Speleonectes cokei, Yager, Jill, 2013

Yager, Jill, 2013, Speleonectes cokei, new species of Remipedia (Crustacea: Speleonectidae) from a submerged ocean cave near Caye Chapel, Belize, Zootaxa 3710 (4), pp. 354-362 : 354-361

Speleonectes cokei , new species

Figures 1–5

Type locality. Caye Chapel Cave, Caye Chapel, Belize

Material examined. Holotype, U.S. National Museum of Natural History (USNM) #1202676, 19.5 mm, 36 trunk segments; collected by Frank Bounting, 17 April 1989. Paratypes: USNM #1202677, 30 mm, 40 trunk segments, partially dissected; USNM #1202679, 13.8 mm, 33 trunk segments; collected by Frank Bounting, 17 April 1989; USNM #1202680, 28.6 mm, 38 trunk segments; head and trunk segment 1 dissected for SEM; collected 23 July 1987 by Jim Coke.

Etymology. The species is named to honor Jim Coke, cave diver, explorer, founder of the Quintana Roo Speleological Survey. Jim’s work has led to a better understanding of the cenotes and submerged caves of the Yucatan Peninsula.

Diagnosis. A long speleonectid, up to 30 mm in length and bearing up to 40 trunk segments; antenna 1 dorsal ramus with 12 segments, ventral ramus with 10; exopod of antenna 2 with about 58 plumose setae along margin; maxilla 1 segment 2 with 9–10 spines along margin of plate-like medial endite; caudal rami about 5 times length of anal segment.

Description. Body elongate, without eyes or pigment. Maximum length of specimens examined 30 mm. Cephalic shield small, tapered anteriorly, about 1/12th total body length, covering first trunk segment. Trunk elongate; maximum number of trunk segments of material examined 40. Most trunk segments similar, subrectangular, with rounded lateral tergites; posteriormost segments becoming reduced with pointed lateral tergites. Swimming appendages may be lacking on posterior segment. Sternal bars very narrow, isomorphic.

Frontal filaments long, tapering distally, bearing short slender medial process.

Antenna 1 ( Fig.1 B) biramous, slender, short, about 1/6th length of body. Protopod 2-segmented; proximal segment with rows of dense, long ribbon-like aesthetascs; distal segment bifurcate. Dorsal ramus with 11–12 slender segments, most segments with clusters of aesthetascs along medial margin, and small scattered setae; terminal segment with fine terminal setae. Ventral ramus short, slightly less than ½ length of dorsal ramus, 9-10 segments, basal segments weakly divided, clusters of distomedial aesthetascs and short setae on margins; distal segment with terminal setae.

Antenna 2 ( Fig. 1 C) a paddle like biramous appendage. Protopod 2-segmented; proximal segment with 5 medial setae, distal segment with about 14 setae. Endopod curves laterally; segment 1 with 10 setae on outer margin; segment 2 with 6; segment 3 ovoid, bearing about 28 setae along entire margin, including a terminal double row of about 10 setae each. Exopod a single large oval article with about 58 setae along margin. All setae plumose with long plumules.

Labrum ( Fig. 4 A) prominent, bulbous, anterior end subtriangular, posterior end subrectangular and rounded laterally; dense patch of fine, short, ribbon-like setae along posteriomedial margin ( Fig. 4 A). Paragnath ( Fig. 4 B) lies directly under plate-like endite of maxilla 1, segment 2; thick fringe of fine short setae along terminal margin.

Mandibles ( Figs. 1 D, E) well developed; molar process broad, flat, bearing thick, multitipped setules. Left mandible with 4-cusped incisor process and irregular crescent-shaped lacinia mobilis; right mandible with 3- cusped incisor process and 3-cusped lacinia mobilis.

First maxilla ( Fig. 2 A) 7-segmented, uniramous, robust. Segment 1 ( Fig.4 D) a long, slender medial endite with one long, stout, posterior apical spine and 3 pairs of opposing terminal spines, anteriormost serrated, all spines sclerotized; dorsal row of 5 small subterminal spine-like setules and smaller setules basally. Segment 2 ( Fig.4 C) with elongate, plate-like medial endite scattered with setules; posteromedial margin with 9 to 10 spines, anteriormost serrate; spines flanked dorsally with row of long spine-like setae and short aesthetascs; anterolateral margin with at least 10 moderately long setae interspersed with many small setules; cluster of 4 moderately long posterobasal setae. Segment 3 with well-developed conical medial endite bearing 2 robust, broad-based, sclerotized cone setae, each with tiny papilla-like projections on distomedial surface; row of about 10 anterior setae and short, subterminal posterior row of 6–8 setae of assorted lengths; anterior setae longer and more robust than posterior setae. Segment 4 robust, bearing well developed conical medial endite with 2 large cone setae as on segment 3; row of about 12 long anterior setae, short row of 10 long to short posterior setae; point of flexion between segments 4 and 5. Segment 5 shorter, slightly less robust than segment 4; cluster or short row of about 8 anterior and posterior long distomedial setae. Segment 6 very short with rows of anterior and posterior distolateral and distomedial simple setae, about 12 setae each. Segment 7 short, terminating in stout fanglike claw with visible duct, slightly over 1 ½ times the length of segment 6; a cluster of about 12 long simple setae basal to fang.

