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Research Article
Oahutanais makalii, a new genus and species of colletteid tanaidacean (Crustacea, Peracarida) from shelf-waters off Hawaii, with a taxonomic key
expand article infoAndres G Morales Núñez‡, Kim Larsen§, William Cooke|
‡ University of Maryland Eastern Shore (UMES), Princess Anne, United States of America
§ ENSPAC Department of Environmental, Social and Spatial Change, Roskilde, Denmark
| Marine Environmental Research, University of Hawaii at Manoa, Hawaii, United States of America

Corresponding author: Andres Morales Núñez ( amoralesnunez@yahoo.es )

Academic editor: Michael Ohl
© 2016 Andres Morales Núñez, Kim Larsen, William Cooke.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation: Morales-Núñez AG, Larsen K, Cooke WJ (2016) Oahutanais makalii, a new genus and species of colletteid tanaidacean (Crustacea, Peracarida) from shelf-waters off Hawaii, with a taxonomic key. Zoosystematics and Evolution 92(1): 1-12. https://doi.org/10.3897/zse.92.5581
ZooBank: urn:lsid:zoobank.org:pub:F8F8D8A7-BBD5-4A58-81EC-48DA1B09A88B
Open Access

Abstract

A new colletteid tanaidacean, Oahutanais makalii gen. et sp. n., is described from Hawaiian coastal waters at depths ranging from 19 to 102 m. The new taxon is tentatively designated as a new genus, although it displays many features in common with the genus Leptognathiella. The new species is distinguished from the morphologically similar tanaidomorphans by having (1) a small body, less than 1.0 mm (reproductively active specimens), (2) a maxillule with two bifid spiniform setae; (3) a maxilliped palp article-2 with geniculate, finely pectinate spiniform seta on sub-distal inner margin, (4) a cheliped attachment ventrally via sclerite not connected to the carapace, and (5) the pereopods 1 to 6 with ischial seta shorter than the merus. A key to the five extant genera of Colletteidae in the North Pacific Ocean is presented herein.

Resumen

Un nuevo tanaidáceo, Oahutanais makalii gen. et sp. n., es descrito de las aguas costeras Hawaianas a un rango de profundidad de 19 a 102. La nueva especie es tentativamente designada como un nuevo género, aunque presenta muchas características en común con el género Leptognathiella. La nueva especie puede ser distinguida de especies morfológicamente similares por tener (1) cuerpo pequeño, menor a un 1.0 mm (especímenes reproductivamente activos), (2) maxílula con dos setas espiniformes bífidas, (3) margen interno subdistal del segundo artejo del palpo del maxillípedo con una seta espiniforme doblada y finamente pectinada, (4) quelípedo adjunto ventralmente por medio del esclerito no conectado al caparazón, and (5) isquio de los pereiópodos 1 al 6 con una seta más corta que el mero. Una clave es presentada para separar los cinco géneros de la familia Colletteidae presentes en el norte del océano Pacífico.

Key Words

Tanaidacea , Colletteidae , Oahutanais makalii , new species, Pacific Ocean, taxonomy

Introduction

The Tanaidacean fauna from the Hawaiian Islands has received little attention so far. Recently, David and Heard (2015) described a new metapseudid, Cryptapseudes lerory David & Heard, 2015 from Niihau Island. They presented a detailed list on the current status of twelve species of tanaidaceans previously reported from the Hawaiian archipelago. A small, blind undescribed genus and species of tanaidacean belonging to the family Colletteidae Larsen & Wilson, 2002 was repeatedly collected throughout two decades of annual-US-EPA-mandated-benthic-community-monitoring at four Honolulu wastewater treatment plant outfalls (Fig. 1).

Figure 1. 

Map of study area, indicating the sampling stations where Oahutanais makalii gen. et sp. n., were found.

