Neaxius mclaughlinae, Ngoc-Ho, 2006

Ngoc-Ho, Nguyen, 2006, A new species of Neaxius Borradaile, 1903 from the Gulf of Guinea (Crustacea, Decapoda, Thalassinidea, Strahlaxiidae), Zoosystema 28 (2), pp. 409-415 : 410-414

publication ID	https://doi.org/ 10.5281/zenodo.5392725
persistent identifier	https://treatment.plazi.org/id/AD7287F3-FFD0-946D-32EF-FACED1AC32E2
treatment provided by	Marcus
scientific name	Neaxius mclaughlinae
status	sp. nov.

Treatment

Neaxius mclaughlinae n. sp.

( Figs 1 View FIG ; 2 View FIG )

? “ Axiidae new species ” – Wirtz & Debelius 2003: 137, fig.

TYPE MATERIAL. — Holotype: Gulf of Guinea. Principe Island, Praia Pequena, CALYPSO 1956, stn P 18, diving, 3-4 m, 3.VII.1956, ♂ cl 23.5 mm, tl 65 mm (MNHN- Th 1196).

Paratype: idem, stn P 13, ibidem, diving, 3 m, 28. VI.1956, ♂ cl 18 mm, tl 49 mm (MNHN-Th 1195).

MATERIAL OF NEAXIUS VIVESI (BOUVIER, 1895) EXAM- INED. — Lower California. L. Diguet leg., 202-1894, ♂ lectotype (present designation) cl 35 mm, tl 98 mm (MNHN-Th 194); 2 ♂ paralectotypes cl 28 and 27 mm, tl 81 and 75 mm (MNHN-Th 193).

Gulf of California. South of San Jose Island, L. Diguet leg., 118-97, 1 ♂, partly dried, cl 27 mm (MNHN-Th 510).

ETYMOLOGY. — The new species is named for Pat McLaughlin honouring her valuable contributions to the study of cirripeds and decapod Crustacea. The dedication is fitting as material of this new species was first separated by the late Michèle de Saint Laurent, a good friend of Pat McLaughlin.

DISTRIBUTION. — Known only from the type locality.

DIAGNOSIS. — Carapace with rostral border continuous with anterior part of lateral carina of gastric region, altogether with seven or eight teeth. Anterolateral border with four to six spines; cervical groove with seven to nine spines laterally. Telson approximately as broad as long with three prominent tranverse carinae equally long and distant from one another, distal carina well separated from posterior border.

Article 2 of antennal peduncle with three or four upper and two lateral spines; acicle large with four to six lower spines. Maxilliped 3 merus with four lower and one upper distal spines; carpus with three lower spines.

Major pereopod 1 with two lower spines on basis and four lower spines on ischium; merus with four to seven spines on upper border and 11 on lower border, those on distal half placed at a slightly higher level; carpus bearing large lower distal spine and three lower lateral distal spines, upper border unarmed, propodus unarmed; fixed finger with large conical tooth near middle of cutting edge. Pereopod 2 unarmed except for two lower spines on ischium; pereopod 4 propodus and dactylus carrying spiniform setae.

DESCRIPTION

Carapace ( Fig. 1A, B View FIG ) with bifid and slightly depressed rostrum reaching beyond eyes; lateral rostral border continuous with anterior part of lateral carina of gastric region, altogether with seven or eight teeth; median rostral carina with four tubercles. Anterolateral border of carapace with four to six spines. Eyestalks nearly reaching distal border of second article of antennular peduncle, cylindrical; cornea hemispherical, distal, weakly pigmented. Epistome with two lateral spines. Gastric region weakly convex; cervical groove well defined with seven to nine spines laterally. Pleuron of abdominal somite 1 ( Fig. 1A View FIG ) tapering with one or two ventral spinules; pleuron of abdominal somite 2 overlapping that of somite 1 and 3, rounded ventrally with six to 10 ventral spinules; pleura of somite 3 and 4 with three and one spinule respectively, both as well as pleuron of somite 5 bearing lateral setae.Telson ( Fig. 1D View FIG ) slightly shorter than greatest breadth; three prominent tranverse carinae of approximately same length, equally distant from one another, with distal one well apart from posterior border; lateral border convex near proximal third, tapering posteriorly; posterior border approximately straight with median spinule.

Antennular peduncle ( Figs 1B View FIG ; 2A View FIG ) unarmed, with article 2 about as long as article 3. Antennal peduncle ( Figs 1B View FIG ; 2B View FIG ) with article 2 pointed distally carrying three or four upper spines and two lateral spines, article 3 with lower spine; acicle large, distally acute with mesial spine ( Fig. 1B View FIG ) and four to six lower spines; article 4 nearly twice as long as article 5.

Mandible, maxillule, maxille, maxilliped 1 and 2 similar to that of Neaxius trondlei , maxille without posterior seta (see Ngoc-Ho 2005: figs 6C, 7E, F, I).

