Eiconaxius gololobovi, Poore & Dworschak, 2018

Poore, Gary C. B. & Dworschak, Peter C., 2018, The Eiconaxius cristagalli species complex (Decapoda, Axiidea, Axiidae), Memoirs of Museum Victoria 77, pp. 105-120 : 111-114

Eiconaxius gololobovi sp. nov.

(http://zoobank.org/urn:lsid:zoobank.org:act:6BA2620A-9AF9-

4536-AD2F-4C0E980F65D8)

Figures 4c , 5–8

Material examined. Holotype. SW Indian Ocean, Gololobov Bank, ‘ Coral’ seamount, 41°21.0283'S, 42°55.145'E, 1117 m ( RV James Cook cruise JC606, code 996) NHMW 25659 (male, 7.8 mm).

Paratypes. SW Indian Ocean, Gololobov Bank, ‘ Coral’ seamount, 41°21.767'S, 42°54.907'E, 686.5 m, NHMW 25658 (male, 6.8 mm), NHMW 25660 (female, 6.1 mm), NHMW 25661 (male, 7.7 mm), NHMW 25662 (male, 5.1 mm), NHMW 25663 (female, 5.4 mm), NHMW 25664 (female, 6.8 mm), NHMW 25665 (male, 4.8 mm), NHMW 25666 (male, 8.3 mm), NHMW 25667 (ovigerous female, 9.1 mm), NHMW 25668 (ovigerous female, 8.1 mm), NHMW 25669 (male, 7.0 mm), NHMW 25670 (ovigerous female, 8.0 mm), NHMW 25671 (male, 6.2 mm), NHMW 25672 (male, 5.6 mm), NHMW 25673 (female, 5.6 mm), NHMW 25674 (ovigerous female, 8.8 mm), MNHN IU-2016-8156 (male, 7.4 mm), NMV J71648 (male, 7.8 mm), NHMW 26058 (male, 6.1 mm), NHMW 26059 (female, 6.8 mm) .

Other material. Madagascar. S of Pt Barrow , 25°39'S, 44°16'E, 986–991 m ( ATIMO VATAE stn CP3596), MNHN IU-2014-12083 (ovigerous female, 7.4 mm) .

Mozambique Channel , Geyser Bank, between Malekula and Ambrym islands, 12°18'S, 46°27'E, 920–935 m (BIOMAGLO stn DW4791), MNHN IU-2017-530 (male, 6.4 mm) .

Diagnosis. Rostrum parallel-sided proximally, with acute apex, 1.2–1.3 times as long as wide. Median carina erect, with clear dentition; sublateral gastric carinae present, diverging widely from base of median carina; lateral gastric carina continuous with short overlap of ridges posterior to confluence of submedian carinae. Major cheliped, merus lower margin with 2 spines near midpoint, or with single denticle; palm wider distally than at midpoint, upper margin smooth, carinate, or denticulate (juveniles); fixed finger about half as long as upper margin of palm, cutting edge crenellate, with row of diminishing rounded teeth; dactylus cutting edge smooth. Minor cheliped, palm upper margin significantly less than greatest width; distolateral margin with prominent triangular tooth at base of dactylus; fixed finger cutting edge smooth, straight.

Description of holotype. Carapace smooth, few obsolete tubercles on gastric region between carinae. Rostrum 0.18 carapace length, concave dorsally, tapering distally to acute tip, 1.35 times as long as wide at base, with c. 8 obscure teeth on lateral margins, depressed below level of median carina, continuous with lateral carinae, without ventral tooth. Lateral gastric carina unarmed, with posterior section weakly separated from, but almost overlapping anterior section. Submedian gastric carina smooth, together curved and converging on median carina, slightly longer than lateral gastric carina. Median gastric carina prominent, erect, reaching midpoint of rostrum, with 9 erect teeth becoming pentagonal anteriorly.

Pleuron 1 posteroventrally acute; pleura 2, 3 truncate, posteroventrally acute; pleuron 4 truncate, posteroventrally subacute, with anteroventral tooth; pleuron 5 rounded; pleuron 6 with acute posteroventral angle; pleonite 6 dorsal posterior margin denticulate.

Eyestalk, reaching half length of rostrum; cornea white. Antennular peduncle reaching two-thirds length of antennal article 4; article 1 unarmed. Antennal article 1 unarmed; article 2 with distal spine an elongate triangular blade, reaching two-thirds length of article 4; scaphocerite a vertical blade, reaching to end of article 5; article 3 lower margin with distomesial tooth; article 5 about half length of article 4.

Maxilliped 3 coxa unarmed; ischium with tubercle; crista dentata of c. 15 similar obsolete teeth; merus and carpus unarmed; exopod reaching beyond midpoint of merus.

Major cheliped merus lower margin convex, with 3 minute teeth, upper margin with minute blunt tooth; carpus lower margin with 1 distal tooth; propodus upper margin carinate, angled distally, length 1.15 greatest height, lower margin smooth, lateral face with few minute tubercles; mesial face smooth; fixed finger 0.7 times as long as upper palm, cutting edge with proximal U-shaped notch, 10 diminishing triangular teeth, with longitudinal lateral ridge; distolateral margin of palm weakly evenly convex; distomesial margin of palm convex; dactylus distally curved, upper margin carinate, cutting edge smooth, weakly convex proximally.

Minor cheliped shorter and more slender than major, palm 0.9 times height of major palm; merus lower margin with minute tooth at midpoint; carpus lower margin with 1 distal tooth; propodus dilating, upper margin carinate, with obscure proximal notch, 0.85 times greatest height, lower margin smooth, lateral and mesial faces smooth; fixed finger 1.4 times as long as upper palm, cutting edge weakly serrate, with longitudinal lateral ridge; distolateral margin of palm oblique, with prominent triangular tooth in gape; distomesial margin of palm oblique-convex, with 2 tubercles in gape; dactylus distally curved, upper margin carinate, cutting edge smooth.