The family Colletteidae was erected during a phylogenetic revision of the superfamily Paratanaoidea Lang, 1949 to accommodate genera not assigned to any family, most being anarthurids (sensuGuţu and Sieg 1999) and leptognathiids: nevertheless, the systematic support for creating this family was admittedly weak (Larsen and Wilson 2002: 215) and incomplete (Larsen 2005; Bird and Larsen 2009). After thirteen years, the family currently holds 15 genera, which have been reported from the North and South Pacific Ocean, North and South Atlantic Ocean, Gulf of Mexico, Indian Ocean, Arctic Ocean and Antarctic Ocean (Table 1). The description of this new Hawaiian genus and species as well as an identification key to the five extant genera of Colletteidae in the North Pacific Ocean is presented here.

Table 1.
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Listing of the 16 currently recognized genera within the family Colletteidae, including information on distribution and depth range. NW = northwest; NE = northeast; SW = southwest; SE = southeast; and GoM = Gulf of Mexico.

Genus Geographical area Depth range (m)
Bascestus Błażewicz-Paszkowycz & Bamber, 2012 SW Pacific (Tasmania Sea) 37–49
Caudalonga Larsen, 2005 NW Atlantic (GoM) 625
Cetiopyge Larsen & Heard, 2002 NW Atlantic (GoM) 213–2060
Cheliasetosatanais Larsen & Araújo-Silva, 2014 North Equatorial Pacific 4259–4261
Collettea Lang, 1973 NW and North Equatorial Pacific; NE Atlantic and GoM; SW Indian Ocean; Artic and Antarctic Ocean 291–6142
Filitanais Kudinova-Pasternak, 1973 NW and NE Pacific; NW and SE Atlantic, and GoM; SE Indian Ocean; Artic and Antarctic Ocean 1070–6109
Haplocope Sars, 1882 NE Atlantic 22–1632
Isopodidus Larsen & Heard, 2002 NW Atlantic (GoM) 860–983
Leptognathiella Hansen, 1913 NE Atlantic 213–4822
Leptognathiopsis Holdich & Bird, 1986 NE Atlantic 22–5622
Macrinella Lang, 1971 NE Atlantic 1870
Nematotanais Bird & Holdich, 1985 NE Atlantic 1378–1510
Nippognathiopsis Błażewicz-Paszkowycz, Bamber & Jóźwiak, 2013 NW Pacific (Japan) 517–521
Oahutanais gen. n. North Central Pacific (Hawaii) 19–102
Pseudoleptognathia Sieg, 1986 Artic Ocean 70–106
Subulella Holdich & Bird, 1986 Atlantic Ocean 12–2610

Materials and methods

Bulk sediment collections were made by divers or with benthic grabs, depending upon depth, sieved through 0.5 mm screens and preserved in 10% buffered formalin.

Specimens were dissected under an Olympus ZS-16 stereomicroscope. Appendages were mounted on glass slides in glycerine and observed with an Olympus BX41 microscope, and drawings were made with a camera Lucida. Additional material was examined under the Hitachi S-4800 Scanning Electron Microscope (SEM) at the Pacific Biosciences Research Center (PBRC)Biological Electron Microscope Facility (BEMF). Illustrations were prepared with Adobe Illustrator CS6 Extended.

Type material has been deposited in the National Museum of Natural History, Smithsonian Institution, Washington DC, (USNM), Gulf Coast Research LaboratoryMuseum, Ocean Springs, Mississippi MS, (GCRL), and the Bernice Pauahi Bishop Museum(BPBM), Honolulu Hawaii. All measurements are in millimetres (mm). Total body length (TL) is measured from the tip of the rostrum to the end or tip of the telson. Terminology used in this description follows that of Larsen (2003). In our description the total length of the dactylus includes the unguis.

