Macrolabrum maui, Bird, Graham J. & Webber, W. Richard, 2015

Bird, Graham J. & Webber, W. Richard, 2015, The first pagurapseudid species (Peracarida: Tanaidacea) from New Zealand with remarks on paguridean (Decapoda: Paguridea) and pagurapseudid convergence and competition, Zootaxa 3995 (5), pp. 149-168 : 151-161

Macrolabrum maui n. sp.

(Plates 1–2; Figs 1–6 )

Material examined. Holotype —female (CR.023525), GJB/2-12, Corallina (with Hormosira banksii ), outer reef, LWS, Waima, Tokomaru Bay, East Cape region, 38.1100°S 178.3465°E, 12 January 2012, collected by G.J. Bird.

Allotype —male (CR.023526), GJB/1-12.

Paratypes —two manca-III (CR. 023528), seven preparatory females (CR.023530, one on microslide CR.023530/1), one ovigerous female (CR.023528), five males (CR.023529), GJB/1-12; one manca-II (CR.023531), four manca-III (CR.023532), sixteen preparatory females (CR.023533) (one on microslides, CR.023535, 0 23536, 023537), one preparatory female (on microslide, CR.023538), nine males (one with antennule dissected on microslide) CR.023534; one individual photographed in shell (CR. 023162), one individual photographed removed from shell (CR. 023163), 39 individuals in Eatoniella spp. (CR.023527).

Other topotypical material— one individual in Eatoniella sp., GJB/1-12; eight neuters/indet, four in mollusc shells (three in Eatoniella sp., one in Pisinna sp., GJB/2-12; five individuals in Eatoniella spp., in one individual in Merelina sp., one individual in Pisinna sp., GJB/4-12.

Etymology. Noun in apposition, alluding to the Māori mythological character Maui , found in the sea wrapped in seaweed after his birth, and a well-known holiday camper-van firm in NZ – mobile homes as in pagurapseudids and hermit crabs

Type locality. Among coralline turf and Carpophylum plumosum var. capillifolium holdfasts, lower eulittoral rock platforms, Waima, Tokomaru Bay, East Cape region, North Island, New Zealand, 38.1100°S 178.3465°E.

PLATE 1. Macrolabrum maui n. sp. Paratype (CR. 023163) removed from shell, entire.

PLATE 2. Macrolabrum maui n. sp. Paratype (CR. 023162) within shell of Eatoniella olivacea .

Diagnosis. Female: Carapace without lateral spines, rostrum simple. Antennule peduncle article-1 with medial spine and lateral spines/apophyses; accessory flagellum one-segmented, main flagellum two-segmented. Cheliped basis with superoproximal spine; carpus with double row of inferior spiniform apophyses or serrations. Pereopod -1 carpus and propodus each with three inferior spines; dactylus with three inferior spines. Pereopods 2–3 propodus half length of carpus. Pereopod-6 carpus with two plumose setae. Pleopods present, two pairs, peduncle with three setae. Uropod endopod three-segmented, exopod one-segmented. Male: Antennule stouter; cheliped dimorphism weak or absent.

Description. Ovigerous and preparatory female: Habitus ( Figs 1 ; 2A, D, Plate 1) with dark purple-brown pigmentation, particularly on carapace; length 2.2–3.0 mm. Cephalothorax ( Fig. 2 A) as long as broad, with weakly convex lateral margins; rostrum ( Fig. 2 B) subtriangular, with rugose-denticulate margin; epistome ( Fig. 2 C) acuminate, projecting beyond rostrum or deflexed; carapace lateral margins with four setae, dorsum with two rows of three (or four) setae; eyes distinct, with pointed apex, blackish. Pereon with pereonite-1 shortest with posterolateral apophyses, pereonites 2–3 equal, pereonites 4 and 6 longer, equal, pereonite-5 longest; setation as figured. Pleon ( Fig. 2 D) cylindrical, tapering posteriorly, lateral margins with group of plumose setae (three on pleonites 1–4, two on pleonite-5), other setation as figured. Pleotelson as long as pleonite-5, with dorsolateral, inferolateral and terminal setae.

