Theosbaena kiatwongchai, Rogers, D. Christopher & Sanoamuang, La-Orsri, 2016

Rogers, D. Christopher & Sanoamuang, La-Orsri, 2016, A new Theosbaena (Thermosbaenacea: Halosbaenidae) from Thailand, Zootaxa 4109 (4), pp. 471-478 : 472-476

Theosbaena kiatwongchai n. sp.

( Figures 1 and 2 )

Type Material. Holotype (male USNM 1254717): Thailand: Nakhon Sawan: Takhli District: Takhli Subdistrict: Chon Dua Village: permanent pool in Tham Nam limestone cave, Tham Phet—Tham Thong Forest Park in the Chon Dua Mountains, 15˚18’14”N, 100˚23’39”E, 86 metres above sea level; 13 September 2015; K. Makruemtet and S. Promprasith. Allotype (female USNM 1254718): same data as holotype. Paratype (2 males (one dissected), 2 females USNM 1254719): same data as holotype.

Etymology. The specific epithet “ kiatwongchai ” is a Thai word for “family (or genus) name with honor and victory”. The name describes the victory of finding so rare an organism, and also honors Mr. Danai Kiatwongchai , the founder of Cave Conservation group at Tham Phet—Tham Thong Forest Park for his work in protecting these fragile habitats. The gender is masculine.

Specific diagnosis. Theosbaena kiatwongchai n. sp. is generally similar to the basic form of the nominal species, T. cambodjiana . Theosbaena kiatwongchai n. sp. is readily separated from T. cambodjiana by the form of the telson, which is cleft, and the lack of pleopod I.

Description. Male. Body ( Fig. 1 A) length 3.7–4.2 mm from head anterior margin to telson distal margin. Ocular scales ( Fig. 1 B) broadly rounded, with longest dimension in medial third. Ocular scale 1.3 times as long as broad, overlapping base of antenna I.

Carapace extending to pereonite III.

Antenna I ( Fig. 1 A) 0.8 times body length, biramous, peduncle of three articles, proximal article with a pair of subapical macrosetae at dorsolateral corner. Antenna I peduncle article II with a pair of subapical macrosetae at dorsolateral corner and two distoventral macrosetae directed ventrally. Antenna I peduncle article III apparently inerm. Primary flagellum with 25 articles, secondary flagellum with 13 articles, each with a distoapical spiniform seta. Terminal article on each flagellum with three apical setae.

Antenna II 0.2 times body length, uniramous, peduncle of three articles, distal two articles with a longitudinal dorsal row of spiniform setae. Flagellum of 11 articles, terminal article with two apical setae.

Labrum subcircular, 2.3 times as long as broad, smooth, distal margin with fine, short microsetae. Labrum and labium without peculiarities.

Mandible with palp of three articles, basal article conical, expanding distally, inerm; article II subcylindrical, lateral surface, distal portion bearing six macrosetae; article III subcylindrical, lateral and distal surface bearing six macrosetae. Corpus mandibula broadly triangular, divided into pars incisive, a lacinia mobilis (absent in right mandible) that is apically dentate, a row of macrosetae, and a medial triangular pars molaris, margined with macrosetae.

Labium deeply cleft, margined with macrosetae, with cleft margined with microsetae.

Maxilla I with praecoxal endite and basipodal endite margined with stout macrosetae; endopodite bearing a palp of two articles, with proximal article inerm, distal article with four macrosetae and twice as long as proximal palpomere.

Maxilla II coxopodal endite medial surface margined with plumose macrosetae; basipod with three endites, each margined with macrosetae; basipod apex margined with macrosetae. Endopodite of two articles; proximal article with one distal macroseta; distal article with seven macrosetae.

Maxilliped ( Fig. 1 C) epipod (not figured) lamellar, narrow, margined with fine setae, extending just beyond exopod. Exopod extremely reduced, as broad as long, with elongate pectinate macrosetae, reaching just short of endopod distal margin. Endopod broad, lateral margin straight, apical fifth of anterior surface and distal margin with stout pectinate spines and macrosetae; more macrosetae medially than at apex, apex with more spines. Endopod medial margin inerm. Endite projecting, subacute, and apparently inerm.

Gnathopod ( Fig. 1 D) uniramous, basoischium broad, nearly twice as long as broad, bearing single subdistal anterior macroseta. Merus slightly longer than basoischium. Carpus expanded distally, bearing a longitudinal row of four slightly curved macrosetae on medial margin; each macroseta subequal in length to carpus. Propodus subrectangular, bearing longitudinal row of two slightly curved macrosetae on medial margin equal in length; each macroseta about one half length of propodus. Dactylus expanded, with distal end twice as wide as proximal.

Dactylus distal margin convex. Unguis formed by single curved spine at distolateral corner. Dactylus distomedial angle with longitudinal row of short setae.