Systematics

Order Tanaidacea Dana, 1849
Suborder Tanaidomorpha Sieg, 1980
Superfamily Paratanaoidea Lang, 1949
Family Colletteidae Larsen & Wilson, 2002

Oahutanais gen. n.

http://zoobank.org/14D4711E-DF66-4CFB-8530-437AA7F9F4AB

Generic diagnosis

Female: Small, 0.8–0.9 mm, slender body, parallel-sided. Carapace extending laterally to cover (dorsally) the cheliped attachments. Carapace not connected with the cheliped sclerites Pereonites wider than long. Antennule with four articles and minute terminal segment, shorter than carapace, article-2 with dorsal symmetric projection overlapping basal part of article-3, terminal segment minute and covered by article-4 (only visible with scanning electron microscope image). Antenna with six articles. Labium without distolateral spines. Maxillule with seven distal spiniform setae (two bifid); maxillipedal palp article-2 with geniculate, finely-pectinate spiniform seta on distal inner margin (serrations visible at magnification 100×). Cheliped attached via sclerite just anterior to the posterior margin of the cephalothorax, very close to the midventral line. Pereopods 1 to 6 attached ventrally. Pereopods 1–3 relatively slender; ischial seta shorter than merus. Pereopods 4–6 not stouter than pereopods 1–3; ischial setae shorter than merus. Pleopods absent in females. Uropods longer than pleotelson; basal article shorter than pleotelson, without distal apophyses; exopod uni-articulated, slightly longer than endopod article-1.

Male unknown.

Type species

Oahutanais makalii sp. n.

Etymology

Named after “O’ahu Island”, where the material used in this study was collected, plus suffix - tanais.

Gender

Masculine.

Distribution

Hawaii Islands at depths ranging from 19 to 102 meters.

Remarks

The family Colletteidae has been considered as polyphyletic (Larsen and Wilson 2002; Błażewicz-Paszkowycz and Poore 2008; Błażewicz-Paszkowycz et al. 2013) and it is currently composed of 15 genera (WoRMS); unfortunately, most of the genera included within this diverse family need revision (e.g. Leptognathiella Hansen, 1913 and Filitanais Kudinova-Pasternak, 1973). The females of Oahutanais gen. n. can be identified by having a small body (less than 1 mm in length of reproductively active specimens), cheliped attached just anterior to the posterior margin of the cephalothorax, very close to the midventral line, not in contact with carapace lateral margin, and pereopods 1 to 6 attached ventrally. Oahutanais gen. n. appears to be most closely related to the genera, Leptognathiella Bird and Holdich, 1984 from the Atlantic or Gulf of México (Larsen 2005; Larsen et al. 2006), Leptognathiopsis Holdich & Bird, 1986 from the North Atlantic (Holdich and Bird 1986), and several species of Leptognathia G.O. Sars, 1882 sensu stricto (see Larsen and Shimomura 2007: 12) in having pereonites wider than long, pointed molars, females without pleopods (only in some species of Leptognathiella and Leptognathia), and uropod structure. However, the Oahutanais can be distinguished from the Atlantic species of Leptognathiopsis and Leptognathiella by having 1) the maxilliped palp article-2 with geniculate, finely pectinate spiniform seta on sub-distal margin, 2) pereopods 1–3 with basis slender, and 3) pereopod ischial setae shorter than merus.

The new genus also shows similarities with the monotypic genus Nippognathiopsis Błażewicz-Paszkowycz, Bamber & Jóźwiak, 2013, recently described from 517–1356 m in waters off Japan. However, Oahutanais can be differentiated by 1) its pereonites are wider than long, 2) the antennal article-1 is longer than the distal three articles and minute terminal segment combined (shorter in Nippognathiopsis), 3) the maxilliped endites have a medial small process (two oval tubercles in Nippognathiopsis), 4) the maxilliped palp article-2 has a geniculate, finely pectinate spiniform seta on the sub-distal margin, and 5) pereopods 1–6 are slender. Although the presence of the geniculate, finely pectinate spiniform seta in the maxilliped palp article-2 separates Oahutanais from the other genera within the family Colletteidae, it is possible that this spiniform seta has been overlooked in the original description of Nippognathiopsis, as well as in other colletteids due to their small overall size. Unfortunately, no information is available on the form of the cheliped attachment in Nippognathiopsis.

