Cocotanais puravida Esquete, sp. nov.
Creators: name: Esquete, Patricia
name: Sibaja-Cordero, Jeffrey A.
name: Troncoso, Jesús S.
Publisher: name: Zenodo
Year: 2013
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Tanaidacea
Leptocheliidae
Cocotanais
Cocotanais puravida

description: Cocotanais puravida Esquete, sp. nov.
Figures 2–7
Material. Female Holotype, MNCN 20.04/9144, St. 13; Male Allotype, MNCN 20.04/9145 St. 13.. Other paratypes: two males, two females, MNCN 20.04/9146, St. 13; 23 females, St. 4; six females, one male, St. 5; two females, St. 6; eight females, two males, St. 9; ten females, one male, St. 10; 268 females, 69 males, St, 13; one female, St. 14; 53 females, twelve males, St. 17; one male, St. 18; three females, one male, St. 19; four females, two males, St. 20; one female, St. 27. All coll. J.S. Troncoso, April 2010.
Description of female. Holotype (Figure 2 A, B) 2.9 mm long, 7.6 times as long as wide. Cephalothorax subrectangular, 2.2 times as long as wide, 0.7 times as long as pereonites 1–3 together, rostrum smooth, ocular lobes conspicuous, eyes present. Pereonites 1–6 respectively 2.1, 1.5, 1.1, 0.9, 1.0, and 1.1 times as broad as long, first pereonite the shortest, pereonites 2–3 and 6 subequal in length, about twice as long as the first. Pereonites 4–5 slightly longer. Pleonites subequal. Pleotelson semicircular, with one pair of posterodistal setae.
Antennule (Figure 2 C) peduncle of three articles, first article 3.3 times as long as broad, with one proximal penicillate seta, and one medial and one subdistal tufts of penicillate setae, and one long, subdistal simple seta; second article 1.4 times as long as broad, bearing one long, dorsodistal seta and one short, ventrodistal seta; third article four times as long as broad, bearing three long, distal setae and two short, distal setae; flagellum uniarticulate, minute, eccentric, bearing two distal setae and one aesthetasc.
Antenna (Figure 2 D) of six articles, proximal article about as long as broad, widening distally, naked; second article 1.5 times as long as broad, bearing one dorsodistal seta and one ventrodistal spine; third article 1.1 times as long as broad, with one dorsodistal spine; fourth article the longest, 5 times as long as broad, bearing four subdistal setae: fifth article 2.7 times as long as broad, bearing two distal setae; sixth article minute, bearing long, distal setae.
Labrum (Figure 3 A) ovate, setulose. Left mandible (Figure 3 B) pars incisiva with proximal and distal crenulations, lacinia mobilis large, wider distally, crenulate, pars molaris with tooth-like protrusions. Right mandible (Figure 3 C) pars incisiva crenulated and distally bifid, pars molaris similar to that of left mandible. Labium (Figure 3 D) setulose, without palp. Maxillule (Figure 3 E) with ten distal spines, and one dorsal seta, palp with two distal plumose setae. Maxilliped (Figure 3 F) endite distal margin setulose on distal and outer margin, with one outer spinulose seta and two flat spines, one subdistal triangular flat spine, inner margin with two coupling hooks; basis with two long setae; palp first article naked, second article with three distal inner setae, third article with seven inner setae, terminal article with one subdistal and four terminal setae.
Cheliped (Figure 3 G–J) basis naked, 1.6 times as long as broad; merus ovate, longer than half of carpus, with two ventral setae; carpus 1.9 times as long as broad, with four ventral and one dorsal setae; chela fixed finger with two ventral and three outer setae, cutting edge crenulate, palm with one outer seta, subdistal triangular apophysis, and inner row of three pectinate spines and eleven setules near the articulation with dactylus; dactylus naked.
Pereopods 1–4 with oostegites. Pereopod 1 (Figure 4 A) coxa bearing one seta; basis slender, four times as long as broad, with two dorsoproximal setae, longer than width of basis; ischium bearing one seta: merus subtriangular, naked; carpus as long as merus, bearing one ventrodistal and two dorsodistal setae; propodus as long as carpus and propodus together, bearing one ventral and three dorsal, subdistal setae, and one dorsodistal spinule; dactylus slender, unguis longer, dactylus and unguis together about as long as propodus
Pereopod 2 (Figure 4 B) basis cylindrical, 3.3 times as long as broad, bearing two dorsomedial penicillate setae and one ventral seta; ischium bearing one ventral seta; merus subtriangular, naked; carpus as long as merus, bearing ventral and dorsal distal setae; propodus about as long as merus and carpus together, bearing one ventral short seta, two dorsal setae, and one dorsal distal spinule; dactylus and unguis 0.3 times as long as propodus.
Pereopod 3 similar to pereopod 2.
Pereopod 4 (Figure 4 C) basis swollen, twice as long as broad, bearing two ventral plumose setae; ischium with two ventral setae; merus and carpus together 0.8 times as long as basis; merus subtriangular, with two inferodistal spines, each bearing a fine setule; carpus 2.5 times as long as wide, bearing three spines; propodus about as long as carpus, bearing two ventral serrulate spines, two dorsal spinules and one dorsodistal seta; dactylus strongly curved, unguis about 1/5 of the length of the dactylus.