Pereopod 2 ischium lower margin unarmed; merus lower margin unarmed; carpus as long as propodus upper margin; propodus upper margin 2.2 times as long as dactylus. Pereopod 3 merus unarmed; propodus 2.8 times as long as dactylus, with 5 rows of 1– 4 spiniform setae; dactylus spatulate, with 11 spiniform setae along oblique margin, plus unguis, and 2 rows of 3 facial spiniform setae. Pereopod 4 merus more slender than that of pereopod 3; propodus 2.8 times as long as dactylus, with 6 rows of 2–5 spiniform setae; dactylus spatulate, with 12 spiniform setae along oblique margin, plus unguis, and 2 oblique rows of 3 facial spiniform setae. Pereopod 5 dactylus spatulate, with 11 spiniform setae along oblique margin, plus unguis, without facial spiniform seta.

Pleopod 2 with appendices interna and masculina of similar lengths, 0.8 length of proximal endopod. Uropodal endopod 1.9 times as long as wide, oval, anterior-distal margin with 10 evenly-spaced teeth, last distal, without longitudinal ridge.

Uropodal exopod 1.4 times as long as wide, oval, anterior margin with small irregular teeth over distal two-thirds, without longitudinal rib.

Telson 1.5 times as long as wide, widest at third length, then tapering to posterolateral angles, lateral margin upturned, obscurely denticulate, distal margin obtusely angled, with posteromedian spine; dorsal face smooth.

Etymology. For Ya. K. Gololobov (1909–1980), Russian oceanographer, for whom the Gololobov Bank on the Southwest Indian Ocean Ridge is named, of which the type locality, ‘Coral’ seamount, is part.

Distribution. Gololobov Bank, Mozambique Channel, southwest Indian Ocean; 686–1117 m depth.

Remarks. Eiconaxius gololobovi sp. nov. is known from 21 specimens ranging 4.8–9.1 mm in carapace length collected from sponges by ROV on the Gololobov Bank, plus two from nearby localities in the Mozambique Channel. The species is distinguished from others in this group by the regularly dentate cutting edge of the fixed finger of the major cheliped (simple in other species) and from most species by the hiatus in the lateral carina. The dentition of cheliped fingers is obsolete in the ovigerous female from Madagascar ( Fig. 8l, m ). This individual has a more acute rostrum than others ( Fig. 8i ) but in this is similar to at least one smaller male ( Fig. 8b ) from Mozambique Channel. While several individuals display the distinctive pentagonal teeth on the median carina ( Fig. 5d ) (like children’s drawings of little houses), others have a similar number of more irregular teeth ( Figs 7g , 8a, h ) but in the smallest specimen dentition is obsolete ( Fig. 7a ). The upper margin of the propodus of the chelipeds often has a clear proximal notch ( Figs 5h, i , 7i, j ) but it is not obvious on the major cheliped of larger individuals ( Figs 5f, g , 8d, e, l ). The smallest individuals differ in having this margin serrate and a prominent tooth on the upper margin of the dactylus ( Figs 7c–f ).

Figures

Figure 4. Eiconaxius dongshaensis sp. nov., holotype, NTOU A01439 (female, 10.0 mm) – a, habitus, in vivo. b, habitus in host sponge (photos, Tin-Yam Chan). Eiconaxius gololobovi sp. nov., unspecified specimen – c, habitus, in vivo (photo, David Shale).

Figure 5. Eiconaxius gololobovi sp. nov., holotype, NHMW 25659 (male, 7.8 mm) – a, carapace, pleon, lateral. b, c, anterior carapace, antennule, antenna, lateral and dorsal. d, median carina. e, pleomere 6, telson, right uropod. f, g, right major cheliped, lateral and mesial. h, i, left minor cheliped, lateral and mesial. Scale bar = 1 mm (except b–d).

Figure 6. Eiconaxius gololobovi sp. nov., holotype, NHMW 25659 (male, 7.8 mm) – a, b, maxilliped 3, anterior detail of merus. c, pereopod 2. d, e, right pereopod 3, detail of dactylus. f, g, right pereopod 4, detail of dactylus, h, i, right pereopod 5, detail of dactylus. j, pleopod 2, proximal endopod, appendices interna and masculina. Scale = 1 mm (except b, e, g, i)..

Figure 7. Eiconaxius gololobovi sp. nov., NHMW 25662 (male, 5.1 mm) – a, anterior carapace, antenna, lateral. b, anterior carapace, dorsal. c, d, right major cheliped, lateral and mesial. e, f, left minor cheliped, lateral and mesial. NHMW 25658 (male, 6.8 mm) – g, anterior carapace. h, pleomere 6, telson, right uropod. i, left major cheliped, j, right minor cheliped. Scales = 1 mm.

Figure 8. Eiconaxius gololobovi sp. nov., MNHN IU-2013-7046 (male, 6.4 mm) – a, carapace, pleon, lateral. b, carapace, dorsal. c, pleomere 6, telson, right uropod. d, e, right major cheliped, lateral and mesial. NMV J71648 (male, 7.8 mm) – f, right minor cheliped, propodus distolateral margin. MNHN IU-2016-8156 (male, 7.4 mm) – g, right minor cheliped, propodus distomesial margin. MNHN IU-2014-12083 (ovigerous female, 7.4 mm) – h, carapace, antennule, antenna, lateral. i, carapace, antennule, antenna, dorsal. j, right epimera of pleomeres 1–6. k, pleomere 6, telson, left uropod. l, m right major cheliped, lateral and mesial. n, o, left minor cheliped, lateral and mesial. Scale bars = 1 mm.