Thalassomya gutae, Oliveira, Caroline Silva Neubern De, Silva, Fabio Laurindo Da & Trivinho-Strixino, Susana, 2013

Oliveira, Caroline Silva Neubern De, Silva, Fabio Laurindo Da & Trivinho-Strixino, Susana, 2013, Thalassomya gutae sp. n., a new marine chironomid (Diptera: Chironomidae: Telmatogetoninae) from the Brazilian coast, Zootaxa 3701 (5), pp. 589-595 : 590-591

Thalassomya gutae sp. n.

( Fig. 1–22 )

Type material. Holotype male, Brazil, SP, Bertioga, Praia da Baleia, 1.iv.2013, C. S. N. Oliveira (P1–01, LEIA/ UFSCar). Paratypes: 1pharate male with larval exuviae (P1–02, LEIA/UFSCar), 1 pupa with larval exuviae (P1– 0 3, LEIA/UFSCar), 3 pupae (P1–04, P1–05, P1–06, LEIA/UFSCar), 3 larvae (P1–07, P1–08, P1–09, LEIA/ UFSCar) as holotype.

Diagnostic characters. Thalassomya gutae sp. n. differs from other Thalassomya species by the combination of the following characters. Male: scutellum with high number of scutellars; dorso basal lobe of gonocoxite stout; apex of endomere not setose, covering partially the aedeagus.

Pupa: thoracic horn tubular without distolateral projections. Larva: mandible with apical tooth and 4 inner teeth; mentum with single medial tooth and five pairs of lateral teeth

Etymology. Named in honor of Maria Augusta (Guta) Machado for her assistance in collecting the species in Bertioga, Brazil.

Description. Adult male (n = 1–2)

Size. Total length 3.89–4.36 mm. Wing length 1.91 mm. Total length/wing length 1.63. Wing length/length of profemur 1.99.

Coloration. Head brown; maxillary palp pale brown. Thorax pale brown. Wing membrane covered with fine punctuation due to microtrichia, Costa and radial veins dark pigmented. Legs pale brown. Hypopygium pale brown, covered with small setae.

Head ( Figs 1–4 ). Temporals 66, multiserial ( Fig. 1 ). Tentorium 166 μm long, stipes not measurable( Fig. 2 ). Clypeus 134 μm long, 124 μm wide at largest part, bearing 11 setae. Cibarial pump with well-developed cornua and torma, 99 μm long ( Fig. 3 ). Palp 5-segmented, basal segmented indistinct, 2 and 3 globular; 4 and 5 elongated; sensilla capitata on subapex of 3, lengths of palpomeres2–5 (in μm): 26; 77; 154; 185. Antenna with 6 flagellomeres, flagellum 331 μm long ( Fig. 4 ). Diameter of pedicel 75 μm. Antennal setae present, but reduced. AR 0.77.

Thorax ( Fig. 5 ). Antepronotals 12, acrostichals 22, uniserial, starting at anterior of scutum. Humerals 9, distinct from prealars and anterior dorsocentrals. Dorsocentrals 18, uniserial, starting close to anterior margin of scutum. Prescutellars 1. Prealars 15. Preepisternals 8. Scutellars ca 40. Anapleural suture ratio 0.56. Anepisternals, supraalars and postnotals absent.

Wing. Width 0.50 mm. Costa 1.88 mm long, slightly produced beyond R4+5, almost reaching apex of wing, densely setose as in R, R1 and R4+5. M1+2, M3+4, Cu1 and An scarcely discernible, bare. VR 1.44. Brachiolum with 2 setae. Squama with 18 setae.

Legs ( Figs. 6–7 ). Legs elongate, with large coxa on foreleg. Ta4 cordiform, Ta5 cylindrical. Fore leg: width at apex of tibia 56 μm, tibia with single, apical and pectinate spur 69 μm long. Mid leg: width at apex of tibia 75 μm, tibia with two apical and pectinate spurs, 63 μm long. Hind leg: width at apex of tibia 75μm, tibia with two apical and pectinate spurs, 63 μm long. Empodium very long, pectinately plumose. Pulvilli present ( Figs. 6, 7 ). Outer claw pectinate on fore and middle legs ( Fig. 6 ), simple on hind ( Fig. 7 ), with a pair of hyaline lanceolated lamellae on all claws. Lengths and proportion of leg segments as in Table 1 .

Hypopygium ( Fig. 8 ). Tergite IX straight with 6 dorsal setae. Apex of endomere not setose, covering partially the aedeagus. Aedeagus distinct, 97–99 μm long. Gonocoxite 174–217 μm long, 95–108 μm wide. GcR 1.82–2.01. Dorsobasal lobe of gonocoxite stout ( Fig. 8 ). Gonostylus 99–100 μm long, broader medially, tapering distally to a rounded tip, bearing some large setae. Phallapodeme 128 μm long, with 2 proximo-medially projections. Sternapodeme absent. HR 1.95–2.88. HV 2.88–4.05.

Pupa (n = 5 unless otherwise stated)

Size. Abdomen 3.20–5.16 (4) mm long.

