Thalassosmittia ballestai Moubayed-Breil, 2019

Moubayed-Breil, Joel & Dominici, Jean-Marie, 2019, CLUNIO BOUDOURESQUEI SP. N. AND THALASSOSMITTIA BALLESTAI SP. N., TWO TYRRHENIAN MARINE SPECIES OCCURRING IN SCANDOLA NATURE RESERVE, WEST CORSICA (DIPTERA: CHIRONOMIDAE) Abstract, CHIRONOMUS Journal of Chironomidae Research 32 (32), pp. 4-24 : 15-21

Thalassosmittia ballestai Moubayed-Breil , sp. n.

Thalassosmittia sp. 1 , in Moubayed-Breil & Ashe (2012), Moubayed Breil et al. (2013).

http://zoobank.org/ 0C9795ED-02C6-47BB-A8A1- 190480BE9EEA

Material examined

Holotype. France, West Corsica, Scandola Nature Reserve, Focolara Bay ( Fig. 14 ), 42° 21′ 25″ N, 8° 34′ 0″ E; 1 male pharate adult, leg. J. Moubayed-Breil, 03. VI.2015. Locality No. 31 in Moubayed-Breil & Ashe (2012), locality No. 30 in Moubayed-Breil et al. (2013). Marine water temperature: 10-12°C (min.), 22-24°C (max.).

Paratypes (all leg J.M-B.): 3 pupal exuviae (2 males and 1 female), same locality as for holotype, 03.VI.2015 .

Holotype (mounted on 1 slide) and 2 pupal exuviae (1 male and 1 female) are deposited in the collections of the Zoologische Staatssammlung München ( ZSM), Munich , Germany. Additional paratypes are deposited in the senior author’s collection.

Diagnostic characters

Though the pupal exuviae of T. ballestai sp. n. apparently shows a close morphological resemblance with that of T. thalassophila (distribution pattern of armament on tergites and shape of anal lobe), some relevant specific characters found in the male adult (shape of tergite IX, anal point and inferior volsella) will sufficiently separate the species described here from other related members of genus Thalassosmittia by the below listed characters.

Male adult: Temporals with 3 inner and 3 verticals; last flagellomere of antenna distinctly clubbed, abruptly narrowing distally and bearing a brush of curved sensilla chaetica; antennal groove reaching segments 2, AR 0.72; lobes of antepronotum widely opened; antepronotals absent. Brachiolum with 1 seta, veins and squama bare. Tarsomere ta 5 of PI-PII wider and rounded apically; spurs present on tarsomeres ta 1 -ta 4; sensilla chaetica present on tibia and tarsomeres ta 1 -ta 4 of PI-PIII. Tergite anal band absent on tergite IX; anal point drop-like shaped and bearing a rounded setiferous lobe at base; virga with 2 closely grouped spines; inferior volsella rounded lobe-like shaped with bifid basal margin; gonostylus distinctly swollen at base and thinner distally when viewed laterally.

Pupal exuviae: Frontal apotome with sub-cylindrical tubercles; dorsocentral Dc 1 distances between dorsocentral Dc 1 vestigial about 5-7 µm long; Dc 1 and Dc 2 separated by 25 µm, Dc 2 and Dc 3 by 70 µm; transverse row of hooks and orally directed pins present on conjunctives of sternites IV/V-VII/VIII is occasionally absent on IV/V; anal lobe sub-trapezoidal, genital sac distinctly swollen distally and bearing an apical finger-like tubercle. Pedes spurii A and Pedes spurii B absent. Anal lobe sub-trapezoidal to sub-triangular, bearing 2 subequal macrosetae on dorsal side; genital sac swollen distally, bearing a projecting outwards tubercle.

Etymology: the new species is named ‘ ballestai’ in honour of our colleague Laurent Ballesta (Andromède Océanologie, Carnon, South France) who is still an active marine biologist studying and preserving the Mediterranean marine fauna and flora including the protected area of Scandola Nature Reserve, which represents a precious and valuable inheritance area.

