Nesotanais thalassinus Stępień, 2025

(SOSA), Senckenberg Ocean Species Alliance, Andrade, Luiz F., Boyko, Christopher B., Brandt, Angelika, Buge, Barbara, Dávila Jiménez, Yasmín, Henseler, Mats, Hernández Alcántara, Pablo, Jóźwiak, Piotr, Knauber, Henry, Marcondes Machado, Fabrizio, Martínez-Muñoz, Carlos A., Momtazi, Farzaneh, Nakadera, Yumi, Qiu, Jian-Wen, Riehl, Torben, Rouse, Greg W., Sigwart, Julia D., Sirenko, Boris, Souza-Filho, Jesser F., Steger, Jan, Stępień, Anna, Tilic, Ekin, Trautwein, Bianca, Vončina, Katarzyna, Williams, Jason D. & Zhang, Junlong, 2025, Ocean Species Discoveries 13 – 27 — Taxonomic contributions to the diversity of Polychaeta, Mollusca and Crustacea, Biodiversity Data Journal 13, pp. e 160349-e 160349 : e160349-

Nesotanais thalassinus Stępień sp. nov.

Materials

Type status: Holotype. Occurrence: occurrenceDetails: Great Barrier reef, Lizard Island, Coconut beach; catalogNumber: W 60130 ; occurrenceRemarks: coral rubble - coarse; individualCount: 1; sex: female; lifeStage: preadult; reproductiveCondition: non-ovigerous; establishmentMeans: native; occurrenceStatus: present; occurrenceID: 6D4B5965-C019-5186-ADF9-CDAA8945EA1E; Taxon: scientificName: Nesotanais thalassinus Stępień ; kingdom: Animalia; phylum: Arthropoda; class: Malacostraca; order: Tanaidacea ; family: Nototanaidae ; genus: Nesotanais ; specificEpithet: thalassinus ; taxonRank: species; scientificNameAuthorship: Stępień; nomenclaturalCode: ICZN; Location: higherGeography: Pacific Ocean; waterBody: Southeast Pacific Ocean; island: Lizard Island; country: Australia; countryCode: AU; locality: Great Barrier Reef, station CGLI 003 ; verbatimDepth: 2 m; verbatimLatitude: 14°41'28.2"S; verbatimLongitude: 145°28'11.3"E; decimalLatitude: - 14.69117; decimalLongitude: 145.4698; Identification: identifiedBy: Anna Stępień; dateIdentified: 2025; Event: samplingProtocol: scuba diving, sieved throught 0.3 mm mesh; eventDate: 04-05 - 2008; habitat: coral rubble - coarse; fieldNumber: CGLI 003; Record Level: institutionID: https://www.museum.qld.gov.au/tropics; institutionCode: QMT; basisOfRecord: PreservedSpecimen

Type status: Paratype. Occurrence: occurrenceDetails: Great Barrier reef, Lizard Island, Hicks Reef; catalogNumber: QMT W 60131 ; occurrenceRemarks: dead coral heads on spur; individualCount: 1; sex: male; lifeStage: adult; establishmentMeans: native; occurrenceStatus: present; occurrenceID: FE49FC73-1E49-5F36-9FAC-2B455068960C; Taxon: scientificName: Nesotanais thalassinus Stępień ; kingdom: Animalia; phylum: Arthropoda; class: Malacostraca; order: Tanaidacea ; family: Nototanaidae ; genus: Nesotanais ; specificEpithet: thalassinus ; taxonRank: species; scientificNameAuthorship: Stępień; nomenclaturalCode: ICZN; taxonRemarks: used as allotype; Location: higherGeography: Pacific Ocean; waterBody: Southeast Pacific Ocean; island: Lizard Island; country: Australia; countryCode: AU; locality: Great Barrier Reef, station LIZ 09-16 D ; verbatimDepth: 16 m; verbatimLatitude: 14°26'52.9"S; verbatimLongitude: 145°29'57.1"E; decimalLatitude: - 14.44803; decimalLongitude: 145.4992; Identification: identifiedBy: Anna Stępień; dateIdentified: 2025; Event: samplingProtocol: scuba diving, sieved throught 0.3 mm mesh; eventDate: 21-02 - 2009; habitat: dead coral heads on spur; fieldNumber: LIZ 09-16 D; Record Level: institutionID: https://www.museum.qld.gov.au/tropics; institutionCode: QMT; basisOfRecord: PreservedSpecimen

