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Iotrochota revisited: a new sponge and review of species from the western tropical Atlantic (Poecilosclerida:Iotrochotidae)

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Iotrochota revisited: a new sponge and review of species from the western tropical Atlantic (Poecilosclerida:Iotrochotidae)
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  Introduction Discovery of an undescribed species of the genus  Iotrochota inBelize prompted this review of all known taxa in the group.  Iotrochota currently comprises ~12 species, most of which have been described from tropical seas; only one species is knownfrom the Arctic. Various authors placed the genus in differentfamilies of Poecilosclerida, including Desmacididae,Desmacidonidae, Esperiopsidae, Myxillidae and Tedaniidae, but it has finally been assigned to Iotrochotidae Dendy, 1922(van Soest 2002). The type species,  I. birotulata (Higgin, 1877:as  Halichondria) is Caribbean (first described from Venezuelaand Jamaica); a senior synonym,  Hyrtios musciformis Duchassaing & Michelotti, 1864, also from the West Indies (StThomas), was suppressed as nomen oblitum (Wiedenmayer 1977) in favour of Higgin’s well-established and often-cited name,  I. birotulata. The Bahama population of  Iotrochota differs from  I. birotulata  by having a strongly reduced spicula-tion (Wiedenmayer 1977) and was therefore described as a sep-arate species,  I. imminuta (Pulitzer-Finali, 1986). However, our study of type material at the Yale Peabody Museum of NaturalHistory shows that  I. imminuta is a junior synonym of  Hirciniaatra Whitfield, 1901 (from Nassau, Bahamas), which previousauthors, who had not examined the skeleton, thought to be con-specific with  I. birotulata (Wiedenmayer 1977; van Soest2002).  Iotrochota birotulata is known as a very common and char-acteristic shallow-water species in Caribbean reef, mangrove and seagrass environments and has been pictured and described inseveral monographs and field guides (e.g. de Laubenfels 1932,1936; Hechtel 1965; Wiedenmayer 1977; Colin 1978; GómezLópez and Green 1984; van Soest 1984; Pulitzer-Finali 1986;Zea 1987; Humann 1992; Gómez 2002; van Soest 2002). Threeother species from the tropical western Atlantic are  I. imminuta ,mentioned above,  I. bistylata Boury-Esnault, 1973, off Braziland  I. agglomerata Lehnert & van Soest, 1999, from Jamaica.During an ongoing study of the sponges of Belize, we found a species of  Iotrochota that clearly differs from the others and will be described below. To determine the morphological and anatomical variability of taxonomic characters among westernAtlantic populations of the genus, we examined a large number of specimens of the type species,  I. birotulata , from the entirezoogeographic range, including various habitats in Belize. Wethen compared the results with data from other species provided  by previous authors (Table 1) or from specimens examined by us. Materials and methods This paper is part of a project analysing the silicon cycle in theBelizean section of the Mesoamerican barrier reef ecosystem.The general setting of the Carrie Bow Cay research area  Invertebrate Systematics , 2007, 21 , 173–18510.1071/IS060401445-5226/07/020173© CSIRO 2007 Klaus Rützler  A,C , Manuel Maldonado  B , Carla Piantoni  A and Ana Riesgo  B A Smithsonian Institution, Department of Invertebrate Zoology, MRC 163, Washington, DC 20013-7012, USA. B Centro de Estudios Avanzados de Blanes (CSIC), Department of Aquatic Ecology, Acceso Cala St Francesc 14, Blanes 17300, Girona, Spain. C Corresponding author. Email: ruetzler@si.edu Abstract. The systematics of tropical and subtropical western Atlantic species of  Iotrochota is re-examined in light of the discovery of an undescribed species.  Iotrochota birotulata (Higgin), the type species, is found to have more charactersthan previously recognised and is redefined with emphasis on a skeleton of spongin fibres containing stout, curved stylesand strongyles (category I) and an interstitial spiculation consisting mainly of longer, slender and straight styles (II).  Iotrochota bistylata Boury-Esnault is confirmed as a synonym of the above. The new species, named  I. arenosa , sp. nov.,differs in external morphology, strong mucus development, incorporation of sand and interstitial spicules that are mainlylong, straight strongyles.  