Lohmannella sulensis, Bartsch, 2020

Bartsch, Ilse, 2020, Lohmannella (Acari, Halacaridae) from a cold-water coral reef off Norway, description of two new and a list of North Atlantic species, Zootaxa 4722 (3), pp. 277-286 : 281-283

Lohmannella sulensis spec. nov.

( Figs 17–32 )

Material examined. Holotype female, ZMH-A0002059, Sula Ridge, 64°05’N, 8°02’E, 285 m, 31 July 1999, POSEIDON Cruise 254, submersible dive JAGO 20 J; coll. W. Michaelis and T. Pape.

Additional material. Two deutonymphs, both from Sula Ridge, 64°05’N, 8°02’E, 285 m, 31 July 1999, POSEIDON Cruise 254, one from dive JAGO 20J and one from dive 22J1-10; coll. W. Michaelis and T. Pape .

Diagnosis. Length of female 386 µm. Surface of plates without marked ornamentation. AD wide, L:W equalling 1:1.5. PD slightly wider than long; its anterior part wider than posterior half. Length ratio AD:PD about 1:1.2. Gland pores vestigial. Anterior part of GA ovate. GA with at least 48 pgs. Gnathosoma slender, length 0.9 times of that of idiosoma. Rostrum longer than gnathosomal base. Palps slender. Length of P-2 7.2 times the basal width. P-4 slender. Length P-2 equalling 2.6 times that of P-4. Leg I almost as long as idiosoma, leg IV somewhat longer. Tibiae I to IV with 6, 3, 2, 2 bipectinate ventral setae. All tarsi with four dorsal setae and 2, 1, 2, 1 bipectinate ventral setae.

Description. Idiosomal length of holotype female 386 µm, width 310 µm. Integument delicately and uniformly coated with minute papillae, each one less than 1 µm in diameter; no further ornamentation of plates recognizable (mite densely fouled with a biofilm and debris which obscure outline and ornamentation of plates and striated integument). Length of AD 132 µm, width 202 µm, L:W 1:1.5, anterior and posterior margin truncate, lateral margins arched. AD widest about halfway between anterior and posterior margin of AD ( Fig. 17 ). OC rhomboidal, lateral and medial margins parallel; length 101 µm, width 65 µm. Anterior cornea distinct, posterior cornea faintly delimited. Length of PD 165 µm, width 170 µm, median part of anterior margin truncate, corners widely rounded, then converging, plate widest at a distance of 1/3 of length of PD. Length AD:PD 1:1.2. Gland pores vestigial. Pair of ds-1 90 µm long, following setae minute, 3–4 µm long. Setae ds-1 on AD at 0.3. Pairs of ds-2, ds-3 and ds- 4 in striated integument; ds-5 on PD at about 0.5; ds-6 on anal plates immediately adjacent to anal sclerites ( Fig. 17 ).

Length of AE 126 µm, width 310 µm, posterior margin truncate ( Fig. 18 ); plate with three ventral and, at least on one side, with a marginal seta ( Fig. 18 ) (other side with dense fouling). Length of PE 196 µm; PE ending at the level of 0.8 (in relation to length of idiosoma). Dorsally a single seta seen, ventrally three setae. Length of GA 202 µm, width 142 µm; plate in anterior half ovate, lateral margins parallel. Length of GF 65 µm, width 45 µm. Distance from anterior margin of GF to that of GA 1.4 times length of GF. GA with at least 48 pgs (pgs partly obscured by fouling and debris). Each genital sclerite with four subgenital setae, 20–22 µm in length. Genital acetabula internal, small, 5–6 µm in diameter ( Fig. 19 ).

Length of gnathosoma 354 µm, i.e. 0.9 times the length of idiosoma. Length of rostrum 205 µm, i.e. almost 0.6 times the length of gnathosoma ( Fig. 20 ). Length of palps about 284 µm, that of P-1 to P-4 35 µm, 211 µm, 11 µm, and 82 µm, respectively. Length of P-2 7.2 times its basal width. P-2 and P-3 each with dorsal-dorsomedial lamellar projection. P-2 6.0 times longer than P-1 and 2.6 times longer than P-4. P-2 with two dorsal setae, basal seta in basal fifth. P-4 with three setae, two apical ones distinctly separated, and one spur-like seta at 0.4 ( Fig. 21 ); apex with dorsolateral solenidion and a blunt, apically delicately dentate spine (claw), 10 µm in length.

