Batillipes acuticauda, Menechella, Agustín G., Bulnes, Verónica N. & Cazzaniga, Néstor J., 2015

Menechella, Agustín G., Bulnes, Verónica N. & Cazzaniga, Néstor J., 2015, A new Batillipedidae (Tardigrada, Arthrotardigrada) from Argentina, Zootaxa 4032 (3), pp. 339-344 : 340-343

Batillipes acuticauda n. sp.

( Figure 1 –2, Table 1 )

Diagnosis. Small sized Batillipes without eyespots; caudal apparatus consists of a broad-based spike, sharpening distally, directly inserted on the body surface; lateral processes between legs III and IV flattened, four times longer than wide, extending from short after the insertion of the third pair of legs up to the insertion of cirrus E; cephalic appendages long; spine of leg IV short; cirrus E inserted dorsally to the leg IV; all toes of leg IV of different length.

Type locality. Sandy midlittoral at Monte Hermoso, Buenos Aires Province, Argentina (38°59’33” S 61°15’55” W).

Type series. Holotype: Adult female (In-MACN 39773), in one slide, collected on June 6, 2013 by A. Menechella. Paratypes: Five adult specimens (In-MACN 39774); each specimen in one slide, all collected on June 6, 2013 by A. Menechella.

Other studied material (not in the type series): 48 specimens collected from April to June 2013 at the type locality and preserved as vouchers in our laboratory, A. Menechella leg.

Etymology. The specific name acuticauda is a compound Latin noun meaning “sharp tail”.

Description of the holotype. Body length from the anterior margin to the base of the caudal appendage 91.2 μm; body width between legs III and IV 36.5 μm (40.02 U). Body broaden towards the rear end, hyaline (Fig. 2). Cuticle with small punctuations. Evident constriction between head and body ( Fig. 1 A). All cephalic appendages sharply pointed, with short cirrophori. Medial dorsal cirrus 12.5 μm long (13.71 U), inserted dorsally. Antero-dorsal internal cirrus 15.8 μm long (17.32 U) with an apparent cirrophorus (1.38 μm); antero-ventral external cirrus 8.8 μm (9.65 U). With a small dome-like papilla (secondary clava) between the internal and external cirri. Lateral cirrus (17.3 μm long: 18.97 U) and primary clava (14.5 μm: 15.90 U) originated from the same cirrophorus. Primary clava undivided, cylindrical and smooth, with rounded tips and the van der Land’s body inside its base. Eyespots absent. Buccal tube 9.5 μm long (10.42 U); pharyngeal bulb 11.3 x 10.4 μm (12.39 x 11.40 U). Stylets located on stylets’ supports. Pharyngeal bulb with three placoids.

Small rounded lateral processes between the first three pairs of legs. Lateral processes extending from short after the insertion of leg III up to the insertion of leg IV flattened and elongated (18.3 μm: 20.07 U). Caudal apparatus single, broadly based conical spike (12.7 μm: 13.93 U) sharpening distally ( Fig. 1 C).

The rosette-like female gonopore is situated 6 μm ahead of the anus, with a connecting groove. The anus consists of two enlarged cuticular lobes ( Fig. 1 B). All toes of different length in every leg (leg IV: 2.9, 6.1, 2.1, 6.8, 3.2 and 1.9 μm). Suction discs roughly rectangular (1.82 x 1.25 μm). Leg IV sense organs slender, with a spike-like terminal portion (5.7 μm: 6.25 U). Cirrus E long (14.1 μm: 15.46 U) and slender, located dorsally to the insertion of leg IV.

Size variability of the studied material is shown on Table 1 .

Batillipes acuticauda n. sp. belongs to the species group D defined by Kristensen & Mackness (2000) by having uneven 3rd and 4th toes on leg IV. It differs from most other species of the genus by the caudal apparatus, which is conical and odd.

FIGURE 2. Batillipes acuticauda n. sp. Ventral view of an adult female specimen. Abbreviations: an—anus; bt—buccal tube; cacaudal appendage; cE—cirrus E; ec—external cirrus; go—gonopore; ic—internal cirrus; lc—lateral cirrus; mc—median cirrus; pbpharyngeal bulb; pc—primary clava; pr1-4—lateral processes 1–4; sc—secondary clava; se1-4—leg sense organs 1–4; st—stylet. Scale bar: 50 µm.

