Munida chathamensis Baba, 1974

Ahyong, Shane T., Schnabel, Kareen E. & Baba, Keiji, 2015, Southern High Latitude Squat Lobsters: Galatheoidea and Chirostyloidea from Macquarie Ridge with Description of a New Species of Uroptychus, Records of the Australian Museum 67 (4), pp. 109-128 : 120-122

Munida chathamensis Baba, 1974

Fig. 7

Munida chathamensis Baba, 1974: 388–390 , figs 6, 7 (type locality: Chatham Rise, New Zealand, 44°44.0'S, 175°42.0'W, 995–1110 m).— Baba, 2005: 260 (key, synonymies).— Baba et al., 2008: 90 (synonymies).

Type material. ZLKU-15553, female holotype (cl 11.5 mm, pcl 7.4 mm), Chatham Rise, 44°44.0'S, 175°42.0'E, 995–1110 m, mud, 16 July 1968, RV “Kaiyo Maru” sta. 36 .

Other material examined. Macquarie Ridge: NIWA 11027 , 1 male (cl 13.4, pcl 9.5 mm), Spastic Spider seamount, 48°33.03'S, 164°57.07'E, 1067 m, 13 December 1998, stn. Z9586 ; NIWA 39630 , 2 males (cl 9.3, pcl 6.1; cl 10.8, pcl 7.1 mm), 1 ov. female (pcl 12.4 mm), Spastic Spider seamount, 48°31.57'S, 164°56.44'E, 1364– 1096 m, 30 March 2008, TAN0803/21 ; NIWA 39702 , 1 male (cl 20.9, pcl 14.3 mm), 1 female (cl 14.4, pcl 10.2 mm), Clementsville seamount, 50°05.710'S, 163°27.66'E, 1697– 1091 m, 1 April 2008, TAN0803/32 .

Christable Seamount: NIWA 46526 , 5 males (pcl 8.4–25.1 mm), 5 ov. females (pcl 13.0– 16.9 mm), 50°56.56'S, 164°36.55'E, 1140– 1105 m, TAN0306/6, 14 April 2003 ; NIWA 46527 , 2 males (pcl 14.1 mm; 1 damaged), 6 females (cl 20.2, pcl 12.9; cl 21.2, pcl 14.2 mm; others damaged), 50°56.56'S, 164°36.55'E, 1140– 1105 m, TAN0306/6, 14 April 2003 ; NIWA 46528 , 2 males (cl 20.3, pcl 13.5; cl 24.4, pcl 16.5 mm), 2 ov. females (cl 24.2, pcl 16.6; cl 24.9, pcl 16.7 mm), 50°56.30'S, 164°33.16'E, 1053– 998 m, 14 April 2003 , TAN0306/4; NIWA 76183 , 1 male (cl 30.5, pcl 20.6 mm), 50°56.30'S, 164°33.16'E, 1053– 998 m, 14 April 2003 , TAN0306/4.

Campbell Plateau: NIWA 11612 , 1 female (cl 13.5 mm, pcl 9.0 mm), SE of Campbell Island , 53°59.80'S, 171°13.20'E, 1075 m, 21 September 1978, stn. S46 .

Diagnosis. Carapace with long, scattered setae; transverse striae widely spaced, often intervened by short striae or scales; with transverse row of 6–8 epigastric spines; with granules and scattered spinules on anterolateral region; with or without postcervical spine. Rostrum spiniform. Supraocular spines divergent. Margins of carapace with 5 spines posterior to cervical groove. Thoracic sternite 4 at most with few short striae; sternites 5–7 smooth. Abdominal tergite 2 with row of 6–9 (usually 6) spines on anterior border; remaining tergites unarmed. Eye with cornea dilated, maximum diameter about one-third distance between anterolateral spines. Basal antennular article overreaching cornea; with 2 terminal spines, mesial shorter; ventral surface with spine near midlength. Basal antennal article with strong mesial spine; article 2 with mesial and lateral terminal spines, neither overreaching article 3; article 3 with lateral spine. Maxilliped 3 ischium with distal flexor spine; merus flexor margin with subequal distal and proximal spine, or distal spine slightly smaller. P1 slender, 2–3 × cl; palm upper and inner margin spinose, spines extending onto pollex including row of spines originating close to lateral margin with apices often overhanging lateral margins, especially in small specimens. P2–3 meri with spinose extensor and flexor margins. P4 extensor and flexor margins with distal spine. P2–4 dactyli with movable spines distributed along entire flexor margin and slender corneous seta at base of unguis.

