Halmyrapseudes gutui, Kakui, Keiichi & Angsupanich, Saowapa, 2013

Kakui, Keiichi & Angsupanich, Saowapa, 2013, Description of three species of Halmyrapseudes (Crustacea: Tanaidacea: Parapseudidae), with a discussion of biogeography, Zootaxa 3736 (4), pp. 345-367 : 347-356

Halmyrapseudes gutui sp. nov.

Figures 2–6

Halmyrapseudes sp.: Phetchaiya (2009).

Material examined. Holotype: ovigerous female (ZIHU-4380, BL 4.35, CW 0.76, 7 slides and 1 vial), 6°46′59″N, 99°45′49″E (retrieved from Google Earth), Lidee Island, Thailand, mangrove area, 1.4–2.1% organic carbon, sandy clay loam, salinity 34 ‰, 28 November 2010, collected by S. Angsupanich.

Allotype: adult male (ZIHU-4381, BL 3.20, CW 0.63, 7 slides and 1 vial). Same collection data as for holotype.

Paratypes: 2 preparatory females (ZIHU-4382, 4386: BL 3.27, CW 0.61, 4 slides; BL 3.07, CW 0.62, 3 slides and 1 vial); 3 ovigerous females (ZIHU-4383, 4387, 4388: BL 3.81, CW 0.64, 6 slides and 1 vial; BL 3.16, CW 0.57, 3 slides and 1 vial; BL 4.31, CW 0.68, 3 slides and 1 vial); 7 subadult males (ZIHU-4384, 4385, 4394–4398: BL 3.06, CW 0.59, 1 slide; BL 2.60, CW 0.50, 1 vial including detached chelipeds and remaining body; BL 4.01, CW 0.68, 4 slides and 1 vial; BL 2.81, CW 0.56, 3 slides and 1 vial; BL 2.63, CW 0.54, 3 slides and 1 vial; BL 3.58, CW 0.65, 3 slides and 1 vial; BL 2.73, CW 0.55, 3 slides and 1 vial); 5 adult males (ZIHU-4389–4393: BL 3.57, CW 0.60, 5 slides and 1 vial; BL 3.48, CW 0.64, 5 slides and 1 vial; BL 2.97, CW 0.57, 3 slides and 1 vial; BL 3.23, CW 0.63, 3 slides and 1 vial; BL 2.90, CW 0.58, 3 slides and 1 vial); 15 and 15 individuals (each consisting of 5 adult males, 4 subadult males, 5 ovigerous females, and 1 preparatory female; ZIHU-4399, NSMT- Cr 22359; all intact). Same collection data as for holotype.

Diagnosis. Lacinia mobilis with 3 teeth. Mandibular palp article 2 without dorsal simple setae. Pereopod 1 carpus with 0,1 or 1,1 ventral simple setae proximal to each spiniform seta.

Etymology. The species is named after Modest Guţu in recognition of his great contributions to the knowledge of the Thai tanaidacean fauna.

Description of ovigerous female. The description is based primarily on the holotype, with some observations from paratypes ZIHU-4382 and 4383.

Body ( Fig. 2 A, C, a1) dorsoventrally flattened, 5.7 times as long as wide. Cephalothorax 0.14 times BL, 0.82 times as long as wide, with two pairs of lateral simple setae. Posterior region with dorsal groove. Eyes well defined; with ommatidia pigmented. Rostrum rounded. Pereonites each with several anterior and posterior simple setae on lateral margins (plumose setae on pereonite 6). Pleon 0.27 times BL. Pleonites all wider than long, with triangular epimera, and dorsolateral and lateral plumose setae. Pleotelson slightly longer than wide, longer than three pleonites combined, with plumose setae as illustrated.

Antennule ( Fig. 3 A, a1) 1.2 times as long as carapace. Article 1 0.66 times as long as remaining articles and outer flagellum combined, with four outer and four inner simple setae, and several minute simple setae and plumose sensory setae on outer margin. Article 2 0.4 times as long as article 1, with four outer, one mid-inner and three inner distal simple setae, and five distal plumose sensory setae. Article 3 0.4 times as long as article 2, distally with one outer and three inner simple setae. Article 4 with two plumose sensory setae, and two simple setae and one plumose sensory seta at insertion of inner flagellum. Outer flagellum with seven articles; four terminal articles with three, zero, one, five simple setae (from proximal to distal), respectively; penultimate article with one aesthetasc; other articles each with simple setae as illustrated. Inner flagellum with two articles; article 1 with one plumose sensory seta; article 2 with three simple setae and one plumose sensory seta.