Batillipes acuticauda n. sp. differs from B. lesteri by the absence of eyespots; the form of the cephalic cirri (filiform in the new species, with swollen tips in B. lesteri ); the spade-shaped suction discs (ovoid with a conspicuous brace in B. lesteri ); the entirely different caudal apparatus and lateral processes between the legs III and IV.

The spade-shaped suction discs and the body folds behind the legs III of Batillipes acuticauda n. sp. are similar in B. tubernatis , but the latter is about twice the size; it has not either a constriction between the head and body, lateral processes between leg pairs III and IV, or a caudal appendage. In the original description of B. tubernatis, Pollock (1971) described no caudal appendage, but Höfling-Epiphanio (1972), McKirdy (1975) and Cavalcanti-da-Rocha et al. (2009) reported the occurrence of individuals with a pointed caudal appendage. The morphometric data provided by McKirdy (1975) allow to discriminate B. acuticauda n. sp. from B. tubernatis as the caudal apparatus of the former is nearly twice as long than in the caudated B. tubernatis (10.6 U vs 5.9 U).

The last two species of Batillipes that have been described ( B. spinicauda Gallo D’Addabbo et al., 2005 and B. solitarius Jørgensen et al., 2014 ) differ from B. acuticauda n. sp. in the toe-pattern, lateral processes, and caudal appendage.

The conical caudal apparatus of Batillipes acuticauda n. sp. resembles that of B. philippinensis Chang & Rho, 1997 and B. similis Schulz, 1955 (D'Addabbo et al., 1999) . However, while B. similis possesses a prominent wing-shaped lateral body process between legs III and IV, in B. acuticauda n. sp. the fourth lateral process is flattened, elongated, extending from short after the insertion of leg III up to the insertion of cirrus E.

Batillipes philippinensis is characterized by a posterior body expansion, smooth clavae and well developed cephalic appendages like B. acuticauda n. sp. However, the third and fourth toes of the leg IV are of the same length in B. philippinensis ( Kristensen & Mackness, 2000) , the spine of the leg IV is long (20.8 U) ( Chan & Rho, 1997), and the fourth lateral process are represented by a protuberance on each side. B. acuticauda n. sp. differs from B. philippinensis because all the toes of the leg IV are of different length, the spine is short (6.25 U), and the lateral process between legs III and IV is well developed.

Figures

FIGURE 1. Batillipes acuticauda n. sp. (MACN 39773 - Ty): A, anterior body of the holotype (arrow: head-body constriction); B, posterior body of the holotype (arrows indicate the position of the gonopore and anus); C, detail of the caudal appendage. Scale bars A-B-C: 15 µm.

Tables

TABLE 1. Size parameters of Batillipes acuticauda n. sp. (in µm). For paired structures, the measurements were taken on the right appendage. Data are presented as mean ± standard deviation [minimum – maximum]. Final numbers in the last column (n = x) indicate the number of specimens (other than the type series) on which the measurement of each character was possible.

	Holotype Paratypes (n = 5)	Other studied specimens (n = 48)
Body length	91.2 103.5 ± 12.3 [84.6–116.0]	104.6 ± 13.2 [74.6–125.8] n = 48
Median cirrus	12.5 16.1 ± 2.6 [12.6–18.2]	16.5 ± 2.2 [11.8–22.3] n = 30
Internal cirrus	15.8 16.6 ± 2.5 [13.5–19.7]	16.8 ± 1.5 [13.5–21.5] n = 33
External cirrus	8.8 9.8 ± 1.3 [7.6–10.8]	9.6 ± 1.1 [6.6–11.6] n = 34
Lateral cirrus	17.3 23.9 ± 2.5 [19.8–26.2]	22.9 ± 2.7 [15.1–28.5] n = 38
Clava	14.5 15.3 ± 1.3 [13.7–16.8]	14.9 ± 1.3 [11.1–16.7] n = 41
Cirrus E	14.1 11.3 ± 2.4 [8.8–13.7]	11.2 ± 2.6 [6.1–16.4] n = 38
Leg IV spike	5.7 5.9 ± 1.0 [4.3–6.7]	6.1 ± 0.8 [4.0–7.9] n = 44
Caudal spike	12.7 9.7 ± 1.3 [7.9–10.9]	11.0 ± 2.3 [4.9–15.3] n = 47
Discussion