Antennule ( Fig. 2 E) typical; peduncle article-1 2.7 times ltb, with one spine on mesial margin, and distal row (ca. five) of lateral spines; article-2, 1.7 times ltb, as long as articles 3–4 combined; article-3 just longer than broad; article-4 (common) shorter than broad; accessory flagellum one-segmented, longer than segment-1 of main flagellum; main flagellum two-segmented, each with one aesthetasc; other setation as figured. Antenna ( Fig. 2 F) short and robust, with five apparent articles; proximal article (probably two fused, sensu Błażewicz-Paszkowycz & Bamber 2012) about as long as broad, with superior and inferior spines or serrations, two simple setae and one PSS; article-2 short, with superior and inferior distal spine, with one simple seta and one PSS; article-3 smaller than article-2, with superior and inferior distal spine and two PSS; article-4 longer than broad, just longer than article-2, with one simple seta and one PSS; terminal article (flagellum) very short with long terminal seta, a small simple seta and three PSS.

Labrum (not figured), typical. Mandibles ( Figs 3 A–B) typical; left incisor with four small denticles, lacinia flared, excavate at tip, setiferous lobe with five or six bifurcate setae; molar cylindrical, simple; palp article-1 short, with outer spines and inner plumose seta; article-2 with three distal setae, article-3 with four terminal setae; right mandible similar but lacinia absent, base of incisor serrate. Labium ( Fig. 3 C) typical, outer lobe setulate, palp conical, with two terminal setae, and more proximal setules. Maxillule ( Figs 3 D–E) typical, inner endite with four terminal setae, outer endite with about ten stout setae. Maxilla ( Fig. 3 F) typical, lobes of moveable endite hardly distinguished, except by setal type; outer lobe of fixed endite with pectinate setae and three multifurcate setae, inner lobe with about seven pectinate setae. Maxilliped ( Figs 3 G–K) robust, basis with crenulate superior and serrate inferior margin, latter with two plumose setae; palp articles 1–2 with serrate superior process and inner margin; articles 3–4 smooth-margined; setation as figured; endite with six excavate-tipped and two finely pectinate distal setae, two stout inner coupling hooks and mesial row of small pectinate setae. Epignath not recovered.

Cheliped ( Figs 4 A–B) basis 1.4 times ltb, with two proximal (superior and inferior) spines, inferior margin with three plumose and two pectinate setae; merus with serrate inferodistal margin and acuminate apophysis, with one inferior and three outer plumose setae, inner surface with one pectinate seta; carpus about twice as long as broad, inferior margin with two serrate rows separated by shallow groove, and several setae, superior margin with pectinate and simple setae; propodus (with superior margin canted inwards) about as long as carpus, three times longer than broad, with one superodistal seta, two setae near articulation with dactylus, and two long inner setae; fixed finger with about four or five inferior setae and four near incisive margin that has three sharp distal teeth; dactylus with inner seta and three setae near articulation with unguis; right and left chelipeds equal or right only slightly larger.