Type status: Paratype. Occurrence: occurrenceDetails: Great Barrier reef, Lizard Island, Hicks Reef; catalogNumber: QMT W 60135 ; occurrenceRemarks: dead coral heads on spur; individualCount: 2; sex: female; lifeStage: preadult; reproductiveCondition: non-ovigerous; establishmentMeans: native; occurrenceStatus: present; occurrenceID: DA129350-B0E0-5431-823A-BB234F56831A; Taxon: scientificName: Nesotanais thalassinus Stępień ; kingdom: Animalia; phylum: Arthropoda; class: Malacostraca; order: Tanaidacea ; family: Nototanaidae ; genus: Nesotanais ; specificEpithet: thalassinus ; taxonRank: species; scientificNameAuthorship: Stępień; nomenclaturalCode: ICZN; Location: higherGeography: Pacific Ocean; waterBody: Southeast Pacific Ocean; island: Lizard Island; country: Australia; countryCode: AU; locality: Great Barrier Reef, station LIZ 09-16 D ; verbatimDepth: 16 m; verbatimLatitude: 14°26'52.9"S; verbatimLongitude: 145°29'57.1"E; decimalLatitude: - 14.44803; decimalLongitude: 145.4992; Identification: identifiedBy: Anna Stępień; dateIdentified: 2025; Event: samplingProtocol: scuba diving, sieved throught 0.3 mm mesh; eventDate: 21-02 - 2009; habitat: dead coral heads on spur; fieldNumber: LIZ 09-16 D; Record Level: institutionID: https://www.museum.qld.gov.au/tropics; institutionCode: QMT; basisOfRecord: PreservedSpecimen

Type status: Paratype. Occurrence: occurrenceDetails: Great Barrier reef, Lizard Island, Yonge Reef; catalogNumber: QMT W 60136 ; occurrenceRemarks: small coral rubble on sand; individualCount: 1; sex: female; lifeStage: preadult; reproductiveCondition: non-ovigerous; establishmentMeans: native; occurrenceStatus: present; occurrenceID: BA9EFA71-15DA-5D69-A018-D809D5DBFD81; Taxon: scientificName: Nesotanais thalassinus Stępień ; kingdom: Animalia; phylum: Arthropoda; class: Malacostraca; order: Tanaidacea ; family: Nototanaidae ; genus: Nesotanais ; specificEpithet: thalassinus ; taxonRank: species; scientificNameAuthorship: Stępień; nomenclaturalCode: ICZN; Location: higherGeography: Pacific Ocean; waterBody: Southeast Pacific Ocean; island: Lizard Island; country: Australia; countryCode: AU; locality: Great Barrier Reef, station LIZ 09-10 F ; verbatimDepth: 15 m; verbatimLatitude: 14°36'49.8"S; verbatimLongitude: 145°37'05.5"E; decimalLatitude: - 14.61383; decimalLongitude: 145.6182; Identification: identifiedBy: Anna Stępień; dateIdentified: 2025; Event: samplingProtocol: scuba diving, sieved throught 0.3 mm mesh; eventDate: 18-02 - 2009; habitat: small coral rubble on sand; fieldNumber: LIZ 09-10 F; Record Level: institutionID: https://www.museum.qld.gov.au/tropics; institutionCode: QMT; basisOfRecord: PreservedSpecimen

Type status: Paratype. Occurrence: occurrenceDetails: Great Barrier reef, Lizard Island; occurrenceRemarks: coral rubble; individualCount: 1; sex: female; lifeStage: preadult; reproductiveCondition: non-ovigerous; establishmentMeans: native; occurrenceStatus: present; occurrenceID: AFC89B5B-D047-55F4-A501-5E566B06C215; Taxon: scientificName: Nesotanais thalassinus Stępień ; kingdom: Animalia; phylum: Arthropoda; class: Malacostraca; order: Tanaidacea ; family: Nototanaidae ; genus: Nesotanais ; specificEpithet: thalassinus ; taxonRank: species; scientificNameAuthorship: Stępień; nomenclaturalCode: ICZN; Location: higherGeography: Pacific Ocean; waterBody: Southeast Pacific Ocean; island: Lizard Island; country: Australia; countryCode: AU; locality: Great Barrier Reef, station CGLI 025 A ; verbatimDepth: 12 m; verbatimLatitude: 14°38'44.4"S; verbatimLongitude: 145°27'11.7"E; decimalLatitude: - 14.64567; decimalLongitude: 145.45325; Identification: identifiedBy: Anna Stępień; dateIdentified: 2025; Event: samplingProtocol: scuba diving, sieved throught 0.3 mm mesh; eventDate: 14-04 - 2008; habitat: coral rubble; fieldNumber: CGLI 025 A; Record Level: institutionID: https://www.museum.qld.gov.au/tropics; institutionCode: QMT; basisOfRecord: PreservedSpecimen

