Espeleonaushonia palauensis Alvarez, Villalobos & Iliffe, 2010, sp. nov.
Creators: name: Alvarez, Fernando
name: Villalobos, Jose Luis
name: Iliffe, Thomas M.
Publisher: name: Zenodo
Year: 2010
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Laomediidae
Espeleonaushonia
Espeleonaushonia palauensis

description: Espeleonaushonia palauensis sp. nov.
(Figs. 1–3)
Material examined. Holotype, female, cl 10.0 mm, tl 23.3 mm; 5 December 2007; underwater cave (7°20.32’ N, 134° 31.97 E), depth of ~ 20 m, about 90 m from entrance in almost total darkness, Airai State, Babeldaob Island, Republic of Palau; collected by Marcel Hagendijk; CNCR 25876.
Description. Carapace subcylindrical, 43% of total length, linea thalassinica evident (Figs. 1, 2 a). Rostrum elongate, acute, tip turned upwards, reaching distal margin of antennal peduncle. Base of rostrum with strong spines, turned upwards. In dorsal view, anterior portion of orbit with small spine (Fig. 2 a). Orbital and antennal spines prominent. Dorsal surface of carapace with spines arranged in a median row, and laterally with two pairs of convergent rows: internal one straight, external one becoming organized anterior to cervical groove, slightly curved, ending behind orbit (Fig. 2 a). Lateral surface of carapace, between linea thalassinica and ventral margin, with elongate field of spines starting behind antennal spine, spines decreasing in size posteriorly. Posterior margin of carapace with row of 13 large submarginal spines (Fig. 2 a).
Eyes well developed, with anterior small digitiform projection, superior portion partially covered laterally by orbital spine (Fig. 2 f). Cornea well pigmented, faceted, occupying anterior portion of eye. Eyes visible in dorsal and lateral views (Figs. 1, 2 a).
Abdomen as long as cephalothorax, carinate (Fig. 1). First pleomere the shortest, ventral margin rounded not serrate, with salient dorsal carina; in lateral view dorsal carina ending anteriorly and posteriorly in acute tips, dorsal margin straight. Second pleomere strongly carinate with broadly rounded pleura; in lateral view dorsal carina similar to that of first pleomere with anterior and posterior acute tips. Third pleomere strongly carinate, longer than second, pleura broadly rounded; in lateral view carina rounded without acute endings. Pleomeres 4–6 with low but evident carina, posteroventral angles of pleurae with 2–4 acute teeth; fourth pleomere longer than fifth and sixth.
Telson 1.14 times as long as its maximum width, posterior margin rounded bearing long plumose setae (Fig. 2 b). Posterior half of lateral margins with three strong teeth. Dorsal surface with elevation forming a triangular tooth along median axis close to anterior margin, two low ridges on each side and spines scattered irregularly over posterior portion. Uropods with median ridge, rounded distal margins bearing long plumose setae, and complete, finely serrate, transverse sutures. Both pairs longer than telson and with complete diaerisis, endopod longer than exopod. Lateral margin of endopod with strong acute tooth at level of transverse suture; lateral margin of exopod with 6 teeth.
Antennule with peduncle consisting of three articles; external flagellum with 16 articles, internal one with 14, both with long terminal seta. Antenna with scaphocerite reaching second article of antennular flagellum, lateral margin of scaphocerite with 4 teeth plus one strong distal tooth, distal margin at an oblique angle relative to main body axis, with long plumose setae (Figs. 2 a, 3a). Proximal 5 articles of antenna robust, forming peduncle; in ventral view (Fig. 3 d), coxa with opening of antennal; basis, ischium and merus with 2 strong distal spines, carpus with 3 spines; basis and carpus with few simple long setae along lateral margin; ischium, merus and carpus with few long plumose setae along inner margin. Second article of antennal flagellum elongate (Fig. 3 d).
Mandible with molar and incissor processes fused, forming cavity to receive palp (Fig. 3 c). Incissor process with 8 acute, triangular teeth; molar process with 7 low, blunt teeth. Palp 2-segmented, external margin with plumose seate decreasing in size distally, distal article digitiform, ending in rounded tip.
