Melinnopsis gardelli, Gunton & Kupriyanova & Alvestad, 2020

Gunton, Laetitia M., Kupriyanova, Elena & Alvestad, Tom, 2020, Two New Deep-water Species of Ampharetidae (Annelida: Polychaeta) from the Eastern Australian Continental Margin, Records of the Australian Museum 72 (4), pp. 101-121 : 106-110

publication ID	https://doi.org/ 10.3853/j.2201-4349.72.2020.1763
publication LSID	lsid:zoobank.org:pub:78FA352E-E590-4AA2-9C07-D963C36A7F5D
persistent identifier	https://treatment.plazi.org/id/D98E867B-B70F-42C3-AAEA-BD178B01D424
taxon LSID	lsid:zoobank.org:act:D98E867B-B70F-42C3-AAEA-BD178B01D424
treatment provided by	Felipe
scientific name	Melinnopsis gardelli
status	sp. nov.

Treatment

Melinnopsis gardelli sp. nov.

urn:lsid:zoobank.org:act:D98E867B-B70F-42C3-AAEA-BD178B01D424

Figs 2–5 View Figure 2 View Figure 3 View Figure 4 View Figure 5

Holotype incomplete missing part of long buccal tentacle: AM W.50735, IN2017_ V03 operation ( OPS) 056, Australia, New South Wales, Jervis Commonwealth Marine Reserve, Beam Trawl (start 35°19'58.8"S 151°15'28.8"E, 2650 m; end 35°19'55.2"S 151°12'50.4"E, 2636 m) 29/5/2017 GoogleMaps . Paratypes: AM W.53131 and AM W.52539 (mounted for SEM), OPS 056 Australia, New South Wales, Jervis Commonwealth Marine Reserve, Beam Trawl (start 35°19'58.8"S 151°15'28.8"E, 2650 m; end 35°19'55.2"S 151°12'50.4"E, 2636 m) 29/5/2017 GoogleMaps .

Other material examined. Total 47 specimens. (2 specimens) AM W.51476, W.51480 OPS 004 Australia, Tasmania, Freycinet Commonwealth Marine Reserve, Beam Trawl (start 41°43'51.6"S 149°7'12"E, 2820 m; end 41°47'27.6"S 149°9'21.6"E, 2751 m) 18/05/2017. (2 specimens) AM W.50424 OPS 044 Australia, New South Wales, off Bermagui, Beam Trawl (start 36°21'18"S 150°38'38.4"E, 2821 m; end 36°18'54"S 150°39'3.6"E, 2687 m) 27/05/2017. (38 specimens) AM W.50395, W.50735, W.52987, W.52988, W.50370, W.50394, W.50396, W.53107, W.50398, OPS 056 Australia, New South Wales, Jervis Commonwealth Marine Reserve , Beam Trawl (start 35°19'58.8"S 151°15'28.8"E, 2650 m; end 35°19'55.2"S 151°12'50.4"E, 2636 m) 29/5/2017. (2 specimens) AM W.50736, W.50411 OPS 090 Australia, New South Wales, off Byron Bay , Beam Trawl (start 28°40'37.2"S 154°12'10.8"E, 2587 m; end 28°42'32.4"S 154°11'24"E, 2562 m) 07/06/2017. (1 specimen) AM W.50412, OPS 101 Australia, Queensland, off Moreton Bay , Beam Trawl (start 26°56'45.6"S 153°56'42"E, 2520 m; end 26°58'15.6"S 153°57'3.6"E, 2576 m) 09/06/2017. (2 specimen) AM W.50418, W.50419, OPS 122 Australia, Queensland, Coral Sea Commonwealth Marine Reserve Beam Trawl, (start 23°45'3.6"S 154°38'20.4"E, 2369 m; end 23°46'22.8"S 154°36'57.6"E, 2329 m) 13/06/2017 GoogleMaps .

Description (based on holotype). Holotype 40 mm length for more than 60 chaetigers ( Fig. 2A View Figure 2 ), widest at post-branchial region 4 mm ( Fig. 2B View Figure 2 ), thereafter gradually tapering to abdomen (1 mm width) and pygidium. Thorax with 16 chaetigers; neurochaetae as small acicular spines on segments II–V and uncini on remaining> 56 chaetigers.

Prostomium with well-defined anterior and posterior sections separated by a pair of deep transverse nuchal slits meeting mid-dorsally ( Fig. 2C View Figure 2 ). Anterior part of prostomium whole, without any distinct lobes, and with a slightly raised lip ( Fig. 2C View Figure 2 ). No eyespots or pigmented glandular bands present. Segments I and II obscured by dorsal branchial ridge. Segment I continued ventrally forming lower margin of mouth with low crenulations on the ventral side, variation in other specimens no crenulations.

Buccal tentacles in holotype one large ridged stump, six damaged smaller tentacles arranged in three pairs arising from large membranous lip ( Fig. 2C View Figure 2 ). Small tentacles smooth and grooved. Variation other specimens, one long buccal tentacle, ridged at base becoming smooth along length, measuring up to 34 mm and 6 smaller tentacles (3 pairs) length around 2 mm length.

Lateral wings of anterior body between prostomium and segment V highly arched ( Fig. 2D View Figure 2 ).

Segment I collar-like, laterally and ventrally encompassing head region. Branchiae emerging together on dorsal branchial ridge at level of segment II–III, arranged in two basally fused groups of four, three branchiae in front and one situated slightly behind (towards the anterior) ( Fig. 2B View Figure 2 ). Inner- and anteriormost branchia of each group joined by low membrane (less than 10% branchial length). Branchiae in cross-section slightly flattened smooth with central groove, gently tapering to filiform tips. Branchiae roughly one fifth the length of longest buccal tentacle. Outer pair of branchiae longest. Variation in other specimens, branchiae circular in cross section.

