Batillipes solitarius

Jørgensen, Aslak, Boesgaard, Tom M., Møbjerg, Nadja & Kristensen, Reinhardt M., 2014, The tardigrade fauna of Australian marine caves: With descriptions of nine new species of Arthrotardigrada, Zootaxa 3802 (4), pp. 401-443 : 405-408

Description of Batillipes solitarius nov. sp.

Diagnosis. A small-sized Batillipes without eye spots. Long tubular undivided primary clava. Large secondary clava concave lens-shaped. The long cephalic cirri have swollen distal tips with a tuft of additional sensory filaments on the lateral, internal and median cirri. The external cirri also have swollen tips but lack these tufts. Spines on legs I–III without clear cirrophori. Four lateral processes with the second being spinous and the rest blunt. Blunt and indistinct caudal appendage. Digits with oval discs and average sized braces. Digit pattern of the fourth foot show digits III and IV to be of equal length, and smaller than the other digits. The dorsal cuticle is finely punctuated comprising very small pillars.

Type material. A single female specimen [ ZMUC TAR 1284] was collected at 18–20 m depth on 11 January 1999 in Fish Rock Cave in New South Wales, Australia. The type material is deposited at The Natural History Museum of Denmark, University of Copenhagen, Denmark.

Etymology. Only a single specimen was found, hence the name “ solitarius ”.

Description of the holotype. The holotypic female is in the simplex stage without placoids; 124 µm long and with a maximum width of 47 µm between the third and fourth pair of legs (Fig. 1). The stylets and stylet supports are under formation. The head is typically trapezoid with 11 cephalic appendages. The median cirrus is 22 µm long, the internal cirrus 16 µm long and the lateral cirrus 36 µm long, all have swollen tips with a tuft of additional sensory filaments. The external cirrus, also with a swollen tip, is 20 µm long and lacks the tufts. The lateral cirrus is situated in a dorsal position to the primary clava on a shared cirrophore. The tubular primary clava is 24 µm long with a terminal pore and does not have a constriction. The large secondary clava is ca. 13 µm wide and 3 µm high with a concave lens-shaped appearance. Eye spots are absent.

The buccal tube is 14 µm long and the pharyngeal bulb measure 15 x 16 µm. The stylets are ca. 14 µm long; however as the specimen is in the simplex stage neither stylet supports nor placoids could be observed.

The first lateral process between the head and the first pair of legs is 4 µm long and blunt. The second lateral process between the first and second leg pairs is 5 µm long and spinous. Both the third and fourth lateral processes are blunt and 6 µm and 8 µm long, respectively. The caudal appendage is blunt and indistinct protruding ca. 2.5 µm from the body.

The first three pairs of legs have digits, which are respectively 7 µm long (digits 1, 4 and 6), 4 µm long (digit 2) and 11 µm long (digits 3 and 5). The fourth pair of legs has two short ventral digits of equal in length (digits III and IV; 9 µm long), two long lateral digits (digits I and VI; 13 µm long) and two long dorsal digits (digits II and V; 14 µm long). The digits have oval suction discs (2.9 x 2.1 µm) and average-sized braces. The leg sense organs do not resemble the cephalic cirri as they lack the swollen tips and additional sensory tufts. The leg sense organs on legs I–III are simple spines, 6 µm long, and without clear cirrophori. The sense organ on leg IV has a pronounced 6 µm long cirriphorus and a simple spine 14 µm long (leg IV sense organ is broken in the preparation).

The cirrus E is 16 µm long with a small cirrophorus and it is placed dorsal between the lateral process and the fourth leg.

The dorsal cuticle is finely punctuated consisting of very small pillars.

A single dorsal ovary with numerous oocytes is present. The rosette-like female gonopore (ca. 3.5 µm) is situated 10 µm anterior of the anus without a connecting groove. The anus consists of two enlarged lateral cuticular lobes and a small terminal lobe.

Morphometric data of the holotypic female of B. solitarius nov. sp. is presented in Table 2.

Remarks. The unique characters of Batillipes solitarius nov. sp. are the tufts of additional filaments on the median, internal and lateral cirri, and the concave lens-shaped secondary clava. Hallas & Kristensen (1982) described a “star-like array of projections” terminally in the internal and external cirri in Echiniscoides pollocki Hallas & Kristensen, 1982 which superficially resemble the tufts in B. solitarius nov. sp. The digit pattern on leg IV, with digits III and IV being equal in length, groups B. solitarius nov. sp. in the largest group of batillipedids (see Kristensen & Mackness 2000). The swollen tips of the cephalic cirri are only observed in B. solitarius and in another Australian species B. lesteri (see Kristensen & Mackness 2000). In general batillipedids are members of the intertidal fauna, the new species represent a member of the infrequently described subtidal batillipedids. Batillipes similis and two new undescribed species of Batillipes are also present subtidally at the Faroe Bank where they were collected at depths of 104 to 260 m ( Hansen et al. 2001).

FIGURE 1. Drawing of the holotypic female of Batillipes solitarius nov. sp. (ventral view). The specimen is in simplex stage and viewed from the ventral surface. Abbreviations: an—anus; br—brain; bt—buccal tube; ca—caudal ala; cE—cirrus E; di1—6— digits 1–6; ec—external cirrus; ga—ganglion; go—gonopore; ic—internal cirrus: lc—lateral cirrus; mc—median cirrus; mg—midgut; mo—mouth cone; ov—ovary; pc—primary clava; pr1—4—lateral processes 1–4; sc—secondary clava; se1–4—leg sense organs 1–4; st—stylet.