Bird and Larsen (2009) mentioned that this character, the cheliped-cephalothorax attachment position, is an important feature that has been overlooked or has not been recorded or illustrated by many authors, even today. So far within the family Colletteidae, only Błażewicz-Paszkowycz and Bamber (2012) and this study have included detailed information and illustrations showing the real point of insertion of the cheliped and how far it is located from pereonite-1. Thus, Oahutanais can be separated from Bascestus Błażewicz-Paszkowycz & Bamber, 2012 by having 1) the cheliped attached just anterior to the posterior margin of the cephalothorax (more anterior in Bascestus), 2) females without pleopods (pleopods present in Bascestus), and 3) exopod uni-articulated (bi-articulated in Bascestus).

The ventral cheliped attachment without contact with the carapace lateral margin (Fig. 8B–C) is an interesting and rare character among tanaidomorphans, and it has so far only been recorded from another colletteid, Isopodidus Larsen & Heard, 2002, but this highly modified genus differs in many other aspects from Oahutanais.

Oahutanais makalii sp. n.

http://zoobank.org/934BF56A-4CE7-40FE-B1DC-1F93E8EDD24B
Figures 2, 3, 4, 5, 6, 7, 8

Type material

Holotype Adult ♀, length 0.9 mm, (USMN 1283305), BPOBS Station (Stn) HB4-R1 (21° 16’47.7’’N – 158° 01’38.1’’W), depth 62 m, substrata: “predominantly fine and medium sand”, coll. by City and County of Honolulu Oceanographic Team, March 2013.

Paratypes. Four ♀♀ (USMN 1283306); four ♀♀ (GCRL 06534); and six ♀♀ (BPBM 2015.097; four on SEM stubs and two in alcohol), SIOBS Stn D3A (21° 16’55.3’’N – 157° 53’49.9’’W), depth 49 m, substrata “primarily coarse sediment including shell fragments”, coll. by City and County of Honolulu Oceanographic Team, October 2014. Additional specimens from the type locality are in the collection of the authors.

Other material examined

Thirteen ♀♀, one ovigerous ♀, two ♀♀ with remains of marsupium, SIOBS Stn D3A (21° 16’55.3’N – 157° 53’49.9’W), depth 49 m, substrata “primarily coarse sediment including shell fragments”, coll. by City and County of Honolulu Oceanographic Team, October 2014; 27 specimens (spec), MOBS Stn D (21° 25’ 32.3”N – 157° 42’ 53.6”W), depth 30 m, October 2013; two spec, SIOBS Stn C1A (21° 17’ 38.3”N – 157° 55’ 28.3”W), depth 19.2 m, October 2014; one spec, SIOBS Stn C5A (21° 16’ 53.9”N – 157° 51’ 25.4”W), depth 20.1 m, October 2014; two spec, SIOBS Stn D1 (21° 17’ 23.2”N – 157° 55’ 29.8”W), depth 49.1 m, October 2014; three spec, SIOBS Stn D2 (21° 16’ 55.2”N – 157° 54’ 36.3”W), depth 56.4 m, October 2014; 40 spec, SIOBS Stn D3A (21° 16’ 55.9”N – 157° 53’ 48.8”W), depth 50 m, October 2014; 16 spec, SIOBS Stn D5 (21° 16’ 36.8”N – 157° 51’ 33.9”W) depth 52.1 m, October 2014; eight spec, SIOBS – Stn D6 (21° 16’ 02.5”N – 157° 50’ 46.4”W) depth 50.0 m, October 2014; two spec, SIOBS Stn E1 (21° 17’ 09.5”N – 157° 55’ 32.2”W), depth 102.4 m, October 2014; 49 spec, SIOBS Stn E3 (21° 16’ 42.9”N – 157° 53’ 49.5”W), depth 84.4 m, October 2014; three spec, SIOBS Stn E5 (21° 16’ 22.5”N – 157° 51’ 40.3”W) 101.5 m, October 2014; four spec, SIOBS Stn E6 (21° 15’ 51.1”N – 157° 50’ 57.2”W) depth102.4 m, October 2014; 7 spec, WOBS Stn Z (21° 25’ 38.8”N – 158° 11’ 48.1”W) depth 29.3 m, October 2014.