Type status: Paratype. Occurrence: occurrenceDetails: Great Barrier reef, Lizard Island; catalogNumber: QMT W 60134 ; occurrenceRemarks: dead coral heads on reef edge; individualCount: 3; sex: female; lifeStage: preadult; reproductiveCondition: non-ovigerous; establishmentMeans: native; occurrenceStatus: present; occurrenceID: E8684079-496A-5108-97AE-7AB7C4A52EC5; Taxon: scientificName: Nesotanais thalassinus Stępień ; kingdom: Animalia; phylum: Arthropoda; class: Malacostraca; order: Tanaidacea ; family: Nototanaidae ; genus: Nesotanais ; specificEpithet: thalassinus ; taxonRank: species; scientificNameAuthorship: Stępień; nomenclaturalCode: ICZN; Location: higherGeography: Pacific Ocean; waterBody: Southeast Pacific Ocean; island: Lizard Island; country: Australia; countryCode: AU; locality: Great Barrier Reef, station LIZ 09-16 E ; verbatimDepth: 5-7 m; verbatimLatitude: 14°26'52.9"S; verbatimLongitude: 145°29'57.1"E; decimalLatitude: - 14.44803; decimalLongitude: 145.4992; Identification: identifiedBy: Anna Stępień; dateIdentified: 2025; Event: samplingProtocol: scuba diving, sieved throught 0.3 mm mesh; eventDate: 21-02 - 2009; habitat: dead coral heads on reef edge; fieldNumber: LIZ 09-16 E; Record Level: institutionID: https://www.museum.qld.gov.au/tropics; institutionCode: QMT; basisOfRecord: PreservedSpecimen

Type status: Paratype. Occurrence: occurrenceDetails: Great Barrier reef, Lizard Island; catalogNumber: QMT W 60137 ; occurrenceRemarks: dead Pocillopora head; individualCount: 4; sex: female; lifeStage: preadult; reproductiveCondition: non-ovigerous; establishmentMeans: native; occurrenceStatus: present; occurrenceID: 276EFB7B-7369-5853-B0C1-FFB91E960EA4; Taxon: scientificName: Nesotanais thalassinus Stępień ; kingdom: Animalia; phylum: Arthropoda; class: Malacostraca; order: Tanaidacea ; family: Nototanaidae ; genus: Nesotanais ; specificEpithet: thalassinus ; taxonRank: species; scientificNameAuthorship: Stępień; nomenclaturalCode: ICZN; Location: higherGeography: Pacific Ocean; waterBody: Southeast Pacific Ocean; island: Lizard Island; country: Australia; countryCode: AU; locality: Great Barrier Reef, station CGLI 008 A ; verbatimDepth: 8 m; verbatimLatitude: 14°38'55.4"S; verbatimLongitude: 145°26'59.5"E; decimalLatitude: - 14.64872; decimalLongitude: 145.44987; Identification: identifiedBy: Anna Stępień; dateIdentified: 2025; Event: samplingProtocol: scuba diving, sieved throught 0.3 mm mesh; eventDate: 06-04 - 2008; habitat: dead Pocillopora head; fieldNumber: CGLI 008 A; Record Level: institutionID: https://www.museum.qld.gov.au/tropics; institutionCode: QMT; basisOfRecord: PreservedSpecimen