Maxillule with palp 2-segmented, articles subequal in size, digitiform, with rounded tips; proximal article with few scattered simple setae (Fig. 3 b). Proximal lacinia becoming wider distally, surface with scattered simple setae, distal margin rounded bearing long simple setae on internal portion and strong, thick, spiniform setae on external portion. Posterior lacinia subtrapezoidal, bearing marginal and submarginal long simple setae.
Maxilla with palp 2/3 length of upper lobe of distal endite, distal margin with simple long setae (Fig. 3 e). Distal endite bilobed, upper lobe two times as wide as lower one; upper lobe bordered distally with long plumose setae and proximally with long simple setae as lower lobe. Medial endite digitiform, distal margin with long simple setae. Proximal endite broad, bordered with long simple setae. Scaphognathite approximately 3 times as long as wide; anterior lobe subrectangular, margin with long plumose setae decreasing in size posteriorly; posterior lobe tapering distally, distal margin truncate bearing 8 very long simple setae; internal margin forming a triangular projection bearing minute teeth.
First maxilliped with basipod subrectangular, surface with a median row of simple setae, gnathal margin divided in two endites, ornamented with long plumose setae increasing in size distally (Fig. 3 f). Distal endite oval shaped with marginal and submarginal long thin setae, shorter than endopod. Endopod biarticulated, proximal 2/3 of proximal article narrow, with medial row of short setae; distal article expanding distally into a trapezoidal surface, margin with scattered long simple setae. Exopod with basal article elongate, distal margin rounded, expanded to form an evident caridean lobe bearing long plumose setae; second article elongate, narrow, with few scattered short setae; distal articles with long setae. Epipod with upper lobe oval shaped, margin with minute teeth irregularly placed, lower lobe shorter, ending in truncate margin with series of minute teeth; surface with scattered minute spines. Well developed podobranch present.
Second maxilliped with endopod 5-segmented (Fig. 3 g); ischium short, with few long plumose setae, merus the longest article, with inner row of short setae and external row of long simple setae; carpus and merus shorter than dactylus, with scattered setae; dactylus with distal margin rounded, bearing marginal and submarginal long, thin setae. Exopod with long and robust basal article, with scattered short setae and row of long thin setae along inner margin; second article subrectangular, ¼ length of first one; distal articles with long setae. Epipod triangular, lower margins formed by minute teeth. Large podobranch present.
Third maxilliped pediform, with endopod 5-segmented (Fig. 2 d); ischium with internal margin produced into a border with large, strong teeth, one row of short setae, one row of large simple setae next to row of minute spines. Merus with two longitudinal rows of strong acute teeth; carpus and propodus simple, with scattered long setae. Dactylus elongate, digitiform, with dense comb-like internal row of short setae, with scattered long setae elsewhere. Exopod with basal article long and slender, with scattered setae; second article simple, distal articles bearing long setae. Epipod subtriangular, margin bordered with teeth of varying sizes. Podobranch present.
First pereopod strong, subchelate; right pereopod missing (Fig. 1). Ischium simple, about ½ merus length. Merus becoming wider distally, distal portion with scattered large teeth (Fig. 2 c). Carpus short, with 2 large teeth along distal margin. Propodus 1.4 times as long as merus, 2 times as long as wide; dorsal margin with fine row of blunt tubercles along carina, and row of small spines along external portion; external margin with irregularly spaced teeth, increasing in size distally; internal margin with strong triangular projection, proximal portion oblique to longitudinal axis of article, with 2 strong teeth and ending in large strong tooth limiting palmar border, distal portion with 12 small teeth, one large tooth and 8 small teeth. Dactylus curved, more than ¾ length of propodus, ending distally in acute tip, with short setae along internal margin and long setae along external margin.
Second pair of pereopods short and simple, not reaching distal portion of merus of first pereopod (Figs. 1, 2 e). Merus the longest article, about as long as ischium, carpus and propodus combined. Dactylus short, densely covered with setae along external margin, internal margin finely serrate.
Third to fifth pairs of pereopods simple and similar in shape and length, third pair the longest (Fig. 2 e). Third pair with merus the longest article, about 2 times as long as ischium, subequal in length to propodus, 2.6 times length of carpus, 2.2 times length of dactylus; dactylus lanceolate, with row of setae along external margin, proximal half of flexor margin finely serrate. Fourth pair similar to third, differing in having propodus as the longest article, equal in length to that of third pereopod. Fifth pair similar to third and fourth, propodus the longest article, dactylus longer than in third and fourth pairs.
