Litarachna bruneiensis, Pešić, Vladimir, Chatterjee, Tapas, Marshall, David J. & Pavićević, Ana, 2011

Pešić, Vladimir, Chatterjee, Tapas, Marshall, David J. & Pavićević, Ana, 2011, New records of water mites (Acari: Hydrachnidia) from Brunei Darussalam, Borneo, with descriptions of two new species, Zootaxa 3018, pp. 50-58 : 55-57

Litarachna bruneiensis sp. nov.

( Fig. 4 )

Type series. Holotype, male, Brunei Darussalam, Kota Batu, Sangai Brunei Estuary and Bay, 4º56'N, 115º1'E, 10.iii.2011, mud flat and mangroves, leg. T. Chatterjee & D. J. Marshall. Paratypes: 7 males, 14 females, 4 deutonymphs, same data as holotype, one male, two females and one deutonymph dissected and slide mounted in Hoyer's fluid.

Diagnosis. The lateral apodemes of Cx-IV shorter than medial apodemes, the latter of moderate length; P-2 ventrally with small triangular extension, P-2 L 70–90 µm in both sexes, ventrodistal angle of P-3 ending in a small pointed tubercle.

Description. Male (holotype, in parentheses measurements of paratype). Idiosoma L/W 306/225 (303–372/ 216–306, n = 3). Cx-I separated medially. Suture lines Cx-I/II and Cx-III/IV complete, suture lines Cx-II/III incomplete. Posterior margin of Cx-IV strongly concave, with two pairs of apodemes; the lateral ones shorter than the medial ones, the latter of moderate length. Genital field L/W 38 (40)/32 (31), consisting of a sclerotized ring with 2–3 setae on each side. Posterior, lateral and anterior reaches of genital field with numerous setae ( Fig. 4A ). A pair of large glandularia-like platelets with one large and two small pores and three pairs of wheel-like acetabula (sensu Cook 1996) or specialized glandularia (sensu Tuzovskij 1978) posterior to genital field. Two of these wheel-like structures large with many radiating spokes, the most posterior small with less radiating spokes. Excretory pore unsclerotized, near the posterior idiosoma margin. Palp ( Fig. 4D ), dL: P-1, 15; P-2, 66 (63); P-3, 34 (35); P-4, 75 (75); P-5, 25 (26); P-2/P-4 L ratio 0.88 (0.84); P-2 with ventrally with small triangular extension, P-3 ventrodistal angle ending in a small pointed projection, P-4 slightly curved and without setal tubercles. Legs: dL of I-Leg-4–6 ( Fig. 4F ): 44 (49), 60 (66), 72 (80); dL of IV-Leg-4–6: 103 (102), 112 (110), 99 (103); III-Leg-4 with 1 swimming seta, III-Leg-5 with 2 swimming setae, IV-Leg-4 with one swimming seta, IV-Leg-5 with 2 swimming setae.

Female (n = 2): similar to male, except for shape of the genital field. Idiosoma L/W 297–309/236–250, n = 3 (ovigerous females: L/W 403–447/328–381, n = 2). Genital field L/W 54–62/43–50), pregenital and postgenital sclerite fused, forming a complete ring around the gonopore ( Fig. 4B ). Palp ( Figs. 4G–H ) dL: P-2, 72; P-3, 34–35; P-4, 76–85; P-5, 25–27; P-2/P-4 L ratio 0.85–0.95; palp setation as in male. Legs: dL of I-Leg-4–6: 45–48, 60–65, 71–75; dL of IV-Leg-4–6: 101–107, 109–117, 102–110; number of swimming setae as in the male.

Deutonymph. General morphology as in adults, but lacking a genital field ( Fig. 4I ). Idiosoma L/W 188–219/ 133–137 (n = 2); palp: dL: P-1, 10; P-2, 39; P-3, 20; P-4, 45; P-5, 18; P-2/P-4 L ratio 0.87; dL of I-Leg-4–6: 26, 35, 45.

Remarks. Litarachna bruneiensis sp. nov. belongs to the L. halei species group which is characterized by the presence of a ventral tubercle on P-2, the absence of ventral tubercle on P- 4 in both sexes and pregenital and postgenital sclerite fused in the female and forming a complete ring around the gonopore. So far, three species of this group are known: Litarachna halei (Womersley, 1937) from South Australia, L. muelleri Smit, 2008 from Malaysia and L. triangularis Smit 2009 from Singapore.

Litarachna halei can be distinguished by very long medial apodemes of Cx-IV and larger dimensions of the palp segments (L P-4, 162 µm in male, 180 µm in female, data taken from Smit 2003). Litarachna muelleri differs in having lateral apodemes of Cx-IV as long as, or slightly shorter than, medial apodemes and with P-2 more stockier ( Smit 2008). Litarachna triangularis , a species known from a single female, differs in distinctly shorter lateral apodemes of Cx-IV and a larger ventral tubercle on P-2 ( Smit 2009). Moreover, Litarachna bruneiensis sp. nov., is characterized by the ventrodistal angle of P-3 ending in a small pointed tubercle, a character illustrated only for L. halei (see: Smit 2003, fig. 21) but not in two other species.

Almost nothing is known of the life history of members of the family Pontarachnidae and the larva (if it exists as a free living stage) and its host (if any) are unknown ( Cook 1996). Two ovigerous females from our material contained a few very large eggs (maximum diameter of slide mounted egg L 213 µm), suggesting the possibility that parasitic larval stage is bypassed.

Etymology. The species is named after the country of the type locality.

Habitat. Marine littoral; specimens of Litarachna bruneiensis were collected from dense Avicennia marina (Forssk.) Vierh. pneumatophore mat (depth about 2 m).

Distribution. Brunei Darussalam; known only from the type locality.

Figures

FIGURE 4 A – I. Litarachna bruneiensis sp. nov. (A, C – F = male, B, G – H = female, I = deutonymph): A – B, I = idiosoma, ventral view; C = gonopore; D = palp; E = ejaculatory complex; F = I-Leg- 5 and - 6; G – H = palp (P- 1 missing). Scale bars = 100 μm.