Description. Carapace: Dorsum with long, scattered setae and short fine setae on striae. Transverse striae widely spaced, often intervened by short striae or scales; cervical groove distinct; with transverse row of 6–8 (usually 6) epigastric spines, of which pair behind supraocular spines largest; parahepatic region with granules and 1–4 (usually 2 or 3) spinules; anterior branchial region with short rugae and 1 or 2 spines; rarely with postcervical spine. Frontal margins slightly oblique; rostrum spiniform, faintly upcurved, length 0.4–[0.6] pcl. Supraocular spines slightly divergent, deflected dorsally, length 0.4–[0.5] rostral length. Anterolateral spine well developed, situated at anterolateral angle, extending almost to sinus between rostrum and supraocular spine. Hepatic margin anterior to cervical groove with short spine behind anterolateral spine. Branchial margin with 5 slender, curved spines posterior to cervical groove.

Sternum: Sternite 3 transverse, medially emarginate, laterally rounded to subtruncate. Sternite 4 triangular, wider than long, margins straight to faintly convex, anterior apex rounded, narrower than sternite 3; sternites 5–7 smooth; ridges demarcating fourth to seventh sternites feebly granular.

Abdomen: Tergites with scattered setae. Tergite 2 with row of 6–8 (usually 6) spines on anterior border and uninterrupted transverse stria; remaining tergites unarmed. Tergite 3 with 1 uninterrupted transverse stria. Tergite 4 with 2 uninterrupted transverse striae. Telson length 0.8– [0.9] × width; lateral margins lined with coarse golden setae, few fine setae in females.

Eye: Cornea dilated, with maximum corneal diameter almost one-third distance between anterolateral spines; few, widely spaced eyelashes.

Antennule: Basal article overreaching cornea; with 2 terminal spines, mesial shorter; with two lateral spines, distal markedly longer than proximal; midventral surface with prominent spine.

Antenna: Basal article of peduncle with strong mesial spine. Article 2 with distomesial and distolateral spines, neither overreaching article 3. Article 3 with distolateral spine; unarmed distomesially.

Maxilliped 3: Ischium with distal flexor spine. Merus flexor margin with prominent proximal and distal spine, lengths subequal or distal slightly shorter, intervening margin unarmed or with 1 spine or 1 or 2 tubercles; extensor margin unarmed.

Pereopod 1 (cheliped): Slender, adult length 2.9–3.9 pcl (males), [1.8]–3.2 pcl (females); sparsely setose; strongly spinose, with longitudinal rows of spines. Dorsal margin of dactylus with proximal spine and row of small spines along proximal three-fourths of length; occlusal margin denticulate. Propodus palm upper and inner margin spinose, spines extending onto pollex including row of spines originating close to lateral margin with apices often overhanging lateral margins, especially in small specimens; palm length about 3 × height, dorsal margin slightly longer than dactylus; pollex with 1 or 2 small subterminal spines, occlusal margin denticulate, outer margin unarmed. Carpus length about 2.5 × height, multispinose. Merus with numerous irregularly distributed spines on lateral, dorsal and mesial surfaces.

