Gastrops willistoni Cresson 1914
Creators: name: Camargo, Alexssandro
name: Souza, Franciele Cristina De
name: Zatwarnicki, Tadeusz
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Diptera
Ephydridae
Gastrops
Gastrops willistoni

description: Gastrops willistoni Cresson   
 Diagnosis adult. Medium-size species, body length 3.6–4.5 mm (n=5); general color dark brown (Fig. 3); pedicel and postpedicel yellowish brown; arista with 12–14 rays; head sparsely golden tomentose (Fig. 3B, C, D); mesonotum golden tomentose with two (sometimes four) greyish stripes; scutellum flattened with one pair of small apical tubercles bearing marginal setae, without lateral tubercles (Fig. 3B, C); wings hyaline without infuscate pattern (Fig. 3E); femora black; tibiae brown; tarsi reddish brown (Fig. 3A) (Lizarralde de Grosso 1998; Zatwarnicki & Hagenlund 2017).   
  Description of immature stages. Third instar larva  (Figs. 4, 5): main body length 6.11–9.66 mm (n=10); breathing tube length: 0.68–1.05 mm (evaginated n=5) and 0.28–0.67 mm (invaginated n=5); maximum width in dorsal view 0.87–1.57 mm (n=10); whitish and yellowish to dark yellow (after fixation) except anterior spiracles yellowish, posterior spiracular caps dark brown and cephalopharyngeal skeleton black; shape fusiform, thoracic segments telescoping anteriorly, caudal segment retractile, invaginated in most preserved specimens, directed upward and bifurcate distally; anterior segments somewhat retracted and invaginated or completely evaginated in preserved specimens; segment 1 (pseudocephalic) projected anteriorly in two small lobes (antennomaxillary lobes), each lobe with minute antenna directed anteriorly (anteroventrally in invaginated specimens); maxillary sensory papilla ventral to each antenna, slightly smaller, directed anteroventrally (ventrally in invaginated specimens); oral ridges beneath maxillary papillae in direction to oral region with 3–4 clusters of minute dark brown spinules arranged in short rows (Figs. 4A, 5A, 6 A–C); segment 2 (prothoracic) with anterior ventral half (postoral border) with a cluster of 10–12 rows of dark brown spinules, disappearing laterally, dorsal anterior margin (approx. 1/3 of segment length) with a cluster of 8–9 rows of dark brown spinules diminishing in size posteriorly, remainder of segment glabrous; anterior spiracles whitish or yellowish (brown in some preserved specimens) (Figs. 4 A–C, 5A, B) present at posterior border, retractile, almost completely invaginated and enclosed under anterior margin of mesothoracic segment in the majority of preserved specimens (only a few ones completely evaginated), fan-shaped in lateral view with basal trunk branching in smaller 11–18 twigs (finger-like ramifications) connected by a thin lamellae almost until tip (Fig 5B); segment 3 (mesothoracic) with spinule band completely encircling anterior margin, composed of 4–6 rows of irregularly arranged stout spinules, mid-laterally with a very slight prominence that continues ventrally, remainder of segment with somewhat sparse and almost translucent spinules, except posterior margin (approx. 1/4 of segment length) which is bare; segment 4 (metathoracic) with spinule band of 4–6 rows completely encircling anterior margin, mid-ventrally with a belt of 3–4 rows of spinules diminishing laterally, posterior margin with a band of spinules (6–7 rows) that completely encircles posterior margin, this posterior band expands laterally and obliquely, slightly directing forward, ventrally it is divided in two bands by a central bare spot (fusiform-ellipsoid shape) with 2–3 rows of spinules anteriorly and 3–4 posteriorly to this ventral bare spot, mid-dorsal and lateral parts of segment covered by translucent sparse spinules, except ventrally between anterior band, ventral belt and posterior band of spinules, bare; segment 5 (first abdominal) with ventral belt of spinules diminishing laterally and directed forward, meeting the posterior spinule band from segment 4, posterior spinule band from segment 5 directed forward laterally and interrupted ventrally by a bare spot as in segment 4, dorsal part of segment covered by sparse translucent spinules, ventral areas between anterior and posterior band and ventral belt of spinules bare; segments 6–11 covered with same pattern of spinules as segment 5; segment 12 (Figs. 4 A–C, 5D–I) with one small fleshy conic projection on each dorsolateral side (not easily visible in all specimens), dorsally with a band of 4–5 dark brown spinules, connecting to the posterior band from segment 11 and a ventral band of 3–4 rows of dark brown spinules not connected to other bands (anterior to perianal pad), a few sparse translucent spinules dorsally and laterally; perianal pad bilobed (Fig. 5F, I) (very rounded and distinct in some preserved specimens) slightly prominent at posterior margin, dark yellow; mid-posterior margin of perianal pad with a small, conical, spinule patch (like a pine cone), covered with dark brown spinules that are directed anteriorly (opposite to body spinules, which are directed posteriorly) (Fig. 5F, I); breathing tube (Figs. 4 A–C, 5D–I) telescopic, tapering distally, bifurcate before apex, formed by two sections; first section with sparse translucent spinules dorsally, denser ventrally with 8–10 fleshy lobes around the posterior margin (with the aspect of a flower in some preserved specimens, though in some specimens these lobes are not very conspicuous (Fig. 5E, F); second section retractile, densely covered with larger spinules on basal half, posterior half glabrous and bifurcate; posterior spiracular caps rounded apically, dark brown with dark yellow basal half; three reniform spiracular openings bent medially (with C-shape aspect); ecdysial scar rounded and lighter in color surrounded at external lateral margin by the three spiracular openings (Fig. 5C). The spinules covering the larvae have the basal half with almost same integument color and apical half dark brown. Some spinules are bifid or seem to be cut and then regrown, normally disposed in pairs on the rows with their shapes resembling a comma (based on 10 specimens collected in the field and fixed in the laboratory).   
