Holothuria (Cystipus) casoae a new species of sea cucumber (Echinodermata: Holothuroidea) from the central-eastern Pacific Ocean

Holothuria (Cystipus) casoae n. sp. is described from the central-eastern Pacific, from depths between 45 and 100 m. The main characters separating H. (C.) casoae from the rest of the species included in the subgenus Cystipus are the presence of a prominent fringe of 10 or more conical papillae along each side of the body and the presence of tables with a spinose rim, the pillars of the spire are short ending in a complex spiny crown with a small central circular opening. This new species is distinctive in the genus Holothuria, subgenus Cystipus, but shows some similarities to H. (C.) cubana ludwig, 1875, H. (C.) inhabilis selenka, 1867 and H. (C.) pseudofossor deichmann, 1930.

inTroducTion Holothuriidae comprise a large, worldwide-distributed family of aspidochirotid sea cucumbers of which several species are of high commercial value.in the past, their classification was extremely unstable.Pearson (1914) was the first who tried to arrange the mass of species under the name Holothuria linnaeus, 1767 into manageable groups.As he was working on specimens that mainly originated from the indian ocean, his analysis was bound to be incomplete for the distribution of Holothuria, which is (now) known to be almost cosmopolitan (Tortonese, 1965;rowe, 1969;Tommasi, 1969;clark and rowe, 1971;Maluf, 1988;Hendler et al., 1995;Massin, 1999;samyn and Massin, 2003).Within the genus Holothuria, Pearson (1914) recognized five subgenera: Bohadschia, Actinopyga, Argiodia, Halodeima andThymiosycia. When Panning (1929-1935) reviewed the mass of species under Holothuria he recognized Actinopyga, Bohadschia, Holothuria and Microthele as subgenera but retained the majority of the species under Holothuria sensu stricto. in 1944 Panning revised this perspective and elevated Actinopyga, Bohadschia and Microthele to generic rank.deichmann (1958) later revaluated Holothuria on the basis of new east Pacific material.But deichmann (1958) did not recognize the genus Holothuria sensu linnaeus, 1758 thereby disregarding the official list of generic names in zoology (see rowe, 1969).
rowe (1969) revised the Holohturiidae and suggested that the deichmann taxa should be regarded as subgenera rather than genera, and stated that she was the only specialist after Panning (1929Panning ( -1944) ) who had attempted to simplify the chaotically organized mass of species into more manageable groups.rowe (1969) also stated that Brandthothuria deichmann, 1958 and Paramicrothele caso, 1964 are junior synonyms of Thymiosycia Pearson, 1914;Fossothuria deichmann, 1958 andJaegerothuria deichmann, 1958