Male adult

(n = 2, 1 pharate; Figs 11a, 11 c-h, 12a)

Total length 1.55-1.60 mm. Wing length 1.05-1.10 mm. Colouration variable in general, contrasting from light brown to brown even to greenish; Head, antenna, halters and legs light brown; thorax with mesonotal stripes contrasting light brown to brown; anal segment and inferior volsella distinctly contrasting brown to hyaline; wing translucent. Head. Eyes bare between ommatidia, nearly circular with dorso-median extension; inner lateral margin bare. Vertex and coronal area ( Fig. 11a ) distinctly triangular and orally projecting, basal and median margins of coronal triangle much thicker than distal part, coronal setae absent. Temporals uniserial including 3 inner and 2 outer verticals. Clypeus semicircular to sub-rectangular, with about 16-18 setae in 3-4 rows. Palp-5 segmented, segments 1-2 fused, length (µm) of palpomeres 1-5: 15, 25, 47, 63, 80; third palpomere with 2 sensilla clavata and 3 sensilla coeloconica located distally. Antenna 550 µm long; last flagellomere 230 µm long, distinctly clubbed distally, distal half abruptly narrowing and bearing a brush of curved sensilla chaetica; antennal groove reaching segments 2; AR 0.72. Thorax. Lobes of antepronotum ( Fig. 11c ) widely opened; antepronotals absent; acrostichals 26 in 1-2 rows; dorsocentrals 9 in 1 row; prealars 3; supraalars absent. Humeral pit indistinct. Scutellum semicircular, with 4 uniserial setae. Wing. Brachiolum with 1 seta. Veins and squama bare. Legs. Tarsomere ta 5 of PI-PII wider in its distal part and rounded apically; tibial spurs of PI-PIII spiniform; spurs present on tarsomeres ta 1 -ta 4. Sensilla chaetica present in low number on tibia and tarsomeres ta 1 -ta 4 of PI-PIII: on ta 1 -ta 4 (proximally and distally); only distally on tibiae. Length (µm) and proportions of prothoracic (PI), mesothoracic (PII) and metathoracic (PIII) legs as in Table 3 .

Abdomen. Hypopygium in dorsal, ventral and lateral view as in Figs 11 e-f, 12a ( Fig. 11e , dorsal; Fig. 11f , ventral with tergite and anal point removed; Fig. 12a , lateral). Tergite IX semicircular, posterior area with a dark circular setiferous band located close to the base of anal point, which is clearly visible in lateral view ( Fig. 11d ). Anal point ( Figs 11d, 11e , 12a ) about 40-45 µm long, 70-75 µm maximum width at base; broadly triangular at base and drop-like shaped in its remaining part; lateral and apical margins densely covered with setae. Laterosternite IX with 6 setae (3 on each side). Sternapodeme, transverse sternapodeme and phallapodeme as in Fig. 11f , basal part orally projecting, basal part of coxapodeme semicircular and projecting inwards. Virga ( Figs 11e, 11g ) about 40 µm long, consists of 2 long curved spines. Gonocoxite about 265 µm long, 75 µm maximum width, much wider at base, narrowing distally to a rounded apex, inner margin with 10-11 stout setae. Inferior volsella large lobe-like shaped, rounded apically with posterior margin distinctly bi-lobed, apical and caudal parts contrasting and hyaline. Gonostylus in dorsal ( Fig. 11e ) and lateral view ( Fig. 11h ) 105 µm long, 30 µm maximum width; swollen medially and less wide distally when view laterally; posterior margin sinuous and swollen medially; crista dorsalis low and widely extended is clearly visible only in dorsal view; megaseta present and well-developed.

Pupal exuviae

(n = 5, 2 males and 3 females; Figs 12c, 12 e-k, 13a, 13e)

Total length 1.65-1.70 mm. General colouration contrasting brown to dark brown; frontal apotome with anterior half covered with fine wrinkles; antero-median area of cephalothorax and suture of thorax markedly rugulose and wrinkled; abdomen yellowish to pale, anal lobe and genital sac brown to dark brown. Cephalothorax as in Figs 12c and 13a ; frontal apotome ( Fig. 13a ) triangular with pointed lateral expansions; frontal tubercles about 40-45 µm high, sub-cylindrical and well-developed, frontal setae about 70 µm long, separated by 25-30 µm. Thorax as in Fig. 12c . Median antepronotal nearly subequal (90 and 80-85 µm long), lateral antepronotal and prealars absent; precorneals 85, 80 and 90 µm long. Dorsocentrals consist of 3 unequal setae, length (in µm) of Dc 1 -Dc 3: Dc 1, vestigial about 5-7; Dc 2, 55; Dc 3, 70; distance (in µm) between: Dc 1 to Dc 2 25, Dc 2 to Dc 3 70.