Pereopod II coxa pronounced, rounded. Exopod 0.8 times length of endopod, composed of two articles: basal article rectangular, with spine at distolateral corner. Distal article originating on distomedial angle of proximal article, lanceolate, with long plumose macrosetae along distal two thirds of medial margin and distal third of lateral margin. Basis subcylindrical, inerm, twice as long as wide. Ischiomerus subcylindrical, twice as long as wide, bearing a stout spiniform macroseta half as long as the distolateral angle of the article. Carpus subcylindrical, expanded distally, 1.7 times longer than wide, bearing one medial and one lateral distal spiniform macroseta. Propodus anterioposteriorly flattened, approximately six times longer than wide, medial margin bearing longitudinal row of well-spaced, spiniform macrosetae, each longer than article’s width. Propodus lateral margin bearing two subapical macrosetae distally, each about as long as article’s width. Dactylus anterioposteriorly flattened, margins converging into truncated apex; apex half as wide as base. Dactylus apex with single elongate spine (unguis), 1.5 times as long as dactylus. Pereopods III through V (Fig. 5E) similar to pereopod II.

Pereopod VI ( Fig. 1 F) coxa pronounced, rounded. Exopod 0.8 times length of endopod, composed of two articles: proximal article subrectangular, expanded distally, 1.6 times wider at distal end than base, with single macroseta at distolateral corner. Distal article originating on distomedial angle of proximal article. Distal article lanceolate, margined in long, plumose macrosetae. Basis subcylindrical, inerm, twice as long as wide. Ischiomerus subcylindrical, 2.3 times as long as wide, bearing a single, stout anteriolateral spiniform macroseta as long as article on distolateral angle; medial margin with three macrosetae, each as long as article’s width. Carpus subcylindrical, expanded distally, 1.4 times longer than wide, bearing one spiniform macroseta distally at each side. Propodus anterioposteriorly flattened, approximately six times longer than wide, medial margin bearing a longitudinal row of well-spaced, spiniform macrosetae, each longer than article’s width. Propodus lateral margin bearing two subapical macrosetae, each about as long as article’s width. Dactylus anterioposteriorly flattened, margins converging to a truncated apex; apex 0.7 times as wide as base. Dactylus apex with single elongate spine (unguis), 1.5 times as long as the dactylus, and two subapical macrosetae on medial margin.

Pereopod VII ( Fig. 1 G) coxa pronounced, rounded, bearing an elongate penial lobe. Exopod 0.5 times length of endopod, composed of one article, lanceolate, and inerm. Basis subcylindrical, inerm, twice as long as wide. Ischiomerus subcylindrical, 2.3 times as long as wide, bearing stout distolateral spiniform macroseta as long as the article; medial margin bearing one macroseta at midlength, half as long as article’s width. Carpus subcylindrical, expanded distally, 1.6 times longer than wide, bearing one distal spiniform macrosetae at each side and one macroseta on medial margin. Propodus anterioposteriorly flattened, approximately six times longer than wide, distal fourth of medial margin bearing longitudinal row of well-spaced, spiniform macrosetae, each longer than article’s width. Propodus lateral margin bearing two subapical macrosetae, each about as long as article’s width. Dactylus anterioposteriorly flattened, margins converging to a truncated apex; apex 0.7 times as wide as base. Dactylus with single elongate spine (unguis).

Penial lobe ( Fig. 1 G) fusiform, apically rounded, inerm.

Pleopod I absent. Pleopod II ( Fig. 1 H) of one small article, subtriangular with two distal macrosetae. Distomedial macroseta as long as pleopod, distolateral macroseta four times as long as pleopod.

Uropod ( Fig. 1 I) protopod inerm. Endopod ovate, of one article, as long as protopod; lateral margin bearing small spiniform macrosetae; medial margin bearing two filiform macrosetae at midlength, otherwise bearing small spiniform macrosetae; distomedial margin bearing long, plumose macrosetae, equal in length to basal width of endopod; distolateral margin bearing seven elongate stout macrosetae: lateralmost macroseta apically aciculate, with next four macrosetae each progressively longer, longest macroseta longer than endopod width, last two macrosetae approximately one half length of longest macroseta. Exopod of two articles, proximal article with straight lateral margin armed with row of stout spines; medial margin convex, widest at middle, with row of plumose macrosetae; distolateral angle of article bearing large spine nearly half length of exopod’s distal article; distomedial angle bearing two elongate spiniform macrosetae, each 0.8 times length of exopod’s distal article. Distal article subovate, lateral margined with elongate, plumose macrosetae; medial edge margined with stout spines, spines becoming progressively longer towards; article apex with single elongate spine 0.8 times length of article.

