolitan ne 18 Encentrum striatum Althaus, 1957 ins, bsl, sft 0 Black Sea, GMx ne 18 Family: Lecanidae Lecane cf. arcuata (Bryce, 1891) svg 0 Cosmopolitan ne 18 Lecane inermis (Bryce, 1892) ben, bsl, sft 0 Cosmopolitan ne 18, 19 Lecane luna (Müller, 1776) ben, bsl, sft 0 Cosmopolitan ne 18 Family: Lepadellidae Colurella adriatica (Ehrenberg, 1831) ben, bsl, sft 0 Cosmopolitan ne 19 Colurella colurus (Ehrenberg, 1830) ben, bsl, sft 0 Cosmopolitan ne 18, 19 Colurella dicentra (Gosse, 1887) ben, bsl, sft 0 Cosmopolitan ne 18 Colurella salina (Althaus, 1957) ben, bsl, sft 0 Germany, GMx ne 19 Family: Lindiidae Lindia sp. ins, bsl, sft 0 ne 19 Family: Proalidae Proales minima (Montet, 1915) ins, bsl, sft 0 Europe, GMx ne 19 1

6 Sørensen ~ 537 Checklist of Rotifera from the Gulf of Mexico. (continued) Taxon Habitat- Biology Depth (m) Overall geographic range GMx range References / Endnotes Family: Notommatidae Cephalodella gibba (Ehrenberg, 1938) ben, bsl, sft 0 Cosmopolitan ne 19 Family: Trichocercidae Trichocerca marina (Daday, 1890) plk, cep 0 Holarctic ne 18, 19 Trichocerca taurocephala (Hauer, 1931) ins, bsl, sft 0 Cosmopolitan ne 18, 19 1 Proales minima is probably synonymous with P. halophila (see De Smet 1996)

Introduction to. Kinorhyncha and Gnathostomulida

Introduction to. Kinorhyncha and Gnathostomulida Introduction to Kinorhyncha and Gnathostomulida Block course on Zoology and Evolution, Biozentrum, Uni. Basel Martin V. Sørensen Associate Professor and curator of microscopic invertebrates Dias 1 Natural