Coloration. exuvia pale brown and thoracic horn brown.

Cephalothorax ( Figs 9–11 ). Frontal setae elongated, arising directly from frontal apotome. Frontal apotome rugose and heavily sclerotized ( Fig. 9 ). Thorax and antennal sheath very rugose. Thoracic setation on both sides: 1 lateral antepronotal, 2 precorneals, 3 dorsocentrals, 1 prealar, 2 metanotals. Wing sheath smooth, 1081–1613 μm long ( Fig. 10 ). Thoracic horn tubular, elongated, 306–388 μm long and 31–63 μm wide, connect directly to adult spiracle. Plastron plate subapical with rosette( Fig. 11 ). Thoracic horn ratio 6.89–9.81.

Abdomen ( Figs 12–14 ). All tergites covered by shagreen of small spinules. Sternite III with distinctive anteromedian area of raised tubercles ( Fig.12 ). Tergites and sternites III-VI each with 2 posterolateral groups of anteriorly directed spines ( Fig. 12 ). Tergite VIII with 3 pairs of setae on dorsal and ventral surfaces. Tergites VIII and IX developed as subcircular terminal disc. Terminal disc with pattern of glabrous polygonal tubercles ( Fig. 14 ), ventral and dorsal surface with 2 setae on each side of genital sacs ( Fig. 15 ). Tergite IX with fringe of 120 short setae, reaching the posterior margin. Genital sac not extending to posterior margin of disc.

Larva (n = 5 unless otherwise stated)

Coloration. Head brown, with occipital margin dark brown. Distal tooth of mandible and mentum dark brown. Abdomen pale yellow. Posterior parapod claws all dark.

Head. Length 675–788 (3) μm, 500–600 (3) μm wide. Surface very granulose with polygonal scales. All head capsule setae simple. Cephalic index 0.76–0.87.

Antenna ( Fig. 16 ). Very short, 4-segmented, 20–46 μm long. Basal segment 23–35 μm long, with ring organ placed 4–5 μm from base, second segment 6–12 μm long. AR 1.25–1.73. Antennal blade bifid, subequal to flagellum. Lauterborn organ small.

Labrum ( Figs 17–19 ). Frontal apotomeand sclerites as in figure 17. All setae well developed, simple. Chaetae of labrum serrated. Pecten epipharyngis consisting of 3 strongly toothed scales. Premandible broad and heavily sclerotized, with 1 weak apical tooth, 77–91 (4) μm long( Fig. 19 ).

Maxilla. Palp with all sensilla and setae reduced on membranous apex. One of the anterior seta maxillaris developed as a hyaline, multilobed lamella.

Mandible ( Fig. 20 ). Length 169–214 μm. Apical tooth longer than any of the 4 inner teeth. Seta subdentalis elongated. Seta interna with 6 branches, fine and simple.

Mentum ( Fig. 21 ). Mentum 174 µm long, with a large median tooth and five pairs of lateral teeth, decreasing in size laterally; the outermost weak. Ventromental plates weak, beard absent. Seta submenti 128 µm long.

Premento-hypopharyngeal complex. Labial palp with common base. Ligula and paraligula inconspicuous. M appendage divided into numerous apically serrate, elongated lamellae. Pecten hypopharyngis apparently absent.

Body ( Fig. 22 ). Setation weak. Parapods well developed; anterior fused basally, covered with small spines basally, posterior separate, with 3 anal setae. All claws simple. Procercus and anal tubules absent.

Adult female. Unknown

Ecology. Immatures of Thalassomya gutae sp. n. were collected on rocks in the intertidal marine zone, in southeastern Brazilian coast. The adults were observed flying actively over rocks in the splash zone close to the high water mark. There is no evidence of lunar periodicity of pupation or emergence.

Figures

FIGURES 1 – 8. Thalassomya gutae sp. n., male. (1) Head. (2) Tentorium. (3) Cibarial pump. (4) Antenna. (5) Thorax. (6) Fore leg claw. (7) Hind leg claw. (8) Hypopygium, left: dorsal aspect, right: ventral aspect.

FIGURES 9 – 15. Thalassomya gutae sp. n., pupa. (9) Frontal apotome. (10) Thorax. (11) Thoracic horn. (12) Sternite III. (13) Shagreen. (14) Terminal disc surface. (15) Terminal disc, left: dorsal aspect, right: ventral aspect.

FIGURES 16 – 22. Thalassomya gutae sp. n., larva. (16) Antenna. (17) Frontal apotome and sclerites. (18) Labrum and epipharynx. (19) Premandible. (20) Mandible. (21) Mentum. (22) Caudal end.

Tables

TABLE 1. Lengths (in µm) and proportions of leg segments in Thalassomya gutae sp. n., male (n = 1).

Fe	Ti	ta1	ta2	ta3
p1 956	1206	825	331	156
p2 1475	1406	669	243	156
p3 1500	1769	956	500	250
ta4	ta5	LR	BV	SV
p1 81	112	0.68	4.39	2.62
p2 69	94	0 48	6.31	4.31
p3 156	94	0.54	4.23	3.42