Caenanthura ibex, Bamber, 2008

Bamber, Roger N., 2008, New species of anthurid and arcturid isopod (Crustacea: Peracarida: Isopoda) from Hong Kong, Journal of Natural History 42 (9 - 12), pp. 855-876 : 856-870

publication ID	https://doi.org/ 10.1080/00222930701850489
persistent identifier	https://treatment.plazi.org/id/47486621-8A6E-FFB8-FE0F-7237FC54A6BB
treatment provided by	Felipe
scientific name	Caenanthura ibex
status	sp. nov.

Treatment

Caenanthura ibex View in CoL sp. nov.

( Figures 1–3 View Figure 1 View Figure 2 View Figure 3 )

Material

One female, holotype (registration no. NHM.2003.1), five females, paratypes (NHM.2003.2-6), station D, Conic Island Cave , Hong Kong, 22 ° 219540 N 114 ° 239220 E; sediment 16% gravel, 53% sand, 31% silt/clay, depth 19 m. Coll. N.J. Evans and P.F. Clark, 25 October 2002 .

Description of female

Body ( Figure 1A View Figure 1 ) 8 mm long (rostrum to tip of telson), slender, ten times as long as wide, white in life, exoskeleton smooth and strongly calcified. Cephalon small, 0.8 times as long as wide, half length of pereonite 3; eyes absent, rostrum small, triangular, as long as ocular lobes. Seven free pereonites respectively 1.4, 1, 1.4, 1.6, 1.4, 0.9 and 0.45 times as long as wide, pereonite 4 longest, thence 5.3.152.6.7; no setation nor mid-dorsal pits. Pleonites 1 to 5 completely fused.

First to third antennule peduncle articles bearing two, three and two plumose setae, respectively ( Figure 1B View Figure 1 ); flagellum of five articles, first two articles subequal with single distal setae, third article naked, longest (as long as first two articles together), fourth and fifth articles very small, fourth naked, fifth with four distal setae and two aesthetascs.

Antenna ( Figure 1C View Figure 1 ) peduncle article 2 longest, with fine inner setae; third to fifth articles subequal, fourth with distal plumose seta, fifth distally encircled with setae including five plumose setae; flagellum of four articles, each very finely setulose (‘‘bristly’’), third and fourth articles with nine distal setae.

Mandible ( Figure 1D View Figure 1 ) with two-articled palp bearing single distal seta, single seta on outer margin of proximal article and fine setules; lamina dentata with elaborate serrations; pars molaris weak. Maxilla ( Figure 1E View Figure 1 ) with strong distal and four subdistal teeth. Maxilliped ( Figure 1F View Figure 1 ) palp of two articles, both with fine setules in addition to stronger spines (as figured), distal article elongate, endite absent.

First pereopod ( Figure 2A View Figure 2 ) robust, subchelate; basis bulbous, as long as ischium, ischium 1.6 times as long as wide, merus 2.5 times as wide as long, carpus triangular with fine setae forming comb-rows along ventral margin; propodus bulbous, palmar margin convoluted with comb rows, row of six setae at base of dactylus; dactylus ventrally with comb rows, distally with row of short lateral setae and stout spine at base of claw.

Pereopods 2 to 7 ( Figures 2B, D View Figure 2 ) generally similar, basis and ischium subequal, former with plumose seta, latter with dorsal and ventral rows of setae; merus half length of ischium; carpus longer ventrally than dorsally, with ventrodistal combrow; propodus with distal spine bearing flagellar-seta on proximal margin and row of teeth on distal margin; dactylus with ventral and lateral comb-rows (‘‘fringed scales’’ of Negoescu 1980) and distal spine adjacent to claw ( Figure 2C View Figure 2 ). Pereopods 2 to 5 propodus ventral (palmar) margin with comb-rows ( Figures 2B,C View Figure 2 ); pereopods 6 and 7 carpi subtriangular, propodal palmar margin with serrations ( Figures 2D, E View Figure 2 ).

First pleopod with operculiform exopod and four sigmoid spines (‘‘retinaculae’’) on inner margin of basis.