Pereopods 2–4 (walking legs): Similar, length decreasing posteriorly. P2–3 merus extensor margin with 9–16 [13–14] and 9–15[9–10] spines, respectively; flexor margin with 5–9[7] and 4–9[5–6] spines, respectively. P4 merus extensor margin with 2–7[6] spinules along proximal half and distal one-third with 1–3 spinules in addition to distal spine; flexor margin with 1–6[3] spines. Carpus of P2, 3 and 4 with 3–7[4], 3–4[3] and 1–2[1] extensor spines, respectively (distal and antepenultimate longest); 1 flexor spine. Propodus extensor margin with 1 or 2 small spines (P2) or unarmed (P3–4); flexor margin of P2, 3 and 4 with 6–10[8–9], 5–8[5–6], 4–7[5] movable spines, respectively. Dactylus of P2, 3 and 4 with [11]–17, [11]–15, 10–15[12– 13] movable spines, respectively, distributed along entire flexor margin; with slender corneous seta at base of unguis.

Remarks. Prior to the present study, Munida chathamensis , was known only from the holotype from the Chatham Rise. The new records of M. chathamensis from the Campbell Rise and Macquarie Ridge, however, extend its distribution southwards into Subantarctic waters. Moreover, the species is re-figured and re-described based on the holotype and large series examined herein. Munida chathamensis very closely resembles two other Subantarctic species, M. spinosa Henderson, 1885 [south Atlantic Ocean: Rio de la Plata] and M. spicae Macpherson & de Saint Laurent, 2002 [south Indian Ocean: Prince Edward, Crozet, Saint Paul and New Amsterdam islands]. The three species uniquely share a ventral spine near the midlength of the basal antennular segment. The distinctions between the three species are subtle, with M. chathamensis differing from M. spicae and M. spinosa in having straight instead slightly convex margins of the fourth thoracic sternite and less oblique frontal margins of the carapace. Munida chathamensis might also mature at a larger size than M. spicae ; the smallest reported ovigerous female of M. spicae (pcl 6.2 mm, Macpherson & de Saint Laurent, 2002) is half the size of the smallest ovigerous M. chathamensis reported here (pcl 12.4 mm, NIWA 39630). The distinctions between M. spicae and M. spinosa , however, are presently ambiguous and require further study. Munida chathamensis , M. spicae and M. spinosa form a discrete group within the genus and together have an essentially circumpolar distribution suggesting this group evolved in the Southern Ocean, perhaps under the influence of the West Wind Drift.

Morphological variation is evident in typical cheliped sexual dimorphism (proportionally longer and stouter in adult males), in the length of the cheliped spines (proportionally longer in smaller specimens) and in the prominent development of the distolateral spine on antennal peduncle article 3, except in the smallest specimens in which the spines are minute (males, pcl 6.1–7.1 mm, NIWA 39630; Fig. 7 I ). Of these, the 6.1 mm male (NIWA 39630) has a rhizocephalan externa under the abdomen.

Of the regional species, M. chathamensis most closely resembles M. isos , with which it is sometimes sympatric; the two species are readily separated by the presence in M. chathamensis of the ventral spine on the basal antennular article, the size of the distal flexor spine on the maxilliped 3 carpus (subequal to or slightly shorter than the proximal spine in M. chathamensis ; markedly smaller in M. isos ), a generally more slender antennular peduncle article 2 in M. isos , and the consistent presence of a distolateral spine on antennular peduncle article 3 (usually absent in M. isos ).

Distribution. New Zealand, from the Chatham Rise south to the Campbell Plateau and seamounts on Macquarie Ridge; 995–1697 m.

Figures

Figure 7. Munida chathamensis Baba, 1974.(A–H) male pcl 20.6 mm, Christable Seamount (NIWA 76183). (I) male pcl 6.1 mm, Spastic Spider Seamount (NIWA 39630). (A) carapace and abdomen. (B) right antenna and antennule, ventral. (C) right maxilliped 3. (D) right P1 (setae omitted). (E–G) right P2–4 (setae omitted). (H) sternal plastron. (I) right antenna, ventral. Scale:A, D–G = 5.0 mm; B, C, H = 2.5 mm; I = 0.5 mm.