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A new species of polychaete worm from Juan Fernandez Archipelago, Chile, Scoloplos juanfernandezensis n. sp. (Polychaeta: Orbiniidae).

Orbiniids comprise a family of worldwide distributed, moderate sized, sediment burrowers and non-selective deposit-feeders polychaetes found in all depths, from shallow tidal zone to abyssal deep water. They are easily recognized by the form of their elongate body divided into a wide anterior thoracic region formed of firm, muscular, dorso-ventrally flattened expanded segments and a posterior abdominal region consisting of numerous, soft and fragile segments that are rounded in cross section. The prostomium is smooth, conical, more or less acutely pointed, globular, broad, or spatulate; without any sensory appendages or palps, but nuchal slits or depressions are sometimes present; with a pair of small eyes sometimes present. The proboscis is unarmed and when everted is either saclike or branched. The peristomium consists of one or two achaetous rings (Blake, 1996; Glasby, 2000; SolisWeiss et al., 2009). Worldwide, the Orbiniidae consist of 17 genera and about 150 species (Zhadan et al, 2015).

The polychaete fauna of the Juan Fernandez Archipelago (JFA) has been understudied with only few investigations. Ehlers (1901) studied the polychaetes collected by the German zoologist Dr. Ludwig H. Plate, along the Chilean coast and the JFA, from May 1893 to May 1895; Augener (1922) studied the polychaetes collected by Kare Backstrom in the JFA during the Swedish Pacific Expedition, 19161917; and more recently, Blake (1983) studied the Spionidae collected in the JFA by the R/V Anton Bruun, from November 1965 to May 1966, as part of the Southeastern Pacific Biological and Oceanographic Program (SEPBOP).

Rozbaczylo & Castilla (1987) reviewed the polychaete literature from the JFA and reported 43 known species of polychaetes distributed in 18 families, with a 25% of endemism.

In this study, we report for the first time the presence of the family Orbiniidae in the Juan Fernandez Archipelago and we describe a new species of the genus Scoloplos, S. juanfernandezensis n. sp. The new species is characterized, and differs from other species of the genus mainly by the location of the first pair of branchiae, by having dichotomously branched branchiae in the mid-posterior chaetigers, the absence of subpodial papillae and the morphology of the parapodia.

Recent studies by Blake (2000), Kruse et al. (2004), Bleidorn (2005), Bleidorn et al. (2009), Dean & Blake (2015), and Zhadan et al. (2015) have helped to clarify some questions about the family Orbiniidae and the genus Scoloplos. Blake (2000), Bleidom (2005), Bleidorn et al. (2009) and Dean & Blake (2015) have considered the subgenera Scoloplos and Leodamas as separate genera because they are not closely related and do not constitute sister groups.

The Juan Fernandez Archipelago is located in the Southeastern Pacific Ocean, approximately 650 km west from Valparaiso and is constituted from three main islands: Robinson Crusoe (33[degrees]37'S, 78[degrees]51'W), Santa Clara (33[degrees]42'S, 79[degrees]01'W), and Alejandro Selkirk (33[degrees]45'S, 80[degrees]45'W) (Rozbaczylo & Castilla, 1987). Benthic samples were collected in various locations around the Robinson Crusoe Island (33[degrees]37'S, 78[degrees]51'W) (Fig. I), by means of SCUBA, from depths between 4 and 10 m, between the years 2008 and 2012. Specimens were fixed in 10% formalin and preserved in 70% ethanol. Specimens were observed and photographed with a stereomicroscope, a trinocular phase contrast microscope with a high resolution digital camera. Drawings of Figure 2 were made with a drawing tube on a stereoscopic microscope (Figs. 2, 3c) was taken with a Cyber-shot camera. To add contrast to external structures, such as parapodia, branchiae, and papillae, the specimens were dyed with methyl green, Rose Bengal and an aqueous solution of methylene blue. Type specimens have been deposited in the Museo Nacional de Historia Natural, Santiago (MNHNCL ANN), and in the "Coleccion de Flora y Fauna Profesor Patricio Sanchez Reyes", Departamento de Ecologia, Facultad de Ciencias Biologicas, Pontificia Universidad Catolica de Chile, Santiago (SSUC). Non-type specimens are deposited in the reference collection of FAUNAMAR Ltda., Santiago.