Type status: Paratype. Occurrence: occurrenceDetails: Great Barrier reef, Lizard Island; catalogNumber: QMT W 60138 ; occurrenceRemarks: Halimeda and rubble; individualCount: 1; sex: female; lifeStage: preadult; reproductiveCondition: non-ovigerous; establishmentMeans: native; occurrenceStatus: present; occurrenceID: 5381E519-2B75-5506-B2A9-16CFFF4CDF8D; Taxon: scientificName: Nesotanais thalassinus Stępień ; kingdom: Animalia; phylum: Arthropoda; class: Malacostraca; order: Tanaidacea ; family: Nototanaidae ; genus: Nesotanais ; specificEpithet: thalassinus ; taxonRank: species; scientificNameAuthorship: Stępień; nomenclaturalCode: ICZN; Location: higherGeography: Pacific Ocean; waterBody: Southeast Pacific Ocean; island: Lizard Island; country: Australia; countryCode: AU; locality: Great Barrier Reef, station CGLI 012 ; verbatimDepth: 3 m; verbatimLatitude: 14°41'13.5"S; verbatimLongitude: 145°27'56.2"E; decimalLatitude: - 14.68708; decimalLongitude: 145.4656; Identification: identifiedBy: Anna Stępień; dateIdentified: 2025; Event: samplingProtocol: scuba diving, sieved throught 0.3 mm mesh; eventDate: 07-04 - 2008; habitat: Halimeda and rubble; fieldNumber: CGLI 012; Record Level: institutionID: https://www.museum.qld.gov.au/tropics; institutionCode: QMT; basisOfRecord: PreservedSpecimen

Type status: Paratype. Occurrence: occurrenceDetails: Great Barrier reef, Lizard Island; catalogNumber: QMT W 60132 ; individualCount: 8; sex: female; lifeStage: preadult; reproductiveCondition: non-ovigerous; establishmentMeans: native; occurrenceStatus: present; occurrenceID: 5D065D9D-0771-5933-8514-B6FE5F9990A2; Taxon: scientificName: Nesotanais thalassinus Stępień ; kingdom: Animalia; phylum: Arthropoda; class: Malacostraca; order: Tanaidacea ; family: Nototanaidae ; genus: Nesotanais ; specificEpithet: thalassinus ; taxonRank: species; scientificNameAuthorship: Stępień; nomenclaturalCode: ICZN; Location: higherGeography: Pacific Ocean; waterBody: Southeast Pacific Ocean; island: Lizard Island; country: Australia; countryCode: AU; locality: Great Barrier Reef, station LIZ 09-02 B ; verbatimDepth: 13 m; verbatimLatitude: 14°22'13.3"S; verbatimLongitude: 145°21'56.9"E; decimalLatitude: - 14.37036; decimalLongitude: 145.3658; Identification: identifiedBy: Anna Stępień; dateIdentified: 2025; Event: samplingProtocol: scuba diving, sieved throught 0.3 mm mesh; eventDate: 24-02 - 2009; habitat: coral ruble; fieldNumber: LIZ 09-02 B; Record Level: institutionID: https://www.museum.qld.gov.au/tropics; institutionCode: QMT; basisOfRecord: PreservedSpecimen

Type status: Paratype. Occurrence: occurrenceDetails: Great Barrier reef, Lizard Island; catalogNumber: QMT W 60139 ; occurrenceRemarks: rubble; individualCount: 1; sex: female; lifeStage: preadult; reproductiveCondition: non-ovigerous; establishmentMeans: native; occurrenceStatus: present; occurrenceID: 21D09A8C-D5F5-54EA-8EAE-A4DA5D211317; Taxon: scientificName: Nesotanais thalassinus Stępień ; kingdom: Animalia; phylum: Arthropoda; class: Malacostraca; order: Tanaidacea ; family: Nototanaidae ; genus: Nesotanais ; specificEpithet: thalassinus ; taxonRank: species; scientificNameAuthorship: Stępień; nomenclaturalCode: ICZN; Location: higherGeography: Pacific Ocean; waterBody: Southeast Pacific Ocean; island: Lizard Island; country: Australia; countryCode: AU; locality: Great Barrier Reef, station CGLI 046 C ; verbatimDepth: 15 m; verbatimLatitude: 14°34'47.0"S; verbatimLongitude: 145°36'36.4"E; decimalLatitude: - 14.57972; decimalLongitude: 145.6101; Identification: identifiedBy: Anna Stępień; dateIdentified: 2025; Event: samplingProtocol: scuba diving, sieved throught 0.3 mm mesh; eventDate: 20-04 - 2008; habitat: rubble; fieldNumber: CGLI 046 C; Record Level: institutionID: https://www.museum.qld.gov.au/tropics; institutionCode: QMT; basisOfRecord: PreservedSpecimen

