Neoanchistus nasalis Holthuis, 1986

de Gier, Werner & Fransen, Charles H. J. M., 2023, Polka-dotted treasures: Revising a clade of ascidian- and bivalve-associated shrimps (Caridea: Palaemonidae), Contributions to Zoology 92 (3), pp. 179-282 : 237-244

Neoanchistus nasalis Holthuis, 1986

(fig. 28B, C, 29)

Neoanchistus nasalis Holthuis, 1986: 264-269, figs. 1-2 [type locality: artificial reef near Raysut Harbour, Dhofar, southern Oman, 16°57’45”N

54°00’E, in Chlamys townsendi (= Mimachlamys townsendi (G. B. Sowerby III, 1895)) ]; Hogarth, 1989:111;Müller, 1993:39(listed); Fransen, 1994a: 107, 111, fig. 2f; Li, 2000: 81, fig. 82 (listed); Bruce, 2006: table 1 (listed); De Grave & Fransen, 2011: 353 (listed); Dobson et al., 2014: 9, appendix 1; Dobson et al., 2016: fig. 7, suppl. inf. I.

Neanchistus nasalis – Hogarth, 1989: 111 [erroneous spelling].

Material examined. INDIAN OCEAN: Remarks. Dactyli of ambulatory pereiopods

1 male pocl. 9.8 mm, 2 ovigerous females are very similar to those of Tympanicheles

pocl. 12.4 14.3 mm ( RMNH. CRUS.D.36608), pectinis , both with a minute accessory tooth, Southern Oman, Dhofar, artificial reef near dorsal transverse rims on the corpus, and dor- Raysut Harbour , 16°57’45”N 54°00’E, 24.ii.1983, sally minutely spinulate unguis. Chela of sec-

in Chlamys townsendi (G.B. Sowerby) , coll. ond pereiopods show differences in setation

P.J. Hogarth, no. 41, site no. IJI. – 1 speci- of the fixed finger, in two specimens it is promen, pocl. 10 mm ( RMNH. CRUS.D.36608), vided with a dense cover of long setae on the Southern Oman, Raysut, 9.x.1983, depth 10 ventral margin (fig. 29C), in the largest chela

m, in C. townsendi , coll. P.J. Hogarth, no. 335. the number of setae is much smaller.

1 non ovigerous female pocl. 4.0 mm ( RMNH. Colour (fig. 28B, C). Similar pattern as the CRUS.D.48724), Oman, Masicoh, C1, no more other species in the genus. The colouration

data, don. MNHN, Paris through A. Anker, patterns on the appendages is, however, dif- 2000. ferent from N. cardiodytes . In N. cardiodytes , Diagnosis. Rostrum stout, depressed, the spotted pattern forms connected, continextending halfway second segment anten- uous ‘bands’, most visible in the major chelinular peduncle, without teeth nor setae, peds and walking legs. In N. nasalis , the spots broadened in dorsal view by thick lateral are distinguishable and separated from each expansions, distally rounded, proximally not other.

constricted. Carapace without spines. Inferior Host. Pectinidae : Mimachlamys townsendi orbital angle strongly produced. Anterolateral (G.B. Sowerby, 1895) (Holthuis, 1986; Hogarth, angle of carapace broadly rounded, produced. 1989; Fransen, 1994a).

Basal segment of antennular peduncle dis- Distribution. Type-locality: Raysut, tolaterally rounded; outer flagellum fused Southern Oman (cf. Holthuis, 1986; Hogarth,

in basal seven segments, shorter free ramus 1989; Fransen, 1994a). Now recorded for the

with about four segments. Scaphocerite with second time from Oman (fig. 28B, C).

almost straight lateral margins; slit between

distolateral tooth and lamina shallow. First Genus Paranchistus Holthuis, 1952

pereiopods with sub-spatulate, densely setose Paranchistus Holthuis, 1952: 5 , 13, 91. Type chela; lateral cutting edges proximally gaping, species, by original designation: Anchistus distally minutely pectinate; merus without biunguiculatus Borradaile, 1898 (a junior subpeg-like spinules on inner margin of proximal jective synonym of Pontonia armata H. Milne

part. Palm of second pereiopods with oblong Edwards, 1837). Gender: masculine.