Taxonomic account

Genus Scoloplos Blainville, 1828

Diagnosis. Prostomium pointed, conical; single achaetous peristomial ring. Thoracic neuropodia bearing crenulated capillaries and hooks arranged in one or more rows; abdominal furcate and flailed notochaetae present or absent. Abdominal neuropodia with embedded, non-projecting acicula. Branchiae simple or branched, from chaetiger 8 or later. 1-2 thoracic neuropodial podial papillae, 0-2 thoracic subpodial papillae, 0-4 abdominal subpodial papillae, stomach papillae absent (Zhadan et al, 2015). Scoloplos juanfernandezensis n. sp. (Figs. 2a-m', 3a-3c).

Material examined. Juan Fernandez Archipelago, Robinson Crusoe Island, 33[degrees]37'S, 78[degrees]51'W, in front of El Pangal, 4 m depth, Alvaro Palma, coll., 11 March 2008, holotype (MNHNCL ANN-15017) and paratypes (MNHNCL ANN-15018 and MNHNCL ANN-15019); in front of Bahia Villagra, 10 m depth, 12 September 2008 paratype (SSUC 9008); in front of Sal Si Puedes, 4-10 m depth, 1 August 2012, paratype (SSUC 9009); in front of Punta Loberia, 4-10 m depth, 20 January 2011, paratype (MNHNCL ANN-15020); in front of Bahia Padre, 9 m depth, 4 November 2008, paratypes (SSUC 9010 and SSUC 9011); in front of El Frances, 4-10 m depth, 19 January 2011, paratype (MNHNCL ANN-15021); in front of El Palillo, 4-10 m depth, 16 January 2011, paratype (MNHNCL ANN-15022); in front of El Ingles, 10 m depth, 20 November 2008, FAUNAMAR reference collection (No00011); in front of El Ingles, 4-10 m depth, 28 March 2010, paratype (SSUC 9012); in front of El Pangal, 6 m depth, 1 November 2008, paratype (SSUC 9013); in front of El Pangal, 4.5 m depth, 3 November 2008, FAUNAMAR reference collection (No00014) and FAUNAMAR reference collection (No00015); in front of El Pangal, 6 m depth, 1 November 2008, paratype (MNHNCL ANN-15023); in front of El Palillo, 4-10 m depth, 3 July 2010, paratype (SSUC 9014).