Iotrochota atra (Whitfield), thought to be a synonym of  I. birotulata , is recognised as a separatespecies occurring exclusively in the Bahamas and is found to be a senior synonym of  I. imminuta Pulitzer-Finali; it ismorphologically very similar to  I. birotulata , but lacks birotulae and has a strongly reduced skeleton of megascleres(mostly one category of delicate strongyles).  Iotrochota agglomerata Lehnert & van Soest is recognised as the fourthdistinct species for its unusual colour (orange), thinly encrusting habit and special spiculation (styles with tylostylotemodifications). Additional keywords: Caribbean coral reefs, distributional ecology, diversity, new species, Porifera, sympatric distri- bution, systematic revision. Iotrochota  revisited: a new sponge and review of species fromthe western tropical Atlantic (Poecilosclerida:Iotrochotidae) www.publish.csiro.au/journals/is CSIRO PUBLISHING  K. Rützler et al. 174  Invertebrate Systematics    T  a   b   l  e   1 .        I     o      t     r     o     c       h     o      t     a   s  p   i  c  u   l  e   t  y  p  e  s  a  n   d   d   i  m  e  n  s   i  o  n  s  r  e  p  o  r   t  e   d   i  n   t   h  e   l   i   t  e  r  a   t  u  r  e   f  o  r  w  e  s   t  e  r  n   A   t   l  a  n   t   i  c  s  p  e  c   i  e  s    M  e  a  s  u  r  e  m  e  n   t  s  a  r  e  r  a  n  g  e  s   (   l  e  n  g   t   h ,  o  r   l  e  n  g   t   h       ×   w   i   d   t   h   )  a  n   d  m  e  a  n  s   (  w   h  e  r  e  a  v  a   i   l  a   b   l  e   )  ;   i  n  µ  m .   N   R  =  n  o   t  r  e  p  o  r   t  e   d   S  p  e  c   i  e  s   S   t  y   l  e  s   I   S   t  y   l  e  s   I   I   S   t  r  o  n  g  y   l  e  s   I   S   t  r  o  n  g  y   l  e  s   I   I   O  x  e  a  s   B   i  r  o   t  u   l  a  s   A  u   t   h  o  r    I .   b   i  r  o   t  u   l  a   t  a 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   ]   N   R   N   R   1   5   0  –   1   9   0       ×    2 .   5   N   R   N   R   N   R   P  u   l   i   t  z  e  r  -   F   i  n  a   l   i   (   1   9   8   6   )    I .  a  g  g   l  o  m  e  r  a   t  e    J  a  m  a   i  c  a   2   5   6  –   3   9   0       ×    3  –   6   (  a   f   f .   t  y   l  o  s   t  y   l  e  s   )   N   R   N   R   N   R   N   R   1   2  –   1   8   L  e   h  n  e  r   t  a  n   d  v  a  n   S  o  e  s   t   (   1   9   9   9   )   Invertebrate Systematics 175 (16°48.1 ′  N, 88°04.9 ′ W) has been described by Rützler and Macintyre (1982) and Rützler et al  . (2000). Material was col-lected by free diving or SCUBA, fixed in formaldehyde–seawa-ter (10%) or glutaraldehyde in sodium-cacodylate buffer withsucrose (1.5%), followed by preservation in 70% ethylenealcohol. Hand sections, ground epoxy sections and spicule preparations were made as previously described (Rützler 1978).Scanning electron microscope (SEM) preparations were made by the usual liquid-ashing of tissue in fuming nitric acid, fol-lowed by thorough rinsing in distilled water and multiplechanges of ethylene alcohol; dried spicule mounts were gold coated and viewed on a Philips XL-30 ESEM (environmentalSEM, Eindhoven, The Netherlands) at 500 × , 600 × , 800 × , 2500 × and 4000 ×  primary magnification. Spicule measurements (25for each type and dimension) were made by light microscopyand from SEM images. We distinguished between megascleresthat were primarily part of the skeleton fibres (styles I,strongyles I) and interstitial megascleres that were mostly seenfree (single or in strands) in the cellular tissue (category II).Museum designations are: AMNH, American Museum of  Natural History, New York; USNM, United States NationalMuseum (National Museum of Natural History), SmithsonianInstitution, Washington, DC; YPM, Yale Peabody Museum of  Natural History, Yale University, New Haven, CT. Family IOTROCHOTIDAE Dendy, 1922 Diagnosis  Poecilosclerida (Myxillina) with reticulate or hymedesmioid choanosomal skeleton of megascleres cemented by spongin;with birotulae as microscleres (Dendy 1922; see also van Soest2002). Genus Iotrochota  Ridley, 1884  Hiattrochota de Laubenfels, 1950: 20.  