oval tympanal organ in proximal two-third to Diagnosis. Large sized shrimps of subcythree-fourth of medio-ventral surface; dac- lindrical body form. Rostrum well developed,

tylus of second chela strongly hooked, over- compressed, with or without indistinct shalreaching fixed finger, one large triangular low dorsal and distal teeth, lateral carinae tooth at about one-third of its length; fixed fin- feebly developed. Carapace smooth, glabrous;

ger with 10–12 small teeth in the proximal half orbit feebly developed, inferior orbital angle

of which the distalmost largest. Ambulatory distinct, slightly produced, antennal spine pereiopods with propodi with distoventral well developed, basally broad; hepatic, spine, spines, with simple stout dactyli, with one, if present, small, articulating; supraorbital seldom two, minute accessory teeth; unguis and epigastric spines absent; anterolateral

with minute scale-like spinulation dorsally. margin rounded Downloaded, slightly from Brill produced.com 06. /24 Abdomen /2024 12:38:05 AM via Open Access. This is an open access article distributed under the terms of the CC-BY 4.0 license. https://creativecommons.org/licenses/by/4.0/

smooth, glabrous, third segment not postero- posterolaterally acutely produced, exopod dorsally produced, anterior pleura rounded, with small mobile distolateral spine, without posterior blunt. Telson with two pairs of distolateral tooth.

dorsal spines in distal half, three pairs of The genus is monospecific with Pontonia posterior spines. Eye small, cornea globular. armata H.Milne Edwards,1837 (= Paranchistus Antennula normal, upper flagellum biramous, armatus (H. Mile Edwards, 1837)) as its short ramus reduced. Antenna with basicer- type species. Paranchistus liui Li, Bruce & ite unarmed, scaphocerite well developed Manning, 2004, Paranchistus nobilii Holthuis , with distolateral tooth. Epistome unarmed. 1952, Paranchistus pycnodontae Bruce, 1978 , Mandible normal, without palp, molar pro- and Paranchistus spondylis Suzuki, 1971 are cess robust, incisor process dentate; maxillula herby transfered to Polkamenes . Paranchistus with feebly bilobed palp; maxilla with simple ornatus Holthuis, 1952 is transfered to palp, basal endite broad, bilobed, proximal Tympanicheles .

lobe much smaller than distal lobe, coxal

endite obsolete, scaphognathite broad; first Paranchistus armatus (H. Milne Edwards, maxilliped with palp, basally broad, distally 1837)

slender, basal endite broad, well separated (figs. 30–32)

from coxal endite by suture, exopod well Pontonia armata H. Milne Edwards, 1837: 359 developed, caridean lobe broad, flagellum [type locality: près de côtes de la Nouvellewith numerous plumose setae distally, epi- Irlande]; Broderip , 1841: 421 (listed); Lucas, pod bilobed; second maxilliped with normal 1851: 183; Sharp, 1893: 119 (listed) .

endopod, dactylar segment slender, concave, Anchistus biunguiculatus Borradaile, 1898: 387 ; exopod well developed, broad, coxa medially Borradaile, 1900: 408, pl. 36 fig. 5; Borradaile, slightly produced, epipod rectangular, with- 1917: 388; Hayashi, 2005: 515.

out podobranch; third maxilliped with endo- Anchistus? armatus – Borradaile, 1898: 387 pod slender, ischiomerus and basis partly (listed); Borradaile, 1917: 389 (listed).

fused, exopod with numerous plumose setae Tridacnocaris biunguiculata – Nobili, 1899: 235 distally, coxa with oval lateral plate, with [type locality: British New Guinea].

rudimentary arthrobranch. Fourth thoracic Anchistus oshimai Kubo, 1949: 26 , figs. 1, 2 sternite without median process. First perei- [type locality: Helen Atoll].

opods slender, chelae with fingers spatulate, Paranchistus biunguiculatus – Holthuis, 1952: non-cannulate, lateral cutting edges minutely 13, 93, figs. 36–38; Holthuis, 1953: 56; Holthuis, pectinate. Second pereiopods well developed, 1955: 62, fig. 32b (listed); Rosewater, 1965: 370; similar, subequal, dactylus strongly hooked, McNeill, 1968: 21; Miyake & Fujino, 1968: 417; overreaching fixed finger, with three broad Suzuki, 1971: 110; Bruce, 1972a: 221 (listed); teeth in proximal half, fixed finger with series Bruce, 1975a: 162 (listed); Bruce, 1975b: 27;

of teeth in proximal part; propodus with- Bruce, 1976f: 59 (listed); Devaney & Bruce, out ventral oval tympanal organ proximally. 1987: 230 (listed).

