Calastacus myalup, 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 : 248

Calastacus myalup sp. nov.

Figures 17 , 42

Material examined. Holotype. WA, off Bunbury, 33°00.35'S, 114°34.12'E – 32°59.37'S, 114°34.55'E (stn SS10-2005 067), 423– 397 m, 29 Nov 2005, NMV J53460 (hermaphrodite, cl. 8.0 mm, tl. 19 mm; carapace damaged, pereopods 1 missing, 1 egg case on pleopod 3).

Paratype. Collected with holotype, NMV J58382 (hermaphrodite, cl. 8.0 mm, tl. 19 mm; most pereopods missing) .

Description of hermaphrodite holotype. Carapace smooth except for slight rugosity between supraocular spines. Rostrum 0.5 times length of front-to-cervical groove, acute, unarmed anterior to supraocular spine, not continuous with lateral gastric carinae. Supraocular spines prominent. Lateral gastric carina absent. Submedian gastric carina absent. Median gastric carina unarmed. Abdominal pleuron 1 twice as deep as middorsal length, short, ventrally rounded; pleuron 2 broad, lateral length 1.3 times dorsal length, anteroventrally rounded; pleura 3–5 rounded; pleura 6 rounded.

Eyestalk 0.4 length of rostrum; cornea unpigmented.

Antennular peduncle reaching two-thirds along antennal article 4. Antennal article 1 with 1 sharp spine and spinule on lower distal margin; article 2 distal spine slender, directed slightly inwards, reaching distally to middle of antennal article 4; scaphocerite slender, directed slightly upwards, reaching distally to middle of antennal article 4; article 3 with sharp distal spine on lower margin; article 4 little longer than article 2 (excluding distal spine); article 5 about half length of article 4. Maxilliped 3 basis unarmed; ischium unarmed on lower margin; crista dentata with 20 teeth; merus with 2 long spines on lower margin; carpus unarmed.

Pereopods 1 coxa with 1 spine; basis unarmed; remainder missing.

Pereopod 2 ischium unarmed; merus unarmed; carpus 0.7 length of chela. Pereopod 3 merus unarmed; propodus 3 times as long as dactylus, with oblique rows of simple setae but without robust setae. Pereopod 4 unarmed; propodus 3 times as long as dactylus, with oblique rows of simple setae distally but without robust setae. Pereopod 5 unarmed; propodus with oblique rows of simple setae distally but without robust setae, with short rounded fixed finger; dactylus broken.

Pleopod 1 article 2 0.8 length of article 1, leaf-like, concave posteromesially, hooks representing the appendix interna on a blunt lobe on broad triangular anterior fold, lateral fold almost semicircular, the pair together forming a broad open tube joined anteriorly by the hooks. Pleopod 2 endopod of 2 articles (third weakly differentiated), all articles more or less in line with peduncle, with thumb-like appendix interna at base of article 2, setae of appendix masculina not well differentiated from more distal setae (as in other species); exopod half length of endopod.

Telson 1.6 times as long as wide, widest proximally, then approximately parallel-sided, lateral margin unarmed, distal margin semicircular without posteromedian spine, posterolateral region rounded; dorsal face without spines on obsolete oblique row. Uropodal endopod 2.0 times as long as wide, without lateral spines, longitudinal ridge unarmed. Uropodal exopod 2.0 times as long as wide, without lateral spines, 2 obsolete longitudinal ribs unarmed, posterolateral angle with 1 fixed spine and 1 robust seta; transverse suture with 11 robust setae of varying lengths.

Etymology. Myalup is a settlement on the coast close to the type locality (noun in apposition).

Distribution. WA, south-western coast, 400 m depth.

Remarks. The new species differs from C. crosnieri and C. inflatus , the two West Pacific species, in having narrower uropods.

Figures

Figure 17. Calastacus myalup sp. nov. a, lateral view. b, dorsal view of carapace, peduncles of antennule and antenna. c, telson and right uropod. d, maxilliped 3. e–h, pereopods 2–4 (right except e). i, j, right and left pleopod 1 (right from anterolateral view, left from mesial view). k, pleopod 2. All figures from holotype.

Figure 42. Calastacus myalup sp. nov. Photomicrographs of (left to right) maxilla 1, maxilla 2 (posterior epipod seta missing), maxilliped 1, maxilliped 2.