Ischyromene kokotahi, Bruce, Niel L, 2006

Bruce, Niel L, 2006, A new species of Ischyromene Racovitza, 1908 (Sphaeromatidae: Isopoda: Crustacea) from intertidal marine habitats in New Zealand, Zootaxa 1220, pp. 19-34 : 24-32

Ischyromene kokotahi sp. nov.

( Figs 1–4 )

Material

Holotype: ♂ (3.8 mm), NIWA sea wall, Evans Bay, Wellington, 41°18.192’S, 174°48.370’E, 14 December 2004, intertidal barnacles and Mytilus , coll. N.L. Bruce & S. Lischinski ( NIWA 23091).

Paratypes: Ψ (non­ovig. 3.5mm), same data as holotype ( NIWA 23092). ♂ (4.1 mm [dissected; earlier damage to pleopods and one P7]), Ψ (non­ovig. 3.0 mm), 1 imm (2.6 mm damaged), NIWA sea wall, Evans Bay, Wellington, 41°18.190’S, 174°48.370’E, 14 January 2005, low intertidal Mytilus with encrusting barnacles, coll. N.L. Bruce ( NIWA 23093).

Additional material: ♂ (3.4 mm) Auckland, 36°50.655’S, 174°46.684’E, 2 April 2003, scrapings from concrete pile, 1.6 m, PS stn AKL029 ( NIWA 23094). ♂ (3.2 mm), Gisborne, 38°40.539’S, 178°01.527’E, 6 Dec 2005, scrapings from concrete pile, 2 m, PS stn 2GIS063 ( NIWA 23095). ♂ (3.8 mm), Burnham Wharf, Wellington, 41°18.708’S, 174°48.707’E, 14 February 2005, pile scrape, PS stn 2WLG002 ( NIWA 23096). Ψ (3.5 mm), Burnham Wharf, Wellington, 41°18.708’S, 174°48.707’E, 14 February 2005, pile scrape, PS stn 2WLG012 ( NMNZ Cr.10855). 2 Ψ (ovig. 3.1, 3.5 mm), overseas passenger terminal, Wellington, 41°17.314’S, 174°47.124’E, 17 February 2005, pile scrape, PS stn WLG105 ( NIWA 230101).

Also examined: Ischyromene bicarinata Harrison, 1981 : Holotype, NHM 1980.222.1; 5 paratypes 1980.223.5, Mediterranean, Israel (details agree with that published). Ischyromene condita ( Hurley & Jansen, 1977) : 16 specimens, ♂, Ψ and mancas (♂ 3.3 and Ψ 3.5 mm drawn, Fig. 5 ), St Clair, Dunedin, 25 Jan 1968, intertidal algae… heavy turf E 973, coll. J.L. Barnard ( NIWA 23097). [Note: These specimens were under an unpublished species name, but appear to be those reported by Hurley & Jansen (1977) as I. condita from that station number and locality; the type material of I. condita is held at the Canterbury Museum, Christchurch, but it was not possible to obtain this material on loan.] 35 specimens, ♂, Ψ and mancas, of I. condita of Poore (1981, misidentification), The Snares Islands, New Zealand ( NMNZ Cr.2331, 3 tubes).

Description

Male. Body about 2.2 times as long as greatest width, strongly vaulted, lateral margins subparallel, widest at pereonite 6; dorsal surfaces smooth. Head anterior margin with single weak transverse ridge, rostral process weakly distinct, visible in dorsal view; 1.5 times as long as pereonite 1. Pereonite 1 about as long as pereonite 2 (in lateral view), unornamented; pereonites 2–6 subequal in length, 7 longest; pereonite 7 posterior margin dorsally produced forming posterior ridge, with single sublateral indentation on each side. Coxae without evident sutures. Pleon with evident sutures without sublateral ‘keys’. Pleotelson with 2 conspicuous, longitudinal, submedial irregular carina, each with 3 nodules; laterally adjacent to each carina is an irregular row of separate nodules, decreasing in size posteriorly; pleotelson sinus posteriorly closed, opening dorsally, laterally with dorsal rim, with anterior spine in sinus cavity.

Antennule peduncle article 1 2.9 times as long as wide, about 2.6 times as long as article 2; posterior margin of both articles 1 and 2 with brush­tipped sensory setae, article 1 with 2 anterior bush tipped setae; article 3 about 1.5 times as long as article 2, 0.6 times as long as article 1, 2.8 times as long as wide; flagellum 7­articled, extending to midpereonite 1, about 1.7 times as long article 3. Antenna peduncle articles 1 shortest, 2–4 subequal in length and slightly longer than article 1; article 4 about 1.2 times as long as article 3, about 0.6 as long as article 5; flagellum 1.1 times as long as peduncle, extending to posterior of pereonite 4, with 18 articles.