Leg segments cylindrical. Leg I almost as long as idiosoma, leg IV somewhat longer. Trochanters I to IV very short ( Figs 22–25 ). Telofemora I and II slightly longer than tibiae I and II, telofemora III and IV shorter than tibiae. Tarsi I and II shorter than these legs’ telofemora and tibiae, tarsi III and IV longer than the other leg segments. Chaetotaxy of legs I to IV (apical eupathidia and pas of tarsi omitted): leg I, 1, 3, 7, 7, 11, 6; leg II, 1, 3, 6, 7, 10, 5; leg III, 1, 3, 6, 5, 8, 6; leg IV, 1, 2, 5, 5, 7, 5. Genua I to IV with 4, 3, 2, 2 ventral setae; 3, 1, 0, 0 of setae distinctly bipectinate. Tibiae I to IV with 6, 5, 4, 3 ventral setae; 6, 3, 2, 2 of these bipectinate. Tarsi I to IV with 2, 1, 2, 1 bipectinate ventral setae, respectively. All tarsi with four dorsal setae. Solenidion on tarsus I in dorsolateral, that on tarsus II in dorsomedial position. Dorsal setae on tarsi III and IV (from basal to apical) about 65, 35, 50, 45 µm in length; short second seta may represent a solenidion. Tip of tarsus I with a pair of doubled pas, a pair of ventral eupathidia and a single ventral eupathidium ( Fig. 26 ). Apex of tarsus II with single lateral and medial pas and a single ventrolateral and ventromedial eupathidium ( Fig. 27 ). On tarsi III and IV lateral pas singlets, medial pas doublets ( Fig. 28 ). Claws with minute accessory process. Claws not conspicuously slender. Claws on tarsus I about 6 times longer than wide; their length 30 µm, their width in the middle of the claw almost 6 µm.

Idiosomal length of two deutonymphs 286 and 301 µm. AD and PD not as wide as these plates in adults ( Fig. 31 ). Genital plate almost rectangular, with two pairs of pgs, minute sgs and internal genital acetabula ( Fig. 32 ). Gnathosoma slender ( Fig. 29 ), its length 0.8 times that of idiosoma; L:W equalling 2.6:1. Pair of P-1 immediately adjacent, partly indented but not fused ( Fig. 30 ).

Etymology. The name is derived from the name of the locality, the Sula ridge.

Remarks. The most obvious characters of Lohmannella sulensis are: AD 1.5 times wider than long, PD rather short compared to the AD (length AD:PD equalling 1:1.2), gland pores vestigial, gnathosoma almost as long as idiosoma (0.9 times), rostrum and palps slender and length of P-2 about 2.6 times that of P-4, legs long, slender, tibia I with six bipectinate ventral bristles, and tarsus of leg IV with four dorsal setae. None of the presently known North Atlantic species is similar to L. sulensis . Amongst the world-wide spread Lohmannella species three share several characters with L. s ulensis. Lohmannella cygna Bartsch, 1988 has an unusual wide AD and a long and slender gnathosoma, but P-4 is short compared to P-2, tibia I has four pairs of bipectinate setae and tarsus IV three dorsal setae ( Bartsch 1988). In L. fukushimai Imamura, 1968 both gnathosoma, palps and P-4 are strikingly long, but tibia I bears seven bipectinate ventral setae and tarsus IV three dorsal setae ( Imamura 1968; Bartsch 1993). Lohmannella lamellipes Newell, 1984 is another species with a wide AD and long P-4; calculating from the length of the palps, the gnathosoma may equal almost 0.9 times the length of the idiosoma. In contrast to all other Lohmannella species most leg segments of L. lamellipes are not cylindrical but have conspicuous lamellae ( Newell 1984).

Biology. The mode of life is not known but because of its delicate integument, wide plates and long legs, Lohannella sulensis is expected to live in a sheltered habitat below the shelf zone, below a depth of about 200 m.

Figures

FIGURES 17–23. Lohmannella sulensis nov. spec., female, 17, idiosoma, dorsal; 18, idiosoma, ventral; 19, genitoanal plate, female; 20, gnathosoma, lateral; 21, palp, medial; 22, leg I, medial; 23, leg II, medial. (gac, genital acetabula; L-Gn, length of gnathosoma; L-B, length of gnathosomal base; L-Ro, length of rostrum) (Scale bar = 50 µm)

FIGURES 24–32. Lohmannella sulensis nov. spec., 24, leg III, medial, female; 25, leg IV, medial, female; 26, apical part of tarsus I, lateral, female (medial setae in broken line, ventral seta dotted, medial claw omitted); 27, apical part of tarsus II, medial, female (lateral setae in broken line, lateral parambulacral seta and claw omitted); 28, tip of tarsus III, ventromedial, female; 29, gnathosoma, ventral, deutonymph; 30, part of gnathosoma and basal palpal segment, dorsal, deutonymph; 31, idiosoma, dorsal, deutonymph; 32, genitoanal plate, ventral, deutonymph. (Scale bar = 50 µm)