Sarah Atherton

Acanthodasys caribbeanensis sp. n., a new species of Thaumastodermatidae (Gastrotricha, Macrodasyida) from Belize and Panama

Abstract We describe one new species of Acanthodasys (Gastrotricha, Macrodasyida, Thaumastodermatidae) collected from sublittoral sites around Carrie Bow Cay, Belize and Isla Colón in the Bocas del Toro archipelago, Panama. Though eight species of Acanthodasys are currently recognized, no species has yet been reported from the Caribbean. Acanthodasys caribbeanensis sp. n. is characterized by the lack of lateral adhesive tubes, the presence of ventrolateral adhesive tubes, and with cuticular armature in the form of both spineless and spined scales. The spineless scales are not elliptical as in other species of Acanthodasys, but are instead variable in shape and closely resemble the spineless scales of species of Diplodasys. Spined scales bear uniancres up to 50 µm long and are the largest reported in the genus. Uniancres are arranged dorsally around the mouth rim and distributed in five distinguishable columns. Adult size varies from 325–625 µm long.

Two new species of Musellifer (Gastrotricha: Chaetonotida) from Florida and Tobago and the systematic placement of the genus within Paucitubulatina

Abstract Two new species of marine Gastrotricha, Musellifer reichardti sp. nov. and Musellifer tridentatus sp. nov. (Chaetonotida: Paucitubulatina: Muselliferidae), are described from the Atlantic coast of Florida (USA) and the west coast of Tobago (Trinidad and Tobago), respectively. Both new species are peculiar in that they lack a muzzle bearing the mouth, which is a diagnostic character of the genus. They correspond well to the diagnosis of Musellifer in other morphological features, and genetic data from the 18S rDNA gene of M. reichardti sp. nov. further support the inclusion of the new species in the genus Musellifer. Musellifer reichardti sp. nov. is distinguished by the following combination of characters: blunt head with reduced muzzle; dorsal patches of naked cuticle bearing sensory cilia on either side of the head; ventral locomotory cilia restricted to the pharyngeal region; spined scales; caudal furca with naked adhesive tubes. The new species is a simultaneous hermaphrodite with posterior paired ovaries, paired testes located at mid-body length, and a posterior frontal organ. M. tridentatus sp. nov. is the first species within the genus exhibiting two types of dorsal/lateral scales: anteriormost dorsal and lateral trident-shaped scales and smooth strongly overlapping dorsal scales. The systematic placement of Musellifer within the Paucitubulatina is discussed and emended diagnoses are given for Muselliferidae and Musellifer.

Urodasys poculostylis sp. nov., a new stylet-bearing gastrotrich (Macrodasyida) from Capron Shoal, Florida

Abstract A new species of marine Gastrotricha, Urodasys poculostylis sp. nov. (Macrodasyida: Macrodasyidae), is described from the sublittoral sediments of Capron Shoal, Florida. The new species is a simultaneous hermaphrodite with a single left testis, a stylet bulb and a frontal organ. The stylet bulb bears a cup-shaped sclerotic stylet up to 20 µm long. Several specimens possessed a large spermatophore within the frontal organ. Urodasys poculostylis sp. nov. can be further distinguished by the presence of three pairs of anterior adhesive tubes distributed in two rows, 14–17 pairs of lateral adhesive tubes with staggered insertions, 5–7 pairs of ventrolateral adhesive tubes, 12–15 pairs of dorsolateral adhesive tubes and two dorsal adhesive tubes.