Pereopod 5 as pereopod 4.
Pereopod 6 (Figure 4 D) basis swollen, twice as long as broad, naked; ischium with one ventral seta; merus and carpus together 0.7 times as long as basis; merus with two ventral short spines; carpus with three ventral spines, each bearing a fine setule; propodus 0.7 times as long as merus and carpus together, bearing one pair of ventral serrulate spines, one dorsal spinule and one stule, and three dorsodistal setae; dactylus and unguis fused into a claw, curved.
Pleopods (Figure 4 E) all alike, with single simple outer seta on basis. One inner plumose seta on endopod. Outer margin of endopod and exopod each with row of plumose setae.
Uropod (Figure 4 F) biramous, basis naked; exopod of one segment, about 2.5 times as long as broad, bearing three terminal setae; endopod of four segments, first segment naked, segments 2–4 bearing terminal setae.
Description of male. Allotype (Figure 5 A, B) 2.4 mm long, 5.5 times as long as broad. Cephalothorax subtriangular, narrowed at base, 1.4 times as long as broad, 1.3 times as long as pereonites 1–3, frontal margin forming a rhomboidal rostrum; ocular lobes triangular; eyes present. Pereonites 1–6 respectively 4.1, 1.8, 1.8, 1.3, 1.3, 1.7 times as broad as long. Pleonites subequal. Pleotelson semicircular, bearing one pair of terminal setae.
Antennule (Figure 5 C) first peduncle article 4.2 times as long as broad, bearing one subdistal seta; second article 0.5 times as long as first, bearing one subdistal seta; third article 0.5 times as long as previous, bearing two terminal setae; flagellum of five segments; first segment about as long as third peduncular article, bearing proximal and distal rows of six and three aesthetascs respectively; second and third segmenta subequal, about half as long as first, bearing distal row of six aesthetascs; fourth segment minute, bearing a single, broad aesthetasc; last segment minute, eccentric, bearing terminal setae, one as long as the flagellum.
Antenna (Figure 5 D) of six articles; first article naked, about as long as broad; second and third subequal in length, about twice as long as first, second article bearing dorsal and ventral robust setae, third article bearing a ventral robust seta; fourth article about as long as articles 1.3 together, bearing subterminal setae; fifth article 0.3 times as long as previous; terminal article minute, bearing long distal setae.
Mouthparts atrophied.
Cheliped (Figure 6) forcipate; basis about as long as broad, naked, inner face with a medial distal, rounded tubercle; merus modified, oblique, shorter than half of carpus, with one seta on inner face and one seta on outer; carpus 0.9 times as long as broad, ventrally with carpal flanges, overlapped to accommodate the fixed finger, inner flange bearing two setae; propodus palm 1.8 times as long as broad, with distoventral triangular apophysis, inner face bearing a row of pectinate spines near articulation with dactylus, outer face with rounded spur and one seta, fixed finger distally angled, 0.8 times as long as palm, bearing 4 setae; dactylus 1.1 times as long as palm, with two ventral spinules.
Pereopod 1 (Figure 7 A) slender; basis cylindrical, 5.3 times as long as broad, naked; ischium with one ventral seta; merus subtriangular, about twice as long as broad, naked; carpus cylindrical, 2.2 times as long as broad, bearing subdistal setae; propodus slender, 0.8 times as long as merus and carpus together, bearing ventrally one subdistal seta, dorsally one pair of long, straight, subdistal setae and one distal spinule, dorsal surface with fine setules; dactylus with unguis together 0.7 times as long as propodus, unguis bearing a setule.
Pereopod 2 (Figure 7 B) basis 4.4 times as long as broad, with two dorsal penicillate setae; ischium bearing one ventral seta; merus subtriangular, 0.3 times as long as basis, naked; carpus 1.1 times as long as merus, bearing subdistal setae And dorsodistal spinule; propodus 0.8 times as long as merus and carpus together, ventrally with one subterminal spine, dorsally with one pair of long, straight setae, one short seta and one terminal spine; dactylus curved, dactylus and unguis about half of length of propodus.
Pereopod 3 as pereopod 2
Pereopods 4–6 alike (Figure 6 C, D); basis swollen, twice as long as broad, naked; ischium with one ventral seta; merus subtriangular, with two ventral, subterminal spines, one stouter; carpus 1.4 times as long as merus, bearing three ventral, terminal compound spines, one stouter, and dorsal terminal setae; propodus 1.2 times as long as carpus, with two ventral, subterminal spines and three dorsal, terminal slender spines; dactylus and unguis 0.6 times as long as propodus, unguis bearing a setule.
Pleopods as in female.
Uropods as in female.
Etymology. “Pura vida” is a common idiomatic expression in Costa Rica, literally meaning in Spanish “pure life”, used there for greeting, saying goodbye, expressing admiration towards a situation, object or person, or simply for expressing well being (Stewart, 2005). Noun in apposition.