MATeriAls And MeTHods
The material originates from three scientific collections: colección nacional de equinodermos, instituto de ciencias del Mar y limnología, universidad nacional Autónoma de México (icMl-unAM), los Angeles county Museum (lAcM), and national Museum of natural History, smithsonian institution (usnM).
ossicles were extracted from pieces of skin (4 mm square) from the mid-dorsal and mid-ventral body wall, tube feet, papillae and tentacles.The skin was dissolved in fresh household bleach in centrifuge tubes.After centrifugation at 2750 rpm for 10 minutes, bleach was pipetted off and the ossicles were flooded and centrifuged three times with ethyl alcohol.After drying, suitable ossicles were criticalpoint dried, mounted on a cylindrical double coated conductive carbon tape stub, sputter coated with gold, and photographed using a leica stereoscan 440 laB6 scanning electron microscope (seM).sYsTeMATics order Aspidochirotida grube, 1840 family Holothuriidae ludwig, 1894 genus Holothuria linnaeus, 1767 subgenus Cystipus Haacke, 1880Diagnosis (after rowe, 1969: 155).Tentacles 20; pedicels more or less confined to the ventral ambulacral areas, papillae small and scattered dorsally, a lateral flange of papillae sometimes evident, anal papillae and "collar" of papillae around the base of the tentacles not apparent; body wall not very thick, usually about 2 (1-8) mm, often gritty to the touch; body rather vermiform or dorsoventrally flattened; size small to moderate, up to 200 mm long; calcareous ring fairly stout with radial plates as long as the interradial plates; ossicles consisting of tables with usually knobbed disc and low spire bearing many short spines, which are sometimes so numerous and closely crowded that they may almost obscure the disc or become connected to the knobs on the margin of the disc forming a fenestrated sphere, buttons usually simple with large regularly or irregularly arranged knobs and generally 3-4 pairs, but up to 7 pairs, of relatively small holes which may become obscured somewhat by the immensity of the knobs, buttons rarely modified into fenestrated ellipsoids.Etymology.We take great pleasure in naming this species after dr.María elena caso Muñóz foremost researcher of the echinoderms of Mexico for many decades.
Description.Preserved specimens 28-85 mm in length.colour in alcohol beige, trivium with two narrow light brown stripes running along the body; numerous tiny dark brown spots distributed irregularly over the dorsum.Body wall with numerous, irregular transverse wrinkles.specimens >90 mm long with a prominent fringe of 10 or more conical papillae on sides.Body wall covered by scattered, short, cylindrical tube feet, distributed evenly over both the ventral and dorsal surfaces.Bivium also bears a few conical papillae of the same size as those on the lateral fringe.
Mouth ventral, surrounded by 20 white, small tentacles (holotype: 0.5 to 0.9 cm).Anus terminal, with no anal papillae.Body wall up to 4 mm thick.
ossicles of the ventral and dorsal body wall tables and knobbed buttons.Tables (figs.2A, B,   c) numerous, disc 60-90 µm across, central holes of various sizes; disc quadrangular more or less rounded with a spinose rim; pillars of spire short (0-1 cross beam) ending in a complex spiny crown with a small central circular opening.Buttons (fig.2e) numerous, 90-102 µm long, with 3-8 pairs of holes; rim of button knobbed.Ventral tube feet with plates, buttons, modified buttons, rods and tables.Plates (fig.2d) up to 100 µm long, with up to five rows of holes.rods (fig.2i) up to 100 µm long.Tables similar in small and large specimens; disc from 70 to 80 µm across with a rim always more or less spinose; disc always perforated by one central hole, 8-9 medium sized holes and a variable number of smaller peripheral holes; spire variably developed, often reduced.end plate of ventral tube feet up to 700 µm across.dorsal papillae with buttons from 50-90 µm long, with 3-6 pairs of holes; tables similar to those in the body wall; small modified knobbed buttons are also present (fig.2g), from 46-50 µm long, with 2-3 pairs holes; more numerous in small specimens.dorsal tube feet with tables, buttons and rods similar to those in the ventral tube feet, both in size and shape.end plate of dorsal tube feet 600-700 µm across.Tentacles with spiny to smooth rods (fig.2H), 270-500 µm long with spiny, forked or perforated extremities; small tables under development (~38 µm across) are also common (fig.2f).longitudinal muscles divided, prominent.calcareous ring (fig.3A) with radial plates as wide as the length of the interradial plate.single, well developed Polian vesicle, 1/6 of body length.cuvierian tubules present.stone canal very short ending in an irregular oval madreporic plate (fig.2B).respiratory trees dendritic, extending forward to half the length of the body.
Distribution.Holothuria (Cystipus) casoae is known from the gulf of california to the isla del coco, costa rica, in the central-eastern Pacific, 45-100 depth, on sand and rubble sediments.The main characters separating H. (C.) casoae from the rest of the species included in the subgenus Cystipus are the presence of a prominent fringe of 10 or more conical papillae along each side of the body, the presence of tables with spinose rims, and the pillars of the spire are short ending in a complex spiny crown with a small central circular opening.AcKnoWledgeMenTs dr.claude Massin made a critical review of the manuscript.Many thanks to dr. david l.Pawson, cynthia Ahearn (smithsonian institution) and dr.Yves samyn (Brussels) who provided valuable comments on an early draft of this paper.dr.gordon Hendler kindly loaned the lAcM material.We thank sarita frontana uribe for preparing figure 1 and the ossicles for seM.Yolanda ornelas (laboratorio de Microscopía electrónica, icMl, unAM) for her help with seM.We are also grateful to Alicia duran (icMl, unAM) for her technical support.
are junior synonyms of Cystipus Haacke, 1880; Ludwigothuria deichmann, 1958 is the junior synonym of Halodeima Pearson, 1914; and Microthele sensu deichmann, 1958 has nothing to do with Microthele Brandt, 1835, hence Microthele sensu deichmann, 1958 was replaced with a new subgenus, i.e.Platyperona rowe, 1969.rowe (1969) formed five new subgenera to accommodate the remaining species.later on, two other subgenera, , spire low, solid, ending in numerous teeth, and "the tables seem never to develop into such complicated forms as in the case of H. cubana".H. (C.) casoae has tables that can develop into complicated forms like in H. (C.) cubana.