Epistome anteriorly with median portion produced and narrowly rounded, without lateral constriction. Left mandible incisor with 3 cusps, lacinia mobilis with 3 cusps, spine row of 6 broad­based plumose spines; molar process round; palp article 2 0.7 times as long as article 1, distolateral margin with 7 biserrate setae, becoming progressively longer distally; article 3 with 11 serrate setae, terminal seta being longest. Maxillule mesial lobe with 4 long, strongly pectinate RS and 2 shorter simple RS, lateral lobe with 11 peripheral RS on gnathal surface, twelfth seta set between these; 3 proximomesial RS strongly serrate; single biserrate seta present in distomesial surface. Maxilla lateral lobe with 6 curved nodular RS, and middle lobe with 5 curved bluntly serrate RS, mesial lobe with 13 serrate and biserrate RS, proximal seta longest. Maxilliped endite lateral margin sinuate, distal margin with 1 simple acute RS at distomesial angle, distomesial margin with 2 CP RS, distal margin with 4 blunt and 1 acute CP stout RS and 4 sinuate and elongate CP RS; palp articles 2–4 lobed; articles 2–5 with about 12, 18, 14 and 8 setae respectively.

Pereopod 1 basis about 2.8 times as long as greatest width, approximately 1.7 times as long as propodus; margins large without setae or scale­setae; ischium 0.8 times as long as propodus, 2.2 times as long as greatest width, superior margin with 1 mid­distal acute short simple RS, distal superior margin with distinct spine­like scales, distal inferior margin with short sparse scale­setae; merus about 0.5 as long as ischium, as long as greatest width, superior distal angle with 1 acute simple RS, inferior margin with dense setulose fringe, inferior distal margin with 3 long simple setae; carpus approximately as long as wide, inferior margin 0.5 times as long as merus, with dense setulose fringe, inferior distal angle with 2 simple setae; propodus 2.0 times as long as greatest width, inferior margin dense setulose fringe and 2 simple setae, distal angle with 1 long and 1 short serrate RS; dactylus 0.5 times as long as propodus, inferior margin with prominent serrate cuticular scales, secondary unguis with 1 major and 2 minor cusps. Pereopods 2 and 3 longer than pereopod 1, not markedly slender. Pereopod 2 ischium 2.7 times as long as greatest width, superior distal margin with 1 proximal acute RS and 1 acute RS at midpoint, inferior margin setulose, distal angle with 1 short slender seta; merus 0.6 times as long as ischium, inferior margin with setulose fringe, with 2 slender setae, superior distal angle with 1 short, simple seta; carpus 1.1 times as long as merus, 1.8 times as long as wide, anterodistal angle with 1 simple and 1 palmate setae, inferior margin setulose, with 4 slender setae; propodus 0.9 times as long as ischium, 3.2 times as long as wide, superior distal angle with 1 simple and 1 palmate setae, inferior margin setulose, with 6 slender setae. Pereopods 5–7 similar, longer than pereopods 2 and 3. Pereopod 7 basis 3.1 times as long as greatest width, inferodistal angle with 1 acute RS, superior margin with 2 proximal palmate seta; ischium 0.7 times as long as basis, 3.0 times as long as greatest width, superior margin with 1 short proximal RS and 1 prominent acute RS at midlength; merus 0.5 times as long as ischium, 1.3 times as long as wide, superior distal margin with 1 long simple seta, inferior margin setulose with 2 simple setae; carpus 0.9 times as long as merus, 1.6 times as long as wide, distolateral margin with 5 biserrate RS, inferior margin setulose with 3 slender setae; propodus 0.7 times as long as ischium, 2.9 times as long as wide, superior distal angle with 2 slender setae, inferior margin setulose, with 3 simple setae midlength and 3 cluster of slender setae distally; dactylus 0.5 as long as propodus.

Penial processes set mutually adjacent, each 2.5 as long as basal width, distally bluntly rounded.

Pleopod 1 exopod and endopod with 16 and 15 PMS respectively; endopod 0.8 as long as exopod, 1.7 times as long as greatest width, proximal lateral margin weakly concave; exopod lateral margin angled at mid­length, with short simple setae (PMS largely absent), distal margin rounded; peduncle medial margin with 3 coupling hooks. Pleopod 2 exopod and endopod with 20 and 16 PMS respectively; appendix masculina inserted sub­basally, 11 times as long as basal width, slightly shorter (0.96) than endopod, weakly spatulate, apex narrowly rounded, endopod mesial margin straight, lateral margin weakly convex distally, weakly concave proximally; exopod axis oblique, 0.6 times as long as endopod, distal margin broadly rounded. Pleopod 3 exopod and endopod with 23 and 15 PMS respectively. Pleopod 4 both rami with prominent thick ridges; endopod distal margins simple, proximomesial lobe present; exopod lateral margin with ~15 fine simple setae. Pleopod 5 both rami with prominent thick ridges, those of exopod indistinct; exopod with 3 scale patches, 2 distal and 1 proximal to suture, lateral margin with ~18 short simple setae.