Etymology. The species is named after the Republic of Palau where the single specimen was collected.
Habitat. The underwater cavern where the new shrimp was collected is in the limestone Rock Islands of Palau. This cave opens directly to the sea at the base of a large aerial limestone cliff. Submerged stalactites occur immediately inside the wide entrance and continue throughout the cave. The interior cavern enlarges to 6–9 m in height, while the sediment floor slopes downwards. About 30–45 m inside the cave from the entrance, the fine sediment bottom levels out at about 15–18 m depth, where a chamber-like passage extends further into the island. Past this point, more stalactite masses block nearly all entrance light where the shrimp was found inhabiting fully marine water on the floor of the cavern. There was no evidence of burrows and the shrimp was observed on the open sediment in an area of near total darkness at about 20 m depth. With the exception of a layer of brackish water near the cave ceiling at about 3 m depth, the water in the cave appears to be fully marine. Abundant red mysids inhabit the entrance zone of the cavern.
Remarks. The new species is placed in Espeleonaushonia because of the following characters: exopod of third maxilliped well developed, reaching middle portion of propodus of endopod; first pereopod with scattered spines on dorsal surface of propodus, with spines along mesial and lateral margins; second pereopod short, not chelate, dactylus densely setose; fifth pereopod with simple dactylus, fourth to sixth abdominal pleura with serrate ventrodistal angle; and both rami of uropods completely divided. However, there are differences in the new species that do not agree completely with the diagnosis proposed by Dworschak et al. (2006) namely: the corneal elements of the eyes are not reduced and abdominal pleura 2 and 3 are not ventrally serrate. The reduction of corneal elements as a diagnostic character for the genus is probably not adequate since two of the three species in the genus, E. manningi and E. palauensis, could be considered to have well pigmented eyes.
The new species can be distinguished from the other two species in the genus by: a first pereopod with a propodus that is shorter and wider, and a dactylus that is more than half the length of the propodus; a more spinous carapace with prominent orbital and antennal spines; an acute rostrum reaching beyond the antennular peduncle, with a pair of lateral acute teeth; a distinct dorsal abdominal carina with acute anterior and posterior tips on pleomeres 1 and 2; and a telson which is subequal in length to the uropodal rami.
Regarding the distribution of the species of Espeleonaushonia, E. augudrea occurs in Cuba and E. manningi in the Bahamas; whereas E. paluensis comes from the tropical southwest Pacific. In that large area only one other species of the related genus Naushonia, N. carinata, occurs on the coast of Vietnam and the Philippines. Both genera, Naushonia and Espeleonaushonia, have a cosmopolitan distribution, occurring in the east and west Pacific, the Caribbean and the west Atlantic, and in the Indian Ocean. Worldwide distributions of marine taxa can be explained through a very old origin or through extended larval dispersal. In the case of these two genera, several authors have reported the presence of larvae in areas where no adults have been found (Goy & Provenzano 1979; Konishi 2001) or in open sea at considerable distances from the typical coastal habitat where adults occur (Fernandes & Bonecker 2008). Furthermore, at least two species have potentially large ranges; N. carinata is known from Nha Trang Bay in Vietnam and the Island of Panglao in the Philippines, about 1500 km away (Dworschak et al. 2006); whereas N. lactoalbida was described from Inhaca Island, Moçambique (Berggren 1992) and later reported from Iriomote Island, Japan, about 10000 km away (Komai 2004). Both facts, the widespread presence of larvae and the potentially large ranges of some species, could suggest that the current distribution pattern does not necessarily derives from a very old origin, but rather is the result of modern processes such as larval dispersal.
description: Published as part of Alvarez, Fernando, Villalobos, Jose Luis & Iliffe, Thomas M., 2010, A new species of mud shrimp of the genus Espeleonaushonia Juarrero & Martínez-Iglesias, 1997 (Decapoda: Gebiidea: Laomediidae) from Palau, pp. 61-68 in Zootaxa 2429 on pages 62-67, DOI: 10.5281/zenodo.194703