Maxilliped 3 ( Fig. 2C View FIG ) coxa with lower spine, ischium unarmed on lower border, with mesial toothed crest as in N. trondlei (see Ngoc-Ho 2005: fig. 7H); four lower spines, larger distally, and one small upper distal spine on merus; three lower spines on carpus; exopod not reaching distal bor- der of merus.

Major pereopod 1 ( Fig. 1A, C View FIG ) on right side in both holotype and paratype, stouter than minor ( Fig. 2D View FIG ) with two lower spines on basis, four spines on ischium; merus with four to seven upper spines and 11 spines on lower border, four of them on proximal half and seven distally placed at slightly higher level; carpus bearing dorsal proximal spinule in paratype ( Fig. 1A View FIG ) absent in holotype, large lower distal spine and three lower lateral distal spines present in both types; propodus with palm slightly longer than fingers, unarmed; fixed finger with small rounded teeth on proximal half of cutting edge and large conical tooth near middle; dactylus with curved tip and obscure round teeth on cutting edge. Pereopod 2 ( Fig. 1E View FIG ) unarmed except for two lower spines on ischium. Pereopod 3 ( Fig. 2E View FIG ), pereopod 4 ( Fig. 2F View FIG ) and pereopod 5 ( Fig. 2G View FIG ) unarmed; pereopod 4 propodus and dactylus carrying spiniform setae; pereopod 5 subchelate.

Gill formula as in Table 1.

Thoracic sternite of pereopod 4 with lateral spine; pereopods 1-4 with coxal spines.

Male pleopod 1 absent, pleopods 2-5 ( Fig. 1F View FIG ) with broad rami and digitiform appendix interna.

Uropod ( Fig. 1D View FIG ) exopod nearly triangular in shape with simple or bifid proximal spine, two curved unarmed carinae and 11-13 spines on posterior border; suture absent; endopod with large obtuse spine on posterolateral angle, two spines on median longitudinal carina and two spines on posterior border.

REMARKS

The gill formula of Neaxius mclaughlinae n. sp. is the same as that of N. acanthus and N. vivesi given by Sakai & de Saint Laurent (1989: 31), and of Neaxius trondlei . The formula presented by Ngoc- Ho (2005: table 2) for the latter species, however, contains errors: single podobranchs are actually present on maxilliped 3 and pereopods 1-4 (instead of pereopods 1-3); and single pleurobranchs are on pereopods 2-5 (instead of pereopods 1-4).

Borradaile (1903: 537) considered species of Neaxius as having no pleurobranchs, however a single small pleurobranch is present on each segment. Except for N. glyptocercus and N. frankeae (of which no material was examined), pleurobranchs are present on pereopods 2-5 in other species of Neaxius .

Neaxius mclaughlinae n. sp. shows some similarities to N. vivesi (Bouvier, 1895) . Three type specimens of the latter species, all males and in fair condition, are in the collection of the MNHN. The paralectotype of cl 28 mm, tl 81 mm is likely to be the one studied and figured by de Man (1925: 56, fig. 2).

Neaxius mclaughlinae n. sp. and N. vivesi (see de Man 1925: 56, fig. 2) are similar in having: 1) lateral border of rostrum and anterior part of lateral carina of gastric region bearing teeth; 2) second article of antennal peduncle with upper and lateral spines; 3) merus of pereopod 1 with spines on whole upper and lower borders; and 4) telson nearly as long as broad with three carinae, distal one apart from posterior border.

They differ by: 1) upper border of pereopod 1 carpus and propodus with spines in N. vivesi (unarmed in N. mclaughlinae n. sp.); 2) lower border of pereopod 2 merus with spines in N. vivesi (unarmed in N. mclaughlinae n. sp.); and 3) distal carina of telson shorter than the others and slightly curved in N. vivesi (all three carinae of telson straight and of same length in N. mclaughlinae n. sp.).

Of the six known Neaxius species , N. acanthus was figured by Kensley et al. (2000: figs 5, 7F); comparison of N. acanthus and N. glyptocercus was given by de Man (1925: 54) and Poore & Griffin (1979: 235). The latter two were compared with N. trondlei in Ngoc-Ho (2005: 61); N. frankeae (see Lemaitre & Ramos 1992: 346) and N. mclaughlinae n. sp. herein are compared with N. vivesi . The main characters differentiating species of Neaxius are summerized in Table 2.

Wirtz & Debelius (2003: 137, fig.) reported an “ Axiidae new species ” from Sao Tomé Island and gave a coloured photograph. The pictured specimen in lateral view shows similarities with Neaxius mclaughlinae n. sp. and was collected from a locality near the type locality of this new species. Nevertheless, no material is available for examination at present, and a definite identification cannot be obtained from a photograph.