Pereopod-1 ( Figs 5 A–F) exopod reniform, with fourteen plumose setae; coxa with two setae (see Fig. 2 A); basis 2.2 times ltb, inferior margin with about five simple setae and one distal plumose seta, superior margin with about eight triangular spines and fringe of eleven plumose setae; ischium as long as broad, inferior margin with two simple setae and one distal plumose seta; merus 2.2 times ltb, with three superodistal pectinate spines (coarse and fine), inferior (outer) margin with about three short simple setae and fringe of four plumose and one long simple setae, inferior (inner) margin with about eight or nine curved setae; carpus just shorter than merus, with one superoproximal simple seta, one long simple superodistal seta, five distal pectinate spines (coarse and fine) and two simple and two plumose inferior setae; propodus rectangular, longer than carpus, as long as merus, inferior margin with two simple setae and two spines, inferodistal margin with one spine, one long and one short simple setae, and one pectinate spine (fine), superodistal margin with one simple seta and two PSS; dactylus as long as propodus, with three inferior simple spines, superior margin with one simple seta and one PSS; unguis slender, half length of dactylus. Pereopod-2 ( Figs 5 G; 6A–B) coxa annular, with two anterior setae, (finger-like oostegite bud in preparatory female); basis rectangular, twice as long as broad, superior margin with PSS and simple seta, outer margin with two pectinate setae, inferodistal margin with plumose seta; ischium with one simple and four pectinate inferodistal setae; merus with three rows of sucker-spines, a simple and plumose inferior seta, and superodistal pectinate seta; carpus slightly shorter than merus, with three rows of sucker-spines, one inferodistal pectinate spine, one stout pectinate distal spine and two superodistal setae; propodus half length of carpus, with two sucker spines, one superior PSS, one long superodistal seta, one robust acuminate spine and one slender pectinate seta; dactylus and unguis as long as propodus, dactylus with superior and inferior accessory spinules. Pereopod-3 ( Fig. 6 C) similar to pereopod-2 but smaller; ischium with four plumose setae; carpus as long as merus; propodus without long superodistal seta.

Pereopod-4 ( Fig. 6 D) generally similar to pereopods 2–3, but smaller than pereopod-3; ischium with three setae; carpus without distal robust spine; propodus with stronger superodistal pectinate spine, longer than dactylus and unguis, with slightly weaker robust pectinate spine and PSS (or thin pectinate seta?). Pereopod-5 ( Fig. 6 E) similar to pereopod-4 but slightly smaller, ischium with only two distal setae. Pereopod-6 ( Fig. 6 F) similar to pereopod-5 but smaller, basis and ischium without distal setae; propodus without superior PSS, distal pectinate setae of equal length.

Pleopod ( Fig. 6 G) peduncle 2.25 times ltb, inner margin with three plumose setae; endopod as long as peduncle, with six plumose setae; exopod with nine plumose setae.

Uropod ( Figs 6 H–J) half as long as pleotelson; peduncle 1.3 times ltb, with one plumose and two simple setae; endopod just longer than peduncle, three-segmented, segments 1–2 short and weakly defined, segment-3with one PSS and three thick setae (largest articulated); exopod one-segmented (or with faint indication of two segments), just longer than segments 1–2 of endopod, with two terminal setae.

Manca-II: without last pair of pereopods or pleopods; length about 1.4 mm.

Manca-III: with rudimentary pereopods-6 and pleopods; length about 1.7 mm.

Male: Habitus slightly more slender than female, with penial cone ( Fig. 2 G) on sternum of pereonite-6; length 1.8–2.2 mm. Antennule ( Fig. 2 H) peduncle articles broader than female, articles 1–4 2.1, 1.1, 1.0, and 0.6 times ltb respectively. Otherwise as female.

Distribution and ecology. Macrolabrum maui n. sp. is known with certainty only from the type locality, but it is highly likely that it is the same species as that from Goat Island, Leigh illustrated by Morton & Miller (1973). Various substrates were inhabited by this pagurapseudid, including Corallina turf on flat bedrock, Carpophyllum and Cystophora fronds and holdfasts and it is probable that it would be found in NZ wherever there is a source of micro-mollusc shells and relative shelter in the eulittoral zone on coasts influenced by warm water currents.

Forty-nine specimens of M. maui were found still within mollusc shells, of which a minimum of five species were present: the eatoniellids Eatoniella limbata (Hutton) , E. olivacea (Hutton) Plate 2, and E. maculosa (Ponder) , the rissoid Merelina lyalliana Suter , and an undescribed species of the anabathrid genus Pisinna Monterosato. Sympatric (and same-sample) tanaidaceans included undescribed species of Cyclopoapseudes Menzies and Metapseudes Stephensen , as well as Parakonarus kopure Bird, 2011 , Paratanais paraoa Bird, 2011 , Acallocheirus echmanomus Bird & Bamber, 2013 , and Zeuxoides rimuwhero Bird, 2008 .