Description. Body long, slender; holotype (MNHNCL ANN-15017) incomplete with 210 chaetigers, 30.1 mm long, thorax 2.2 mm wide, with 17 thoracic chaetigers; smallest complete paratype (MNHNCL ANN-15023) 14.2 mm long; largest complete paratype (SSUC 9008) 83.3 mm long. Thorax dorso-ventrally flattened with 1.5-3.1 mm maximum width; posterior thorax slightly wider than abdomen; abdomen cylindrical (Fig. 2a). Color of preserved specimens brown to pale yellow. Prostomium sharply conical; without eyespots. Single achaetous peristomial ring, shorter than prostomium, broad, bearing a pair of nuchal organs located laterally at anterior border (Fig. 2b). Everted proboscis large, multilobed (Fig. 2a). Thorax with 16-18 chaetigers, usually 17. All parapodia biramous. Subpodial lobes and stomach papillae absent. Thoracic notopodial post-chaetal lobes digitate to triangular, from chaetiger 1 as small papillae (Fig. 2c), reaching two-thirds chaetal length in posterior thoracic chaetigers; thoracic neuropodial post-chaetal lobes papilliform on chaetiger 1-2, then triangular (Figs. 2c-d, 2f). Anterior abdominal notopodial post-chaetal lobes triangular, similar in length to branchiae (Fig. 2g); on mid-posterior and posterior chaetigers, these lobes shorter than branchiae (Figs. 2h-i; 3b-c); abdominal neuropodial post-chaetal lobes are triangular, then gradually becoming narrow and elongated posteriorly; they shorter than notopodial lobes. Straight neuropodial aciculae embedded, not emergent. In last abdominal chaetigers notopodial post-chaetal lobes digitiform and neuropodial post-chaetal lobes papilliform. Lateral organs developed at base of notopodia (Figs. 2k-k'). All thoracic notopodia with crenulated capillary chaetae, fewer in number than in neuropodia (Fig. 2j). All thoracic neuropodia with an anterior J-shaped row (Fig. 2e) of slightly curved serrated hooks with a thin, translucent hood open, like a valve that covers the back distal portion of the hook (Figs. 2m, 2m'), and 3-4 rows of crenulated capillary chaetae (Fig. 2l). From chaetiger 1-10 with up to 10-16 hooks per segment (Fig. 2m). All abdominal chaetae crenulated capillaries. Notopodial furcate chaetae absent. Branchiae emerge from chaetigers 20-28, as short digitate papillae (Fig. 2a), thereafter increasing in size and similar to notopodial lamellae in mid-body segments. By chaetigers 70-80, branchiae begin branching dichotomously and asymmetrically (Fig. 2g). Subsequently, each branch divides again resulting in three terminal filaments between chaetigers 110-170, or four (Figs. 2h-3a). In a fewer cases five terminal filaments occur (Table 1). Posterior abdominal chaetigers shorter in length and with branchiae larger, more close-packed and with 2-4 terminal filaments (Figs. 2i-2j, 2c-3b). Pygidium with anus surrounded by several terminal lobes and with two large ventral cirri (Figs. 3b-3c).

Variation. Branchiae begin on chaetigers 20-28 but starting not always occurs on both sides of the segment at a time. In the same way, the beginning of the branchial branching not always occurs on both sides of the segment at a time, this branching can occur on one side while on the other side it occurs in subsequent segments. The number of branches and the chaetiger where the branching begins varies among specimens, (Table 1); the maximum number of branches observed was six branches in paratype MNHNCL ANN-15022.

In some cases the branchiae start branching in a chaetiger much earlier than in the rest of the specimens. The occurrence of branchiae with two branches start in chaetiger 44, as can be seen with paratype MNHNCL ANN-15020 (Table 1), before the general observed start between chaetigers 70-87; in paratype MNHNCL ANN-15019 the occurrence of branchiae with three branches is in chaetiger 88, before the general observed start between chaetigers 110-160.

Remarks. Scoloplos juanfernandezensis n. sp. belongs to a small group of species of Scoloplos with branched branchiae in the abdominal segments. This characteristic is shared with two other species: Scoloplos cylindrifer Ehlers, 1905 (= S. (L.) dendrobranchus Hartman, 1957) from New Zealand and Leodamas latum (Chamberlin, 1919) from Pacific side of Panama. Scoloplos juanfernandezensis n. sp. differs from L. latum because the branchiae in the latter begin between segments 5-6 of the thorax and the branching of the branchiae is palmate instead of dichotomous. The other difference with Scoloplos cylindrifer is the absence of emerging abdominal neuropodial aciculae in Scoloplos juanfernandezensis n. sp., Hartman (1957) described this acicula for S. cylindrifer (= S. dendrobranchiatus) distally curved with emergent tip, while in S. juanfernandezensis n. sp. is straight. Thoracic neuropodial hooks are hooded in S. juanfernandezensis and without hood in S. cylindrifer. Also the branchiae begin between chaetigers 10-25 instead of chaetigers 20-28 in Scoloplos juanfernandezensis n. sp. and the thorax has more than 20 segments while in Scoloplos juanfernandezensis n. sp. the thorax has 16-18 chaetigers. Scoloplos cylindrifer is known only from New Zealand and Australia in intertidal zones, associated with sand, Zostera beds and mixed substrates. S. juanfernandezensis n. sp. specimens were collected in shallow subtidal depths of 4 to 10 m from sand in hard bottom.