Type status: Paratype. Occurrence: occurrenceDetails: Great Barrier reef, Lizard Island; catalogNumber: QMT W 60140 ; occurrenceRemarks: no data; individualCount: 1; sex: male; lifeStage: adult; establishmentMeans: native; occurrenceStatus: present; occurrenceID: 0ED2B6E6-336B-5A30-957E-B2871D5C05B5; Taxon: scientificName: Nesotanais thalassinus Stępień ; kingdom: Animalia; phylum: Arthropoda; class: Malacostraca; order: Tanaidacea ; family: Nototanaidae ; genus: Nesotanais ; specificEpithet: thalassinus ; taxonRank: species; scientificNameAuthorship: Stępień; nomenclaturalCode: ICZN; Location: higherGeography: Pacific Ocean; waterBody: Southeast Pacific Ocean; island: Lizard Island; country: Australia; countryCode: AU; locality: Great Barrier Reef, station CGLI 018 B ; verbatimDepth: 2 m; verbatimLatitude: 14°41'20.4"S; verbatimLongitude: 145°28'12.0"E; decimalLatitude: - 14.689; decimalLongitude: 145.47; Identification: identifiedBy: Anna Stępień; dateIdentified: 2025; Event: samplingProtocol: scuba diving, sieved throught 0.3 mm mesh; eventDate: 2008; habitat: no data; fieldNumber: CGLI 018 B; Record Level: institutionID: https://www.museum.qld.gov.au/tropics; institutionCode: QMT; basisOfRecord: PreservedSpecimen

Description

Non-ovigerous female holotype: Habitus (Fig. 56 A, B). Body length (BL) = 1.3 mm, 5.4 times as long as wide (L: W). Ceph 1.2 L: W, 0.2 × BL, pear-shaped, with pair of proximal setae. Pereon 3.5 L: W, 0.6 × BL. Prn 1–6: 0.3, 0.4, 0.5, 0.6, 0.6, 0.4 L: W, respectively. Pleon with Plt 0.2 × BL. Pl 1–5 same size, 0.2 L: W. Plt 0.5 L: W, with rounded apex.

A 1 (Fig. 57 A): art 1 2.6 L: W, 3.6 × art 2, with two simple and two broom setae; art 2 1.2 L: W, 0.7 × art 3, with three broom and three simple setae; art 3 3.1 L: W, with aesthetasc and four simple setae.

A 2 (Fig. 57 B): art 2 0.7 L: W, 1.2 × art 3, with simple seta; art 3 0.6 L: W, 0.3 × art 4, with inner seta; art 4 5.0 L: W, 1.3 × art 4, with broom seta and three simple setae; art 5 3.2 L: W, with simple seta; art 6 minute, with five setae.

Mouthparts. Lbr (Fig. 57 E) hood-shaped, setose. Left md (Fig. 57 F) incisor denticulated, lacinia mobilis as large as incisor, molar broad. Right md (Fig. 57 G, G’) incisor denticulated, molar broad. Lb (Fig. 57 H) bilobated, setose on distal corners. Mx 1 (Fig. 57 I, I’) endite with eight distal spines, palp with two setae. Mx 2 (Fig. 57 J) ovate. Mxp (Fig. 57 K) basis with simple seta; art 1 naked; art 2 with three setae; art 3 and art 4 with four setae each. Endite with one, two rounded tubercles and simple seta distally.

Ch (Fig. 58 A) basis 1.5 L: W; merus with simple ventral seta and short seta at mid-surface; carpus 1.8 L: W; propodus palm 2.0 L: W, with proximal seta and row of inner setae near dactylus insertion; fixed finger 1.1 L: W, with three inner setae and ventral seta; dactylus little longer than fixed finger.

P 1 (Fig. 58 C) basis with simple seta; ischium with simple seta; propodus with simple subdistal setae and three setae near dactylus insertion; dactylus with unguis 1.2 × propodus. P 2 (Fig. 58 D) carpus with thin and long distal spine; propodus with subdistal seta and distal spine. P 3 (Fig. 58 E) carpus with two elongated distal spines; propodus with two subdistal setae and distal comb of short setae near dactylus insertion; P 4 (Fig. 58 F) ischium with seta; merus with two elongated distal spines; carpus with four elongated distal spines (two located on inner side); carpus with two distal spines and comb of short setae near dactylus insertion. P 5 (Fig. 58 G) similar to P 4, but basis with two broom setae and propodus with three disatl spines. P 6 (Fig. 58 H) similar to P 4, but propodus with three setulose setae near dactylus insertion.

