Ancylomenes australis, Bruce, A. J., 2013

Bruce, A. J., 2013, Ancylomenes australis sp. nov. (Crustacea: Decapoda: Pontoniinae) from South Africa, Zootaxa 3722 (1), pp. 73-82 : 73-82

publication ID	https://doi.org/ 10.11646/zootaxa.3722.1.6
publication LSID	lsid:zoobank.org:pub:CDD14B3E-2E78-4813-B483-0DC2C87F2C9A
DOI	https://doi.org/10.5281/zenodo.6153130
persistent identifier	https://treatment.plazi.org/id/B7593318-834A-FFA9-F1EA-F93084A4FE32
treatment provided by	Plazi
scientific name	Ancylomenes australis
status	sp. nov.

Treatment

Ancylomenes australis sp. nov.

( Figs 1 –7 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 View FIGURE 7 )

Material examined. 1 ovig. ♀, holotype, Sodwana Bay, KwaZulu-Natal, South Africa, coll. Valda Fraser, 32.0 m, 26 May 2013, QM W29196.

Diagnosis. Rostral dentition 5/1, slender, carapace with epigastric tooth, inferior orbital angle distally rounded, third abdominal segment strongly produced posterodorsally, rounded, thick, telson with two pairs of very small dorsal spines at 0.6 and 0.8 of length, median process of ophthalmic somite robust, distally swollen and rounded, second pereiopods unequal, chelae similar, major with single tooth on dactyl, three teeth on fixed finger, minor chela with dactyl toothless, fixed finger with one small tooth, ambulatory dactyls biunguiculate.

Description. Ovigerous ♀, holotype, complete, dissected.

Rostrum ( Fig. 2 View FIGURE 2 C) slender, compressed, short, about 0.7 of CL, reaching to end of penultimate segment of antennular peduncle, dorsal carina raised over proximal two thirds, becoming distally very slender, with four similar slender acute teeth proximally, and one small distal tooth, with sparse interdental setae dorsally, ventral carina obsolete, ventral margin non-carinate, convex proximally, with nine long plumose setae, distal half concave, non-setose, with small acute distal tooth well in advance of distal dorsal tooth.

Carapace ( Fig. 2 View FIGURE 2 AB) smooth, glabrous, slightly compressed, without supraorbital teeth or tubercles, epigastric tooth well developed, at 0.65 of CL, hepatic tooth robust, anterior to level of epigastric tooth, antennal tooth robust, marginal, inferior orbital angle ( Fig. 2 View FIGURE 2 D) strongly produced, distally rounded ( Fig. 5 View FIGURE 5 A), with narrow inner flange, anterolateral carapace margin not advanced, broadly rounded.

Abdomen well developed, third segment with large stout rounded posteromedian expansion, pleura of first three segments enlarged, broadly rounded, fourth rounded and fifth posteriorly angular, with plumose setae, sixth segment ( Fig. 1 View FIGURE 1 ) 0.83 of CL, with small acute posterolateral and posteroventral teeth, posteroventral tooth setose.

Telson ( Fig. 2 View FIGURE 2 J) about 0.75 of CL, 3.1 times longer than anterior width, lateral margins straight, convergent, distal margin broadly angular ( Fig. 5 View FIGURE 5 H), centrally rounded without median point, with inconspicuous short stout subequal dorsal spines ( Fig. 5 View FIGURE 5 H) at 0.6 and 0.8 of telson length, about 0.025 of telson length, lateral posterior spines ( Fig. 5 View FIGURE 5 H), longer than dorsal spines, about 0.4 of intermediate spine length, intermediate spines 0.07 of telson length, robust, 2.4 times longer than slender densely setulose submedian spine.

Epistome with pair of large rounded submedian bosses anteriorly.