Postbranchial dorsal membrane low inconspicuous, located on chaetiger 4 ( Fig. 2B View Figure 2 ). Postbranchial hooks absent. Segmentation visible dorsally in postbranchial area. No visible nephridial papillae.

Notochaetae from segment IV, neurochaetae from segment II ( Fig. 3 View Figure 3 ).

Capillary notochaetae present in 14 thoracic chaetigers starting from segment IV ( Fig. 2D View Figure 2 ). In holotype, notopodial chaetae damaged along length of body, only stubs remaining on many chaetigers. In other specimens, chaetiger 3 (segment IV) with few fine notochaetal capillaries and chaetiger 4 (segment V) with more abundant fine notochaeta arising from small slightly projecting notopodia ( Fig. 2D View Figure 2 ). Short cylindrical notopodia with thicker capillaries evident from chaetiger 5. Notochaeta arranged in double rows, those of anterior rows shorter.

In holotype, abdominal notochaetae lacking. Small, rounded projections, no cilia observed, evident in notopodial positions decreasing in size to pygidium.

Neurochaetae as small acicular spines with lanceolate tips on segment II–V ( Fig. 5A View Figure 5 ). Neuropodial uncini from chaetiger 5 (segment VI), present in 12 thoracic uncinigers ( Fig. 4A View Figure 4 ). Holotype, incomplete, with more than 40 abdominal uncinigers. Variation in other specimens, up to 28 abdominal uncinigers.

Thoracic uncini emerging subdistally on short flaps from chaetigers 5 to 14, distally more like narrow lappets on chaetigers 15 and 16. Abdominal uncini arranged on narrow lappets ( Fig. 4B View Figure 4 ) decreasing in size until pygidium (minute at the end), similar to last two thoracic chaetigers (15 and 16).

Thoracic uncini in single line with around 65 uncini ( Figs 4A, C, D View Figure 4 , 5B View Figure 5 ). Abdominal uncini in single line with around 37 uncini ( Fig. 4B, E, F View Figure 4 ). Uncini of thoracic uncinigers with three teeth in one vertical row over rostral tooth, subrostral process and basal prow ( Figs 4D View Figure 4 , 5C View Figure 5 ). Uncini of abdominal uncinigers with numerous teeth over rostral tooth, subrostral process and basal prow ( Figs 4E, F View Figure 4 , 5D View Figure 5 ).

Pygidium missing in holotype. Other specimens, terminal crenulated anus, bounded dorsolaterally by 8 small indistinct lobes. No anal cirri.

Methyl blue staining pattern. Use of methyl blue reveals in holotype strong staining of prostomium except nuchal slits, strong staining segments I to IV, branchiae lightly speckled along edges, postbranchial membrane ( Fig. 2B View Figure 2 ). Conspicuous stained band immediately behind dorsal fold ending between chaetigers 9 and 10 ( Fig. 2A, B View Figure 2 ). Stained band region shorter in other specimens. Speckled staining laterally between chaetiger 5 to end of thorax. Stained bands (anterior/ posterior direction) on prostomium ventral lobe ( Fig. 2E View Figure 2 ). Strong staining around thirteen ventral shields, staining strong anterior section of ventral shield light staining posterior section of shield, shields cover entire ventral surface of the segment ( Fig. 2E View Figure 2 ). Abdomen staining weak, mainly as light speckles on dorsal side of neuropodial lappets and on small rounded projections in notopodial position.

Tube. Missing in holotype. Some specimens have finegrained sediment tube with some thin green veins running throughout others not, others with Foraminifera. The tube is lined with a thin, stiff clear membrane. Length of tube at least twice as long as specimens.

Distribution. Coral Sea Marine Park to Freycinet Commonwealth Marine Reserve, Tasmania. Eastern Australia.

Etymology. The new species is named gardelli after Rickard Gardell for his generous donation to the Australian Museum Research Institute.

Remarks. The new species has 12 thoracic uncinigers, like nine other species of Melinnopsis ( M. abyssalis , M. annenkovae , M. arctica , M. chadwicki sp. nov., M. collaris , M. dubita , M. monocera , M. rostrata and M. somovi ) ( Table 3). Buccal tentacles of M. abyssalis are all free at base, those of M. gardelli sp. nov. are fused. The original description of M. annenkovae is brief (Uschakov, 1952) and it is difficult to draw morphological comparisons between M. annenkovae and M. gardelli sp. nov. Melinnopsis annenkovae possesses a “well-developed glandular band” on the fourth dorsal segment, but no images or further details are provided, in M. gardelli sp. nov. a glandular band was absent, but a post-branchial dorsal membrane was present on chaetiger 4. Melinnopsis annenkovae has a triangular shaped buccal tentacle while that of M. gardelli sp. nov. is rounded, although tentacle shape may vary within species. Melinnopsis gardelli sp. nov. differs from M. arctica by the absence of papillae on the large buccal tentacle. Melinnopsis collaris is described as having “a large, thin, foliaceous collar about the sides and ventrum to conceal the peristomium” ( Hartman, 1967), this foliaceous collar is not present in M. gardelli sp. nov. Melinnopsis dubita has multiple long buccal tentacles instead of one long one. Melinnopsis monocera aligns well with M. gardelli sp. nov., but differs by the shape of thoracic uncini, M. monocera has two teeth above the rostral tooth whereas M. gardelli sp. nov. has three. Melinnopsis rostrata possesses a denticulated transverse membrane which is absent in M. gardelli . Melinnopsis somovi has three pairs of branchiae, whereas M. gardelli sp. nov. has four pairs. The new species has a conspicuous stained band on the dorsal area when stained with methyl blue, which has not been noted in any other species.