Second maxilla ( Fig. 2 C) 7-segmented, uniramous, longer that maxilla 1; oblique angle between segment 1 and 2; point of flexure between segments 3 and 4; segments 4–7 decreasing in size distally. Segment 1 with 3 digitiform endites ( Figs. 2 D, 5A) increasing in size anteriorly; all endites with 1 long apical spine-like seta, several subterminal, short, spine-like medial setae and aesthetascs; cluster of basal setae and several long robust dorsal setae. Surface of endites with scattered tiny pores and setules. Segment 2 short, slightly enlarged medially bearing 1 short, stout, curved medial spine, with long row of about 8 anterior setae and short row or cluster of about 7 short to moderately long thin posterior setae. Segment 3 elongate, rounded medially with long anterior row of about 15 long setae and shorter posterior row of about 10 short to long setae. Segment 4 slightly shorter than segment 3, with small distomedial lobe terminating in clusters of anterior and posterior distomedial short to very long, thin setae and small cluster of anterior and posterior distolateral short setae. Segment 5 shorter than segment 4 with same configuration of setae. Segment 6 bearing short rows or clusters of anterior and posterior distomedial and distolateral moderately long setae; 4–5 setae on medial margin. Segment 7 ( Fig. 2 B) very short, with terminal claw complex consisting of fused arch of at least 17 denticles and 1 long, stout anterior spine; 1 short, stout anterior spine subterminal to fused arch; opposable thumb-like pad bearing many (at least 40) aesthetascs which fan under claw complex.

Maxilliped ( Fig. 1 A) 9-segmented, similar in shape but longer than maxilla 2 with 1 more segment beyond point of flexure which is between segments 4 and 5. Segments 1 and 2 short, indistinctly articulated, with slightly developed medial lobes bearing 3–6 moderately long anterior setae and cluster of several short posterior setae. Segment 3 longer than segments 1 and 2, developed into slight lobes distomedially; anterior with long row of about 15 short to long setae; posterior with short row of about 10 short to moderately long setae. Segment 4 rounded medially, longer than segment 3, with long anterior row of about 16 long setae and short posterior row of about 10 short to long setae. Segment 5 with small distomedial lobe bearing clusters of about 10 very long anterior and posterior setae; several distolateral short setae. Segment 6 with slightly less defined distomedial lobe; 2 clusters of anterior and posterior distomedial setae, some very long; short row of several setae along distomedial surface; several distolateral short setae. Segment 7 with clusters of many fine, very long anterior and posterior distomedial setae, and clusters of about 8 short distolateral setae. Segment 8 with many rows of anterior and posterior distolateral and distomedial long setae; row of about setae on distomedial margin. Segment 9 ( Fig. 5 B) similar to claw complex on maxilla 2, with stout anterior spine subterminal to arched claw complex; opposable pad.

Trunk limbs ( Fig. 3 B) biramous, natatory, with large protopod, 4-segmented endopod and 3-segmented exopod; exopod slightly longer than endopod; long plumose setae along margins; setation varies with limbs (see Table 3 ). Trunk limb 7 bears circular female gonopore on posterior side of protopod. Trunk limb 14 bears male gonopore as a lobular projection ventral to triangular cuticular projection at base of protopod. Caudal rami ( Fig. 3 A) very slender, about 5 times length of anal segment with scattered setules and small terminal setae.

Observations. Clusters of unidentified small, dark spherical objects are visible on the interior of the protopod of all trunk appendages as well as on the lateral tergites. Certain features of the dissected specimen were slightly asymmetrical. For example, the right antenna 1 had one less segment on both rami than on the left; segment 2 of the first maxilla had 9 spines on the right and 10 on the left. The ventral ramus of antenna 1 on the smaller specimens tends to have fewer segments than larger specimens.