Antennule ( Fig. 2 View FIGURE 2 E) with proximal segment of peduncle ( Fig. 2 View FIGURE 2 F) about 2.5 times longer than central width, medial margin straight, densely setose, with very small acute ventral tooth at about 0.3 of medial length, lateral margin strongly produced distomedially, lobe twice as broad as long, broadly rounded, lateral margin feebly convex with small acute distolateral tooth, about half length of distal lobe ( Fig. 2 View FIGURE 2 F), stylocerite slender, acute, reaching to about 0.3 of segment length, statocyst with granular statolith; intermediate and distal segments short, subcylindrical, subequal, together about 0.5 of proximal segment length, upper flagellum biramous, proximal ten segments fused, short free ramus with four segments, with twenty four groups of aesthetascs over whole flagellum length, longer free ramus with eighteen segments; lower flagellum long, filiform, with twenty eight segments.

Antenna ( Fig. 2 View FIGURE 2 G) with basicerite with robust distolateral tooth, dorsally with two small processes; carpocerite reaching to 0.6 of scaphocerite length, far shorter than scaphocerite, subcylindrical, about 5.5 times longer than wide; merocerite and ischiocerite without special features; scaphocerite ( Fig. 2 View FIGURE 2 H) well developed, reaching beyond antennular peduncle, broad, about 2.5 times longer than wide, distal lamella rounded, lateral margin straight with robust distolateral tooth at 0.8 of length, 0.16 of lateral margin length, far exceeded by distal margin of lamella.

Ophthalmic segment with conspicuous median dorsal projection, at about 45° to body axis, distally expanded, anteroposteriorly bilobed, just below lower margin of rostrum.

Eye ( Fig. 2 View FIGURE 2 I) with cornea globular, diameter about 0.1 of CL, without accessory pigment spot, stalk subcylindrical, slightly swollen proximally, about 2.5 times longer wide.

Mouthparts, left side.

Mandible ( Fig. 3 View FIGURE 3 A) with corpus robust, without palp, molar process ( Fig. 5 View FIGURE 5 B) subcylindrical, obliquely truncate distally, with stout distolateral teeth, one with small setal tuft; incisor process ( Fig. 5 View FIGURE 5 C) normal, tapering to oblique tip with four robust acute teeth, central pair smaller than others.

Maxillula ( Fig. 3 View FIGURE 3 B) with feebly bilobed palp ( Fig. 5 View FIGURE 5 D), lower lobe slightly produced with simple terminal seta on small tubercle; upper lacinia ( Fig. 5 View FIGURE 5 E) short and broad, tapering, distally rounded, dorsal margin convex, with ten simple articulated spines, sparse ventral setae; lower lacinia short, stout, subcylindrical, distally rounded with several long slender serrulate spiniform setae.

Maxilla ( Fig. 3 View FIGURE 3 C) with flattened tapering palp, about 3.0 times longer than basal width, sparsely setose proximolaterally, basal endite without lobes (possibly abnormal), rounded, glabrous, coxal endite fused with basis, rounded, non-setose, scaphognathite normal, broad, about 3.0 times longer than central width, anterior lobe 1.4 times longer than wide, medial margin slightly concave, posterior lobe 1.4 times longer than basal width, all margins setose.

First maxilliped ( Fig. 3 View FIGURE 3 D) with flattened tapering palp with long terminal simple seta, basal and coxal endites fully fused, distally rounded, medial margin straight with numerous slender setae, decreasing proximally, coxal portion expanded, feebly setose, exopod normal, flagellum slender, with four long plumose distal setae, caridean lobe large, about 2.0 times longer than central width, epipod well developed, rounded, bilobed.

Second maxilliped ( Fig. 3 View FIGURE 3 E) with normal endopod, dactylar segment narrow, 2.6 times longer than broad, with numerous long slender serrulate marginal spines, propodal segment antero-medially rounded, slightly produced, with seven long slender marginal spines, carpus, merus and ischiobasis without special features, exopod with slender flagellum with four long plumose terminal setae, coxa produced medially, non-setose, epipod well developed, oval, without podobranch.