Remarks. The present taxon exhibits the general characters of the subfamily Leptocheliinae according to Larsen & Wilson (2002) and the revised diagnoses provided by Bamber (2013). Cocotanais shows affinities with the leptocheliid genera Heterotanais and Pseudonototanais, the principal and most obvious common character being a robust, markedly forcipate male cheliped (as defined by Bird & Holdich, 1989 and Bird & Larsen, 2009) with carpal flanges or shields. Heterotanais is currently included in the subfamily Heterotanaidinae Larsen & Wilson, 2002, mainly owing to the three-articled female antennule and maxilliped endite with two flat spines (Larsen & Wilson, 2002). Nevertheless, Leptocheliinae Lang, 1973 includes the same characters, and the validity of the former is hence under discussion (see Bird & Larsen, 2009; Bamber, 2013). Specimens from ICNP do not share these characters and show more affinities with Leptocheliinae sensu Bird & Larsen (2009) and Bamber (2013). On the other hand, phylogenetic analyses indicate that Pseudonototanais is not monophyletic (Bird & Larsen, 2009); furthermore, males are only described for the type species, Pseudonototanais werthi (Vanhöffen, 1914). This species has been redescribed by Shiino (1978) and Sieg (1980), the latter based on the type material, although both redescriptions show clear differences.
Guţu (2012) recently revised the diagnosis of Pseudonotanais, adding a subgenus P. (Makassaritanais) Guţu, 2012 and two new species, but his diagnosis includes a number of characters that do not correspond with previous illustrations and descriptions of the type species, P. werthi, nor the original diagnosis of the genus given by Lang (1973) (e.g., number of spines on maxilliped endite; number of distal spines on maxillule; basis, merus and carpus of male similar to that of female, inter alia). Consequently, his revision cannot be considered sound, and both the species described by Guţu (op. cit.) and the genus Pseudonototanais itself need to be reassessed. In this scenario, and owing to a number of consistent differences with the aforementioned species, we include the species found in ICNP in a new genus.
The cheliped of Heterotanais differs from that of Cocotanais because it has carpal apophyses directed forward rather than a carpal flange, and lacks a claw on the fixed finger. Additionally in Heterotanais, the male cephalothorax straightens markedly towards the front, the bases of pereopods 4–6 are cylindrical rather than swollen, the female antennule lacks a flagellum, and the maxilliped basis bears only one seta. The cheliped of Pseudonototanais has carpal flanges, and the ornamentation of the maxilliped endite and basis is similar, but the male antennule has only two peduncular articles, the first pereopod basis is notably curved (nearly straight in Cocotanais) and the bases of pereopods 4–6 are not swollen. The male cheliped of P. (Makassaritanais) has no remarkable features on the merus or carpus, and the cutting edge of the fixed finger is notably sinuose, and might be analogous rather than homologous. In addition, the first pereopod basis is curved, the female maxilliped basis has three setae, and the mandibular molar has spinules (absent in Cocotanais, which have tooth-like protrusions). Females of C. puravida also resemble Mesotanais, especially in the ornamentation of the maxilliped endite and basis, but differ in the lack of visual elements, absence of cap-like segment on the antennule, absence of a ventral spine on second article of the antenna, and a cylindrical basis of the posterior pereopods in Mesotanais.
Habitat and ecology. The species had a mean density of 67±5 ind./m2, and occurred in 13 of the 27 stations, with total abundance of 563 individuals (Fig. 1). The overall male/female ratio was 0.26, with an average of 0.28 ±0.13 per sampling site (having omitted those sites where one of the genders was absent).
The species increased in abundance within its depth range (8 to 42 m). The sediment in these stations had an average of 92% sand, 6% gravel and 2% silt + clay, with 2.6% of organic matter (by combustion), and 77% of carbonates (by the back titration method). Two peaks of abundance (337 and 96 individuals, respectively) were found at 300 and 700 µm mean grain size, in poorly sorted, slightly gravelly or gravelly sand. Detailed information on sediment characteristics can be found in Sibaja-Cordero et al. (2012b).
Cocotanais puravida was found free-living in the sediment, but several specimens were found as commensals in the mucus tube of anemones (Infraorder Boloceroidaria), that unfortunately cannot be identified to species level until the scarcely studied taxonomy of the group in the eastern tropical Pacific is solved. A total of 97 individuals (52 females, 42 males) was found inside anemones (see table 1). Also associated with the tubes containing tanaids was the predatory hesionid polychaete Podarkeopsis brevipalpa Hartmann-Schröder, 1959. C. puravida occurred at 13 stations; 11 of these stations also contained this group of cnidarians.
description: Published as part of Esquete, Patricia, Sibaja-Cordero, Jeffrey A. & Troncoso, Jesús S., 2013, A new genus and species of Leptocheliidae (Crustacea: Peracarida: Tanaidacea) from Isla del Coco (Costa Rica), pp. 228-242 in Zootaxa 3741 (2) on pages 230-238, DOI: 10.11646/zootaxa.3741.2.2, http://zenodo.org/record/223935