Chaetonotus triacanthus and Heteroxenotrichula texana two new chaetonotid gastrotrichs from the Gulf of Mexico

The first paucitubulatine chaetonotid gastrotrichs are reported from the Gulf of Mexico. Chaetonotus triacanthus n. sp. and Heteroxenotrichula texana ri. sp. are described from sandy sediment collected along the northern part of Padre Island, Texas, U.S.A. C. triacanthus is characterized by short lamella-bearing spines on the dorsal side of head and neck, three long spines on the dorsal posterior end, and a pair of three-keeled scales on the furcal base. C. texana belongs to the "subterranea"-species group, and is characterized by pedunculated scales that cover the posterior half of the ventral surface. The gastrotrich fauna of the Gulf of Mexico is poorly known. To date, six genera, Acanthodasy, Dolichodasys, Macrodasys, Neodasys, Tetranchyroderma, and Turbanella and three species, Dolichodasys carolinensis, D. elongatus, and Turbanella ocellata have been reported from the region (Fox & Powell, 1986; Friauf, 1968; Meyers et al., 1987, 1988; Ruppert & Shaw, 1977). In the spring of 1992, with the aim of assessing the gastrotrich diversity of the Gulf of Mexico, an extensive qualitative survey along the coasts of Alabama, Mississippi, Louisiana, and Texas was initiated. Herein two new paucitubulatine chaetonotids, the first being reported from the region, are described and figured. A more comprehensive account on the species encountered to date is in preparation. MATERIALS AND METHODS On 16 August 1992, 500 g of intertidal sand were obtained by scooping sediment from the bottom and side of a 0.5-m-deep hole dug in the beach on North Padre Island, Texas, U.S.A. (Fig. 1). Similarly, sediment was obtained on 10 March 1993 from the public beach of Port Aransas, Texas. In both cases, the tide was incoming. Within 48 h, the samples were brought to the laboratory, kept in a coldroom at 14?C, and processed within one week. Gastrotrichs were extracted daily from the sediment by the narcotization-decantation technique of Higgins & Thiel (1988), using a 7% MgC12 solution. Living, relaxed specimens were observed, using differential-interference contrast, under a Microphot-FXA Nikon microscope. At that time, gastrotrichs were photographed and/or re' I thank Dr. J. W. Fleeger for his support throughout the study. Thanks also are due Dr. W. D. Hummon for providing me with important information on gastrotrichs from Grand Isle, Louisiana. Special thanks go to Mrs. Candace Conn for bringing in the first sample of sand from North Padre Island, Texas. Drs. M. Balsamo, W. A. Evans, W. D. Hummon, P. Tongiorgi, and two anonymous reviewers have improved the manuscript with invaluable comments. Mr. Ron Bouchard helped to assemble the figures. Publication costs, in part, are being met by a grant from the Spencer-Tolles Fund of the American Microscopical Society. TRANS. AM. MICROSC. Soc., 113(1): 15-21. 1994. ? Copyright, 1994, by the American Microscopical Society, Inc. This content downloaded from 157.55.39.127 on Tue, 28 Jun 2016 07:01:23 UTC All use subject to http://about.jstor.org/terms TRANS. AM. MICROSC. SOC.