Uropod ( Figure 3 View Figure 3 ) exopod suboval, twice as long as wide, slightly excavate distally, margin crenulate and bearing plumose setae; sympod nearly twice as long as endopod, inner distal corner extended into setose apophysis; endopod surpassing tip of telson, longer than wide, margin simple, outer edge with some plumose setae, distal simple setae longest. Telson ( Figure 3 View Figure 3 ) flat, twice as long as wide and longer than pleon, with two basal statocysts; pair of central distal setae finely plumose, adjacent setae longest, dorsal setae mostly in distal third.

Paratypes all closely similar to holotype. Male unknown.

Etymology

From the Latin for a chamois (noun in apposition), in reference to an incident during the October 2002 Hong Kong Caves Expedition involving two members of the team, the mermaid and the mountain goat.

Remarks

Poore (2001a) relegated Arabanthura Kensley & Reid, 1984 and Indonesanthura Negoescu, 1997 to junior synonyms of Caenanthura . There are thus four species of Caenanthura previously described, the generotype C. siamensis ( Barnard, 1925) from Koh Chang, Thailand at 5 to 9 m depth, C. indica Negoescu, 1980 , from the Persian Gulf and off the mouth of the Red Sea at 2 to 110 m depth on mud, C. enigmatica (Kensley & Reid, 1984) from the northern Arabian Gulf in 1.3 to 3 m depth amongst seagrass and sand, and C. gutui (Negoescu, 1997) from the Java Sea in 1 to 1.5 m on fine muddy sand.

Caenanthura is the only genus of the Anthuridae which has the combination of a 1- or 2-articled mandibular palp and a maxilliped with a biarticulate palp but no endite; the genus is also characterized by pleonites 1 to 5 being fused and longer than wide, and pentagonal carpus on pereopods 4 to 7 (albeit more elongate in the four described species than in the present one). Caenanthura ibex sp. nov. is more similar to C. enigmatica and C. indica in its two-articled mandibular palp as well as the compact basis and ischium of the first pereopod. It differs from both of those species in having a well-serrated lacinia dentata on the mandible, and in having the palm of the first pereopod oblique, and a sympodal apophysis on the uropod as opposed to a continuous inner margin. Unlike C. ibex , C. enigmatica has dorsal pits on pereonites 1, 4, 5 and 6.

The elongate distal article of the maxilliped palp (the fusion of articles 4 and 5) in C. ibex is atypical, that of the other species being semicircular and hardly exceeding the distal apophysis of the proximal article. Equally the lack of a posterodistal spine on the carpus of pereopods 4 to 7, or of a long, strong proximal seta on the palm of pereopod 1 are atypical. These differences do not seem sufficient grounds for separating C. ibex into a new genus.

While one of the more numerous, and quite distinctive, members of the benthos at sampling station D, C. ibex was only taken at this innermost site of Conic Island Cave and not at all outside the cave. With the tanaidacean Pakistanapseudes hodgsoni Bamber, 2000 and the amphipod Harpiniopsis vadiculus (Hirayama, 1987) , it appears to be one of a suite of peracarid crustaceans so far peculiar (in Hong Kong waters) to the innermost sedimentary benthos of this cave.

Amakusanthura Nunomura, 1977 View in CoL

Amakusanthura koonyumae Bamber, 1997 View in CoL

Bamber, 1997: 81–85, Figures 3–5 View Figure 3 View Figure 4 View Figure 5

Material

One preparatory female, station Z, off the mouth of Conic Island Cave, Hong Kong, 22 ° 219540 N 114 ° 239220 E; sediment 1% gravel, 96% sand, 3% silt/clay, depth 13.7 m. Coll. N.J. Evans and P.F. Clark, 25 October 2002 .

Previously known only from the type collection of five females and one male, from the Tolo Channel, Hong Kong, at 2 to 3 m depth on fine to medium sand. The present female specimen is slightly larger (body length 5.63 mm) than the female holotype (5.26 mm) .

Amakusanthura gorgona sp. nov.