Third maxilliped ( Fig. 3 View FIGURE 3 F) reaching to middle of carpocerite, with proximal segment of endopod and basis distinct, proximal segment slender, 6.0 times longer than proximal width, tapering slightly distally, sparsely setose medially, penultimate segment subcylindrical, 0.8 of proximal segment length, 8.0 times longer than wide, with few groups of spiniform setae medially, terminal segment half of proximal segment length, 5.5 times longer than proximal width, tapering distally, with numerous spiniform setae medially, long terminal seta, basis rounded medially, sparsely setose, exopod shorter than ischiomerus, with four plumose distal setae, coxa robust, medial margin straight, non-setose, lateral margin with well developed rounded lateral plate, with small quadrilamellar arthrobranch.

Thoracic sternite s narrow, unarmed.

First pereiopod ( Fig. 4 View FIGURE 4 A) normal, chela ( Fig. 4 View FIGURE 4 B) about 0.4 of CL, palm subcylindrical, slightly compressed, 2.4 times longer than deep, with several rows of short cleaning setae proximo-ventrally, fingers subequal to palm length, slender, simple, cutting edges entire, tips slightly hooked, with dactyl with simple, fixed finger with feebly bidentate, both fingers with numerous groups of long simple setae; carpus 1.25 times chela length, 8.0 times longer than distal width, tapering proximally, with small bunch of long cleaning setae distoventrally; merus about 1.4 times chela length, subequal to carpal length, 10.0 times longer than central width, subcylindrical; ischium 0.5 of meral length, 0.7 of palm length; basis without special features; coxa normal, without ventral process.

Second pereiopods slightly unequal, dissimilar.

Major second pereiopod (right) ( Fig. 4 View FIGURE 4 C) with chela ( Fig. 4 View FIGURE 4 D) subequal to CL, palm subcylindrical, slightly oval in section, about 3.5 times longer than distal depth, smooth, glabrous; fingers ( Fig. 4 View FIGURE 4 E) 0.6 of palm length, with strongly hooked tips (lost in dissection), dactyl about 6.0 times longer than central depth, compressed, dorsal margin convex, tip acute, cutting edge laminar, unarmed; fixed finger about 4.05 times longer than proximal depth, cutting edge laminar, mainly entire, with three well spaced acute recurved teeth ( Fig. 5 View FIGURE 5 F) over central third of length; carpus subequal to palm length, distally expanded, 5.5 times longer than distal width, tapering proximally, unarmed; merus subequal to palm length, subcylindrical, 6.5 times longer than wide, unarmed; ischium 1.2 times palm length, 1.1 times meral length, subcylindrical, 8.0 times longer than distal width, unarmed; basis and coxa robust, without special features.

Minor second pereiopod (left) ( Fig. 4 View FIGURE 4 F) with chela ( Fig. 4 View FIGURE 4 G) about 0.78 of CL, 0.65 of major chela length, palm sub-cylindrical, compressed, about 3.5 times longer than depth, smooth, glabrous; fingers ( Fig. 4 View FIGURE 4 H)) gaping, sparsely setose, about 0.65 of palm length, dactyl compressed, dorsal margin convex, 5.0 times longer than central depth, tip acute, crossing with fixed finger tip, cutting edge, laminar, unarmed, compressed, smooth, cutting edge feebly concave, entire, fixed finger about 3.0 times as long as proximal depth, cutting edge entire, with single small acute tooth at 0.3 of length, finger tips acute, hooked, crossing, with tufts of long simple setae; carpus 1.4 of palm length, distally expanded, 7.0 times longer than distal width, unarmed; merus 1.12 of palm length, 7.5 as long as distal width, unarmed; ischium subequal to carpal length, tapering proximally, unarmed; basis and coxa robust, without special features.

