Batillipes chandrayaani Vishnudattan & Rubal & Nandan 2024, sp. nov.
Creators: name: Vishnudattan, N. K.
name: Rubal, Marcos
name: Nandan, S. Bijoy
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Tardigrada
Heterotardigrada
Arthrotardigrada
Batillipedidae
Batillipes
Batillipes chandrayaani

description: Batillipes chandrayaani sp. nov. Vishnudattan, Rubal & Bijoy Nandan
(Figs. 2–6, Table 1)
Diagnosis. Batillipes species of medium size with trapezoid shaped head bearing a pair of tube-like unconstricted primary clavae and distinct secondary clavae. All the cephalic cirri are sharp tipped at the distal end. Cirrophore of the primary clavae and lateral cirri are separated from the external cirri by an indentation. Lateral region of the head consists of a semi-circular cuticular body projection. Eight segmented dorsal body cuticle, while ventral cuticle is slightly sculptured. All legs contain sensory spines on dorsal region. Long leg IV sensory organ with a van der Land’s organ at the upper mid region and another one proximal to the distal tip. Single pair of lateral body projections found between all pair of legs. Lateral body projection on the caudal segment is longer, hook-shaped and posteriorly oriented. Short “V” shaped caudal spike attached directly on the caudal base. Semi-circular cuticular projection present ventrally on the coxal region of leg II and leg III. On leg IV, toes 3 and 4 are the shortest in which toe 4> toe 3.
Materials examined. Holotype: MB /SBN/VD19: adult female mounted in glycerol.
Paratypes: MB /SBN/VD20-24: glycerol mounted five adult females; MB /SBN/VD25-28: glycerol mounted four adult males.
Type locality: Mini Coral Beach, Mandapam, Maraikayar Pattinam, TamilNadu, southeast Indian coast (9°16’18.54”N, 79°7’53.1”E).
Type depositories: Ten glycerol mounted slides containing holotype and paratypes were submitted to the Marine Biology Museum (voucher no: MB /SBN/VD19-28), of the Department of Marine Biology, Microbiology and Biochemistry, Cochin University of Science and Technology (CUSAT), Fine Arts Avenue, Cochin-682016, Kerala, India
Description of holotype. Adult female has a body length of 147.3 μm and a body width of 41.5 μm between the third and fourth leg pairs (Figs. 2, 3, Table 1). Translucent dorsal body cuticle is divided into eight segments by seven cuticular folds between the first and last pair of legs. The 7 th cuticular fold present anterior to the caudal base is comparatively small (Figs. 2, 4A).
Fine punctations are more evident on the dorsal cuticle while the ventral cuticle is slightly sculptured (Fig. 4B). Trapezoid shaped head with a width of 41.7 μm bearing a normal number of cephalic appendages (Fig. 5A). At their distal end, all cephalic cirri have sharp tips. Neck constriction is absent between body and cephalic region. Internal cirri (21.6 μm) arise from cirrophores (2.4 μm) which are attached on the anterior rim of the cephalic region. Unpaired median cirrus (13.3 μm) arises form a cirrophore which is attached on the anterior-mid cephalic region. External cirri bearing distinct cirrophores (2.2 μm) are 10.5 μm long. Primary clava of 10.2 μm length is unconstricted and tubular in shape with blunt end (Fig. 5A). Lateral cirri (28.7 μm) and primary clava arise from a common pedestal. The cirrophore of the lateral cirri and primary clavae are separated from the cirrophore of the external cirri by an indentation (Fig. 5A). Distinct secondary clava (2.1 μm) is present between the external and internal cirri (Fig. 5A). Eye spots are absent. Conical mouth with a circular opening of 4.2 μm width (Fig. 5D). Pharyngeal bulb is circular with a diameter of 19.5 μm and found 15.3 μm posterior to the anterior cephalic rim. Buccal tube with a length of 20.2 μm and stylets of 23.1 μm were visible. Placoids were not clearly visible in the holotype.