Ambulatory pereiopods with biunguiculate Anchistus armatus – Bruce, 1967: 564; Hipeaudactyli, with large triangular accessory tooth, Jacquotte, 1972b: 9.

with without basal protuberance; unguis Paranchistus armatus – Bruce, 1975c: 49-54, compressed, curved, with few scattered min- figs. 1-3; Bruce, 1979a: 226–227; Bruce, 1983c: ute scale-like spinules; propodi with strong 204; Bruce, 1986: 165; Devaney & Bruce, distoventral spines. Uropod with protopodite 1987: 230Downloaded (listed);from Bruce Brill,.com 1990 06: 16 /24, /18 2024(listed 12:38:05); AM via Open Access. This is an open access article distributed under the terms of the CC-BY 4.0 license. https://creativecommons.org/licenses/by/4.0/

Holthuis, 1993; 160, fig. 151; Müller, 1993: 10 110, fig. 119 (listed); De Grave & Fransen, 2011: (listed); Chace & Bruce, 1993: 90-91 (listed); 357 (listed). Fransen, 1994a: 111 (listed); De Grave, 1999: 134, Material examined. INDONESIA: 1 male pl.2 fig. a; Bruce, 2000: 91-96, figs. 1-2; Li, 2000: pocl. 8.70 mm, 1 Downloaded from ovigerous Brill.com female 06/24/2024 pocl. 12:38:05 AM

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13.77 mm ( RMNH. CRUS.D.46092; GenBank OQ600400 (16S)), Kei Islands, Tanimbar, 16.xi.1990, depth 8–10 m, SCUBA diving, in large Tridacna gigas (L.) (Ø 50cm), coll. Zainal. – 1 male pocl. 5.80 mm ( RMNH. CRUS.D.8991), Moluccas, Obi Latu, shore and reef, 23-27.iv.1930, Siboga Expedition, published by Holthuis, 1952: 93–97, figs. 36–38, as Paranchistus biunguiculatus .

Diagnosis. See diagnosis of genus.

Remarks. In smaller specimens the dorsal teeth on the rostrum are more prominent with setae in between, in larger specimens the teeth become indistinct (Bruce, 1975c: 5). This indicates that the dorsal rostral teeth become less prominent after each moult this in contrast to Anchistus australis and Tympanicheles ornatus where they are placed more distally after each moult. The hepatic spine is nor- 1758) (Kubo, 1949; Rosewater, 1965; McNeill, mally developed in small specimens and 1968; Bruce, 1975c, 1979a, 1983b; De Grave, reduced or absent in larger specimens. 1999). Several authors recorded the species The dactylus of the ambulatory pereio- from Tridacna sp. (Borradaile, 1917; Holthuis, pods is very different from those of other 1952; Bruce, 1975c, 1979b). species in the ‘ Anchistus group’. With E. cus- Distribution. Same presumed distribution as tos and E. custoides it has in common the its host: Tridacna gigas (L., 1758), e.g., Moluccas, sparcely distributed scale-like spinules on the Indonesia to the Marshall Islands. NE Australia unguis, whereas in other species the unguis (cf. McNeill, 1968; Bruce, 1975c); Marshall is densely covered with spinules on the dor- Islands (Holthuis, 1953; Rosewater, 1965; Bruce, sal surface. The broad robust accessory tooth 1975c, 1979b); Eniwetok Atoll (Rosewater, is very different from the slender simple or 1965); Obi latu, Moluccas, Indonesia (Holthuis, minutely spinulate accessory tooth in A. 1952); Aru Islands, Indonesia (Holthuis, 1993) ; miersi , Polkamenes nobilii , P. pycnodontae, P. Batanta and Numfoor Island, New Guinea, spondylis , or the minute accessory tooth in A. Indonesia (Nobili, 1899) ; Papua New Guinea demani , A. australis , N. nasalis , Tympanicheles (De Grave, 1999) ; New Ireland, Papua New ornatus , and T. pectinis . Guinea (cf. H. Milne Edwards, 1837; Bruce, Colour. Various colour descriptions are 1975c); Tubetube, Engineer Islands, Papua New known. “Great Barrier Reef specimens were Guinea (Borradaile, 1898); ‘British New Guinea’ noted to be transparent or whitish. Freshly (southeastern part of Papua New Guinea) preserved specimens showed a dense cover- (Borradaile, 1898); Helen Atoll, Ngaianges ing of minute red chromatophores all over Island and Ngadarak Reef, Palau Islands (Kubo, the body, with similar but more sparse dots 1940, 1949; Miyake & Fujino, 1968). Now newly over de second pereipods.” (cf. Bruce, 1975c: reported from a second locality in the Mollucas: 51). “The ovigerous female in life is transpar- Kei Islands, Tanimbar. ent or light blue with dark blue spots except for the carapace, in which they are enclosed Genus Polkamenes gen. nov. with white rings. The cornea is bitter orange, ZooBank: urn:lsid:zoobank.org:act:7AE1F106- and the stalk is light blue. The antennal fla- EED4-499E-8D49-9 BAFB 5235D9A gellum is reddish purple. The colour of the Diagnosis. Small to moderately sized male is unknown.” (cf. Miyake & Fujino, 1968: shrimps of subcylindrical body form. 417). “Body generally translucent whitish in Rostrum well developed, compressed, with colour, generally and evenly with numerous teeth in distal part, lateral carinae feebly small white and inconspicuous chromato- developed. Carapace smooth, glabrous; orbit phores. Ovary a deep olive green. Antennal feebly developed, inferior orbital angle dispeduncles and eyestalks whitish. Cornea tinct, antennal spine present, supraorbital white. Pereiopods whitish, finely spotted with and epigastric spines absent, hepatic spine red. Caudal fan whitish, more heavily speck- mobile, anterolateral margin not or feebly led with red.” (cf. Bruce, 1979b: 227). From the produced. Abdomen smooth, glabrous, third present specimens was noted that the car- segment not posterodorsally produced, anteapace was more or less translucent and the rior pleura rounded, posterior blunt. Telson antennae were blue. with two pairs of dorsal spines, three pairs Hosts. Only known from giant clams of posterior spines. Eye small, cornea globu- ( Cardiidae : Tridacninae ): Tridacna gigas (L., lar. Antennula Downloaded normal from, proximal Brill.com segment 06/24/2024 12:38 of:05 AM