Iotrochotyla de Laubenfels, 1954: 150.Type species:  Halichondria birotulata Higgin. Type localities: Bay of Kingston, Jamaica (Lectotype) (Ridley 1884; van Soest 2002);Puerto Cabello, off Caracas, Venezuela (Paralectotype). Diagnosis  Iotrochotidae with principal skeleton of smooth megascleres(styles, strongyles) that are typically separable into two shapeand size categories. Iotrochota birotulata  (Higgin) (Figs 1–3; Tables 1, 2)  Halichondria birotulata Higgin, 1877: 296, pl. XIV, figs 11–15. (For further synonyms see Hechtel 1965: 24; Wiedenmayer 1977: 138;Zea 1987: 149; van Soest 2002: 598–599.) Not  Iotrochota birotulata : Bahamas specimens of Higgin 1877: 298;Wiedenmayer 1977: 138. Material examined  Belize: Lighthouse Reef, SW Fore Reef, USNM 32306; Carrie Bow Caylagoon, USNM 32962, USNM 33176, USNM 41358; Carrie Bow Cay, inner fore reef, USNM 47850 (dry); Carrie Bow Cay (1 km WSW), lagoon reef,USNM 47851 (dry); Blue Ground Range, west of Carrie Bow Cay, USNM1091296; Manatee Cay, USNM 1091297; Carrie Bow Cay south, patch reef,USNM 1091298; Carrie Bow Cay south, inner barrier reef, USNM1091299; Carrie Bow Cay south, patch reef, USNM 1091300; Carrie BowCay, lagoon due north-west; USNM 1091301. Brazil: USNM 1091302. Colombia: Rosario Islands, Pajarales, USNM 31970 (dry), USNM 31976(dry); Santa Marta, Punta de Betin, USNM 31992. Florida: Gulf of Mexico,USNM 33965, USNM 33968; West Palm Beach, USNM 1091293; DryTortugas, USNM 22600, USNM 22601, USNM 22604 (dry); Dry Tortugas,Bird Key, USNM 22599; Dry Tortugas, NW Channel, Dry Rocks, USNM31867; Looe Key, Middle Spur, USNM 30400; Florida Keys, USNM1091294, USNM 1091295. Panamá: San Blas Islands, Cichime Cays,USNM 32912. Puerto Rico: La Parguera, SW of Island (near laboratory),USNM 31599, USNM 31603; Montalvo Bay, towards La Parguera, USNM31849. Virgin Islands: St. John Island, Current Hole, USNM 31581; St.Croix Island, east slope of Salt River Canyon, USNM 32242. Diagnosis  Purplish black to greenish, branching erect or repent, moder-ately mucous  Iotrochota . Main skeleton composed of network of fibres containing tightly packed megascleres bound byspongin. Megascleres curved, stout styles (mean length × width:167 × 6.5 µm) and strongyles (mean length × width: 181 × 5.0µm); accessory spicules straight, thin styles – rarelystrongyles – single or in strands (mean length × width: 241 × 4.5µm) and birotulae (mean length 14.9 µm) (Table 2). Morphology of type material  Lectotype, BMNH 1877.3.9.1 (dry, from Jamaica, not examined in this study), described as a branching, sharply conulose speci-men supported by thick (35–100 µm) spicule tracts containingstrongyles (140–230 × 3–5 µm) and styles (140–240 × 3–6 µm)and loosely scattered megascleres and microscleres (birotulae10–15 µm); paralectotype, BMNH 1877.3.9.2 (2 slides, fromVenezuela, not seen by authors) (van Soest 2002: 599, fig.3  A  –   D ). Review of  Iotrochota Fig. 1. Map of  Iotrochota species distribution in the tropical westernAtlantic (see also Tables 1, 2). (Symbols: circles,  Iotrochota agglomerata ;triangles,  I. arenosa ; squares,  I. atra ; diamonds,  I. birotulata ; ?, identifica-tion not confirmed.)  K. Rützler et al. 176  Invertebrate Systematics Description External features  Colour purplish black, with an emerald green sheen over partof the surface. Specimens erect, branching to fan-shaped, or encrusting with sprawling branches. Branches 1–4 cm diameter,depressed, wider where anastomosing and 30–50 cm long, up tonearly 1 m in some calm-water habitats. Surface spiny conulose, particularly noticeable on specimens removed from the water.Conules 0.5–2 mm high, 1–4 mm apart, terminating in fine brushes of protruding fibres. Subectosomal, meandering aquif-erous canals lined by clusters of emerald-green-pigmented cells. Oscula 1–3 mm in diameter, usually conspicuous but notelevated, randomly scattered, 4–5 cm apart. Pores (50–150 µmdiameter) clustered in fields between the conules. Consistency  Stiff and spiny, tough to tear, releasing purplish mucus whenhandled. Anatomy  Ascending fibres 180–450 µm in diameter, connecting fibres40–125 µm. Mesh diameter from 50 µm to more than 1 mm.Fibres composed of closely packed megascleres (curved or undulating, stout styles I and strongyles I) bound by varying Fig. 2.  