Plp (Fig. 58 I) biramous, five pairs, all similar; basis naked; exopod with ten inner setae; endopod with seven inner setae.

U (Fig. 58 J) exopod with two articles, each with simple setae; endopod with two articles, each with broom and simple setae.

Male paratype ( allotype). Habitus (Fig. 56 C) Body length (BL) = 2.0 mm. Ceph 0.2 × BL. Pereon 0.6 × BL. Pleon with Plt 0.2 × BL.

A 1 (Fig. 57 C) art 1 5.8 L: W, 4.0 × atr 2, with eight simple setae and broom seta; art 2 2.6 L: W, 3.0 × art 3, with simple setae; art 3 as long as wide; art 4 with three aesthetascs.

A 2 (Fig. 57 D) art 1 0.7 L: W, 0.4 × art 2; art 2 2.0 L: W, 2.0 × art 3; art 3 as long as wide, 0.2 × art 4, with setae on dorsodistal corner; art 4 6.4 L: W, 3.7 × art 5, with five simple setae; art 5 4.0 L: W, art 6 broken.

Ch (Fig. 58 B) merus with simple ventral seta; carpus quadrate, with two ventral and dorsal setae; propodus strongly dilated downwards to form a flange in ventral edge, with simple proximal setae and row of inner setae near dactylus insertion, fixed finger with two ventral and two inner setae; dactylus with two inner tooth (small and large) and crenulated inner margin.

Type material

Holotype ( QMT W 60130) and paratype ( allotype; QMT W 60131), collected from Lizard Island, Great Barrier Reef, Australia, at depths of 2–16 m in 2008–2009. The holotype is a pre-adult female; the allotype is an adult male. Paratypes ( QMT W 60132 – W 60140) include pre-adult females and two males from multiple stations around Lizard Island ( 2–16 m), collected from coral rubble, dead coral heads, Pocillopora heads and associated rubble habitats.

Material examined

Holotype ( QMT W 60130), ♀ pre-adult, non-ovigerous, Great Barrier Reef, Lizard Island, Coconut Beach, Station CGLI 003, 2 m depth, 14°41′28.2″S, 145°28′11.3″E, coral rubble, collected by scuba diving, 4 May 2008.

Paratype ( allotype; QMT W 60131), ♂ adult, Great Barrier Reef, Lizard Island, Hicks Reef, Station LIZ 09-16 D, 16 m depth, 14°26′52.9″S, 145°29′57.1″E, dead coral heads on spur, collected by scuba diving, 21 February 2009.

Paratypes.

two ♀♀ pre-adults, non-ovigerous ( QMT W 60135), same data as allotype ( LIZ 09-16 D, 16 m depth, 21 Feb 2009). one ♀ pre-adult, non-ovigerous ( QMT W 60133), Lizard Island, Yonge Reef, Station LIZ 09-10 F, 15 m depth, 14°36′49.8″S, 145°37′05.5″E, small coral rubble on sand, 18 Feb 2009. one ♀ preadult, non-ovigerous ( QMT W 60136), Lizard Island, Station CGLI 025 A, 12 m depth, 14°38′44.4″S, 145°27′11.7″E, coral rubble, 14 Apr 2008. three ♀♀ pre-adults, non-ovigerous ( QMT W 60134), Lizard Island, Hicks Reef, station LIZ 09-16 E, 5–7 m depth, 14°26′52.9″S, 145°29′57.1″E, dead coral heads on reef edge, 21 Feb 2009. four ♀♀ pre-adults, non-ovigerous ( QMT W 60137), Lizard Island, Station CGLI 008 A, 8 m depth, 14°38′55.4″S, 145°26′59.5″E, dead Pocillopora head, 6 Apr 2008. one ♀ pre-adult, non-ovigerous ( QMT W 60138), Lizard Island, Station CGLI 012, 3 m depth, 14°41′13.5″S, 145°27′56.2″E, Halimeda and rubble, 7 Apr 2008. eight ♀♀ pre-adults, non-ovigerous ( QMT W 60132), Lizard Island, Station LIZ 09-02 B, 13 m depth, 14°22′13.3″S, 145°21′56.9″E, small coral rubble, 24 Feb 2009. one ♀ pre-adult, non-ovigerous ( QMT W 60139), Lizard Island, Station CGLI 046 C, 15 m depth, 14°34′47.0″S, 145°36′36.4″E, coral rubble, dissected specimen, 20 Apr 2008. one ♂ adult ( QMT W 60140), Lizard Island, Station CGLI 018 B, 2 m depth, 14°41′20.4″S, 145°28′12.0″E, no habitat data, dissected specimen, 2008.