( Figures 4–6 View Figure 4 View Figure 5 View Figure 6 )

Material

One preparatory female, holotype (dissected, fragmentary: registration no. NHM.2003.7), one juvenile, paratype (slide mount), station Z, off the mouth of Conic Island Cave, Hong Kong, 22 ° 219540 N 114 ° 239220 E; sediment 1% gravel, 96% sand, 3% silt/clay, depth 13.7 m. Coll. N.J. Evans and P.F. Clark, 25 October 2002 .

Description of female

Body ( Figures 4A, B View Figure 4 ) small, holotype 4 mm long (rostrum to tip of telson), slender, thirteen times as long as wide, translucent in life with sparse paired pigment patches on pereonites 2, 3, 4 and 7, exoskeleton smooth and weakly calcified. Cephalon small, as long as wide, half length of pereonite 4; small black eyes present, rostrum small, triangular, almost as long as ocular lobes. Seven free pereonites, respectively 1.2, 1.7, 1.4, 1.7, 1.7, 1.7 and 1.0 times as long as wide, pereonites 4 and 5 equal and longest, thence 6.2.3.1.7; no setation nor mid-dorsal pits. Pleonites 1 to 5 completely fused, pleonite 6 distinct with posterior notch in mid-line; pleon 1.3 times as long as wide.

Antennule ( Figure 4C View Figure 4 ) second peduncle article bearing one sensory seta and one simple distal seta, third with one distal seta; flagellum of four articles with three distal aesthetascs.

Antenna ( Figure 4D View Figure 4 ) peduncle article 2 longest; third to fifth articles subequal, respectively with two, two and five distal setae, fifth article also with distal sensory seta; flagellum of three articles, second and third articles one fifth length of first, poorly articulated and with numerous distal setae.

Mandible ( Figure 4E View Figure 4 ) with three-articled palp; first and second articles subequal and each with single distal seta; distal article short, triangular, with small distal seta; lamina dentata simple. Maxilliped ( Figure 4G View Figure 4 ) palp articles, respectively with one, three and four distal setae; first article wider than long, distal two articles with anaxial articulation; endite present, exceeding first palp article.

First pereopod ( Figure 5A View Figure 5 ) robust, subchelate; basis bulbous, as long as ischium, with three sensory setae; ischium twice as long as wide, merus twice as wide as long; carpus triangular, distally with two rows of three setae and two distal comb-rows on ventral margin; propodus bulbous, 2.3 times as long as wide, palmar margin less than half length of propodus, relatively simple without tooth, with two rows of five setae and paired distal setae; dactylus ventrally with tuft of setae and stout spine, claw not distinct.

Pereopods 2 and 3 ( Figure 5B View Figure 5 ) similar to each other, carpus rectangular, propodus not robust, with distal flagellate spine on palm; merus one third length of ischium; dactylus with cutting edge ending in tooth. Pereopods 4 to 7 ( Figures 5C, D View Figure 5 ) similar to each other; basis with sensory setae, merus longer than wide and about half length of ischium, carpus subtriangular (ventral margin much longer than dorsal margin) with distal ventral flagellate spine; propodus and dactylus as pereopods 2 and 3, but pereopods 6 and 7 propodal palmar margin and dactylus cutting edge with serrations ( Figure 5D View Figure 5 ).

First pleopod ( Figure 6A View Figure 6 ) exopod operculiform. Uropod ( Figure 6B View Figure 6 ) exopod elongate, linguiform, without distal notch, bearing plumose marginal setae and short outer surface setae; endopod ( Figure 6C View Figure 6 ) sympod with only distal plumose setae on both margins, 1.15 times as long as endopod, their margins contiguous; endopod not surpassing tip of telson, slender, subtriangular, about twice as long as wide, margin simple, dorsal and distal margins with simple setae, sensory setae on outer surface.

Telson ( Figure 6D View Figure 6 ) flat, linguiform with narrowly pointed distal apex, 2.4 times as long as wide and just shorter than pleon, with two basal statocysts; pair of central short distal setae finely plumose, adjacent pair of longer setae, dorsal setae mostly in distal third, longer marginally than centrally.

Male unknown. Juvenile (2.6 mm long) without pigment patches.

Etymology

From the Greek for a mermaid (noun in apposition), see above under Caenanthura ibex .

