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Speleonectes tanumekes new species
Type locality. – Basil Minns Blue Hole, Great Exuma Island, Exuma Cays, The Bahamas (23º 28’ N, 75º 45’ W); collected in 33-43 m depth of anchihaline cave.
Material examined. – Holotype (27 mm, 40 trunk segments; ZMA Rem.204.577), 1 paratype (20 mm, 38 trunk segments; ZMA Rem.204.574), 10 paratypes (up to 26 mm and 40 trunk segments; JvdH 12-01 A1-3); all specimens were collected from the type locality by B. Kakuk and T. Iliffe, 12 Jan. 2003. The holotype (whole specimen) and 1 paratype (dissected) are preserved in alcohol. The remaining paratypes are preserved in formalin and will be retained in the research collection of the first author (JvdH). Some of the paratypes are prepared for SEM investigations.
Etymology. – The epithet tanumekes (Greek for ‘long-stretched’) refers to the long and slender appearance of this species.
Diagnosis. – Long and slender species, up to 27 mm, largest specimens composed of 38-40 trunk segments (Fig. 1A); pleural tergites weakly developed, with broadly rounded lateral margins in anterior part of trunk, becoming slightly pointed posteriorly; sternal bars sublinear, isomorphic; frontal filaments with short processes; dorsal flagella of antennules short; segment 4 of maxillule subrectangular, with small enditic lobe bearing 2 long, rasp-like spines and several slender setae; maxilla and maxilliped without distinct tagmosis, bearing few clusters of long, marginal setae; horseshoe-type claws of maxilla and maxilliped with 17-20 small denticles; anal somite slightly wider than long; caudal rami slightly longer than anal somite.
Description. – Body distinctly elongate and slender, with a maximum length of 27 mm and up to 40 trunk segments (Fig. 1A). Pleural tergites narrow, with broadly rounded distolateral corners on trunk segments 1-16, becoming slightly acuminate in posterior part of trunk. Sternal bars sublinear and isomorphic. Female gonopores on trunk segment 7 with tiny, triangular projections (Pl. 1E); male gonopores with ovate, rounded lobes (Pl. 1F).
Antennules (Figs. 1A, 2B): Peduncle composed of at least 2 fused segments; proximal component subrectangular (barely dilated ventrally) bearing dense rows of long aesthetascs. Dorsal flagellum relatively short, about twice as long as head shield and 7% of length of body; with up to 13 segments; proximal-most segment apparently partially fused to peduncle. Ventral flagellum with 7-8 segments, less than half as long as dorsal flagellum, slightly shorter than head shield.
Antennae (Fig. 2C): Protopod 2-segmented, distal segment with row of 7-8 setae. Exopod longer and wider than adjacent distal segment of protopod, bearing 26-28 long setae. Endopod bent in a semicircular way; first two proximal segments with 8 and 7 setae, respectively; distal segment with 15-17 setae arranged in two rows (11-12 + 4-5 setae). All setae faintly feathered (see Fig. 1E).
Labrum fleshy, with posterolateral lobes bearing several clusters of fine setules (Fig. 2D).
Mandibles (Fig. 2E, F): Right incisor process with three large denticles; right lacinia mobilis equipped with three larger and several smaller denticles (Fig. 3E; Pl. 1C). Left incisor process with four large denticles; left lacinia mobilis crescent-shaped, bearing several large and small denticles (Fig. 3F; Pl. 1D). Molar processes prominent; distal surface long, ovoid.
Maxillules (Fig. 3A, B): First segment equipped with long, narrow endite bearing 6-7 naked, slender spines distally. Endite of segment 2 broad, spatulate, with 5 setae along distoanterior margin, and 10 short spines on distoposterior margin; all short spines naked except 1 rasp-like spine (Fig. 3E), inserted anteriorly adjacent to row of setae. Third segment short, endite broadly rounded, bearing 2 long, slender, rasp-like spines (Fig. 3E), and a few setae. Segment 4 subrectangular, enditic lobe small, with 2 long, slender, rasp-like spines, and a few setae. Segment 5 slightly shorter and narrower than fourth segment, with a row of distomedial setae. Sixth segment very short, bearing separate rows of setae on distal margins. Claw well developed.