Diagnosis

As the generic diagnosis above.

Etymology

The species name, makali’i, is Hawaiian for tiny or minute and reflects both where the material used in this study was collected and its small size relative to other tanaidaceans within this benthic community.

Type locality

Off Barbers Point Oahu, BPOBS study area (21° 16’47.7’’N – 158° 01’38.1’’W), Hawaii, May 2013.

Description

Based in holotype female, length 0.9 mm (USMN 1283305).).

Body (Fig. 2) length about 0.9 mm, about 8.6 times width.

Figure 2. 

Oahutanais makalii gen. et sp. n., holotype female: dorsal view. Scale bar: 0.5 mm.

Cephalothorax (Figs 2, 6A–B) about 15% of TL, slightly longer than first two pereonites combined, about 1.5 times longer than wide, oval shape (Fig. 6B); with distolateral seta. Eye-lobes absent.

Pereon (Fig. 2): about 60% of TL; pereonites 1–3 and 6 sub-rectangular, wider than long; pereonites 4–5 quadrate.

Pleon (Figs 2, 7A): about 20% of TL; combined length of pleonites 1 to 5 slightly shorter to that of pereonites 5 and 6 combined; all pleonites subequal, much wider than long; pereonite-1 with two simple setae distally.

Pleotelson (Figs 2, 5B) about 5% of TL, same length of pleonites 5 and 6 combined; sub-rectangular, with two broom setae and two simple setae, apex blunt; pleonite-5 with two simple setae distally.

Antennule (Figs 3A, 6A–B): slightly longer than 2/3 length of cephalothorax. Article-1 about 3.1 times long than wide, longer than distal three articles, with three setulose setae and one simple seta along lateral margin. Article-2 about 1.1 times longer than wide, with distodorsal simple seta; with two setulose setae and one long (longer than articles 2 to 4 combined) simple seta on distoventral margin. Article-3 about 1.5 times wider than long, with two simple setae dorsally and one simple seta lateral. Article-4 about 1.4 times longer than wide, with four simple setae of different length. Terminal segment minute and covered by article-4, with one seta and one aesthetasc (only visible with SEM images) (Fig. 6B).

Figure 3. 

Oahutanais makalii gen. et sp. n., holotype female: A antennule, lateral view; B antenna, lateral view; C labrum; D left mandible; E right mandible; F labium; G maxillule; H maxilliped. Scale bars: 0.1 mm.

Antenna (Figs 3B, 6B): article-1 short, asetose. Article-2 about 1.2 times wider than long, with distolateral short seta. Article-3 about 1.3 times wider than long, with distodorsal long simple seta. Article-4 about 3.0 times longer than wide, longer than articles 2 and 3 combined, with one setulose seta and two simple setae on distoventral setae margin. Article-5 about 2.0 times longer than wide, with one simple seta on distolateral margin. Article-6 minute, with five simple setae of unequal length.

Mouthparts: Labrum (Figs 3C, 7A): hood-shaped and finely setose. Mandibles (Fig. 3D–E): left mandible, incisor with two to three uneven denticles; lacinia mobilis narrow, apparently smooth (Fig. 3D). Right mandible incisor with broad and crenulate upper margin (Fig. 3E). Molar process pointed, with small distoventral spines (Fig. 3D–E). Labium (Figs 3F, 6B, 7A): bilobed with distolateral processes. Maxillule (Figs 3G, 6B, 7A): endite with seven distal spiniform setae (two bifid), two sub-distal simple setae, and cluster of setules on distal margin; palp bearing two long terminal setae of unequal length. Maxilla: not recovered.

