Pista hataam, Londono-Mesa, 2012

Londoño-Mesa, Mario H., 2012, New Species of Pista Malmgren, 1866 (Polychaeta: Terebellidae) from the Caribbean, Zootaxa 3317 (1), pp. 39-48 : 45-46

Pista hataam sp. nov.

Figs 3A–K

Material examined: Type material: Holoype: USNM 1157001, Off Quintana Roo, UMML 22.1030 , R/V “Pillsbury”, Sta. 577, Yucatan Basin , Mexican Caribbean (19°52’N 85°29’W), 22.V.1967 ; 4413 m depth.

Description: Holotype incomplete, 32 segments, 14 mm long, thorax 10 mm long, 1.1 mm wide. Tentacular membrane long, with well defined edge; long base with two lateral groups of small, brown eyespots. Tentacles short in preserved condition. Upper lip long, with ventral edges folded; lower lip long, swollen, not covered by ventral edge of first lateral lappets ( Fig. 3A ). Four pairs of lateral lappets; from segment 1, almost as long as upper lip, projected forwards and dorsally near branchiae bases, with lateral edges rounded, well developed, slender margins and swollen bases ( Fig. 3B ); ventral edge U-shaped. Second pair well developed, but not as long as those on first and third segment, with rounded lateral edges projecting between other lappets; connected to the first ventral shield. Third pair longer dorsally, closes to the branchiae bases, and shorter ventrally, directed forwards, with rounded ventral margin, not connected to ventral shield; dorsal margin well developed. Fourth pair the shortest, a thin edge below third pair between base of first notopodium and ventral shield; ventrally connected to ventral shield. Dorsally, segment 4 with free edge developed, carrying two separated, lateral and rounded short lobes projecting anteriorly, with mid-dorsal notch between them. Segments 5–6 with short ventral lappet, between neuropodium and ventral shield. Two pairs of nephridial papillae on segments 6–7, swollen, placed dorsally and posteriorly to notopodium. Fifteen ventral shields from segment 2; first shield swollen, tessellated, separated from second thinner ventral shields. Fourth, fifth, and sixth shields slightly decreasing in size; thereafter of similar size, separated from each other. Two pairs of branched branchiae on segments 2–3 ( Fig. 3C ); first pair missing, scars visible; stalks short, thick, wrinkled, ending in four secondary stalks, arising alternately from the main stem; secondary stalks with dichotomous tips. Notopodia small, from segment 5; 16 notochaetigers; chaetae of one size ( Fig. 3D ), lanceolate, asymmetrically bilimbate, distally acute ( Fig. 3E ). Neuropodia from segment 5; uncini in segments 5–10 in single rows ( Fig. 3F–H ), MF:5:4–5:3–4:1–2, PP and PF thick, long, slightly tapering, finishing in rounded tip; Oc long, slightly convex; Cp with small teeth over a very long MF; USr and Lsr concave, SrP rounded; SrA triangular, reaching the MF tip; AP and AF absent; Bs slightly curved. Uncini in segments 11–20 in intercalated double rows, face to face ( Figs 3I,J ); MF:4–5:4:2–3:2, PP thick; PF short, thick, slightly tapering, finishing in rounded tip; Oc long, convex; Cp with small teeth over stout MF; USr and LSr slightly concave, divided by short, acute SrP; SrA triangular, reaching MF tip; AP and AF folded under convex Bs. Abdominal uncini in single rows ( Fig. 3K ), smaller; MF:4:4–5, PP rounded, PF long, thin; Oc short, slightly convex; Cp with two series of teeth decreasing in size above short MF, as long as twice the longest secondary tooth; Sr straight, SrP acute; SrA not seen; AP and AF absent. Pygidium missing.

Staining pattern by methyl green: Edge of tentacular membrane stains deeply. First pair of lateral lappet stains in two bands, one lighter, external and running parallel to edge, the other darker, at the base of lappet. Second and third pairs of lateral lappets stain completely, but ventral shield is lighter. Ventral shields from segments 4–15 stain dark, in trapezoids. Notopodial glandular tissue absent, thus, dorsally, segment 4 and center of segments 5–6, stain weakly. Tentacles and branchiae do not stain.

Discussion: This specimen differs from the other species of Pista reported here in having a particular staining pattern, in having a pair of short dorsal lobes at the edge of segment 4, separated by membranous tissue, with a mid-dorsal notch, and in having all thoracic uncini with long PP. Pista cetrata from Florida, is, perhaps, the closest species, having two laterodorsal lobes in segment 4 as well, but separated by a more swollen membrane. Nevertheless, the presence in P. cetrata of uncini in single rows, with a longer PP, and a blind cavity or internal pocket in the third pair of lateral lappets are the main characters to distinguish these two species.

Pista hataam sp. nov., differs from P. lizae sp. nov., in that the latter has short second pair of lateral lappets, uncini only from the first three uncinigers with long posterior process, and segment 4 with only one long and rounded mid-dorsal lobe. Finally, P. hataam sp. nov., differs from the other species of Pista described in the Caribbean, in the depth in which this material was collected (4413 m).

Etymology: This species is named using the compound Mayan word ha (water)-taam (deep), due to the depth where the specimen was collected.

Type locality and Distribution: Yucatan Basin , Mexican Caribbean. Found at 4413 m depth .

Figures

FIGURE 3. Pista hataam sp. nov. A. Thoracic region in ventral view. B. Thoracic region in lateral view. C. Thoracic region in dorsal view. D. Fascicle of notochaetae from segment 12. E. Notochaeta from segment 12. F. Uncinus from segment 5. G. Uncinus from segment 6. H. Uncinus from segment 8. I–J. Uncini from segment 11. K. Uncinus from segment 25. Abbreviations, in alphabetical order: Br, Branchia; DLb, Dorsal Lobe; LL, Lateral Lappet; NeP, Neuropodium; NoP, Notopodium; S, Segment; VS, Ventral Shield. Scale bars: A,B,C: 3 mm; D: 0.08 mm; E: 0.05 mm; F–I,K: 0.02 mm; J: 0.03 mm.