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https://creativecommons.org/licenses/by/4.0/ peduncle with distolateral tooth, upper flagellum biramous, flagella short, short ramus reduced. Antenna with basicerite unarmed, scaphocerite well developed. Epistome unarmed. Mandible normal, without palp, molar process robust, incisor process dentate; maxillula with feebly bilobed palp, laciniae normal or broad; maxilla with simple palp, basal endite broad, bilobed, coxal endite obsolete, scaphognathite broad; first maxilliped with slender palp, basal endite broad, fused to coxal endite, exopod well developed, caridean lobe broad, flagellum with numerous plumose setae distally, epipod bilobed; second maxilliped with normal endopod, flagellum with numerous plumose setae distally, epipod subrectangular, without podobranch; third maxilliped with endopod slender, ischiomerus distinct from basis, exopod with numerous plumose setae distally, coxa with oval lateral plate, with rudimentary arthrobranch. Fourth thoracic sternite without median process. First pereiopods chelae with fingers sub-spatulate, cutting edges entire or minutely pectinate. Second pereiopods well developed, similar, unequal, dactylus with large acute triangular tooth in proximal half, fixed finger with series of teeth in proximal part; propodus without ventral oval tympanal organ proximally. Ambulatory pereiopods with simple or biunguiculate dactyli, without basal protuberance; unguis with dorsal pad of fine scale-like spinules. Uropod with protopodite posterolaterally acute, exopod with small mobile distolateral spine.

Etymology. ‘ Polkamenes’: named after the characteristic blue-, red-, and orange-dotted pattern seen on the species’ carapace, abdomen, and appendages ‘Polka dots’ (English, in combination with the common palaemonid suffix ‘- menes ’; see e.g., Ancylomenes Okuno & Bruce, 2010 , Laomenes Clark, 1919 , Periclimenes ). Gender: masculine.

Type species by present designation: Paranchistus pycnodontae Bruce, 1978 (= Polkamenes pycnodontae (Bruce, 1978)) .

We recognize four species: Polkamenes liui (Li, Bruce & Manning, 2004) ; Polkamenes nobilii (Holthuis, 1952) ; Polkamenes pycnodontae (Bruce, 1978) ; and Polkamenes spondylis ( Suzuki, 1971) . All have bivalve hosts. The latter three species, with the biunguiculate ambulatory dactyli, are very similar. Polkamenes nobilii and P. spondylis are only known from a few specimens and DNA sequences could only be obtained from P. pycnodontae . It thus remains unclear if the differences presently used to distinguish these nominal species are indeed species specific or mere intraspecific variation. If more material becomes available, for both morphological and molecular phylogenetic analyses, it will be possible to determine with more certainty if these three nominal species are indeed separate biological species. The species can be distinguished as follows: