Brianola rawaiensis, Chullasorn & Kangtia & Klangsin & Song, 2024

Brianola rawaiensis sp. nov. ( Figs. 1-9 View Fig View Fig View Fig View Fig View Fig View Fig View Fig View Fig View Fig )

Type locality. Intertidal zone at Rawai Beach of Phuket Island, Thailand, 7°46 ʹ 17 ʺ N 98°19 ʹ 15.7 ʺ E GoogleMaps .

Material examined. Holotype: ovigerous female ( NIBR IV0000910337 ) dissected on 8 slides; adult male allotype ( NIBRIV0000910338 ) dissected on 7 slides, 3 females and 3 paratype males ( NIBRIV0000910339 ) preserved in 70% ethanol.

Etymology. The species name refers to the type locality at Rawai muddy sand Beach of Phuket Island.

Description. Female. Habitus ( Fig. 1A, B View Fig ). Body length 992 μm. Body length of paratypes 821 - 1,026 μm (n = 6, mean = 919 μm). Body fusiform, the entire body surface ornamented with minutely punctate on the cephalothorax and thoracic segments, otherwise unornamented and with an entire hyaline frill; prosome gradually tapering anteriorly, few sensilla on the body surface. Nauplius eye not visible. Prosome four-segmented, comprising cephalosome fused to first pedigerous somite, and three free pedigerous somites.

Cephalothorax longer than three prosomites combined, posterior margin of second to fourth prosomites ornamented with rows of hyaline frills. Posterior margin of uroso-

B

mites ornamented with fine spinules and hyaline frills. Rostrum very large, bell-shaped, slightly exceeding the length of antennules, with two sensilla (but could not see).

Urosome ( Fig. 2A, B View Fig ) five-segmented, consisting of rectangular somites, ornamented with rows of fine spinules and hyaline frills dorsally and ventrally, genital doublesomite fused, two abdominal somites, and anal somite. Genital area indistinct, ventrally with one copulatory pore, and two genital apertures ( Fig. 2C View Fig ). Third and fourth urosomites with rows of spinules on the surface and are ornamented with hyaline frills along the outer margin dorsally and ventrally. Anal operculum semicircular and smooth. Caudal rami unsegmented, twice as long as wide, ornamented with spinules on the outer margin. Each ramus ( Figs. 1A View Fig ; 2A, B View Fig ) armed with seven setae: seta I short and located at the outer margin close to seta IV; seta II longer than seta I and III; seta IV shorter than seta V; seta V longest; seta VI short close to seta V; seta VII shortest located close to the insertion point of seta V.

Antennule ( Fig. 3A View Fig ) four-segmented indistinctly, without spinules on the dorsal surface. First segment with five spinules at the inner margin and six pinnate setae at the inner corner. Second segment with seven spinulose and twelve smooth setae plus two aesthetascs. Third segment bearing two spinulate setae and one smooth seta. Distal segment with seven spinulate and six smooth setae. Armature formula: 1-(6), 2-(19 + 2 ae), 3-(3), 4-(13).

Antenna ( Fig. 4A View Fig ). Basis with small spinules on middle and outer margin. Exopod consist of eight segments; fourth segment with one long naked seta; ultimate segment with four pinnate setae. Endopod three-segmented; enp-1 with one long setule and spinular row along outer margin and anterior surface, enp-2 with one naked seta and three spinulose setae, enp-3 with six spinulose setae, one pinnate seta and one naked short seta.

Mandible ( Fig. 4B View Fig ) with large and elongated coxa, without surface ornamentation. Gnathobase well-developed, cutting edge with two rows of strong teeth in different sizes. Basis bearing two naked setae. Endopod two-segmented, enp-1 with two pinnate and one spinulose setae; enp-2 with three plumose setae fused with segment. Exopod one-segmented, with seven naked and three plumose setae.

Maxillule ( Fig. 4C View Fig ). Praecoxa arthrite with two juxtaposed slender setae on anterior surface and with eight dis-

A tal spines. Coxal endite cylindrical, bearing three spinulose setae; epipodite represented by three plumose setae. Basis ornamented with rows of spinules on surface, basal endite bearing six spinulose and two smooth setae. Endopod two-segmented, end-1 bearing three spinulose and two smooth setae; enp-2 bearing four spinulose and two plumose setae. Exopod one-segmented, with six plumose setae fused with segment and one pectinate seta.