Uropod rami subequal in length, distal margins smooth, with numerous marginal setae; endopod lateral margin curving smoothly to form distinct apical angle to mesial margin, 2.4 times as long as wide; exopod wide, lanceolate, lateral margin convex, about 2.0 (1.95) times as long as wide.

Female. Body shape and ornamentation similar to that of male; ovigerous females slightly less vaulted, with the transverse submarginal ridges on pereonite 7 and pleon slightly less well defined.

Size: Adults 3.0 to 4.1 mm; immature specimen 2.6 mm.

Remarks

Ischyromene kokotahi sp. nov. can be recognized by the presence, in males and females, of two prominent irregular sub­mesial longitudinal ridges on the pleotelson together with a dorsally directed and posteriorly closed pleotelson foramen, the anterior margin of which is provided with an acute ‘tooth’; to the lateral side of each longitudinal ridge is a longitudinal row of three nodules. In addition the lateral margins of the pereonites and pleon are conspicuously setose. Only Ischyromene bicarinata Harrison, 1981 has a similar pleotelson ornamentation, but differs in the following character states: the pleotelson posterior margin has a ventrally and posteriorly open exit channel, the uropod rami extend well beyond the posterior margin of the pleotelson, the uropod exopod is more slender than in I. kokotahi , the body lateral margins lack conspicuous setae and the longitudinal ridges on the pleotelson are less nodular.

In New Zealand three species of Ischyromene have a nodular pleotelson (see Hurley & Jansen 1977, as Dynamenella ). Of those, only I. condita has longitudinal ridges on the pleotelson, there being six (in males) more­or­less equally sized and relatively weak ridges as figured by Hurley & Jansen (1977). Examination of specimens referred to I. condita by Hurley & Jansen (1977) reveal numerous differences between that species and I. kokotahi , including differences in pleotelson ornamentation (the dorsum of the pleotelson of I. condita is far more nodular, with small acute points to the nodules), differences in the shape of the foramen (round in I. condita , and lacking lateral flanges) and in the shape of the posterior margin of pereonite 7 and the pleon. These differences are shown in Figure 5 for both male and female I. condita . [Note that other material (Stn E967, Eve Bay, Wellington south coast, 17 specimens, NIWA 23102), identified and reported by Hurley & Jansen (1977) from Wellington as I. condita is a misidentification, so the distribution of I. condita is not accurately known.] Furthermore, I. condita appears to occupy a different habitat from that of I. kokotahi , being described as occurring ‘Under stones, among algae’ while I. kokotahi has been collected from the barnacle and mussel zone in Evans Bay and other semi­sheltered areas.

Poore (1981) reported a large number of specimens of Ischyromene condita [as Dynamenella condita ] from The Snares islands (c. 48°01’S, 166°35’E). The figures and specimens examined here conform neither with Hurley & Jansen’s (1977) figures, nor material of that species examined here ( Fig. 5 ), but do show a strong similarity to I. kokotahi sp. nov. The Snares species differs in a number of details including having the posterior margin of pereonite 7 even (vs. with sub­lateral notches in I. kokotahi ), two smooth sub­median carinae on the pleotelson (vs. conspicuously nodular carinae), lacking conspicuous marginal setae on the coxae (vs. present), a more nodular pleotelson dorsal surface with 5–7 nodules on each side (vs. only three on each side) and a round pleotelson foramen (vs. posteriorly narrowed). The Snares material is an apparently common undescribed species.

Etymology

Reed (2002) gives the Māori name for Evans Bay (type locality) as kokotahi te taniwha, giving the meaning as ‘place of the monstrous seabird’. The epithet uses the noun (noun in apposition).

Figures

FIGURE 1. Ischyromene kokotahi sp. nov. A – F, holotype, remainder paratype. A, dorsal view; B, lateral view; C, frons; D, pleotelson, ventral view; E, pleon, lateral detail (pleonites numbered); F, pleotelson foramen, dorsal view; G, antennule; H, antenna.

FIGURE 2. Ischyromene kokotahi sp. nov. Dissected paratype. A, mandible; B, right mandible, incisor and spine row; C, left mandible, distal; D, mandible palp; E, robust seta, mandible palp article 2; F, maxillule; G, maxillule, detail; H, maxilliped; I, maxilla; J, maxilliped endite, distal margin.

FIGURE 3. Ischyromene kokotahi sp. nov. Dissected paratype. A – C, pereopods 1, 2 and 7 respectively; D, pereopod 1, dactylus; E, robust setae, distal margin of pereopod 7.

FIGURE 4. Ischyromene kokotahi sp. nov. Dissected paratype. A – E, pleopods 1 – 5 respectively; F, appendix masculina apex; G, penes; H, coupling hooks, pleopod 1; I, uropod.

FIGURE 5. Ischyromene condita (Hurley & Jansen, 1977). A, lateral view, ɗ; B and C, dorsal view of pleon and pleotelson of ɗ and Ψ respectively.