Copidognathus rhombognathoideus, new, 2006

Bartsch, Ilse, 2006, Copidognathines (Acari: Halacaridae) In Mangroves Of Singapore. I. Description Of Three Species, Raffles Bulletin of Zoology 54 (1), pp. 83-92 : 88-92

Copidognathus rhombognathoideus, new species

( Figs. 21-41)

Material examined. – Holotype. Female, ZRC.ARA.485, Singapore, northern coast, end of Lim Chu Kang Road, coll. I. Bartsch, 7 Oct.2004.

Paratypes. One female, ZRC.ARA.486, collecting data as above; one male, ZRC.ARA.487, collecting data as above; one protonymph, ZRC.ARA.488, collecting data as above; one female, SMF, collecting data as above; one female, ZMH, collecting data as above; one protonymph, one larva, ZMH, collecting data as above .

Diagnosis. – Length of idiosoma 353-414 µm. Dorsal plates with delicate porosity in large hardly raised areolae. OC about twice as long as wide, with two corneae. PD with two pairs of wide porose costae. Epimeral pores large, ovate, their margins smooth. Male GA with seven to eight pairs of pgs. Gnathosoma short, length of rostrum half that of gnathosomal base. Tibiae I to IV with 2, 2, 1, 1 bipectinate setae. Tarsi III and IV with lateral but no medial pas.

Etymology. – The species is characterized by a dark-green gut content and a gnathosoma with a short rostrum, hence, at low magnification (20-25x), it may easily be mistaken for a representative of the genus Rhombognathus . The specific name with the suffix -ides (Greek), Latinized -ideus, refers to this similarity.

Colour. – Content of idiosoma dark, green or grey-green. Idiosoma and legs generally fouled.

Description. – Female: Length of idiosoma 385-414 µm, that of holotype 414 µm, width 264 µm. Porose areolae of dorsal plates hardly raised; areolae with delicate porosity. Length of AD 117 µm, width 135 µm. Posterior margin almost truncate. AD with three wide almost fused areolae ( Fig. 21); anterior third of AD, the porose areola included, as well as paired areolae with delicate porosity. Length of OC 132 µm, width 67 µm. Plate around corneae slightly raised; integument within raised area and along lateral margin of OC porose. No distinct gland pore but small pore canaliculus in lateral margin. Triangular posterior portion of OC extending to the level of insertion of leg III. Length of PD 274 µm, width 197 µm; anteriad extending far between OC. PD with two pairs of porose costae, 20-25 µm wide, and five panels with small foveae. Distinct gland pores lacking. Dorsal idiosomatic setae short; ds-1 on AD, ds-2 within anteromedial margin of OC, ds-3 to ds-5 on PD within lateral margin of medial porose costae, ds-5 immediately anterior to the level of insertion of leg IV; ds-3 to ds-5 situated almost equidistant. Adanal setae close to anal cone.

Integument of ventral plates uniformly porose. Length of AE 127 µm, width 238 µm. Camerostome with lamella. Pair of small, lamellar epimeral processes in medial edge of insertion of leg I. Ventral setae longer than dorsal idiosomatic setae. AE with three pairs of setae; pair of ovate epimeral pores about 10 µm in length ( Fig. 22). Wall of epimeral porus slightly raised, smooth, without tines ( Fig. 23). Length of PE 224 µm, extending distinctly beyond insertion of leg IV. Length of GA 213 µm, width 157 µm; anterior margin truncate; with three pairs of pgs inserted as illustrated. Length of GO 90 µm, width 60 µm; ovipositor extending beyond GO to the level of anterior pair of pgs. Interval between anterior margin of GA and GO equalling 0.8 times length of GO.

Gnathosoma, rostrum and palps short; length of gnathosoma 112 µm, width 87 µm; its length 0.27 times that of idiosoma. Rostrum triangular in ventral aspect, its length half that of gnathosomal base ( Fig. 24). Palps slender, short, but extending beyond tip of rostrum. P-4 with three basal setae; apically with setula and two spurs. Tectum truncate.