Maxilla ( Fig. 4D View Fig ) comprising praecoxa, coxa, allobasis, and one-segmented endopod. Praecoxa bearing one row of spinules, two praecoxal endites with two pinnate setae and two spinulose setae; coxa ornamented with different sizes of spinules on surface, bearing two coxal endites with three spinulose setae each; basis extended into a strong claw and one spinulose spine, basal endite with two plumose setae. Endopod one-segmented, with seven smooth setae.

Maxilliped ( Fig. 4E View Fig ) phyllopodial, comprising syncoxa (praecox and coxa fused); basis, and one-segmented endopod. Syncoxa bearing one long plumose seta at base and five spinulose and one naked seta. Basis bearing four spinulose setae, and one row of long setules along outer margin. Endopod with three spinulose and four plumose setae.

All swimming legs ( Figs. 5A, B View Fig ; 6A, B View Fig ) biramous; P1 - P4 with three-segmented exopods and endopods. Members of each leg pair are connected by simple intercoxal sclerite.

P1 ( Fig. 5A View Fig ). Coxa with one inner pinnate spine, ornamented with rows of spinules on the surface, outer margin with two setules and five spinules. Basis ornamented with setules distally, with one inner pinnate spine and one outer spinulose seta. Exopod shorter than endopod. Exp-1 with one outer pinnate spine; exp-2 with one outer pectinate spine and one inner plumose seta; exp-3 with one outer pectinate and one outer pinnate spine, one distal pinnate spine and one distal spinulose spine, and one inner plumose seta. Enp-1 and enp-2 with plumose inner seta each; enp-3 with one naked and one pinnate outer spine, one spinulose spine and one plumose seta distally, and one short bare seta and one plumose seta on inner margin.

P2 ( Fig. 5B View Fig ). Coxa ornamented with several spinular rows of unequal length on the anterior surface, and a row of spinules along the outer margin. Basis ornamented with small and large spinules along the outer margin and one outer small seta. Exopod shorter than endopod. Exp-1 with one outer pinnate spine; exp-2 with one outer pinnate spine and one inner plumose seta; exp-3 with one outer pinnate spine, one distal spinulose spine, and one inner plumose seta. Enp-1 and enp-2 with one inner plumose

A B

seta each; enp-3 with one outer pinnate spine, one distal pinnate spine and one distal spinulose spine, and two inner plumose setae.

P3 ( Fig. 6A View Fig ) rather like P2 except for setal formulae. Exp-3 and enp-3 with one outer pinnate spine, one distal pinnate spine and one distal spinulose spine, and one inner plumose seta, respectively.

P4 ( Fig. 6B View Fig ). Coxa and basis ornamentation are almost the same as P2 and P3. Exp-1 and exp-2 with outer pinnate spine each; exp-3 with one outer pinnate spine, one distal pinnate spine and one distal spinulose spine, and one inner pectinate spine. Enp-1with very short smooth inner seta; enp-2 bare; enp-3 with outer bare spine, one distal pinnate spine and one distal spinulose spine, and one inner pectinate spine.

The spine and setal formula of the swimming legs of

Brianoloa rawaiensis sp. nov. are as follows:

Exopod Endopod

P1 0.1.122 1.1.222

P2 0.1.111 1.1.221

P3 0.1.121 1.1.121

P4 0.0.121 1.0.121

P5 ( Fig. 2D View Fig ) reduced, incorporated into somite; connected by deeply incised hyaline frills; with four pinnate setae: outer seta longest, two inner setae equal in length.

Description of allotype male. Habitus is almost as in female ( Fig. 7A, B View Fig ). The body length of the allotype 902 μm. Body length of paratypes males 796 - 929 μm (n = 12, mean = 874 μm). Antennae, mouthparts, swimming legs, and caudal rami as in female. Sexual dimorphisms are expressed in antennules and abdominal somites.

Antennule ( Fig. 9A View Fig ) five-segmented. First segment larg- est, with two smooth and one unipinnate seta, and three small spinules close to the base of the unipinnate seta. Second segment large, with three pinnate, four spinulose, and seven smooth setae/spines and two aesthetascs. Third segment small, with one spinulose and one small smooth seta. Fourth segment large, with two plumose, one spinulose, three pinnate, and one smooth seta and one modified element. Distal segment small, with one pinnate and five smooth setae. Armature formula: 1-(6), 2-(14 +2 ae), 3-(2), 4-(7), 5-(6).

Urosome ( Fig. 8A, B View Fig ) five-segmented and consisting of P5-bearing somite, genital somite, two urosomites, and anal somite. Genital area and P6 oval-shaped ornamented with spinules as Fig. 8C View Fig . Spermatophores paired. P5 with four bipinnate setae ( Fig. 8D View Fig ).