Telson ( Fig. 1 J) 1.2 times longer than basal width, lateral margins converging distally. Apex bilobed, with a wide to narrow median cleft. Each lobe margined with stout macrosetae that become more curved in the medial pairs.

Female. Similar to male in appearance (not figured). Body length 3.4-3.8 mm from head anterior margin to telson distal margin.

Ocular scales broadly rounded, with longest dimension in medial third. Ocular scale 1.3 times as long as broad, overlapping base of antenna I.

Carapace extending to pereonite II. Antenna I 0.8 times body length, biramous, peduncle of three articles, proximal article with a pair of subapical macrosetae at dorsolateral corner. Antenna I peduncle article II with a pair of subapical macrosetae at dorsolateral corner and two distoventral macrosetae directed ventrally. Antenna I peduncle article III apparently inerm. Primary flagellum with 24 articles, secondary flagellum with 10 articles, each with a distoapical spiniform seta. Terminal article on each flagellum with three apical setae.

Antenna II 0.2 times body length, uniramous, peduncle of three articles, distal two articles with a longitudinal dorsal row of spiniform setae. Flagellum of 11 articles, terminal article with two apical setae.

Labrum subcircular, 2.3 times as long as broad, smooth, distal margin with fine, short microsetae. Labrum and labium without peculiarities.

Mandible with palp of three articles, basal article conical, expanding distally, inerm; article II subcylindrical, lateral surface, distal portion bearing six macrosetae; article III subcylindrical, lateral and distal surface bearing six macrosetae. Corpus mandibula broadly triangular, divided into pars incisive, a lacinia mobilis (absent in right mandible) that is apically dentate, a row of macrosetae, and a medial triangular pars molaris, margined with macrosetae.

Labium deeply cleft, margined with macrosetae, with cleft margined with microsetae.

Maxilla I with praecoxal endite and basipodal endite margined with stout macrosetae; endopodite bearing a palp of two articles, with proximal article inerm, distal article with four macrosetae and twice as long as proximal palpomere.

Maxilla II coxopodal endite medial surface margined with plumose macrosetae; basipod with three endites, each margined with macrosetae; basipod apex margined with macrosetae. Endopodite of two articles; proximal article with one distal macroseta; distal article with seven macrosetae.

Maxilliped epipod lamellar, narrow, margined with fine setae, extending just beyond exopod. Exopod extremely reduced, as broad as long, with elongate pectinate macrosetae, reaching just short of endopod distal margin. Endopod broad, lateral margin straight, apical fifth of anterior surface and distal margin with stout pectinate spines and macrosetae; more macrosetae medially than at apex, apex with more spines. Endopod medial margin inerm. Endite projecting, subacute, and apparently inerm.

Gnathopod uniramous, basoischium broad, nearly twice as long as broad, bearing single subdistal anterior macroseta. Merus slightly longer than basoischium. Carpus expanded distally, bearing a longitudinal row of four slightly curved macrosetae on medial margin; each macroseta subequal in length to carpus. Propodus subrectangular, bearing longitudinal row of two slightly curved macrosetae on medial margin equal in length; each macroseta about one half length of propodus. Dactylus expanded, with distal end twice as wide as proximal. Dactylus distal margin convex. Unguis formed by single curved spine at distolateral corner. Dactylus distomedial angle with longitudinal row of short setae.

Pereopod II coxa pronounced, rounded. Exopod 0.8 times length of endopod, composed of two articles: basal article rectangular, with spine at distolateral corner. Distal article originating on distomedial angle of proximal article, lanceolate, with long plumose macrosetae along distal two thirds of medial margin and distal third of lateral margin. Basis subcylindrical, inerm, twice as long as wide. Ischiomerus subcylindrical, twice as long as wide, bearing a stout spiniform macroseta half as long as the distolateral angle of the article. Carpus subcylindrical, expanded distally, 1.7 times longer than wide, bearing one medial and one lateral distal spiniform macroseta. Propodus anterioposteriorly flattened, approximately six times longer than wide, medial margin bearing longitudinal row of well spaced, spiniform macrosetae, each longer than article’s width. Propodus lateral margin bearing two subapical macrosetae distally, each about as long as article’s width. Dactylus anterioposteriorly flattened, margins converging into truncated apex; apex half as wide as base. Dactylus apex with single elongate spine (unguis), 1.5 times as long as dactylus. Pereopods III through V similar to pereopod II.

