Lysiosquilla isos, Ahyong, Shane T., 2004

Ahyong, Shane T., 2004, New species and new records of stomatopod Crustacea from the Philippines, Zootaxa 793, pp. 1-28 : 7-10

Lysiosquilla isos sp. nov. ( Figure 2 )

Material examined. HOLOTYPE: AM P67176, male (TL 123 mm), Balicasag Island, P. Ng et al. from local fishermen, 26 Jul 2003. PARATYPES: ZRC 2003.0682, 2 males (TL 100–117 mm), 1 female (broken, CL 28.20 mm), type locality.

Diagnosis. Ocular scales produced as slender spines, directed anteriorly. A2 scale length 3.05–3.51 width. Rostral plate triangular; from slightly shorter than to slightly longer than broad; broadest at base; apex slightly deflexed; dorsal surface with median carina flanked by shallow sulcus. Raptorial claw dactylus with 6 or 7 (usually 7) teeth. Mandibular palp present. TS8 sternal keel angular, blunt. Pleopod 1 endopod without posterior ‘endite’. AS 5 and 6 smooth, neither with marked wrinkling nor numerous spinules smooth. Telson subquadrate; surface around dorsal bosses with few, broad, shallow pits. Uropodal protopod unarmed dorsally except for spine above proximal exopod articulation.

Description. Eye large, cornea set slightly obliquely on stalk, extending beyond A1 peduncle segment 2; CI 266–392. Ophthalmic somite anterior margin with small median tubercle. Ocular scales produced as slender spines, directed anteriorly.

A1 peduncle length 0.59–0.71 CL. A1 somite dorsal processes low, broad, trianguloid, apices spiniform directed anteriorly. A2 scale length 3.05–3.51; width 0.49–0.54 CL; entire margin setose.

Rostral plate triangular; from slightly shorter than, to slightly longer than broad; broadest at base; apex slightly deflexed; dorsal surface with median carina flanked by shallow sulcus; ventral surface smooth.

Carapace with rounded anterolateral angles; posterior margin concave.

Raptorial claw dactylus with 6 or 7 (usually 7) teeth, proximal tooth minute; outer margin broadly convex, lacking basal notch; carpus dorsal margin terminating in short acute tooth, directed ventrally; propodus longer than carapace, distal margin unarmed; PI 74–83 in males, 94 in female; ischium shorter than half merus length.

Mandibular palp 3­segmented. MXP5 basal segment unarmed; merus with broad flange on inner margin, distally truncate. MXP1–5 each with epipod.

TS5 lateral process obsolete. TS6–7 lateral process broadly rounded. TS8 sternal keel angular, blunt.

Pleopod 1 endopod without posterior ‘endite’.

AS 1–5 with rounded posterolateral angles. AS 5 smooth medially and laterally; posterior margin unarmed.

AS 6 smooth medially; with low, smooth lateral boss flanked mesially by shallow groove; with acute, triangular ventrolateral projection anterior to uropodal articulation; sternum posterior margin unarmed.

Telson subquadrate, broader than long; lateral margins unarmed; submedian teeth obsolete; intermediate and lateral teeth blunt; with blunt intermediate and lateral denticle; surface around dorsal bosses with few, broad, shallow pits.

Uropodal protopod unarmed dorsally except for spine above proximal exopod articulation; without ventral spine anterior to endopod articulation. Uropodal exopod proximal segment unarmed dorsally; inner distal margin with broad, round lobe; outer margin with 8 or 9 movable, distally flattened spines, distalmost reaching midlength of distal segment; distal margin with stout ventral spine. Exopod distal segment longer than proximal segment, with dorsal and ventral median carina. Endopod elongate, length 1.96–2.53 breadth.

Colour in alcohol. Dorsum pale cream with dark brown transverse bands. Carapace with dark spot on gastric groove anteriorly; with diffuse brown transverse band anteriorly (including rostral plate) and medially, and dark transverse brown posterior band. TS5–8 and AS 1–6 each with dark brown transverse band across articulations. Telson dark brown across posterior three­quarters, excepting pale area between bosses. Uropodal protopod dark brown anteriorly; distal two­thirds of endopod black; exopod proximal segment distal half black­brown, extending onto proximal two­thirds of distal segment. A2 protopod with dark anterior margin. A2 scale transparent, with diffuse patch of scattered chromatophores medially. Raptorial claw with diffuse brown patches on segments; carpus dusky, with dark brown posterodistal margin; dactylus and propodus with diffuse brown patches. Pereopods with proximal half dark brown.

Measurements of holotype. TL 123 mm, CL 22.70 mm, A1 peduncle length 11.60 mm, A2 scale length 12.20 mm, cornea width 6.80 mm, propodus of raptorial claw length 29.00 mm.

Etymology. Named isos, Greek , meaning ‘equal’ or ‘like’, alluding to the similarity between the new species and L. sulcirostris .

Remarks. Lysiosquilla isos sp. nov. resembles L. sulcirostris Kemp, 1913 , in having a triangular rostral plate with shallow sulci lateral to the median carina and in lacking the posterior ‘endite’ on the endopod of pleopod 1 in mature males, a feature present in all other congeners. The latter feature mentioned is exhibited by juveniles of other species of Lysiosquilla , so its presence in adult L. isos and L. sulcirostris suggests that the two species are in some respects neotenous.

The new species is readily distinguished from L. sulcirostris by having a blunt and angular instead of posteriorly spinous sternal keel on TS8, in having 6 or 7 instead of 7 or 8 teeth on the dactylus of the raptorial claw, and in having a dark median patch instead of a dark outline on the antennal scale. In having a dark median patch on the antennal scale, L. isos resembles species of Lysiosquillina , most notably Ln. sulcata ( Manning, 1978a) and Ln. glabriuscula ( Lamarck, 1818) .

Distribution. Presently known only from Balicasag Island.

Figures

FIGURE 2. Lysiosquilla isos sp. nov., holotype male TL 123 mm (AM P 67176). A, anterior. B, right raptorial claw, lateral view. C, TS 6 – 8, right. D, TS 8 sternal keel, right lateral view. E, AS 6, telson and uropod. F, right uropod, ventral. G – I, pereopod 1 – 3 endopod. J, right pleopod 1 endopod. Scale A – F = 5.0 mm, G – I = 2.5 mm, J = 3.5 mm.