Type locality. Robinson Crusoe Island (33[degrees]37'S, 78[degrees]51'W), Juan Fernandez Archipelago, Southeastern Pacific Ocean, 4-10 m depth.

Etymology. The name of the species is derived from the name of its type locality, the Juan Fernandez Archipelago; and the suffix indicates it lives in this region.

Distribution. Only known from the type locality, Robinson Crusoe Island, Juan Fernandez Archipelago, Southeastern Pacific Ocean.

DOI: 10.3856/vol45-issue1-fulltext-21

Received: 23 June 2016; Accepted: 2 October 2016

ACKNOWLEDGMENTS

We are greatly thankful to Dr. Alvaro Palma who kindly made specimens available to the first author for study. We thanks Bruno San Martin and Josefina Di Giovanni who helped with the sorting of all the specimens collected by Dr. Alvaro Palma on Robinson Crusoe Island. Funding for this study was provided by Faunamar Ltda., Environmental Consulting Firm and Marine Research.

REFERENCES

Augener, H. 1922. Litorale polychaeten von Juan Fernandez. In: C. Skottsberg (ed.). The natural history of Juan Fernandez and Easter Island, Uppsala, 3: 161-218.

Blake, J.A. 1983. Polychaetes of the family Spionidae from South America, Antarctica and adjacent seas and islands. In: L. Kornicker (ed.). Biology of the Antarctic Seas XIV. American Geophysical Union. Antarctic Res. Ser., 39: 205-287.

Blake, J.A. 1996. Family Orbiniidae Hartman, 1942. In: J.A. Blake, B. Hilbig & P.H. Scott (eds.). Taxonomic atlas of the benthic fauna of the Santa Maria basin and western Santa Barbara Channel. 6--The Annelida Part 3. Polychaeta: Orbiniidae to Cossuridae. Santa Barbara Museum of Natural History, Santa Barbara, pp. 1-26.

Blake, J.A. 2000. A new genus and species of polychaete worm (Family Orbiniidae) from methane seeps in the Gulf of Mexico, with a review of the systematics and phylogenetic interrelationships of the genera Orbiniidae. Cah. Biol. Mar., 41: 435-449.

Bleidorn, C. 2005. Phylogenetic relationships and evolution of Orbiniidae (Annelida, Polychaeta) based on molecular data. J. Linn. Soc. Zool., 144: 59-73.

Bleidorn, C., N. Hill, C. Erseus & R. Tiedemann. 2009. On the role of character loss in orbiniid phylogeny (Annelida): molecules vs morphology. Mol. Phylogenet. Evol., 52(1): 57-69.

Chamberlin, R.V. 1919. Pacific coast Polychaeta collected by Alexander Agassiz. Bull. Mus. Comp. Zool., 63: 251-270.

Dean, H.K. & J.A. Blake. 2015. The Orbiniidae (Annelida: Polychaeta) of Pacific Costa Rica. Zootaxa, 3956(2): 183-198.

Ehlers, E. 1901. Die Anneliden der Sammlung Plate. Fauna Chilens. Zool. Jahrb., Suppl. 5: 251-272.

Ehlers, E. 1905. Neuseelandische Anneliden. Abhandlungen der Koniglichen Gesellschaft der Wissenschaften zu Gottingen Mathematisch-Physikalische Klasse. Neue Folge, 3: 1-80.

Glasby, C.J. 2000. Family Orbiniidae. In: P.L. Beesley, G.J.B. Ross & C.J. Glasby (eds.). Polychaetes and allies: the southern synthesis. Fauna of Australia. Polychaeta Myzostomida, Pogonophora, Echiura, Sipuncula. Melbourne: SORO, 4A: 79-84.