Type locality

Southeast Pacific Ocean, Great Barrier Reef, Lizard Island, Coconut Beach, 2–16 m depth.

Diagnosis

A 1 art 1 with a length-to-width ratio of 2.6; A 2 art 2 only with short seta; elongated cheliped propodus, with a length-to-width ratio of 2.0; male with smooth cheliped surface.

Etymology

The species name thalassinus , derived from Latin meaning " marine ", refers to the environmental preference of this species for fully saline seawater, while most representatives of Nesotanais are associated with brackish habitats.

Distribution

Great Barrier Reef, Australia.

Taxon discussion

The species described herein represents the fifth known member of the genus Nesotanais , the first from the vicinity of Australia and the second from fully saline habitats. Nesotanais lacustris is known from the brackish Lake Tegano on Rennell Island, Solomon Islands ( Shiino 1968), N. maclaughlinae from the vicinity of a marine cave at Palau Island in Micronesia ( Guţu and Iliffe 1989), N. rugula from the brackish Songkhla Lake in Thailand ( Bamber et al. 2003) and N. ryukyuensis from a brackish river on Okinawa Island ( Kakui et al. 2010).

The female of the new Nesotanais species can be distinguished from its congeners by a relatively wide art 1 of A 1, with a length-to-width (L: W) ratio of 2.6 in the new species, compared to 3.5 in N. lacustris and N. rugula and 2.5 in N. ryukyuensis . Furthermore, the new species is characterised by an elongated cheliped propodus with an L: W ratio of 2.0, whereas it is 1.5, 1.2 and 1.2 in N. lacustris , N. ryukyuensis and N. rugula , respectively. Additionally, the dactylus plus unguis of P 1 is relatively long, exceeding the length of the propodus, whereas, in other Nesotanais females, it is either shorter or equal in length.

The male of the new species can be distinguished from N. ryukyuensis and N. rugula by the absence of a series of cuticular ridges on the surface of the cheliped. Both the male and female of the new species can be further differentiated from all other Nesotanais species by the absence of a long, thin spine on art 2 of the A 2, which is present in all previously described species.

Methods

The samples were collected as part of the CENSUS OF CORAL REEFS project (CReefs), from the vicinity of Lizard Island at the Great Barrier Reef. Coral rubble fragments were collected manually during SCUBA diving and placed into 20 - litre buckets containing either a mixture of fresh and seawater or seawater with a few drops of formaldehyde for several hours to encourage the organisms to exit their microhabitats (e. g. tubes and crevices). The samples, with live animals still present, were then washed through a fine 0.3 mm mesh and the residue was examined under a microscope. Tanaidacean specimens were subsequently collected and preserved in 80 % ethanol. Specimens of Nesotanais were dissected with needles, mounted in glycerine on slides and sealed with the melted paraffin. Illustrations were initially made using a microscope equipped with a camera lucida and were subsequently re-drawn digitally using a graphic tablet, following the method described by Coleman (2003).

Repository: The type materials have been deposited at the Queensland Museum Tropics ( QMT).

Figures

Figure 56. Nesotanais thalassinus Stępień, sp. nov. Non-ovigerous female holotype [W 60130], habitus. A Dorsal view; B Lateral view. Adult male allotype [W 60131], habitus; C Lateral view. Scale bars: 1 mm.

Figure 57. Nesotanais thalassinus Stępień, sp. nov. Non-ovigerous female paratype [W 60139] (A – B, F – K), male paratype [W 60140] (C – D). A A 1; B A 2; C A 1; D A 2; E Lbr; F Left Md; G Right Md; G ’ Molar of right Md; H Lbi; I Mx 1 endite; I ’ Mx 1 palp; J Mx 2; K Mxp. Scale bars: 0.1 mm.

Figure 58. Nesotanais thalassinus Stępień, sp. nov., non-ovigerous female paratype [W 60139] (A, C – J), male paratype [W 60140] (B). A Ch; B Ch; C P 1; D P 2; E P 3; F P 4; G P 5; H P 6; I Plp; J U. Scale bars: 0.1 mm.