Third pereiopod ( Fig. 4 View FIGURE 4 I) slender, dactyl ( Fig. 5 View FIGURE 5 G) slender curved compressed, about 0.15 of propod length, 3.0 times longer than basal width, unguis 0.6 of dorsal corpus length, 4.0 times longer than basal width, corpus twice as long as proximal width, tapering slightly, distal width 0.6 of proximal width, with strong accessory tooth distally, 0.6 of unguis length; propod ( Fig. 4 View FIGURE 4 J) about 0.6 of CL, subcylindrical, 13.0 times longer than central depth, with pair of short distoventral spines ( Fig. 5 View FIGURE 5 G), single similar preterminal ventral spine; carpus subcylindrical 0.45 of propod length, unarmed; merus robust, subequal to propod length, subcylindrical, 10.0 times longer than central width, unarmed; ischium 0.4 of meral length, tapering proximally, unarmed; basis and coxa stout, without special features.

Fourth pereiopod ( Fig. 4 View FIGURE 4 K) similar to third, dactyl similar, propod ( Fig. 4 View FIGURE 4 M) s imilar third propod, similarly armed, longer than third; proximal segments similar, propod 0.65 of CL.

Fifth pereiopod ( Fig. 4 View FIGURE 4 L) longer and more slender than third and fourth, dactyl similar.

Pleopods without special features.

Uropods ( Fig. 2 View FIGURE 2 K) with protopodite unarmed; exopod about 1.15 of telson length, 2.7 times longer than wide, lateral margin mainly straight, with well developed distal tooth, without spine medially ( Fig. 5 View FIGURE 5 I), diaeresis well marked; endopod shorter than exopod length, 2.6 times longer than wide.

Ova numerous and small.

Measurements. Postorbital carapace length, 6.1 mm; carapace and rostrum, 10.0 m; total body length (approx.), 32.0 mm; major second pereiopod chela, 6.3 mm; minor second pereiopod chela, 4.0 mm; length of undeveloped ovum, 1.6 mm.

Etymology. From australis (Latin) , southern, with reference to its Southern African distribution.

Host. Unidentified cerianthid anemone. The collector also reports that this shrimp associates with the anemone Heteractis aurora (Quoy & Gaimard, 1833) .

Colouration ( Figs 6–7 View FIGURE 6 View FIGURE 7 ). Generally semi-transparent. Rostrum with teeth white with broader spot of blue proximally, carapace with narrow feebly speckled transverse white band centrally, tapering ventrally, first abdominal tergum with narrow white band dorsally, centre mottled, second tergum with broader transverse white band, centre pinkish, third tergum with large oval white patch, anterior half buff, posterior margin, around base of posterodorsal process, reddish, with narrow whitish margin extending along posterior edge of segment, posterior margin of fifth segment mottled white, posterior margin of sixth segment, proximal caudal fan, uropodal protopodite and proximal rami white, distal halves of rami orange, posterior margin and distal telson white, endopod of exopod with large blue spot medially, anterior to diaeresis, antennae speckled with blue and white, eye with cornea whitish banded with red, stalk with longitudinal dorsal white stripe, continuous over ophthalmic segment, pereiopods mottled white, banded with blue, second pereiopod fingers dense white.

Systematic position. Ancylomenes australis is closely similar to A. venustus (Bruce, 1990) and A. sarasvati (Okuno, 2002) . It shares with these species the following characters; carapace with epigastric tooth; distolateral margin of proximal segment of antennular peduncle rounded; ophthalmic somite with median process well developed; carpus of second pereiopod shorter than chela; ambulatory pereiopods with dactyl biunguiculate, propods with single ventral spine posterior to distoventral spines.

Ancylomenes australis differs from both these species in the form of the rostrum with a dentition of 5/1, dorsal carina elevated proximally with a very slender distal half; inferior orbital angle not acutely pointed distally, with feeble inner flange; third abdominal tergum with large thick, rounded carina posterodorsally, median process of ophthalmic somite distally swollen and blunt; second pereiopod carpus longer than palm; major chela with dactyl unarmed, fixed finger with cutting edge with three small acute recurved teeth on central third.