Maxilliped (Figs 3H, 7A): basis fused, apparently asetose. Endites unfused, with one simple seta and medial small process, outer margin with small spine. Palp: Article-1 asetose. Article-2 with setulose seta on outer margin, inner sub-distal margin with two simple setae and geniculate, finely-pectinate spiniform seta (serrations visible at magnification 100x). Article-3 with two setulose setae on inner margin. Article-4 with subdistal setulose setae and cluster of setules on outer margin (Fig. 7A), inner and distal margin with five setulose setae.

Epignath: not recovered.

Cheliped: (Figs 4A–B, 6A–C, 8): cheliped attached just anterior to the posterior margin of cephalothorax and very close to the midventral line, via sclerite (Figs 6B–C, 8). Basis about 1.9 times longer than wide, with subdistal short seta. Merus triangular, with simple seta on ventral margin. Carpus about 1.8 times longer than wide, anterior margin with distodorsal seta; ventral margin with two simple setae of different length. Propodus about 1.4 times longer than wide, with small simple seta near insertion of dactylus. Fixed finger with crenulated ventral margin, with two ventral setae and three simple setae on outer incisive margin, with two to three sharp denticles on inner margin. Inner surface (Fig. 4B) with three short simple setae (one distinctly longest) at articulation with dactylus. Dactylus with long simple proximal seta on inner side.

Figure 4. 

Oahutanais makalii gen. et sp. n., holotype female: A left cheliped, lateral view; B left chela, inner view. Scale bar: 0.1 mm.

Pereopod-1 (Figs 5A, 8): attached ventrally, coxa with simple seta on anterodistal margin. Basis about 4.0 times longer than wide, asetose. Ischium wider than long, with simple seta shorter than merus. Merus about 1.5 times longer than wide, with two distoventral pectinate setae (Fig. 5H) (one short and one robust, just longer than carpus). Carpus about 1.7 times longer than wide; two pectinate distodorsal setae and one robust pectinate distoventral seta (Fig. 5D). Propodus about 3.1 times longer than wide; distodorsal margin with spine-like apophysis; distoventral margin with one pectinate subdistal seta. Dactylus elongate, together with unguis longer than propodus, dactylus shorter than unguis.

Figure 5. 

Oahutanais makalii gen. et sp. n., holotype female: A pereopod-1; B pereopod-2; C pereopod-3; D pereopod-4; E pereopod-5: F pereopod-6; G uropod; H pectinate seta. Scale bars: 0.1 mm.

Pereopod-2 (Fig. 5B): similar to pereopod-1, except basis and propodus longer. Propodus with ventrodistal pectinate small seta. Dactylus and unguis shorter than propodus.

Pereopod-3 (Fig. 5C): similar in form to pereopod-2, except shorter than other five pereopods.

Pereopod-4 (Figs 5D, 8): attached ventrally, basis about 4.0 times longer than wide, with setulose seta on proximal dorsal margin. Ischium wider than long with two simple setae of unequal length on posterior margin, long seta shorter than merus. Merus about 2.0 times longer than wide, with two distoventral pectinate setae. Carpus about 2.0 times longer than wide, with four pectinate setae of unequal length. Propodus about 3.5 times longer than wide; distodorsal margin with long pectinate setae, reaching beyond the dactylus; distoventral margin with two pectinate setae. Dactylus and unguis longer than propodus, dactylus shorter than unguis.

Pereopod-5 (Fig. 5E): Similar to pereopod-4, except carpus and dactylus longer. Basis with setulose seta on mid-ventral margin.

Pereopod-6 (Fig. 5F): similar to pereopod-5, except basis, carpus, and propodus slightly longer; ischium, merus, and dactylus shorter.

Pleopods: Absent. (Fig. 7B)

Uropod (Figs 5G, 7B): biramous, twice as long as pleotelson, but half as long as entire pleon. Basal article shorter than pleotelson, without distal apophyses. Exopod uni-articulate, slightly longer than endopod article-1, with simple seta on mid-lateral? margin, and two simple distal setae (one longer). Endopod biarticulate, article-1 with three setae (two setulose and one simple) on subdistal inner margin; article-2 with subdistal simple lateral seta, with one setulose and five (four long and one short) simple setae distally.