Pereopod VI coxa pronounced, rounded. Exopod 0.8 times length of endopod, composed of two articles: proximal article subrectangular, expanded distally, 1.6 times wider at distal end than base, with single macroseta at distolateral corner. Distal article originating on distomedial angle of proximal article. Distal article lanceolate, margined in long, plumose macrosetae. Basis subcylindrical, inerm, twice as long as wide. Ischiomerus subcylindrical, 2.3 times as long as wide, bearing a single, stout anteriolateral spiniform macroseta as long as article on distolateral angle; medial margin with three macrosetae, each as long as article’s width. Carpus subcylindrical, expanded distally, 1.4 times longer than wide, bearing one spiniform macroseta distally at each side. Propodus anterioposteriorly flattened, approximately six times longer than wide, medial margin bearing a longitudinal row of well-spaced, spiniform macrosetae, each longer than article’s width. Propodus lateral margin bearing two subapical macrosetae, each about as long as article’s width. Dactylus anterioposteriorly flattened, margins converging to a truncated apex; apex 0.7 times as wide as base. Dactylus apex with single elongate spine (unguis), 1.5 times as long as the dactylus, and two subapical macrosetae on medial margin.

Pereopod VII coxa pronounced, rounded. Exopod 0.5 times length of endopod, composed of one article, lanceolate, and inerm. Basis subcylindrical, inerm, twice as long as wide. Ischiomerus subcylindrical, 2.3 times as long as wide, bearing stout distolateral spiniform macroseta as long as the article; medial margin bearing one macroseta at midlength, half as long as article’s width. Carpus subcylindrical, expanded distally, 1.6 times longer than wide, bearing one distal spiniform macrosetae at each side and one macroseta on medial margin. Propodus anterioposteriorly flattened, approximately six times longer than wide, distal fourth of medial margin bearing longitudinal row of well spaced, spiniform macrosetae, each longer than article’s width. Propodus lateral margin bearing two subapical macrosetae, each about as long as article’s width. Dactylus anterioposteriorly flattened, margins converging to a truncated apex; apex 0.7 times as wide as base. Dactylus with single elongate spine (unguis).

Pleopod I absent. Pleopod II of one small article, subtriangular with two distal macrosetae. Distomedial macroseta as long as pleopod, distolateral macroseta four times as long as pleopod.

Uropod protopod inerm. Endopod ovate, of one article, as long as protopod; lateral margin bearing small spiniform macrosetae; medial margin bearing two filiform macrosetae at midlength, otherwise bearing small spiniform macrosetae; distomedial margin bearing long, plumose macrosetae, equal in length to basal width of endopod; distolateral margin bearing seven elongate stout macrosetae: lateralmost macroseta apically aciculate, with next four macrosetae each progressively longer, longest macroseta longer than endopod width, last two macrosetae approximately one half length of longest macroseta. Exopod of two articles, proximal article with straight lateral margin armed with row of stout spines; medial margin convex, widest at middle, with row of plumose macrosetae; distolateral angle of article bearing large spine nearly half length of exopod’s distal article; distomedial angle bearing two elongate spiniform macrosetae, each 0.8 times length of exopod’s distal article. Distal article subovate, lateral margined with elongate, plumose macrosetae; medial edge margined with stout spines, spines becoming progressively longer towards; article apex with single elongate spine 0.8 times length of article.

Telson 1.2 times longer than basal width, lateral margins converging distally. Apex bilobed, with a wide to narrow median cleft. Each lobe margined with stout spines that become more curved in the medial pairs.

Egg. None present in our material. No brooding females present in the sample.

Variability. Some variation was observed in the number of antennomeres among the T. kiatwongchai n. sp. material: antenna I, primary flagellum ranged from 20 to 25 flagellomeres; antenna I secondary flagellum ranged from 11 to 13 flagellomeres; antenna 2: flagellum ranged from 9 to 11 flagellomeres. The uropods varied in the density of their marginal setation, and the telson cleft ranged from being a narrow slit to a wide notch.

Conservation status. So far, T. kiatwongchai n. sp. is only known from the type locality: a permanent pool in a limestone cave in central Thailand ( Figure 2 ). The cave is situated in the Tham Phet-Tham Thong Forest Park, under the Thailand Royal Forest Department. The Park covers 4.8 km 2, and is surrounded by active rice production. This species meets the definitions of an Endangered Species under the IUCN Red List (2014) criteria, in that its extent of geographic occurrence is a single locality and that the species decline may be projected due to the agricultural practices in the immediate area or stochastic events. Whereas this species is currently in a protected area, there is the potential for ground water contamination by pesticides, herbicides, and fertilizers used in the surrounding rice paddies.

Figures

FIGURE 1. Theosbaena kiatwongchai n. sp. Male. A) Body, left lateral view, limbs excluded. B) Left ocular scale. C) Left maxilliped, anterior view. D) Gnathopod. E) Pereopod V. F) Pereopod VI. G) Pereopod VII. H) Abdominal segment II with pleopods, ventral view. I) Left uropod, dorsal view. J) Telson, dorsal view.

FIGURE 2. Location of Tham Phet-Tham Thong Forest Park, Thailand. Inset depicts Nakhon Sawan, and the position of the cave in Takhli District.