Remarks

Poore and Lew Ton (1988) diagnosed and redefined the genus Amakusanthura , particularly in comparison with the related genera Apanthuropsis and Apanthura (see also Poore and Lew Ton, 1985b). They pointed out the difficulties in distinguishing these genera without mature males; however, the present species, with its elongate pleon, elongate uropod exopod without distal notch, and simple palmar margin of pereopod 1, is excluded from Apanthura , while its mouthparts, inter alia, are distinct from those of Apanthuropsis . The morphology of the maxilliped, with three palp articles, the distal article oblique and without a free mesial margin, the threearticled mandibular palp and the fusion of pleonites 1 to 5 are characteristic of Amakusanthura .

Normally, species of Amakusanthura have dorsal grooves distinguishing pleonites 1 to 3, whereas A. gorgona sp. nov. has no grooves or sutures on the pleon other than that distinguishing pleonites 5 and 6. However, Poore and Lew Ton (1988) described as new two species from Queensland and Western Australia, A. agonis and A. angophora , which also had pleonites 1 to 5 indistinguishable dorsally, although both had deep lateral epimera on the pleon. They, as the present species, were attributed to Amakusanthura on the grounds of pleon length, uropod exopod form and simple palm on pereopod 1. Amakusanthura gorgona is very similar to both of these Australian species, but can be distinguished by its shorter, acute telson (longer than the pleon in the other two) and its proportionately more elongate uropod endopod.

The only other species of Amakusanthura recorded from Hong Kong waters, A. koonyumae , which was also taken with the present species at station Z, has dorsal intersegmental folds between pleonites 1 to 5, a small tooth-like apophysis on the palm of the propodus of the first pereopod, as well as a different morphology of the telson and uropod endopod ( Bamber 1997). Amakusanthura toyamaensis Nunomura, 1992 (q.v.) has dorsolateral indication of the demarcation of the pleonites, no maxilliped endite, and the distal mandibular palp article is the longest.

Cyathura Norman & Stebbing, 1886 View in CoL

Cyathura peirates View in CoL sp. nov.

( Figures 7–9 View Figure 7 View Figure 8 View Figure 9 )

Material

One female, holotype (registration no. NHM.2003.2106), one female, paratype (NHM.2003.2107), Tsim Bei Tsui mudflat, Mai Po, Hong Kong, littoral; August 2002. Coll. Z. Hong. Substratum poorly sorted sand with high organic content.

Description of female

Body ( Figure 7A View Figure 7 ) 11.2 mm long (rostrum to tip of telson), slender, thirteen times as long as wide, with mottled pigmentation from dark brown melanophores on dorsal surfaces, still evident in alcohol-preserved material; exoskeleton smooth. Cephalon small, 0.83 times as long as wide, two-thirds length of pereonite 3; eyes present, small, with pale brown pigmentation in alcohol-preserved material; rostrum conspicuous, rounded, almost as long as ocular lobes. Seven free pereonites respectively 1.6, 1.5, 1.4, 1.6, 1.4, 1.4 and 0.9 times as long as wide, pereonite 4 longest, thence 6.5.152.3.7; no setation nor mid-dorsal pits. Pleon shorter than pereonite 7, 0.8 times as long as wide; pleonites 1 to 5 completely fused, pleonite 6 distinct with posterior split in mid-line.

Antennule ( Figure 7B View Figure 7 ) first to third peduncle articles bearing two, three and one distal plumose sensory setae, respectively; second article with outer row of seven setae longer than article width; flagellum of four articles, first article very short, naked, second article longest (twice as long as other three articles together), third and fourth articles very small, third naked, fourth with three distal setae and three aesthetascs.

Antenna ( Figure 7C View Figure 7 ) peduncle article 2 longest, with fine inner setae; third and fourth articles subequal, fifth a quarter longer with distal plumose seta; flagellum of four articles, second article longest, distal articles with numerous fine setae.

Mandible ( Figure 7D View Figure 7 ) with three-articled palp with numerous fine setae predominantly along outer margin; lamina dentata with sixteen saw-teeth; pars molaris protruding, blunt. Maxilla ( Figure 7E View Figure 7 ) with strong distal and four subdistal teeth blunt and expanded at their tips. Maxilliped ( Figure 7F View Figure 7 ) palp of two articles, both with fine setules in addition to seven stronger mesial setae and one mesiolateral seta on first article, four stronger distomesial setae on second article.