Four pair of conspicuous dorso-lateral body projections are present. A blunt, transparent lateral body projection of 7.1 μm length is present between the head and first pair of legs. A sharp cone shaped lateral body projection of 8.4 μm length is found between first and second pair of legs. A blunt lateral body projection (5.1 μm), with a bend towards anterior region is present between second and third pair of legs. In between the third and fourth pair of legs, a posterior facing hook-shaped lateral body projection of 18.3 μm length is present. Except for the caudal lateral body projection (bp 4), all the body projections (bp 1–3) are lined by a thin transparent cuticle at its margin (Figs. 2, 3B). A semi-circular cuticular projection is present ventrally at the coxal region of leg II and leg III (Fig. 4B)
Sensory spines of varying length (9.3–20.4 μm) are present dorsally on each leg. All the sensory spines on leg I-III are sharp tipped at their distal end. Leg IV sensory organ is 20.4 μm long with a lance like tip and possess a van der Land’s organ in the upper mid region and another one proximal to the distal tip (Fig. 5B). Long, pointed Cirri E are attached dorsolaterally between leg IV and the caudal lateral body projections (Fig. 5C).
Toes of varying length are present on each telescopic legs. Toe 2 (6.1 μm) and toe 4 (8.6 μm) are the shortest while toe 3 (14.4 μm) and toe 5 (17.2 μm) are longest among the first three pair of legs. Toe 6 (11.5 μm) is intermediate in length among leg pairs I-III (Figs. 2, 3A, 6C). On the leg IV, toe 3 (10.7 μm) and toe 4 (14.5 μm) are the shortest, while toe 4 is slightly longer than toe 3. Toe 1 (14.4 μm), toe 2 (20.1 μm) and toe 6 (12.5 μm) are of intermediate length while toe 5 (26.1 μm) is the longest. Toe patterns on the fourth pair of legs corresponds to the Subgroup B1 proposed by Santos et al (2018). Ovoid and transparent suction discs are attached on the distally enlarged stalk of toes (Figs. 2, 3A, 6A).
Faintly visible rosette-shaped female gonopore is present above the circular anus (Fig. 4B). A “V” shaped, triangular caudal spike of 13.7 μm length is attached on the caudal base with a lining of transparent cuticular sheet at its margin (Figs. 2, 3).
Remarks. With the exception of males having a circular gonopore, both sexes are very similar in terms of morphology and measurements. Buccal tube, stylet and placoids were clearly visible in a few paratypes (Fig. 6C). A distinct van der Land’s organ was found in the mid region of primary clava among a very few paratypes (Fig. 6B). Considerable intraspecific variations were found in the shape of caudal lateral body projections among a few additional specimens examined (Figs. 6D–H).
Etymology. The specific epithet chandrayaani refers to Chandrayaan-III, the first ever successful lunar south pole landing space mission hosted by Indian Space Research Organisation (ISRO) in 2023.
Differential diagnosis. Batillipes chandrayaani sp. nov. belongs to the subgroup B1 proposed by Santos et al (2018) based on toe patterns of leg IV. This subgroup contains nine described species i.e., B. africanus Morone De lucia, D´Addabbo Gallo and Grimaldi de Zio, 1988, B. brasiliensis Santos, da Rocha, Gomes Jr and Fontoura, 2017, B. dandarae Santos, da Rocha, Gomes Jr and Fontoura, 2017, B. friaufi Riggin, 1962, B. lesteri Kristensen and Mackness, 2000, B. littoralis Renaud-Debyser, 1959, B. similis Schulz, 1955, B. homocercus Bartels and Fontoura, 2021, and B. ichthyocercus Bartels and Fontoura, 2021 (see Santos et al. 2018; Bartels et al. 2021). Batillipes africanus can be easily distinguished from B. chandrayaani sp. nov. by the absence of lateral body projections and cephalic cirri with swollen distal tips (De Lucia et al. 1988) while B. chandrayaani sp. nov. has conspicuous lateral body projections between all pair of legs and all the cephalic cirri are distally sharp-tipped. Batillipes brasiliensis possess lateral body projections with fringed distal edges between leg III and IV, the external cephalic cirri are distally swollen-tipped and also the leg IV sensory organ is very short (7 µm) whereas in the current species, the lateral body projection between leg III and leg IV is long and hook shaped and the leg IV sensory organ is longer (20 µm) (Santos et al. 2017). The absence of lateral body projections in B. dandarae can be differentiated form B. chandrayaani sp. nov. since the later possesses a conspicuous lateral body projection between all pair of legs (Santos et al. 2017).