Morphological comparisons. Some of the key characters used for defining species of Speleonectes include:

Number of trunk segments and total length

Antenna 1 number of segments on dorsal and ventral rami Antenna 2 number of long, plumose setae on exopod

Maxilla 1, segment 2, number of spines on terminus of plate-like endite Maxilla 2, number of denticles on arch of terminal claw complex Ratio of caudal rami length to anal segment length

Comparisons (see Table 1 ) of S. cokei are made with specimens of S. tulumensis and S. fuchscockburni . These two species were chosen because they are similar in morphology and their type localities are from the southeastern coast of the Yucatan Peninsula. All specimens of S. tulumensis compared were from Carwash Cenote, the type locality. The author examined morphological aspects of 47 specimens of S. tulumensis and four S. cokei specimens from Caye Chapel Cave. One specimen of S. fuchscockburni was examined by the author and several characters were taken from the species description. Speleonectes cokei is very similar in morphology to S. tulumensis . However, S. cokei is a slightly more elongate species, with more trunk segments per mm (see Table 2).

The only other species of Speleonectes with a large number of trunk segments and long length is S. tanumekes Koenemann et al., 2003 . However, S. tanumekes differs from S. cokei in number of antenna 2 exopod setae (28) and number of antenna 1 segments (13 dorsal and 7–8 ventral). In addition, the two species are separated by a large geographical distance. Speleonectes benjamini Yager, 1987 a is the only other species with nearly identical setae on the exopod of antenna 2. However, S. benjamini is an enigmatic species with many characters that differ from other species in the genus Speleonectes .

In addition, most trunk limbs of S. cokei are more setose than those of S. tulumensis , having more plumose and comb setae (see Table 3 .)

Habitat. Caye Chapel Cave begins at a depth of about 3.4 m in the middle of coral ribbon reef flats directly offshore of Caye Chapel. The entrance hole is about one meter in diameter. The cave has the typical inflow and excurrent of ocean blueholes. From the entrance, there is a direct descent into the cave to the top of old breakdown. The cave continues in a north and south direction and seems to be somewhat fracture controlled, with an arching ceiling. To the south the cave goes to a depth of over 27 m and descends on top of breakdown. This section of the cave is highly decorated with stalactites. The breakdown zone has fine silt on the floor and ceiling. A small solution tube continues, changing direction towards the Caye. Exploration was abandoned at the point where the tube became too small. No water chemistry data is available and no information about other fauna is known. The remipedes were collected from a depth of about 30 m and a distance of about 91 m from the surface entrance (Jim Coke, pers. comm.).

Additional remipedes were observed in Giant Cave, located underneath Caye Caulker, about 2 km north of Caye Chapel (Jim Coke, pers. comm.).

The discovery of a new species of remipede off the coast of Belize is not unexpected. Belize is the southernmost section of the eastern side of the Yucatan Peninsula, a huge limestone area home to many submerged caves or cenotes. Several ocean blueholes have been documented off the coast of Belize but little is known about the presence of submerged caves on the mainland. Exploration of the anchialine caves and blueholes of Belize will no doubt yield many new stygobiont species.

Figures

FIGURE 1. Speleonectes cokei n. sp. A. Maxilliped. B. Antenna 1. C. Antenna 2. D. Left mandible. E. Right mandible.

FIGURE 2. Speleonectes cokei n. sp. A. Maxilla 1. B. Claw complex on terminus of maxilla 2. C. Maxilla 2. D. Endite on segment 1, maxilla 2.

FIGURE 3. Speleonectes cokei n. sp. A. Anal segment. B. Trunk appendage 14. C. Comb seta on trunk appendages.

FIGURE 4. Speleonectes cokei n. sp. A. Setose mouth area. B. Paragnath with setose fringe. C. Maxilla 1, segment 2. D. Maxilla 1, segment 1.

FIGURE 5. Speleonectes cokei n. sp. Left. Maxilla 2, medial endite of segment 1; Right. Claw complex at terminus of maxilliped.

Tables

TABLE 3. Comparison of setation patterns in trunk limbs of S. cokei and S. tulumensis. (p = plumose setae; c = comb setae).

Trunk Limbs (TL)	S. cokei	S. tulumensis
TL1 Exopod	Lateral Medial	Lateral Medial
Segment 1	9 p + 4 c 0	1 0
Segment 2	9 p + 5 c 8 p + 2 c	1 p + 1 c 1 p
Segment 3	13 p 11 p	6 p 6 p
TL 14 Exopod
Segment 1	5 p + 7 c 0	6 p + 4 c 0
Segment 2	10 p + 15 c 10 p + 1 c	10 p + 10 c 7 p
Segment 3	17 p 15 p	18 p 15 p

TABLE 1. Morphological comparisons among three species of Speleonectes.

S. cokei	S. tulumensis	S. fuchscockburni
Antenna 1, dorsal ramus segments 12	11	11–12
Antenna 2, exopod setal count 58	32	17
Maxilla 1, segment 2, spines on plate-like 9–10	6–8	9?
Maxilla 2, denticles on claw complex 17	16	10–12
Caudal rami to anal segment length 5x	4x	3x