Legs I and II almost equal-sized ( Figs. 25 and 26). Telofemora I and II somewhat longer than these legs’ tibiae; telofemora III and IV shorter than tibiae ( Figs. 27 and 28). Length:height ratio of telofemora I and II 2.2, that of telofemora III and IV 2.3-2.4. Tarsi without fossa membranes. Integument of lateral flanks of basifemora, telofemora and tibiae I and II and those of trochanters, telofemora and tibiae III and IV with porose areolae ( Fig. 29 ). Leg chaetotaxy: leg I, 1, 2, 5, 4, 7, 7; leg II, 1, 2, 4-5, 4, 7, 4; leg III, 1, 2, 2, 3, 5, 4; leg IV, 0, 2, 2, 3, 5, 3. Telofemur I unilaterally with either 3/2 or 3/1 dorsal/ ventral setae. Tibiae I and II each with two wide, conspicuously bipectinate ventromedial setae and one slender, smooth ventral seta; tibiae III and IV each with one bipectinate ventromedial and one long, slender ventral seta. Dorsal and dorsomedial setae of tarsi I and II at almost the same level, dorsolateral seta moved towards tip of tarsus, close to solenidion. Solenidia short, baculiform ( Figs. 30 and 31 ), that of tarsus I 5 µm in length, of tarsus II 7 µm. Tarsus I with short lamelliform famulus. Tarsi III and IV with four ( Fig. 32 ) and three dorsal setae, respectively. Tarsus I with three ventral setae, one level with dorsal seta and two eupathid setae near tip of tarsus, close to pair of doubled pas. Tarsus II with pair of pas singlets, tarsi III and IV with slender lateral pas; medial pas absent.

Paired claws slender, accessory process vestigial. Pecten lacking. Median claw bidentate.

Male: Length of idiosoma 353 µm. Dorsal aspect similar to that of female. Anterior margin of GA wide, truncate, length of plate 179 µm, width 150 µm. Length of GO 62 µm. Distance to anterior margin of GA 1.3 times length of GO. Seven to eight pairs of pgs arranged scatteredly around GO ( Fig. 33 ). Spermatopositor large, length 115 µm, width 86 µm, extending to anterior margin of GA. Genital sclerites with four pairs of sgs, three of them setiform, one spiniform ( Fig. 34 ). With single pair of internal genital acetabula.

Protonymph: Length of idiosoma 329-334 µm. OC and PD distinctly shorter than in adults ( Fig. 35 ). AD with three porose areolae. PD with pair of porose costae, about 25 µm wide, and three longitudinal panels with small foveae. Pair of ds-2 within striated integument. Pairs of ds-3 to ds-5 on PD, ds-3 and ds-4 close together. AE with pair of ovate epimeral pores. PE shorter than in adults, with one dorsal and two ventral setae. Genital plate separated from anal plate ( Fig. 36 ). Primordial genital slit with numerous papillae. Shape and setation of gnathosoma as in adults. Leg chaetotaxy: leg I, 1, 2, 3, 4, 5, 7; leg II, 1, 2, 3, 4, 5, 4; leg III, 1, 1, 2, 3, 5, 4; leg IV, 0, 1+2, 3, 5, 3. Ventromedial seta of tibia III short and slightly bipectinate ( Fig. 37 ). Basalmost seta of tarsus III situated about halfway between segment’s base and fossary seta.

Larva: Length of idiosoma 224 µm. Shape of dorsal plates similar to those of protonymphs ( Fig. 38 ). AE with pair of ovate epimeral pores and two pairs of ventral setae. PE with single seta ( Fig. 39 ). Chaetotaxy of the three pairs of fivesegmented legs: leg I, 1, 1+3, 4, 5, 7; leg II, 1, 1+3, 4, 5, 4; leg III, 1, 1+2, 3, 5, 4. Ventromedial seta of tibiae I and II large and distinctly bipectinate, that seta of tibia III short, slender, though bipectinate. Basalmost seta of tarsus III close to base of segment ( Fig. 40 ).