Batillipes friaufi can be distinguished from B. chandrayaani sp. nov. by the absence of sensory spines on leg I-III, presence of small papillae on caudal segment and trifurcated caudal appendages attached on caudal base (Riggin, 1962) whereas B. chandrayaani sp. nov. has sensory spines on all pair of legs and the caudal appendage is “V’ shaped. The lateral body projections between leg III and IV are two pointed in B. lesteri while B. chandrayaani sp. nov. possess a single long-hook shaped caudal projection. Cephalic cirri are swollen-tipped in B. lesteri while they are sharp-tipped in B. chandrayaani sp. nov. (Kristensen & Mackness, 2000). Batillipes littoralis has a three pointed caudal spike and possess a sharp lateral tooth on leg IV whereas the current species has a “V” shaped caudal spike and sharp lateral teeth are absent on leg IV (Renaud-Debyser, 1959).
Batillipes chandrayaani sp. nov. can be separated from B. similis by the length of the leg IV sensory organ and the shape of primary clavae. The leg IV sensory organ is longer and reach up to the tip of the longest toe of leg IV whereas, in the current species, the leg IV sensory organ reaches only up to the mid-length of toes. The primary clava is drumstick-shaped in B. similis while its tubular in B. chandrayaani sp. nov. (Schulz, 1955). Batillipes homocercus can be distinguished from B. chandrayaani sp. nov. by the lack of ventro-lateral body projections between head and legs I, legs I-II and II-III. Moreover, ventro-lateral body projections between legs III-IV in B. homocercus have triangular bases and a long thick blunt tip turned backwards while ventro-lateral body projections between legs III-IV in B. chandrayaani sp. nov. are posterior facing and hook-shaped. Additionally, the caudal apparatus in B. homocercus is composed of two sharp spines while in B. chandrayaani sp. nov., the caudal apparatus has a robust triangular shape. In Batillipes homocercus, the dorsal cuticle lacks any segmentation while in B. chandrayaani sp. nov. it is segmented (Bartels & Fontoura, 2021). Finally, B. ichthyocercus lacks ventro-lateral body projections between legs I-II and II-III and the projection between legs III-IV is thin and transparent but well-developed, conical with sharp tips while in B. chandrayaani sp. nov. all the ventro-lateral body projections are present and the caudal lateral body projection is posterior facing and hook-shaped. Similar to B. homocercus, the caudal apparatus in B. ichthyocercus is bifurcate in two arced points while in B. chandrayaani sp. nov. the caudal apparatus has a robust triangular shape. In B. ichthyocercus, the dorsal cuticle lacks any segmentation while in B. chandrayaani sp. nov. the dorsal cuticle is segmented (Bartels & Fontoura, 2021).
Finally, B. chandrayaani sp. nov. presents some uncommon morphological features. The dorsal surface of the body is segmented due to the presence of transversal cuticular folds. Among the 39 described species of the genus Batillipes, only seven have segmented cuticles: B. minius Rubal, Veiga, Fontoura and Sousa-Pinto, 2016, B. tubernatis Pollock, 1971 (see Santos et al. 2019) and B. potiguarensis Santos, da Rocha, Gomes Jr. and Fontoura, 2017 have a similar dorsal segmentation. In Batillipes brasilensis transverse cuticle folds were only observed ventrally, maybe due to detritus accumulation on the dorsal side. Both B. roscoffensis Kristensen, 1978 and B. africanus present segmentation on dorsal and ventral sides. Finally, B. gilmartini McGuity, 1969 present incomplete dorsal cuticular folds that result in plate-like structures. Therefore, the presence of cuticular folds is an uncommon but diverse morphological feature in Batillipes. However, this character may be omitted in early studies and re-examination of type material or new individuals may provide new records of this structure (e.g., Santos et al. 2019).
The presence of semi-circular cuticular projections on the coxal region of leg II and leg III is another uncommon morphological feature of B. chandrayaani sp. nov. This kind of projections has been recorded on four of the 39 described species of Batillipes. In B. rotundiculus Rho, Min and Chang, 1999, this kind of projection was present on leg I and leg II while in B. brasiliensis, it was present on leg I, leg II and leg III. In other species such as B. dandarae and B. potiguarensis, a similar lateral projection was observed in the scapular region of leg I. Once again, this character may be omitted in early studies and re-examination of type material or new individuals may provide new records of this structures.
description: Published as part of Vishnudattan, N. K., Rubal, Marcos & Nandan, S. Bijoy, 2024, A new marine tardigrade species (Heterotardigrada: Batillipedidae) from the southeast coast of India, pp. 488-498 in Zootaxa 5446 (4) on pages 490-496, DOI: 10.11646/zootaxa.5446.4.2, http://zenodo.org/record/11102092