 Cephalopharyngeal skeleton (Figs. 6, 7): mostly dark brown to black pigmented; length 0.90 mm (n=1); mandibles length 0.14mm (n=1) paired and not connected dorsally; narrow, curved downward anteriorly, ventral surface denticulate, broad posteriorly with ventral projection about third of mandible length (Fig. 7A); mandible with 2/3 of its length on pseudocephalic segment and 1/3 on anterior part of prothoracic segment (Fig. 6 A–C); hypopharyngeal sclerite length 0.15 mm (n=1), slightly shorter than mandibles, not fused with mandibles and pharyngeal sclerite, connected ventrally by a narrow, slightly anteriorly arched posterior transverse bar (Fig. 7C), restricted to prothoracic segment (Fig. 6 A–C); labial sclerite under hypopharyngeal sclerite not connected anteriorly with other sclerites, bifurcate, forming two branches (Y-shaped) with rounded apex, posterior branch shorter, half the length of the anterior branch (Fig. 7C); epipharyngeal sclerite with mid-anterior margin truncate with a small recession anterolaterally, forming a curve laterally, without windows, laminate (Fig. 7B); parastomal bar not connected to pharyngeal sclerite (Fig. 7A); pharyngeal sclerite whitish ventrally, occupying posterior half of prothorax and anterior half of mesothorax (Fig. 6 A–C), dorsal cornu large, connected dorsally by a dorsal bridge, each dorsal cornu with a rounded window posteriorly (Fig. 7A); dorsal bridge formed by a strong arm on each side and very broad medially with numerous windows with reticulate aspect (Fig. 7B); ventral cornu as broad as dorsal cornu, without windows, with a slight projection mid-dorsally; floor of pharyngeal sclerite with 8–9 longitudinal striae (Fig. 7C) (based on 1 dissected specimen).   
 Puparium (Figs. 8, 9): main body length 5.10–5.85 mm (n=10) (including anterior spiracles and breathing tube), breathing tube length 0.63–0.82 mm (n=10); maximum width in dorsal view 1.36–1.82 mm (n=10); dark reddish brown; venter arcuate and dorsum only slightly arcuate medially in lateral view; anterior end (thoracic segments) flattened dorsoventrally, slightly curving upward in lateral view (Fig. 8A); anterior margin of segment 2 tapered; posterior end conical and curved upward in lateral view (Fig. 8 A–C); anterior spiracles (Fig. 9A) yellowish, arising from anterolateral corners of puparium with 13–15 finger-like projections interconnected by thin lamella resembling fan-shape; segment 1 and almost entire segment 2 invaginated; dorsal cephalic cap flattened, slightly depressed on segments 4 and 5, delineated by a weak line that extends laterally along segments 3–4 and curving inward along segment 5 reaching the posterior margin of segment 5 (Fig. 8B); segments 6–10 with two annuli dorsally; segment 12 with perianal pad yellowish, wrinkled (Fig. 8C); breathing tube tapering towards apex, bifurcate; posterior spiracle yellowish; arrangement of spinules similar to third instar larva (Fig. 9 B–D) (based on 10 specimens that pupariated in the laboratory).
description: Published as part of Camargo, Alexssandro, Souza, Franciele Cristina De & Zatwarnicki, Tadeusz, 2020, First description of immature stages of Gastropini, Gastrops willistoni Cresson (Diptera: Ephydridae) preying on eggs in a foam nest of Leptodactylus knudseni Heyer (Anura: Leptodactylidae) in Central Amazon, pp. 131-145 in Zootaxa 4869 (1) on pages 135-141, DOI: 10.11646/zootaxa.4869.1.7, http://zenodo.org/record/4418441