Michelaxiopsis nauo, Poore & Collins, 2009

Poore, Gary C. B. & Collins, David J., 2009, Australian Axiidae (Crustacea: Decapoda: Axiidea), Memoirs of Museum Victoria 66 (2), pp. 221-287 : 263

Michelaxiopsis nauo sp. nov.

Figures 27 , 28

Material examined. Holotype. SA, Sir Joseph Banks Group: Roxby I. (34°35’S, 136°19’E), 6 m, in burrow under rocks, N. Holmes, 9 Jan 1988, SAM C6811 (ovigerous female, cl. 24.5 mm).

Paratypes. SA, Reevesby I. (34°31’S, 136°16’E), offshore from Northwest Point, 3 m, under rocks, W. Zeidler, 13 Jan 1984 , SAM C6812 (male, 9.0 mm); Marum I., North Point (34°30’S, 136°15’E), 5–6 m, under rocks, K. Gowlett, 22 Jan 1985 , SAM C6813 (male, 14.5 mm); between Reevesby and Partney Is., opposite Nicholas Bay , 6 m, under dead Pinna shells, K. Gowlett and N. Holmes, 23 Jan 1985 , NMV J59765 (female, cl. 11.0 mm) .

Description of female holotype. Carapace covered with short stiff setae, often in small bunches, and scattered longer setae. Rostrum 0.25 times length of front-to-cervical groove, broadly acute, with 4 lateral spines anterior to supraocular spine, continuous with definite lateral gastric carinae. Supraocular spines barely differentiated from others in row. Lateral gastric carina with obscure low beads fading posteriorly. Submedian gastric carina duplicated in form of a hair-pin, of 20–25 beads in each row, fading posteriorly. Median gastric carina with about 5 erect spines near base of rostrum and about 15 beads fading posteriorly. Abdominal somite 1 pleuron ventrally rounded; pleuron 2 rounded anteriorly and posteriorly; pleura 3–4 posteroventrally rounded, pleuron 5 less so; pleuron 6 rounded.

Eyestalk, 0.5 length of rostrum; cornea pigmented. Antennular peduncle reaching almost to end of antennal article 4; article 1 with sharp stylocerite. Antennal article 2 distal spine slender, directed anteriorly, reaching distally to quarter of antennal article 4; scaphocerite reaching two-thirds length of article 4, simple; article 3 with sharp mesiodistal spine on lower margin. Maxilliped 3 coxa–ischium unarmed; crista dentata of about 20 similar teeth; merus with 4 spines, largest distal; carpus with 1 spine.

Pereopods 1 symmetrical; ischium lower margin with 1 spine; merus upper margin convex, unarmed, lower margin with 6 spines; propodus upper margin tuberculate, lower margin smooth, lateral face with squamous tubercles concentrated on distal two-thirds (absent proximally and from fixed finger),mesial face with squamous tubercles concentrated on distal two-thirds (absent proximally and from fixed finger); fixed finger 0.7 length of upper palm, cutting edge with 1 blunt bicuspid tooth; dactylus upper margin smooth, lateral face smooth, mesial face smooth, cutting edge with blunt tooth at midpoint and notch proximally.

Pereopod 2 ischium lower margin unarmed; merus lower margin unarmed; carpus slightly longer than chela; propodus upper margin 1.2 times as long as dactylus. Pereopod 3 merus lower margin unarmed; propodus 2.5 times as long as dactylus, with 7 transverse rows of 2 or 3 robust setae; dactylus with 2 longitudinal rows of robust setae. Pereopod 4 merus unarmed; propodus 2.1 times as long as dactylus, with 8 transverse rows of 1–4 robust setae; dactylus with 2 longitudinal rows of robust setae. Pereopod 5 propodus 2.2 times as long as dactylus, subchelate, with short fixed finger; dactylus with row of 6 robust setae.

Pleopod 1 a simple, setose article. Pleopods 2–5 each with appendix interna 0.25 length of endopod.

Telson 1.2 times as long as wide, lateral margin with 3 spines, distal margin convex, with posteromedian spine, posterolateral angle with 2 robust setae; dorsal face with 2 spines in each oblique row. Uropodal endopod 1.5 times as long as wide, with 1 lateral spine and 1 distolateral spine, longitudinal ridge with 4–6 spines. Uropodal exopod 1.3 times as long as wide, with 4 lateral spines, 2 longitudinal ribs with 6 and 2 spines, posterolateral angle with 1 fixed spine and 1 robust seta; transverse suture with 7–11 spines.

Male. Pereopods 1 significantly differentiated. Major pereopod 1 ischium lower margin with 1 spine; merus upper margin convex, with 2 spines, lower margin with 5 spines, last longest, lateral face smooth, mesial face smooth; carpus upper margin unarmed, lower margin unarmed; propodus upper margin tuberculate, lower margin smooth, lateral face with squamous tubercles concentrated on distal two-thirds (absent proximally and from fixed finger), mesial face with squamous tubercles concentrated on distal two-thirds (absent proximally and from fixed finger); fixed finger 0.6 length of upper palm, cutting edge with 1 blunt bicuspid tooth and 1 triangular tooth; dactylus upper margin smooth, lateral face smooth, mesial face smooth, cutting edge with blunt tooth at midpoint and notch proximally.

Minor pereopod 1 of similar length and ornamentation as major cheliped but narrower (85% of width) and merus upper margin unarmed.

Etymology. The species is named for the Nauo people of the southern part of the Eyre Peninsula, South Australia, close to the Sir Joseph Banks Group of islands (noun in apposition).

Distribution. SA, Sir Joseph Banks Group of islands; 5–6 m depth.

Remarks. Michelaxiopsis nauo , from South Australia, differs from M. australiensis , from NSW and Victoria, most obviously in having a setose carapace and abdomen. The submedian gastric carina is duplicated, both rows of tubercles continous and fading posteriorly. The anterior-most tubercles of the median gastric carina are decidedly more elevated than posterior ones. The lateral margin of the telson always has three teeth, absent in M. australiensis .

Figures

Figure 27. Michelaxiopsis nauo sp. nov. a, lateral view. b, dorsal view of carapace, peduncles of antennule and antenna. c, telson and left uropod. d, epistome, right antennule and antenna (ventral). e, f, maxilliped 3. g, pereopod 1 (left, lateral). h, i, female pleopods 1, 2. j, lateral anterior carapace and rostrum. a–i from holtype; j from paratype male (SAM C6813).

Figure 28. Michelaxiopsis nauo sp. nov. a–d, pereopods 2–f (with detail of dactylus of pereopod 5). e, major pereopod 1 (right, lateral). f, minor pereopod 1 (right, lateral). a–d from holotype; e, f from paratype male (SAM C6813).