Hartman, O. 1957. Orbiniidae, Apistobranchidae, Paraonidae and Longosomidae. Allan Hancock Pacific Expeditions, 15(3): 211-393.

Kruse, I., M. Strasser & F. Thiermann. 2004. The role of ecological divergence in speciation between intertidal and subtidal Scoloplos armiger (Polychaeta, Orbiniidae). J. Sea Res., 51(2004): 53-62.

Rozbaczylo, N. & J.C. Castilla. 1987. Invertebrados marinos del Archipielago de Juan Fernandez. In: J.C. Castilla (ed.). Islas Oceanicas Chilenas: conocimiento Cientifico y Necesidades de Investigaciones. Ediciones Universidad Catolica de Chile, Santiago, pp. 167-189.

Solis-Weiss, V., M. Hermosa-Salazar, A. Barbosa-Lopez & P. Hernandez-Alcantara. 2009. Chapter 33, Orbiniidae Hartman, 1942. In: J.A. De Leon-Gonzalez, J.R. Batisda-Zavala, L.F. Carrera-Parra, M.E. Garcia-Garza, A. Pena-Rivera, S.I. Salazar-Vallejo & V. Solis-Weiss (eds.). Poliquetos (Annelida: Polychaeta) de Mexico y America Tropical. Universidad Autonoma de Nuevo Leon, Monterrey, pp. 325-354.

Zhadan, A., A. Stupnikova & T. Neretina. 2015. Orbiniidae (Annelida: Errantia) from Lizard Island, Great Barrier Reef, Australia with notes on orbiniid phylogeny. Zootaxa, 4019(1): 773-801.

Nicolas Rozbaczylo (1), Oscar Diaz-Diaz (2) & Nicolas Cataldo (1)

(1) FAUNAMAR Ltda., Consultorias Medioambientales e Investigacion Marina, Santiago, Chile

(2) Laboratorio de Biologia de Poliquetos, Instituto uceanografico de Venezuela Universidad de Oriente, Cumana, Venezuela

Corresponding author: Nicolas Rozbaczylo (nrozbaczylo@gmail.com)

Corresponding editor: Diego Giberto

Caption: Figure 1. Geographical location of the localities where the specimens of Scoloplos fernandezensis n. sp. were collected from 4-10 m depth around the Robinson Crusoe Island, Juan Fernandez Archipelago.

Caption: Figure 2. Scoloplos juanfernandezensis n. sp. a) Anterior end, dorai view, b) anterior end, lateral view, c) first chaetiger, d) chaetiger 10, lateral view, e) chaetiger 10, frontal view, f) chaetiger 17, g) chaetiger 78, h) chaetiger 105, i) chaetiger 300, j) branchiae detail from chaetiger 300, k) lateral organ of chaetiger 300, k') detail of the lateral organ, i) crenulate chaetae, m-m) neuropodial thoracic hooded hook.

Caption: Figure 3. Scoloplos juanfernandezensis n. sp. a) Mid-posterior chaetigers, showing branched branchiae, b) distal end, dorsal view, c) distal end with pygidium in ventrolateral view.
Table 1. Variability of the paratypes: (No): Number of the
specimen; (FMAR *): FAUNAMAR Ltda. reference collection;
SSUC: Coleccion de Flora y Fauna Profesor Patricio Sanchez
Reyes, Departamento de Ecologia, Facultad de Ciencias
Biologicas, Pontificia Universidad Catolica de Chile,
Santiago; MNHNCL ANN: Museo Nacional de Historia Natural,
Santiago, B1: Chaetiger of emergence of the first branchiae,
B2: Chaetiger of continuous emergence of branchiae with two
branches, B3: Chaetiger of continuous emergence of branchiae
with three terminal filaments, B4: Chaetiger of emergence
of the first branchiae with four terminal filaments, or its
absence (X), B5: Presence of branchiae with five (P5) or
six (P6) terminal filaments, or its absence (X).

Scoloplos juanfernandezensis n. sp.