Abdomen. Armament, chaetotaxy and distribution pattern of shagreen with details of armament on tergites and sternites: III-VIII ( Fig. 12e ); V-VII ( Figs 12 f-k). Tergite I and sternites I-IV bare. Anterior transverse rows of spines present on tergites II-VIII, those on tergites VII-VIII are smaller and less extensive; posterior transverse rows of spines present on tergites III-VIII, becoming gradually more extensive on VI-VIII. Conjunctives of tergites III/IV-VII/VIII and sternites IV/V-VII/VIII with rows of hooks and orally directed pin-shaped setae ( Figs 12e, 12 h-k), those on sternite IV/V are occasionally absent ( Fig. 12g ). Caudo-lateral area of tergites and sternites II-VII with a group of short spines ( Figs 12 e-k). Pedes spurii A and PSB absent. Number and distribution pattern of lateral setae on segments I-VII, 2, postero-lateral seta on segments V-VI forked; segment VIII with 3 setae located distally. Anal segment in dorsal and ventral view as in Fig. 13e ; anal lobe sub-trapezoidal to sub-triangular, 130-135 µm long, 135-140 µm minimum width at base, 185-190 µm maximum width at apex, a rounded patch of short spine present medially, apex bearing a finger-like tubercle which is projecting outwards; genital sac 220 µm long, distinctly swollen distally and overreaching apical margin of anal lobe by 70-75 µm; macrosetae consist of 2 subequal setae, about 90-95 µm long, separated by about 35-40 µm.

Larva

Unknown.

Differential diagnosis

Only the pupal exuviae of T. ballestai sp. n. directly key close to those of T. thalassophila , while the male adult is quite different and likely belongs to a local ‘Tyrrhenian element’. On the basis of some relevant specific characters found in the male adult and pupal exuviae, T. ballestai sp. n. is compared, as male adult, to that of T. thalassophila and, as pupal exuviae, to other undescribed morphotypes collected in Corsica, continental France, Italy and Spain. However, T. ballestai sp. n. is easily distinguished from other related species or taxa/species of Thalassosmittia by the following combination of characters.

Male adult: Head with 3 inner verticals ( Fig. 11a ), is bearing 4 in T. thalassophila ( Fig. 11b ); tergite anal band absent on tergite IX ( Figs 11 d-e), is conspicuously present in T. thalassophila ( Figs 11i, 11k ); anal point drop-like shaped and much wider at base ( Fig. 11e ), is parallel-sided with semicircular basal part in T. thalassophila ( Fig. 11k ); virga with 2 closely grouped spines ( Figs 11e, 11g ), consist of 2 inwardly curved spines and horseshoe-shaped in T. thalassophila ( Fig. 11j ); inferior volsella rounded lobe-like shaped with bifid basal margin ( Figs 11e , 12a ), is divided in 2 separate parts in T. thalassophila ( Fig. 12b ); gonostylus in lateral view ( Fig. 11h ), is differently figured in T. thalassophila (lateral, Fig. 11l ).

Male pupal exuviae: Frontal apotome with sub-cylindrical tubercles ( Fig. 13a ), are smaller and fused apically in T. thalassophila ( Fig. 13b ), weakly domed in T. marinus ( Fig. 13c ) and conical in T. sp. 1 ( Fig. 13d ); distances between dorsocentral Dc 1 to Dc 2 and Dc 2 to Dc 3 are respectively 25 and 70 ( Fig. 12c ), while are 15 and 55 in T. thalassophila ( Fig. 12d ); transverse row of hooks and orally directed pins present on conjunctives of sternites V/VI-VII/VIII ( Fig. 12e ) or occasionally absent on IV/V ( Fig. 12g ), is regularly present on conjunctives of sternites IV/V-VII/VIII of T. thalassophila (couplet 196 in Langton 1991); anal lobe ( Fig. 13e ) sub-triangular to sub-trapezoidal, is distinctly triangular in T. thalassophila ( Fig. 13f ), semicircular in T. marinus ( Fig. 13g ), rectangular in T. sp. 1 ( Fig. 13h ) and sub-circular in T. sp. 2 ( Fig. 13i ); genital sac ( Fig. 13e ) distinctly swollen distally with an apical finger-like tubercle apically, is differently figured in T. thalassophila ( Fig. 13f ).