Iotrochota birotulata , live specimens in situ ( a , b ) and microanatomy ( c–g  ). ( a ) Branching erect specimencovered by  Parazoanthus swiftii on a reef off Carrie Bow Cay, Belize, 8 m depth (picture width, 50 cm; photo, MikelBecerro). ( b ) Specimen sprawling over coral rock, Florida Keys, 5 m depth (picture width, 20 cm; photo,M.Becerro). ( c ) Skeleton fibre and accessory megascleres. ( d  ) Spicule-charged spongin fibre with accessory spicule(style II). ( e ) Detail of skeleton fibre showing tightly packed spicules (styles I, strongyles I). (  f  ) Choanocyte cham- bers. (  g  ) Cellular tissue with birotulas (arrow).   Invertebrate Systematics 177 quantities of spongin. Interstitial megascleres (long, thin,straight styles II) common, sometimes occurring in strands.Microscleres are birotulae scattered throughout tissue. Spiculemeasurements summarised in Table 2. Choanocyte chambersaverage 20–30 µm in diameter; they have long thin prosopyles but lack apopyles and open directly into excurrent canals. Ecology and distribution  Common among mangroves and in sea grass ( Thallassia ) beds,sand and dead coral in lagoons and on shallow reefs; typically0.1–20-m depth, a few records to 65-m depth. Association withthe bright yellow to orange epizoic zoanthid  Parazoanthus swiftii (Duchassaing & Michelotti) is common and affects10–25% of the population. This species is among the spongesmost commonly eaten by fish and sea urchins (Randall and Hartman 1968; Santos et al  . 2002).Specimens were collected in the Gulf of Mexico (off Floridaand Mexico), the Atlantic coast of Florida (West Palm Beach),Dry Tortugas and Florida Keys, Cuba, Dominican Republic,Puerto Rico, Virgin Islands, Belize, Colombia, Curaçao,Bonaire, Venezuela, Panama (Atlantic coast), and Brazil.Bahamas specimens are here referred to another species,  I. atra. Remarks  Our specimens of  Iotrochota birotulata agree well with thesrcinal description of the type material from Jamaica and Venezuela (Higgin 1877; van Soest 2002), and several subse-quent analyses, particularly of material from the Dry Tortugas(de Laubenfels 1932, 1936), Jamaica (Hechtel 1965), Curaçao,Bonaire, St Martin, Puerto Rico (van Soest 1984) and Caribbean Colombia (Zea 1987). Differences concern mainlyvariations in spicule type and size and many authors did notdiscriminate between megasclere categories. Higgin (1877)distinguished two spicule forms, a curved ‘subcylindrical one’(our strongyle I), some found pointed at one end, and anassociated ‘long fine straight arcuate spicule’(style II) ‘found also in considerable numbers in the dermal sarcode’(Higgin1877, p.298) (Table 2). He also mentioned similar lookingspecimens from Nassau with spicules of ‘slender cylindricalform, but lacking altogether the flesh-spicules [birotulas]’(Higgin 1877, p. 298), but his plan to examine the relationshipdid not materialise.A detailed discussion of systematics, histology, regenerationand ecology based on reaction of cell suspensions to environ-mental variables was provided by de Laubenfels (1932, 1936) asa result of a field-laboratory study in the Dry Tortugas (Florida).Complementary to our findings in the present study, deLaubenfels observed a flabellate shape in specimens exposed tooscillating currents. Colour in life was described as very dark  purple, with a thin sheen of emerald green over much of surfacecaused by ectosomal archaeocytes containing emerald-greeninclusions. He considered strongyles and styles to be mixed indiscriminately, mostly localised in spongin fibres and hefound very few birotulae, with 12 or 16 clads.Hechtel (1965) studied the species collected from the typelocality, Jamaica. He found long, thin styles and relatively large birotulae (20–30 µm) scattered in the ectosome, styles alsocommon interstitially elsewhere and birotulae abundant near canals. He also noted a reticulation of stout skeleton fibresending in the conules and composed of curved strongyles or anisostrongyles, and less common curved styles, complement-ing to our findings in the present study. Review of  Iotrochota Fig. 3. Spicules (scanning electron micrographs) of  Iotrochota birotulata . ( a ) Curved styles I and strongyles I. ( b ) Straight accessory spicules (styles II). ( c ) Birotulae.

testoso

Apr 28, 2018

testoso

Apr 28, 2018
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