Antenna ( Fig. 3 D) 0.58 times as long as antennule, with nine articles. Article 1 with inner distal lobe bearing seven simple setae. Article 2 with one outer and one inner simple setae. Article 3 with four inner simple setae. Article 4 with one outer and one inner simple setae, and two plumose sensory setae. Article 5 with two outer and four inner simple setae, and four plumose sensory setae. Articles 1–5 combined 0.69 times as long as remaining articles. Articles 6–8 with simple setae as illustrated. Article 9 with five simple setae. Squama with three distal simple setae.

Labrum ( Fig. 4 A) bipartite, with fine setae as illustrated; distal margin slightly convex. Mandibles ( Fig. 4 B–E) with molar process well developed, bearing distal row of denticles. Left mandible ( Fig. 4 B) incisor with four teeth; setiferous lobe with ca. 10 complex setae; lacinia mobilis with three teeth. Right mandible ( Fig. 4 C, D) incisor with four teeth; setiferous lobe with five simple setae and five multifurcate setae. Palp ( Fig. 4 E) with three articles; article 1 with one simple setae and two pinnate setae ventrally; article 2 with 14 ventral pinnate setae; article 3 with seven ventral pinnate setae. Labium ( Fig. 4 F, f1) with lobe bearing outer serration and ventral setation. Palp setulated, with two distal multifurcate setae ( Fig. 4 f1). Maxillule ( Fig. 4 G, g1) with palp bearing three subdistal and one distal setae. Outer endite with 11 distal spiniform setae, two subdistal setae, and outer and inner clump of simple setae. Inner endite curving inward, with four distal setulate setae, several outer simple setae, inner clump of simple setae, and outer process. Maxilla ( Fig. 4 H, h1–3, h 1i) with inner lobe of fixed endite bearing 13 setae and two biserrate setae; outer lobe of fixed endite ( Fig. 4 h1, h 1i) with nine simple setae, two pinnate setae, one upswept pinnate seta ( Fig. 4 h1, arrowhead), two setulate setae, one branched seta, and three multifurcate spiniform setae; inner lobe of movable endite ( Fig. 4 h2) with ca. 15 simple setae and four comb-shaped setae; outer love of movable endite ( Fig. 4 h3) with two subdistal and five distal comb-shaped setae. Maxilliped ( Fig. 4 I, i1–3) with coxa. Basis with seven simple setae. Endite with two simple setae, nine complex spiniform setae, and setulation in distal region; outer region serrated and setulated; inner region with five basally setulate setae and three coupling hooks. Palp article 1 with one ventral simple seta and one outer distal spiniform seta; article 2 with one outer distal spiniform seta, and four inner ventral and 32 inner marginal simple setae; article 3 with 13 narrower and 3 thicker simple setae in inner region; article 4 with three subdistal simple setae and four distal pinnate spiniform setae. Epignath ( Fig. 4 J) cup-shaped, with setulate terminal seta.

Cheliped ( Fig. 5 A, a1–3) with coxa bearing two simple setae. Basis 1.7 times as long as wide, with one short, two inner proximal, and one inner distal simple setae; ventral region with two proximal, six middle, and five subdistal simple setae. Merus with three outer and one inner dorsal simple setae; ventral region with three middle, one subdistal, and five inner distal simple setae. Carpus ca. 2.9 times as long as wide, with 13 outer, 12 inner simple setae in dorsal region; ventral region with six marginal and two outer simple setae. Propodal palm with two outer, two inner dorsal, and one inner ventral simple setae; insertion of dactylus with 7 simple setae and one serrate seta ( Fig. 5 a1). Fixed finger with four ventral simple setae; cutting surface with 11 outer and one inner simple setae, and eight biserrate lamellar setae ( Fig. 5 a2). Dactylus longer than fixed finger, with one simple seta and two pinnate setae in inner region; cutting surface with five narrow serrate setae ( Fig. 5 a3) and three fine setae. Exopod with three articles; distal article with four plumose setae.

