Dibolostethus sicarius Hoffman, 2009

Means, Jackson C., Bouzan, Rodrigo S., Iniesta, Luiz Felipe Moretti, Martínez-Torres, Daniela, Vasquez-Valverde, Luisa F., Brescovit, Antonio D. & Ivanov, Kaloyan, 2023, A review of the previously monotypic tribe Dibolostethini (Chelodesmidae: Chelodesminae) with description of two new species and a summary of the Chelodesmidae of the Tropical Andes Biodiversity Hotspot, European Journal of Taxonomy 885 (1), pp. 65-85 : 71-74

Dibolostethus sicarius Hoffman, 2009

Figs 3A, E , 4A–B , 5 , 8–9

Dibolostethus sicarius Hoffman, 2009: 151 , figs 1–11.

Diagnosis

Adult males of D. sicarius differ from those of D. kattani sp. nov. based on the lack of short, blunt projections on the sternite of the 5 th body ring, and from D. inopinatus sp. nov. and D. kattani sp. nov. based on the following combination of gonopodal characteristics: solenomere relatively straight until gently curving dorsally at apex, tip sinuous ( Fig. 5A ); prefemoral process slightly wider basally, expanded at midpoint and recurved, forming a cup-shaped depression before apex; apex with three lamellate flanges, best seen in anterior view ( Fig. 5B ).

Type material

Holotype ECUADOR • ♂; Los Rios Province [originally reported incorrectly as Pichinchi Province], Rio Palenque Science Center ; [0.588° N, 79.362° W]; 21 Mar. 1977; J. Reiskind leg.; VMNH110810 .

Paratypes ECUADOR • 2 ♀♀; same collection data as for holotype; VMNH110811 , VMNH110812 .

Description

Male (holotype, VMNH110810)

With characteristics typical for the genus. Coloration (preserved in 70% isopropanol): body rings light brown to caramel; antennae and head light yellow; legs light yellow; telson reddish, with posterior margin (= spinnerets region) yellowish. Head: epicranial macrosetae 2+2, interantennal macrosetae 1+1, frontal macrosetae 2+2. Sternites: 4 th body ring with two thin, blade-like acute projections, tips separated throughout, nearly translucent ( Fig. 4A–B ). Gonopod aperture on 7 th body ring oval, rim notably projecting above sternite (0.35 mm), with a deep U-shaped concavity (0.2 mm) on posterior margin.

GONOPODS ( Fig. 5 ). Gonocoxae rounded, equivalent to about three quarters the length of the telopodite; dorsum of left and right gonocoxa with 2 and 3 (possible aberration) macrosetae, respectively. Solenomere long, slender, unbranched, apex falciform and partially enveloped by prefemoral process ( Fig. 5 , S). Prefemoral process: long (similar in length to solenomere), width subequal to solenomere, widening at halfway point with a medial knob before curving laterad into a cup-like structure; apex broad, with a series of lamellate flanges resembling a hammerhead shark in lateral view ( Fig. 5 , PfP).

BODY MEASUREMENTS (mm). Total length 24.8, width of 10 th body segment 1.98. Antennomere lengths (1–7): 0.38, 0.75, 0.85, 0.85, 0.85, 0.85, 0.25. Collum: length 0.5, width 1.4. Podomere lengths of 10 th body ring (1–7): 0.28, 0.55, 0.9, 0.34, 0.53, 0.95, 0.09. Gonopod aperture: length 0.50, width 0.78. Gonopod: length 0.99, width 0.86. Gonocoxae: length 0.63, width 0.36. Telopodite: length 0.98, width 0.31. Telson length 0.78.

Female (paratype, VMNH110811) Coloration (preserved in 70% isopropanol) as in male. Body larger and more robust than male. Similar to male in general body outline and somatic characters, except sternite of 4 th body ring without pair of acute projections, 4 th, 5 th, and 6 th podosterna elevated to a lesser degree, 4 th and 5 th pair of legs not modified, and tibia lacking acute ventro-apical projections.

BODY MEASUREMENTS (mm). Total length 30.95, width of 10 th body segment 2.6. Antennomere lengths (1–7): 0.38, 0.9, 0.93, 0.88, 0.85, 0.83, 0.23. Collum: length 1.0, width 1.7. Podomere lengths of 10 th body ring (1–7): 0.3, 0.53, 0.9, 0.38, 0.45, 0.98, 0.09. Vulvar aperture width 0.56. Posterior margin of vulvar rim: well sclerotized, U-shaped; width 0.13. Vulvae: small, unmodified, setose ( Fig. 8 ); length 0.45, width 0.29. Valves symmetrical. External valve: lateral length 0.5, lateral height 0.44; dorsal length 0.39, dorsal width at midpoint 0.14. Operculum: length 0.06, width 0.21. Telson length 1.15.

Distribution

Herein restricted to the Los Rios Province, Ecuador ( Fig. 9 ).

Figures

Fig. 3. Dibolostethus Hoffman, 2009 somatic characters continued. A, E. Dibolostethus sicarius Hoffman, 2009, holotype, ♂ (VMNH110810). B–D. D. kattani Means, Bouzan, Martínez-Torres & Ivanov sp. nov., holotype, ♂ (ICN-MD-1317-1). A. Coxa 2, mesal view, red arrow = gonopore. B. Left leg 4, posterior view, red arrow = tibial ventro-apical projection. C. Left leg of 5th leg pair showing incrassate femur, red arrow = tibial ventro-apical projection. D. Body ring 5, lateral view, red circle = anterior pair of sternal projections. E. Prefemur 5, red arrow = basal pore. Abbreviations: Cx = coxa; Pf = prefemur.

Fig. 4. Body ring 4, sternal projections. A–B. Dibolostethus sicarius Hoffman, 2009, holotype, ♂ (VMNH110810). C–D. D. inopinatus Means, Bouzan & Ivanov sp. nov., holotype, ♂ (VMNH110813). A, C. Lateral views. B, D. Posterolateral views. Abbreviation: Cx = coxae.

Fig. 5. Dibolostethus sicarius Hoffman, 2009, holotype, ♂ (VMNH110810), left gonopod. A. Lateral view. B. Anterior view. C. Mesal view. Red circles = cingulum. Dashed lines = prostatic groove. Abbreviations: PfP = prefemoral process; S = solenomere.

Fig. 8. Dibolostethus sicarius Hoffman, 2009, paratype, ♀ (VMNH110811), vulvae. A. Left vulva, lateroventral view, with operculum at base. B. Vulvae in situ, held appressed to 2nd leg pair coxae with valve openings facing each other. C. Left vulva, lateral view.

Fig. 9. Distribution of Chelodesmidae spp. in the Tropical Andes Biodiversity Hotspot, by country. Note: the type locality of Dibolostethus sicarius Hoffman, 2009 is included for completeness although it falls just outside of the boundaries of the Tropical Andes Biodiversity Hotspot. For information on these taxa see Supp. file 1.