Ecology and remarks

The examined material of T. ballestai sp. n. (male adults, male pharate adults and pupal were collected in the type locality of Focolara Bay ( Fig. 14 ) located in Scandola Natural Reserve , western Corsica. Additional material including associated larval stages is needed to determine and confirm the ecology of the new described species. While the marine intertidal zone at Focolara Bay is better preserved during winter and spring periods, it still heavily degraded, as other seacoasts around the Mediterranean Basin, by the impact of pollution and ecotourism activities, which highly increase each year between June and September.

The increasing abundance of plastics along the coastal ecosystem, estuarine zones and the littoral marine environment of Corsica (Bastia, Ajaccio, Porto, etc.) including those of Scandola Nature Reserve, has been observed since the last three decades. Inorganic matter, composed of pellet tar and plastics, collected in both drift and troubleau nets (as shown and detailed in Figs 15-16 ), has become more dominant major threat to all types of marine organisms. Small particles of plastics, consisting of several forms of both macro- and micro-particles of 0.5-5 to 10-15 mm size, are systematically found from the surface and water column to the seabed sediment and beach, where marine organisms (especially deposit feeders and detritivores) ingest them. Therefore, these pollutants may adversely impact species that inhabit intertidal zones that cannot adapt to changing conditions via behavioural plasticity; T. ballestai may be among these species. Consequently, a major challenge in marine environmental disciplines (evolutionary biology, ecology, conservation) is to better understand and predict how these sensitive species will respond to the impact of human activities and the rise of sea level, which is directly related to the global warming.

Geographical distribution

Geographical distribution of known Thalassosmittia species from European seacoasts ( Ashe & O’Connor 2012) and the Tyrrhenian sub-region is given in figure 10. Thalasosmittia atlantica ‘✩’ is known only from the western Atlantic seacoasts including the Canary Islands (type-locality), Madeira, Spain and Portugal. Thalasosmittia ballestai sp. n. ‘❄’ is common and abundant in the seashores of Focolara Bay (West Corsica). The records of T. ballestai sp. n. (pupal exuviae) from some seashores in southern France need to be confirmed by the presence of associated material composed of adults and pupae. Thalasosmittia thalassophila ‘✤’ is present along the Atlantic and some Mediterranean seacoasts in Europe including: France, England, Germany, Greece, Ireland, Italy, Netherland, Romania and Spain.

Figures

Figure 11. Male adult of Thalassosmittia spp. Vertex with coronal triangle of: a) T. ballestai sp. n.; b) T. thalassophila. T. ballestai sp. n.: c) lobes of antepronotum; d) tergite IX and anal point, lateral; e) hypopygium, dorsal; f) hypopygium, ventral view with tergite and anal point removed); g) virga; h) gonostylus, lateral. T. thalassophila: i) tergite IX and anal point, lateral; j) virga; k) anal point, dorsal; l) gonostylus, lateral.

Figure 12 a-k). Male adult and pupal exuviae of Thalassosmittia spp. Anal point and inferior volsella in lateral view of: a) T. ballestai sp. n.; b) T. thalassophila. Cephalothorax of: c) T. ballestai sp. n.; d) T. thalassophila. T. ballestai sp. n.: e) chaetotaxy and details of armament on abdominal segments III-VIII; f-g) tergite V in dorsal and ventral view; h-i) tergite VI in dorsal and ventral view; j-k) tergite VII in dorsal and ventral view.

Figure 13. Pupal exuviae of Thalassosmittia spp. Frontal apotome of: a) T. ballestai sp. n.; b) T. thalassophila; c) T. marinus; d) T. sp. 1. Caudal armament of segment VIII and anal segment of: e) T. ballestai sp. n., dorsal and ventral; f) T. thalassophila, dorsal and ventral. Caudal armament of segment VIII and anal segment of: g) T. marinus; h) T. sp. 1; i) T. sp. 2.

Figure 14. The Bay of Focolara at Scandola Nature Reserve, western Corsica. Type locality of Thalassosmittia ballestai sp. n. Photo J.M. Dominici.

Figure 15. Plastics in the form of ‘Macro- and Micro-particles’ (1-5 to 10-15 mm size), collected at Focolara Bay, Scandola Nature Reserve. Photo J. Moubayed-Breil.

Figure 16. Plastics in the form of ‘Macro- and Micro-particles’ (1-5 to 10-15 mm size). Focolara Bay, Scandola Nature Reserve. Photo J. Moubayed-Breil.