Pereopod 1 ( Fig. 6 A, a1) 0.28 times BL, longest of pereopods. Coxa with two simple setae. Basis 0.34 times total pereopod 1 length, 1.62 times as long as wide, with two long and several minute simple setae in dorsal region; ventral margin with eight simple setae; distal region with eight simple setae and one short seta ( Fig. 6 a1: arrowhead). Ischium wider than long, with one short and three long simple setae. Merus widening distally, with five dorsal, one outer, eight inner ventral, five ventral, and one ventrodistal short simple setae, and one inner dorsodistal and one ventral spiniform setae. Carpus slightly shorter than merus, expanded dorsodistally; dorsal region with row of 19 simple setae, two outer simple setae, and one spiniform seta; ventral region with four inner proximal, three inner distal and one outer distal simple setae, and two spiniform setae, with zero and one simple setae proximal to each spiniform seta respectively. Propodus slightly shorter than carpus, with six simple setae, one plumose sensory seta, and two spiniform setae in dorsal region; ventral region with two outer and one distal simple setae, one inner distal serrate seta, and three spiniform setae, with two, two, and one simple setae proximal to each spiniform seta respectively. Dactylus together with unguis shorter than propodus; dactylus with one mid-dorsal simple seta and two ventral serrations; unguis 0.4 times dactylus length. Exopod with three articles; distal article with six plumose setae.

Pereopod 2 ( Fig. 6 B) 0.86 times pereopod 1 length. Coxa with two simple setae. Basis 2.2 times as long as wide, with three ventral and nine ventrodistal simple setae, several minute dorsal simple setae, and several plumose sensory setae. Ischium with one short and four long simple setae. Merus with one outer distal, one mid-inner, five ventral, and one ventrodistal simple setae, one inner dorsodistal seta, one ventrodistal spiniform seta, and one outer conical seta. Carpus as long as merus, expanded dorsodistally; dorsal region with row of 11 simple setae, and four conical setae; ventral region with two inner proximal, two inner distal, and four ventral simple setae, one spiniform seta, and two conical setae. Propodus longer than carpus, with six simple setae, one plumose sensory seta, and one conical seta in dorsal region; ventral region with one inner distal serrate seta, and two spiniform setae, with one and three simple setae proximal to the spiniform setae. Dactylus together with unguis slightly shorter than propodus; dactylus with one mid-dorsal simple seta and two ventrodistal fine setae.

Pereopod 3 ( Fig. 6 C) shorter than pereopod 2. Otherwise like pereopod 2, except merus with ventral conical seta in place of spiniform seta, and numbers of simple setae, plumose sensory setae, and conical setae on each segment slightly different, as illustrated.

Pereopod 4 (ZIHU-4382; Fig. 6 D, d1, 2) with coxa bearing two simple setae. Basis with one middle and three distal simple setae and one plumose sensory seta in ventral region; dorsoproximal region with three plumose sensory setae. Ischium like that of pereopod 3. Merus with one outer, four ventral simple setae, one dorsodistal seta, and two conical setae. Carpus longer than merus; outer region with five simple setae and five conical setae; inner region ( Fig. 6 d1) with six simple setae, two spiniform setae, and one conical seta. Propodus shorter than carpus, with three ventral simple setae, one dorsal plumose sensory seta, two distal pinnate setae, and distal row of ca. 11 serrate setae. Dactylus together with unguis ( Fig. 6 d2) far shorter than on other pereopods, but longer than serrate setae on propodus; setation like that of pereopod 2.

Pereopod 5 (ZIHU-4383; Fig. 6 E, e1, e2) similar to pereopod 4 from coxa to carpus, except carpus additionally with two outer minute simple setae and one inner spiniform seta, and the numbers of simple setae and conical setae on each segment differ slightly, as illustrated. Propodus as long as carpus, with one plumose sensory seta; ventral region with four simple setae, one spiniform seta, and one conical seta; distal region with three long and one short simple setae, three conical setae, one inner setulate seta (ca. 1.3 times as long as serrate seta; Fig. 6 e2), and one inner serrate seta. Dactylus together with unguis like that of pereopod 2.