Number                  Condition         Length (mm)   Width (mm)

SSUC 9008          Complete (entire)         83,3          2,8
MNHNCL Ann-15022   Complete (splited)        73,2          3,1
SSUC 9010          Complete (entire)         61,9          2,9
SSUC 9013          Complete (entire)         54,2          3,1
MNHNCL Ann-15020   Complete (splited)        50,7          2,5
SSUC 9014          Complete (splited)        41,2          3,1
MNHNCL Ann-15019   Complete (entire)         38,3          1,5
MNHNCL Ann-15023   Complete (entire)         14,2          1,7
MNHNCL ANN-15021   Incomplete (splited)      92,8          3,9
(FMAR*)0015        Incomplete (entire)       83,8          3,0
SSUC 9012          Incomplete (splited)      81,1          3,0
MNHNCL ANN-15018   Incomplete (entire)       64,5          3,5
(FMAR*)0014        Incomplete (entire)       63,9          3,0
(FMAR*)0011        Incomplete (entire)       49,2          2,4
SSUC 9011          Incomplete (entire)       48,2          2,8
SSUC 9009          Incomplete (entire)       40,1          3,0
MNHNCL ANN-15017   Incomplete (entire)       30,1          2,2

Scoloplos juanfernandezensis n. sp.

Number                  Condition         Chaetigers   Thorax   B1

SSUC 9008          Complete (entire)         296         18     25
MNHNCL Ann-15022   Complete (splited)        310         17     24
SSUC 9010          Complete (entire)         269         18     28
SSUC 9013          Complete (entire)         263         17     23
MNHNCL Ann-15020   Complete (splited)        208         18     26
SSUC 9014          Complete (splited)        203         17     21
MNHNCL Ann-15019   Complete (entire)         165         18     24
MNHNCL Ann-15023   Complete (entire)         144         17     23
MNHNCL ANN-15021   Incomplete (splited)      337         17     24
(FMAR*)0015        Incomplete (entire)       253         18     25
SSUC 9012          Incomplete (splited)      293         18     28
MNHNCL ANN-15018   Incomplete (entire)       345         17     24
(FMAR*)0014        Incomplete (entire)       262         16     25
(FMAR*)0011        Incomplete (entire)       261         17     21
SSUC 9011          Incomplete (entire)       216         18     27
SSUC 9009          Incomplete (entire)       226         17     21
MNHNCL ANN-15017   Incomplete (entire)       210         17     20

Scoloplos juanfernandezensis n. sp.

Number                  Condition         B2   B3    B4    B5

SSUC 9008          Complete (entire)      74   159   225   P5
MNHNCL Ann-15022   Complete (splited)     77   127   197   P6
SSUC 9010          Complete (entire)      70   158   231   X
SSUC 9013          Complete (entire)      75   137   192   P5
MNHNCL Ann-15020   Complete (splited)     44   112   140   X
SSUC 9014          Complete (splited)     72   145    X    X
MNHNCL Ann-15019   Complete (entire)      72   88     X    X
MNHNCL Ann-15023   Complete (entire)      72   135    X    X
MNHNCL ANN-15021   Incomplete (splited)   70   143   164   P5
(FMAR*)0015        Incomplete (entire)    77   169   177   X
SSUC 9012          Incomplete (splited)   75   120   185   X
MNHNCL ANN-15018   Incomplete (entire)    81   162   163   X
(FMAR*)0014        Incomplete (entire)    78   147   194   X
(FMAR*)0011        Incomplete (entire)    78   149   189   X
SSUC 9011          Incomplete (entire)    72   160   2D    X
SSUC 9009          Incomplete (entire)    83   166    X    X
MNHNCL ANN-15017   Incomplete (entire)    87   134   137   X
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Title Annotation:Short communication
Author:Rozbaczylo, Nicolas; Diaz-Diaz, Oscar; Cataldo, Nicolas
Publication:Latin American Journal of Aquatic Research
Date:Mar 1, 2017
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