The species may be separated in the key below.

1. Rostrum deep proximally, slender distally, dentition 5/1; inferior orbital angle distally blunt; major second pereiopod with fingers with 0/3 teeth, minor pereiopod with 0/1............................................... A. australis sp. nov.

- Rostrum gradually tapering distally, dentition greater than 5/1; inferior orbital angle distally acute; second pereiopod fingers with dentition 2 or more teeth............................................................................ 2

2. Second pereiopods overreaching tip of scaphocerite by distal part of.. merus, cutting borders of fingers with 6–8 small acute, recurved teeth…....................................................................... A. venustus (Bruce) View in CoL

- Second pereiopods overreaching tip of scaphocerite by proximal part of palm, cutting borders of fingers with 2-4 large acute, recurved teeth........................................................................ A. sarasvati (Okuno) View in CoL

These three species may also be separated by the following key to colour patterns, adapted from Okuno (2002): —

1. Ophthalmic somite without white transverse band............................................................ 2

- Ophthalmic somite with white transverse band.............................................................. 4

2. Third abdominal tergum with large white patch over posterior half............................................... 3

- Third abdominal tergum with small V-shaped white patch over posterior half, bordered anteriorly and posteriorly by narrow purple bands; caudal fan centrally white with purple bands posteriorly across and proximal margin of exopod, central region transparent, distal ends of uropods purple margined anteriorly by................................. A sarasvati (Okuno) View in CoL

3. Third abdominal tergum with large cordiform white patch surrounding several small circular pink patches which may be confluent; protopodite blue-white, exopodal ram white, distal third of exopod blue-white with purple blue peripheral margin......................................................................................... A. venustus (Bruce) View in CoL

- Third abdominal tergum with white patch triangular with oval pink patch centrally, transverse white bands across central carapace, second and fourth abdominal terga, anterior caudal fan white, anterior uropods transparent, distal uropods with large pink patch margined anteriorly and posteriorly with white, endopod with large round bright purple spot distomedially................................................................................................ A. australis sp. nov.

4. Numerous other species.................................................................................

Remarks. The discovery of A. australis in South African waters is of particular interest. Reports of species of this genus from east African mainland localities have been infrequent. Ancylomenes aqabai (Bruce, 2008) has been reported from Aqaba, Jordan, in the northern Red Sea, A. longicarpus (Bruce & Svoboda, 1983) also from the Red Sea, and A. holthuisi (Bruce, 1969) , a species of wide Indo-West Pacific distribution, known only from Unguja, Zanzibar, from Bumwini, 36 m (Bruce, 1966); Zanzibar Harbour (Bruce, 1972), and Zanzibar Harbour, Mapape Reef, and Bawi Island (Bruce, 1976). The occurrence of A. australis in South Africa at 27.5° South presents a significant extension of the distribution range for the genus Ancylomenes . The southerly distribution of the new species resembles that of A. aesopius (Bate, 1863) known only from Western Australia and South Australia (Davie, 2002). The two species do not appear to be closely similar.

Two features are of interest in A. australis , the epistome and the uropod. In A. kobayashi (Okuno & Nomura, 2002) , A. speciosus (Okuno, 2004) , A. sarasvati (Okuno, 2002) and A. luteomaculatus Okuno & Bruce, 2009 , the epistome is noted to be unarmed. This contrasts strongly with the presence in A. australis of a conspicuous pair of well developed hemispherical submedian protuberances on the anterior epistome. In A. venustus (Bruce, 1990) a pair of small submedian bosses are noted. On the lateral margin of the uropodal exopod there is a large distolateral tooth but no trace of any spine medially to the tooth as is usual in pontoniine shrimps. The two uropods are exactly similar in this respect and there is no sign of damage. With only a single specimen it can not be decided if this is a taxonomic character or individual variation.