Pereopod 6 ( Fig. 6 F, f1) with coxa bearing three plumose setae. Basis with three plumose sensory setae, dorsal and ventral setal rows consisting of 15 and seven plumose setae, respectively, and three ventrodistal plumose setae. Ischium with one short simple seta and three plumose setae. Merus with eight ventral and one ventrodistal simple setae, and five outer and five dorsal plumose setae. Carpus longer than merus, with 12 long and one short ventral, and one outer distal simple setae, one ventral and one ventrodistal conical setae, two outer plumose conical setae, and seven dorsal and two outer plumose setae. Propodus slightly shorter than carpus, with two dorsodistal simple setae, one ventroproximal and one distal conical setae, three outer plumose conical setae, two distal pinnate setae, five dorsodistal serrate setae bearing short teeth ( Fig. 6 f1), and two distal and 16 ventral serrate setae. Dactylus together with unguis like that of pereopod 2.

Pleopods ( Fig. 3 F) biramous, all similar in shape. Basal article as long as wide, with three inner plumose setae. Exopod slightly wider distally, with one mid-inner, one outer proximal, and 21 outer plumose setae. Endopod much larger than exopod, oval, with 20 plumose setae and one mid-inner distally-hooked plumose seta.

Uropod ( Fig. 3 G, g1) basal article and endopod combined 0.91 times pleon length. Basal article with seven distal simple setae and three inner distal plumose setae. Exopod with four articles; article 1 with one plumose seta; article 4 with four simple setae. Endopod with serially repeated articles bearing simple setae and plumose sensory setae as illustrated.

Description of male allotype. Body ( Fig. 2 B, D, d1) generally similar to that of female, except body 5.1 times as long as wide; cephalothorax 0.18 times and pleon 0.29 times BL; cephalothorax 0.91 times as long as wide; pereonite 6 with keel-like genital cone ( Fig. 2 d1).

Antennule ( Fig. 3 B) 2.36 times as long as carapace. Article 1 0.93 as long as remaining articles and outer flagellum combined. Article 2 0.3 times as long as article 1. Article 3 0.2 times as long as article 2. Setation on articles 1–4 as in female, except five outer simple setae on article 2. Outer flagellum with 11 articles, similar to those of female, except there are aesthetascs on second and fourth articles from the end. Inner flagellum like that of female.

Antenna ( Fig. 3 E) 0.51 times as long as antennule, with 10 articles. Articles 1–5 like those of female, except three simple setae on distal lobe of article 1 and different number of simple setae on each article. Articles 6–9 each with simple setae as illustrated. Article 10 with five simple setae. Squama like that of female.

Mouthparts generally similar to those of female.

Cheliped ( Fig. 5 B) with coxa bearing one simple seta. Basis 1.65 times as long as wide, with one short, one inner proximal, and three inner distal simple setae; ventral region with four middle and five subdistal simple setae. Merus with two outer and one inner dorsal simple setae; ventral region with two middle, one subdistal, and three inner distal simple setae. Carpus with nine outer and nine inner simple setae in dorsal region; ventral region with two outer simple setae; ventral margin with digitiform process bearing six simple setae, and two inner triangular processes. Propodal palm expanded ventroproximally, and two outer, three inner dorsal, one inner ventral, and three ventroproximal simple setae; insertion of dactylus with six simple setae and one serrate seta. Fixed finger with three ventral simple setae; base well separated from base of dactylus; cutting surface with six outer and one inner simple setae, and four biserrate lamellar setae. Dactylus longer than fixed finger, with one simple seta and two pinnate setae in inner region; cutting surface with seven narrow serrate setae and three fine setae. Exopod like that of female.

Pereopods 1–6, pleopods, and uropod similar to those of female, except the number of setae differs slightly.