Maxillae (Fig. 3C): Endites of first segment equipped with 1 apical spine accompanied by a few long and short setae, respectively. Endite of segment 2 broadly rounded, with a single, short spine and a few setae. Third segment with weakly expanded, straight inner margin bearing 2 rows of about 8 long and 2 short setae. Segment 4 shorter than third segment; distal margin expanded, with a cluster of ca. 4 long setae and 1 short seta on inner margin, and 2 short setae on dorsal margin. Fifth segment shorter than segment 4, not expanded distally, but setation subequal to that of segment four. Segment 6 slightly shorter than fifth segment, equipped with separate clusters of setae distally, and a few longer setae on midmedial margin. Arc of horseshoe-type claw finely serrate, composed of 17-20 fine denticles flanked by 2 stouter, separate denticles (Pl. 1B; Fig. 3F).
Maxillipeds long, slender, 9-segmented (Fig. 3D); elbow between segments 4 and 5. Proximal segments 1-3 with oblique, interconnected articulation; segments 1 and 2 bearing a few short medial setae; segment 3 broadly rounded medially, with about 6-7 long and 2 short setae. Fourth segment with weakly expanded, straight ventral margin equipped with some 8-7 long and 2 short setae proximally. Segments 5-7 gradually decreasing in length; segment 5 slightly shorter than segment 4, distal margin weakly expanded, with a medial cluster of about 6 long and short setae. Segment 6 bearing a distomedial cluster of 8 short and long setae. Segment 7 equipped with 9-12 short and long setae along mid- to distomedial margin. Segment 8 longer than segment 7, with several separate clusters of setae on distal and distomedial margins. Claw subequal to that of maxillae (Pl. 1B; Fig. 3F).
Trunk appendages (Fig. 1B-D; description based on larger thoracopods): Segment 1 of exopod with long setae on lateral margin, and about 3 serrate spines on distolateral corner (Fig. 1C); segment 2 bearing setae on both lateral and medial margins, and serrate spines on both distolateral and -medial corners; segment 3 ovate, with long, marginal setae. Endopod slightly shorter than exopod, but similar in shape and setation. All setae faintly feathered (Fig. 1E).
Anal segment slightly wider than long, lateral margins bearing a few short setae and spines (Fig 3G); caudal rami 1.1-1.2 times longer than anal somite, with a few curling setae on medial and apical margins, respectively.
Remarks. – Speleonectes tanumekes has the largest number of trunk segments recorded for remipedes to date. The large number of segments, in combination with weakly developed pleurotergites, gives this species a rather elongate and slender appearance. Both S. epilimnius Yager & Carpenter, 1999, and S. gironensis Yager, 1994, also have narrow pleurotergites, but are characterized by a smaller number of trunk segments (up to 21 and 25 segments, respectively). In addition, S. tanumekes can be clearly distinguished from S. gironensis by differing shapes and setations of maxillules, maxillae and maxillipeds. Speleonectes tanumekes seems morphologically similar to S. epilimnius, but differs from the latter species by having a 13-segmented dorsal antennular flagellum (10-11 segments in S. epilimnius); a relatively large antennal exopod; longer and more slender spines on maxillulary segments 3 and 4; less expanded, straight margins of segments 3 and 4 (proximal to elbow) of maxillae and maxillipeds, respectively (more expanded and rounded in S. epilimnius); and an anal segment wider than long, with caudal rami 1.2 times longer than the anal somite (anal somite longer than wide, with caudal rami 2-2.5 times longer in S. epilimnius).
From Koenemann, Iliffe and van der Ham 2003