A New Family of Arthrotardigrada (Tardigrada: Heterotardigrada) from the Atlantic Coast of Florida, U.S.A.

Abstract

A new interstitial arthrotardigrade, Renaudarctus psammocrypius n. gen., n. sp.. Is described from high-energy marine beaches of Fort Pierce and Boca Raton, Florida. It is found in sechment consisting of stratified layers of coarse quartz sand and shell hash. The tardigrade is distinguished particularly by its dorsal cuticular plates, toes, and claw structure. The Renaudarctidae is established as a new family in the order Arthrotardigrada. A recently described tardigrade, Neostygarctus acanthophorus from a marine cave in Italy, originally placed in the family Stygarctidae, is included in the Renaudarctidae based on toe and claw structure. The phylogenetic relationships of Renaudarctidae to other famihes in Heterotardigrada are discussed. Seven other species of tardigrades found with the new species included: Parasttjgarclus sterreri, Stygarctus gourbaultae, Halechiniscus remanei, Raiarctus colurus, Raiarctus sp., Tanarctus lauricus, and Batillipes bullacaudatus. Only B. bullacaudatus and H. remanei have been reported from the U.S.A. previously. The vertical and horizontal distribution of the tardigrades in the beaches appears to be related to granulometry more than to other physical or chemical factors, including depth in the beach.Since the discovery of the first marine tardigrade, Microlyda Dujardin, 1851, most marine biologists have considered these microscopic metazoans to be a rare component of the marine ecosystem. The first monograph on this phylum (Marcus, 1929) recorded only six marine species, Schulz (1935,1951, 1955) described several new species. Since 1955, the most significant taxonomic contribution has been that of Renaud-Mornant, who has produced 32 publications and described 9 genera and 27 species. In a recent review of the marine Tardigrada (see Renaud-Mornant, 1982), 22 genera of Heterotardigrada were noted. These animals, a total of 56 species, have been found in a wide variety of marine habitats from the deep sea to tropical beaches. ' The material was obtained through the kind cooperation of the Smithsonian Marine Station at Link Port, Florida. We especially acknowledge the technical assistance of William Lee, of the Smithsonian Marine Station at Link Port, who assisted with sampling and processing; the cooperation of Carolyn Gast, of the Department of Invertebrate Zoology, Smithsonian Institution, who prepared the illustrations; and the aid of Marie Wallace, also of the Department of Invertebrate Zoology, who assisted with sample processing and in the preparation of the manuscript. Our appreciation is also expressed to Horton H. Hobbs, Jr., who critically reviewed this manuscript and made many valuable suggestions.

The Mouth Cone and Mouth Ring of Echiniscus viridissimus Peterfi, 1956 (Heterotardigrada) with Comparisons to Corresponding Structures in Other Tardigrades

“…12). b 46 example, distinct mouth cones are present in Echiniscoides species (Kristensen & Hallas, 1980;D'Addabbo Gallo et al, 1992;Miller & Kristensen, 1999) and marine arthrotardigrades such as Renaudarctus (Kristensen & Higgins, 1984), halechiniscids (Grimaldi de Zio et al, 1995/96;Pollock, 1995;Chang & Rho, 1998;Jørgensen & Kristensen, 2001), and stygarctids (McKirdy, 1976). In addition, division of the mouth cone into anterior and posterior portions is more readily visible in some echiniscid genera than it is in Echiniscus viridissimus, where it is difficult to detect (Dewel, unpublished observations).…”

The metameric pattern of Hypsibius dujardini(Eutardigrada) and its relationship to that of other panarthropods

“…Extant tardigrade species inhabit marine, freshwater, and terrestrial habitats [10,11]. The metameric pattern of tardigrades consists of a head, housing a multilobed brain [12][13][14][15][16][17][18], and four segments bearing lobopodal legs [10,11,19,20]. Based on morphological similarities, a close relationship of Tardigrada with two other ancient lineages, Onychophora and Arthropoda, has long been acknowledged; the taxon Panarthropoda was erected in recognition of this relationship [10,12,[20][21][22][23].…”

“…By contrast, under the protocerebral hypothesis, there is no subesophogeal ganglion, because its existence would require the brain to be composed of at least two ganglia. A subesophageal ganglion was included in the brain anatomy interpretations of several studies [13,17,18,20,34]. However, most recent studies of tardigrade brain anatomy have not identified a subesophogeal ganglion [15,[35][36][37].…”

A new intertidal arthrotardigrade, Prostygarctus aculeatus gen. nov., sp. nov. (Tardigrada: Heterotardigrada) from the North of Portugal (Atlantic ocean)

“…However, the associations of the remaining families are still problematic. Hypothesizing phylogenetic relationships among these families, Kristensen and Higgins (1984a) suggest that Neostygarctidae should be merged with Renaudarctidae. Grimaldi de Zio et al (1987Zio et al ( , 1990Zio et al ( , 1992) opposed this view (based mainly on the presence/absence of digitate legs and eyes, shape of primary clavae, cirrophorus structure, and morphology of the pharyngeal apparatus), and supported the hypothesis that armoured arthrotardigrades should be split into the aforementioned families.…”