Variation. The number of simple setae varies among individuals in most positions. The numbers of simple setae in the ventral region of the pereopod 1 propodus and carpus, which Guţu (1998) presented as stable characters within species, also vary slightly: the pereopod 1 propodus has 2,2,2 simple setae in most specimens, but 2,2,1 (ZIHU-4380, 4393, 4394), 2,1,2 (ZIHU-4382, 4396), and 1,1,2 (ZIHU-4392), 2,3,3 (ZIHU-4395) were observed; the pereopod 1 carpus has zero (in ZIHU-4380, 4393, 4394, 4396) or one (in the other 13 specimens we observed) simple seta, which is proximal to the more proximal of the two ventral spiniform setae. One mid-inner simple seta on the pereopod 2 merus, one inner proximal simple seta on the pereopod 3 carpus, and one conical seta on the pereopod 6 carpus seen in the holotype specimen are absent in the other specimens. The number of conical setae on pereopods 2–6 also differs in most positions; an additional conical seta sometimes appears on the pereopods 2 and 3 propodi. Some spiniform setae are sometimes replaced by conical setae, and vice versa; for example, the ventrodistal spiniform seta on the pereopod 2 merus is a conical seta in six females and two subadult males, and the ventrodistal conical seta on the pereopod 3 merus is spiniform in one adult male and two subadult males. The numbers of plumose setae on pereopod 6 and the pleopodal rami are variable. The ornamentation on the plumose setae on pereopod 6 seems to be easily shed, leading these plumose setae to appear as simple setae.

The number of articles in the antenna is nine or 10 in males (articles 1–5 are similar in all antennae), and the number of articles in the outer flagellum of antennule is six or seven in females and 9–12 in males.

The shape of the expansion on the male chelipedal carpus, as with congeners, varies ontogenetically: in small subadults, it consists of one outer and one inner semicircular expansions ( Fig. 5 D); in medium-sized subadults, the inner expansion is incompletely divided ( Fig. 5 C); and adults have one outer digitiform and two inner triangular processes ( Fig. 5 B).

Marked sexual dimorphism is evident in the length of article 1 of the antennule, the number of articles in and the number of aesthetascs on the outer flagellum of antennule, and the shape of the cheliped.

The following might be teratological character states: the pereopod 1 propodus bears only two ventral spiniform setae in one (ZIHU-4395) of 18 individuals; also, as in males, there is an aesthetasc on the fouth article from the end in the outer flagellum of the antennule in one (ZIHU-4386) of six females.

Remarks. Halmyrapseudes gutui sp. nov. is the seventh species described in this genus. In lacking any dorsal simple setae on the article 2 of the mandibular palp, it closely resembles H. cooperi , H. killaiyensis , and H. thaumastocheles . Although the Halmyrapseudes specimens we observed show more or less variation in the number of simple setae and even the conical setae in most positions, H. gutui differs from the latter three species in the number of ventral simple setae proximal to each spiniform seta on the pereopod 1 carpus, the number of teeth on the lacinia mobilis, the number of inner proximal simple setae on the pereopod 4 basis, the length of the inner distal setulate seta on the pereopod 5 propodus, and several other characters, as summarized in Table 1 .

Ventral serrate setae on pereopod 6 propodus All subequal in Distal one longer All subequal All subequal in

length than the others in length length† Expansion type in male chelipedal carpus Type 3 Type 1 Type 3 Type 3 This species is abundant in the mangrove environment (salinity 31–35‰), reaching densities as high as 9987 individuals/m2. It was occasionally collected from a coral area (salinity 33‰) and a sandy channel (salinity 31‰) surrounding Lidee Island (Phetchaiya 2009).

Tables

TABLE 1. Comparison among Halmyrapseudes gutui sp. nov., H. cooperi, H. killaiyensis, and H. thaumastocheles. *, †, after Băcescu’s (1981) and Monod’s (1935) figures, respectively, although not clearly mentioned in the text. ND, no data.

Characters	H. gutui sp. nov.	H. cooperi	H. killaiyensis	H. thaumastocheles
No. of inner simple setae on article 1 of antennule	4 or 5	3	4 or 5; 6*	6 or 7†
Teeth on lacinia mobilis	3	3	4	4
No. of spiniform setae on outer endite of maxillule	11	11	11	9
No. of mid-ventral simple setae on chelipedal basis	4–8	1 or 2	5–7; 2*	4, 5, or 7†
No. of ventral simple setae proximal to each spiniform seta on pereopod 1 carpus	0,1 or 1,1	4,2, 2,2 or 4,3	2,1 or 1,1	3,2 or 3,1†
No. of inner proximal simple setae on pereopod 1 carpus	2–4	1	1	1 or 3†
No. of mid-ventral simple setae on pereopod 4 basis	1	2 in male, 0 in female	0	ND
Length ratio of inner distal setulate seta/ serrate seta on pereopod 5 propodus	ca. 1.3	ca. 2.0	ca. 2.6	ND