Remarks. The antennule flagella segment-count of two (main) and one (accessory) places Macrolabrum maui close to M. impedimenta , M. haikung and M. tangaroa among the Australian species (see Błażewicz-Paszkowycz & Bamber 2012). The uropod segment count is less easy to compare because of its uncertain state but it differs from both M. impedimenta and M. tangaroa that have two endopodal segments – the other species have three. It is also comparable to that group of species with a double row of apophyses on the inferior margin of the cheliped carpus: M. boeri , M. haikung , M. sarda , M. tangaroa , and M. trifidus . However, this character is not confined to Macrolabrum but is also expressed in several species of Pagurotanais . In most respects M. maui is perhaps closest morphologically to M. distonyx , from the bathyal zone off New Caledonia, differing in having cheliped carpus serrations, one lateral antennular apophysis, and more complex antennal spination.

The sex ratio of the sample population is 27:17, i.e. 1.6:1, females to males; a similar, 1:1, field population sex ratio (with a larger sample size) was found by Messing (1983) for Pagurapseudes largoensis McSweeny, 1982 . This rough parity for M. maui suggests that the males, although being on average smaller, are a permanent component of the population, especially as they have functional mouthparts. Together with body-size data (also supporting the findings of Messing 1983) it implies that M. maui is also dioecious, the males (minimum size measured: 1.8 mm) arising directly from mancae (maximum size measured: 1.7 mm).

Some offshore (<200 m) samples from northern NZ contain a few other pagurapseudid specimens, probably a Pagurapseudes species and another species of Macrolabrum , but the available material is too sparse and deficient to allow full taxonomic treatment.

Figures

FIGURE 1. Macrolabrum maui n. sp. Holotype female (CR. 023525). Scale bar: 0.5 mm.

FIGURE 2. Macrolabrum maui n. sp. Paratype preparatory female (CR. 023530): A, habitus, anterior; B, rostrum; C, epistome (lateral); D, pleon; E, antennule; F, antenna. Paratype male (CR. 023534): G, penial cone on pereonite- 6 (pereopod removed for clarity); H, antennule. Scale bars: (i) 0.5 mm for A, D, G, 0.25 mm for B – C; (ii) 0.25 mm for E – F, H.

FIGURE 3. Macrolabrum maui n. sp. Paratype preparatory female (CR. 023538): A, left mandible; B, right mandible; C, labium; D, maxillule; E, maxillule inner endite; F, maxilla; G, maxilliped basis and palp; H, maxilliped palp article- 2 outer margin, different specimen; J, maxilliped palp article- 4; K, maxilliped endite. Scale bar: 0.25 mm.

FIGURE 4. Macrolabrum maui n. sp. Paratype preparatory female (CR. 023536): A, right cheliped; B, left cheliped (inner view). Scale bar: 0.25 mm.

FIGURE 5. Macrolabrum maui n. sp. Paratype preparatory female (CR. 023536): A, pereopod- 1 exopod; B, pereopod- 1 (with indication of exopod position at rest); C, pereopod- 1 merus inner setation; D – E, pereopod- 1 carpus inner setae; F, pereopod- 1 propodus inner seta; G, pereopod- 2 (for size comparison), and G’ obscured carpal pectinate seta. Scale bar 0.25 mm.

FIGURE 6. Macrolabrum maui n. sp. Paratype preparatory female (CR. 023535): A, pereopod- 2,) and A’, obscured carpal pectinate seta; B, pereopod- 2 propodus and claw, for clarity; C – E, pereopods 3 – 6 respectively; G, pleopod; H, uropod, lateral; J, uropod endopod, for clarity, setae omitted. Scale bar: 0.25 mm.