First pereopod ( Figure 8A View Figure 8 ) robust, subchelate; basis bulbous, as long as wide, with median dorsal row of five setae; ischium as long as basis with fine setae ventrally, merus nearly three times as wide as long without conspicuous dorsal spinose apophysis, carpus triangular with fine setae along ventral margin, distally extended; propodus bulbous, twice as long as wide, palmar margin with sparse longer setae and dense fine setae, and tooth-like apophysis at about half length; dactylus ventrally with fine setae in comb rows, distally with three lateral setae and stout spine with pair of adjacent fine setae at base of claw; claw as long as dactylus.

Pereopods 2 to 7 (P2 to P7: Figures 8B View Figure 8 to D) generally similar, basis and ischium subequal, former with plumose sensory seta; ischium to propodus with rows of fine setae along ventral margin. Ischium with longer ventral setae distally, row of five longer dorsal setae on P2 reducing to three on P5, and none on P6 or P7. Merus, carpus and propodus similarly more setose on anterior pereopods. Merus extended by dorsodistal setose apophysis on P2, thus as wide as long; two-thirds length of ischium and longer than wide on P5 and P7 with smaller dorsal apophysis. Carpus covered dorsally by distal apophysis of merus on P2, thus almost rectangular; triangular on P5, quadrangular with longer free dorsal margin on P7. Propodus with ventral comb rows on anterior pereopods, flattened spines on P7, distally with stout bidenticulate spine on all pereopods; dactylus with ventral comb-rows and distal spine and paired setae adjacent to claw; claw half length of dactylus.

First pleopod ( Figure 9A View Figure 9 ) exopod operculiform. Uropod exopod ( Figure 9B View Figure 9 ) linguiform, 2.6 times as long as wide, margin bearing plumose setae and few longer simple setae, outer surface with ‘‘down’’ of fine setae; sympod ( Figure 9C View Figure 9 ) nearly twice as long as endopod, inner distal corner extended into setose apophysis; endopod surpassing tip of telson, subtriangular, longer than wide, distally with longer simple setae, central distal seta plumose, three dorsodistal sensory setae. Telson ( Figure 9D View Figure 9 ) flat, 2.4 times as long as wide and longer than pleon, with two basal statocysts; lateral margins parallel, finely setose; longer setae on distal fifth of margins, dorsolateral distal setae longest.

Paratype closely similar to holotype. Male unknown.

Etymology

From the Greek for a pirate (noun in apposition), in reference to a theme of the October 2002 Hong Kong Caves Expedition .

Remarks

The only anthuridean genus with a 3-articled mandibular palp, biarticulate maxilliped palp, and pleonites 1 to 5 fused and together wider than long is Cyathura .

No species of Cyathura have been recorded previously from Hong Kong. Dang (1965) described C. truncata from Vietnam; Nunomura (1974, 1977, 1992, 2001) and Nunomura and Hagino (2000) described as new six species from Japan, together with an unnamed specimen, of which C. peirates sp. nov. is most similar to C. muromiensis Nakamura, 1974 ; as well as being without the dorsal pigmentation shown by C. peirates . Cyathura muromiensis differs in having fewer teeth on the mandibular ‘‘cutting flange’’, fewer setae on the distal palp article, and a narrower merus on the posterior pereopods. Poore and Lew Ton (1985a) described the three species known from Australia. Cyathura peirates differs from all of these species in the shape of its telson, as well as the morphology of its mouthparts and uropod endopod, and the short merus on pereopod 2. Of those other species from the broad region, only C. hakea Poore & Lew Ton, 1985 , C. furcata Nunomura and Hagino, 2000 and C. shinjikoensis Nunomura, 2001 have complex dorsal pigmentation; the first species has a shorter, blunter rostrum and sparser setation on the pereopods; all three have different setation on the mandibular palp. The blunt distal spines on the maxilla of the present species are also found in a number of the Japanese species (Nunomura, loc. cit.).