A new species of sublittoral marine gastrotrich, Lepidodasys ligni sp. n. (Macrodasyida, Lepidodasyidae), from the Atlantic coast of Florida

Abstract A new species of Lepidodasys is described from sublittoral sandy sediments off the Atlantic coast of Florida. Lepidodasys ligni sp. n. is a small species (≤ 450 µm) with a crossed-helical pattern of small, non-keeled, non-imbricated scales on the dorsal and lateral body surfaces, two columns of ventral, interciliary scales that form a herringbone pattern, and a series of anterior, lateral, dorsal and posterior adhesive tubes. Similar to Lepidodasys castoroides from the Faroe Islands, the new species possesses a caudal constriction that demarcates the posterior end containing the caudal organ. The frontal organ lies within the posterior constriction, which is heavily invested with somatic circular muscles. These muscles are also present throughout the trunk and represent a novel condition for species of Lepidodasys,which were previously considered to lack somatic circular muscles. Posterior of the caudal constriction is a large, barrel-shaped caudal organ that is wrapped in a series of interdigitating, spindle-shaped, incomplete circular muscle fibers. The caudal organ contains a sclerotized central canal, but the absence of distal cuticular endpieces distinguishes the new species from its morphologically similar congener, Lepidodasys castoroides.

First record and a description of a new species of Oregodasys (Gastrotricha: Macrodasyida: Thaumastodermatidae) from Tobago

Abstract A new species of Oregodasys (Gastrotricha: Macrodasyida: Thaumastodermatidae) is described from sublittoral sediments on the island of Tobago. Oregodasys ashleigha sp. nov. is 430–465 μm long and characterized by the presence of a pair of large and elliptical red ocelli, numerous cirri (21–23) restricted to the posterior end, and an inflated, bilobed caudum. Adhesive tubes are present in four series as TbA (10/side), TbL (10/side), TbVL (up to 45/side), and TbP (up to 51 total). The structure of the reproductive system is characteristic of the genus and defined by posterior ovaries, a single right testis, a bipartite caudal organ complex, and a frontal organ. The bipartite caudal organ complex is distinctly muscular, with the right-side caudal organ wrapped in spiral muscles and the left-center side caudal organ wrapped in circular muscles.

Tetranchyroderma bronchostylus sp. nov., the first known gastrotrich (Gastrotricha) with a sclerotic canal in the caudal organ

Abstract A new species of Tetranchyroderma (Macrodasyida: Gastrotricha) is described from coarse sediments at 9 m depth at Capron Shoals, Florida. Tetranchyroderma bronchostylus sp. nov. is distinguished primarily by the presence of a sclerotic canal within the accessory caudal organ, and represents the first species of Tetranchyroderma described with such a feature. The following combination of characters further distinguish this species from its congeners: an oral hood with a scalloped margin, paired cephalic tentacles, paired sensorial organs, a pentancrous cuticle, three pairs of dorsolateral adhesive tubes, one pair of ventrolateral adhesive tubes in the pharyngeal region and up to 11 pairs of ventrolateral tubes in the trunk region, and one pair of lateral adhesive tubes close to the paired caudal pedicles.

Acanthodasys paurocactus sp. n., a new species of Thaumastodermatidae (Gastrotricha, Macrodasyida) with multiple scale types from Capron Shoal, Florida.

Abstract A new species of Acanthodasys (Gastrotricha, Macrodasyida, Thaumastodermatidae) is described from sublittoral sediments off the Atlantic coast of Florida. Acanthodasys paurocactus sp. n. is a relatively small species (to 450 µm long) with a strap-shaped outline, a series of anterior, lateral, and ventrolateral adhesive tubes, paired caudal pedicles with posterior adhesive tubes, and a morphologically diverse cuticle. The cuticle contains both spined and unspined scales. Unspined scales are present in two general shapes: lanceolate and eye shaped, with some transitional shapes. All scales have a thickened rim and depressed central region; some scales of both shapes bear either one or more central bumps, a parallel ridge, or a perpendicular ridge that gives the appearance of a cross-shaped pattern under transmitted light. Spined scales are somewhat quadrangular in shape and bear uniancres to 15 µm long with a cross-shaped sectional profile. The new species is now one of five described species to possess both spined and spineless scales, and only one of two species to possess two types of spineless scales (the second species is an incompletely described specimen from Norway).