Male. Unknown.

Ovigerous female. As above. When embryos were present, six (smaller embryos) was the most observed; typically only three or fewer were present.

Figure 6. 

Oahutanais makalii gen. et sp. n., paratype female (SEM images): A enlargement of anterior end showing part of the carapace, antennules, and carpus to dactylus of left cheliped, dorsal view; B enlargement of the cephalothorax and pereonites-1; C enlargement of anterior part showing how the carapace covers the antennules, antennas, mouthparts, and left cheliped, ventral view.

Figure 7. 

Oahutanais makalii gen. et sp. n., paratype female (SEM images): A enlargement of mouthparts; B enlargement of posterior end showing pleonites 1 to 5, pleotelson, and uropods.

Figure 8. 

Oahutanais makalii gen. et sp. n., paratype female (SEM images): A ventral view of habitus; B enlargement of mid-anterior part of habitus, lateral view; C enlargement of union of cephalothorax and pereonite-1.

Remarks

Among the family Colletteidae, Oahutanais makalii sp. n. shows some similarities with Cetiopyge mira Larsen and Heard, 2002, Isopodidus janum Larsen and Heard, 2002, and Collettea minima Hansen, 1913 (see Larsen 2000) in having the unusual presence of bifurcate spiniform terminal setae on the maxillule endite; however, the presence of this kind of setae has also been reported in some species of other families such as the Tanaellidae Larsen & Wilson, 2002 (Arthrura andriashevi Kudinova-Pasternak, 1966), Cryptocopidae Sieg, 1977 (Curtichelia expressa Kudinova-Pasternak, 1987), and Paratanaoideaincertae sedis (Parafilitanais mexicanus Larsen, 2002). Larsen and Heard (2002) suggested that this setal character could have a wider occurrence in the deep-sea species, since it has only been reported in specimens collected in deep waters. Our results indicated that the presence of these unusual setae is not restricted to deep-sea Tanaidacea, since Oahutanais makalii was found in shallow waters (<105 m).

Key to the genera of Colletteidae in the North Pacific Ocean (females only)

1 Pleotelson terminating in a dorsal plate covering the uropods 2
– Pleonites not terminating in a dorsal plate covering the uropods 3
2 Pleonites almost as long as individual pereonites and pleotelson Filitanais [western and eastern North Pacific]
– Pleonites not as long as individual pereonites and pleotelson Collettea [western North Pacific]
3 Propodus of pereopod-6 with three distodorsal spiniform seta Cheliasetosatanais [equatorial North Pacific]
– Propodus of pereopod-6 with one distodorsal spiniform seta 4
4 Antennal article-1 longer than distal three articles. Maxilliped endites with medial small process Oahutanais gen. n. [north Central Pacific]
– Antennal article-1 shorter than distal three articles. Endites with two oval tubercles Nippognathiopsis [western North Pacific]

Remarks on ecology

A complete description of the surrounding benthic communities at these four study areas is beyond the scope of this paper, although the following observations are offered. Oahutanais makalii occurs from 19 to 102 m. A single specimen per replicate correlated to a minimum density of 220 ind.m2. The maximum density for this species observed at any station was 5,070 ind.m2; far below densities recorded for the most abundant small crustaceans (over 50,000 ind.m2). No associated tubes were observed with the specimens.

Acknowledgments

Processing, sorting, preliminary identification and enumeration for all specimens described herein was supported by the City and County of Honolulu, Department of Environmental Services contract SC-ENV-1200115 to the Water Resources Research Center University of Hawaii (WJC). AGM-N and KL were not supported by any funding grant. The invaluable assistance in preparation and examination of the SEM material by Tina M. (Weatherby) Carvalho, (PBRC-BEMF) is gratefully acknowledged. We wish to express our gratitude to Graham Bird for his comments and suggestions on the early version of this paper. We are most grateful for the helpful and constructive criticism provided by the three anonymous reviews. We take full responsibility for any differing systematic or taxonomic interpretations.

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