Variations. – The anterior part of the PD is rather wide in the holotype female but less wide in a paratype female ( Fig. 41 ). Telofemur II mostly bears 3/2 dorsal/ventral setae; in the holotype one ventral seta is lacking .

Remarks. – Copidognathus rhombognathoideus is most similar to C. lutarius Bartsch, 2003 . They share characters such as the ornamentation of the dorsal plates, ovate epimeral pores, very short triangular rostrum and short palps, wide bipectinate setae on the tibiae, single pas on the tarsi III and IV, and dark, green gut content. Distinguishing characters are: the size of the porose areolae on AD (three large, fused areolae in C. rhombognathoideus , three small areolae in C. lutarius ), the shape of the PD (anterior margin truncate in C. rhombognathoideus but ovate in C. lutarius ), the position of the ventral seta on tarsus I (in basal half in C. rhombognathoideus but moved to distal half in C. lutarius ).

Copidognathus balakrishnani Chatterjee, 2000 , a species found amongst green algae in Cochin backwater, Kerala, India ( Chatterjee, 2000), and C. caloglossae Proches, 2002 , from Bayhead Lagoon, Durban Harbour and mangrove forests, KwaZulu-Natal and Inhambane, South Africa and Mozambique (Proches, 2002), have similar short rostra and palps as the two above mentioned species, a PD with four wide porose costae, legs with porose integument, and conspicuously stout bipectinate setae on tibiae I and II. Copidognathus balakrishnani differs from C. lutarius and C. rhombognathoideus in that the PD outside the porose costae is reticulate (with delicate foveae in C. lutarius and C. rhombognathoideus ), there are three panels outside the porose costae (five in C. lutarius and C. rhombognathoideus ), and tarsi III and IV bear two pas (a single one in C. lutarius and C. rhombognathoideus ). The anterior margin of the PD of C. caloglossae is much wider than in the other species, the ds-2 is near the medial corner of the OC instead of in the anteromedial margin as in the other species, and the GA in both female and male is very long compared to the AE.

Copidognathus lutarius and C. rhombognathoideus differ from Copidognathus congeners by the combination of (1) dark, green or grey-green gut content, (2) very short, triangular rostrum and small palps, (3) large ovate epimeral pores with smooth margins, (4) short solenidia, and (5) absence of a medial parambulacral seta on tarsi III and IV. The habitus as well as the collecting data of C. balakrishnani and C. caloglossae demonstrate relationship to C. lutarius and C. rhombognathoideus , but the remarkable colour of the gut content is not mentioned in the descriptions of C. balakrishnani and C. caloglossae ( Chatterjee, 2000; Proches, 2002), the epimeral pores are not mentioned, in neither the text nor the illustrations ( Chatterjee, 2000; Proches, 2002), and according to Chatterjee (2000), tarsi III and IV of C. balakrishnani bear both medial and lateral pas, and, according to Proches (2002: fig. 3G), at least tarsus III of C. caloglossae has both a lateral and medial pas. The similarity in the general shape may be purely accidental, comparable with the overall similarity demonstrated by some species of the Copidognathus tricorneatus -group and Arhodeoporus eclogarius -group ( Bartsch, 1997b), but the four species may also be closely related and form a species group and the postulated differences the result of the somewhat cursory descriptions of C. balakrishnani and C. caloglossae .

Distribution. – Singapore, amongst muddy sediment and algal turf on pneumatophores.

Figures

Figs.29-41. Copidognathus rhombognathoideus, new species:29, basifemur to tarsus I with porose areolae, lateral; 30, tip of tarsus I, lateral, female (medial setae and claw omitted); 31, tarsus II, lateral, female (medial setae and claw omitted); 32, tarsus III, lateral, female (medial fossary seta and claw omitted); 33, genitoanal plate, male; 34, genital opening, male; 35, idiosoma, dorsal, protonymph; 36, idiosoma, ventral, protonymph; 37, tibia and tarsus III, medial, protonymph; 38, idiosoma, dorsal, larva; 39, idiosoma, ventral, larva; 40, tarsus III, lateral, larva (lateral seta and claw in broken line), 41, idiosoma, dorsal, female. Scale line = 50 µm.