Periplaneta americana

Herhold, Hollister W, Davis, Steven R, Degrey, Samuel P & Grimaldi, David A, 2023, COMPARATIVE ANATOMY OF THE INSECT TRACHEAL SYSTEM PART 1: INTRODUCTION, APTERYGOTES, PALEOPTERA, POLYNEOPTERA, Bulletin of the American Museum of Natural History 459 (1), pp. 1-184 : 1-184

FAMILY BLATTIDAE Periplaneta americana

“American cockroach”

Figures 107 (lateral), 108 (dorsal), 109 (ventral)

Plates 64 (lateral), 65 (dorsal), 66 (ventral)

The P. americana specimen here was scanned early in the study, frozen to -20° C rather than -80° C, and at relatively coarse resolution (38.6 µm, specimen approximately 3.5 cm in length). Some fluid infilling likely occurred due to the freezing to -20° C, but sufficient detail is present to assess homology of major tracheae and discern substantial visceral tracheal anatomy. Although not described in detail, Blaptica was used as a comparison to infer the likely presence of thoracic tracheae in Periplaneta, in particular branching patterns from the mesothoracic spiracle. The thorax features a network of bandlike visceral tracheae along the dorsum and venter, connecting in various locations throughout. This morphology, combined with the long, broad coxae reminiscent of silverfish, obscures internal thoracic tracheal structures in two-dimensional views. The hypognathous position of the head also results in ventral tracheal views of the thorax being obscured; see figure 110 for a ventral view with head and leg tracheae removed.

Periplaneta has large air spaces in the coxae, and jumping has been filmed at high speed by Smith (2022). The scan here is of relatively coarse resolution (38 µm); it is possible muscle tracheae could be observed at higher resolutions or with contrast-enhancing stains such as iodine or phosphotungstic acid (Gignac et al., 2016).

DESCRIPTION: HEAD: H-DCT and H-VCT present, branching into head capsule in highly networked cagelike arrangement. Mouthparts, H-Ant, and H-Oc determined, but networked nature of head morphology, combined with some apparent fluid infilling, makes assessing homology difficult. Readers are directed to 3D models in the supplementary digital data.

THORAX: T2-S with five branches: H-DCT, H-VCT, T2-DB, T2-AWL, and T2-VB. H-DCT and H-VCT both anteriad, curving slightly medially, with H-DCT proceeding along dorsum and H-VCT along venter. T1-AL branching ventrad off H-VCT. T2-DB short, splitting anteriad into T2-DLT and posteriad as network of cagelike T1-DVi along pronotum. T2-AWL posteriad, with T2-W-c-r splitting dorsad and posteriorly; T2-AWL splits into T2-AL extending into midleg and T2-Wbr, partial in this scan but likely present between T2-S and T3-S. T2-VB likewise short, bifurcating into T2-VC directly ventrad and T2-VLT posteriad. T2-VL branching posteriad close to T2-S, extending into midcoxa and T2-L; T2-VLT continuing posteriad to link with T3-S. T3-S with n branches: T2-PWL, T3-DB, T3-AWL, T2-VLT, and T3-VLT. T3-VB not visible but may be very short. T2-PWL anteriad from T2-S, bifurcating into T2-Wbr anteriad and curving posteriad as T2-PL, joining with T2-AL from anteriad and extending into mid-leg. T3-DB mediad and slightly ventrad, curving posteriorly before extending along dorsum to join with small T2-DLT anteriad and larger T3-DLT posteriad; T3-DC visible at this junction. T3-AWL posteriad, with T3-W-c-r splitting dorsally; T3-AWL continues as T3-AL posteriorly and ventrad into hind leg. T2-VLT mediad, connect- ing anteriorly to T2-S. T3-VLT mediad and slightly posterior, connecting to A1-S via A1-VB.

ABDOMEN: Abdomen featuring numerous visceral tracheae throughout. A1..8-S present. A1-S modified from A2..8-S, with three branches: T3-PWL, A1-DB, A1-VB. T3-PWL anteriad and slightly mediad, curving posteriorly and joining with T3-AL and extending into hind leg; T3-Wbr branching from T3-PWL at apex of curve and extending anteriad to T3-S. A1-DB runs mediad, linking with T3-DLT anteriad and A1-DLT posteriad; A1-DB partial in this scan, likely due to fluid infilling (A1-DB present in B. dubia and G. portentosa). A1-VB mediad and slightly ventrad, extending along venter to A1-VC, connecting to A1-VLT posteriad; A1-MLT posteriad from A1-VB. A n -MLT runs straight, extending posteriad and much smaller than thoracic T3-VLT. A2..7-S branching all similar: A n -DB, A n -VB, and A n -MLT. A n -DB beginning small, expanding into bandlike trachea and intersecting with A n -DLT sections anteriorly and posteriorly in Y-shaped junctions; A n -DC absent. A n -MLT wide and almost bulblike, connecting abdominal spiracles along lateral margin of body wall. A n -VB much smaller and apparently fluid infilled in several spiracles, extending along venter to join with straight A n -VLT anteriad and posteriad in T-shaped junction. A4..8-S with numerous visceral tracheae; readers are encouraged to view 3D models in supplementary digital data.

Figures

FIGURE 107. Periplaneta americana (Blattodea: Blattidae) lateral view.

FIGURE 108. Periplaneta americana (Blattodea: Blattidae) dorsal view.

FIGURE 109. Periplaneta americana (Blattodea: Blattidae) ventral view.

FIGURE 110. Periplaneta ventral view, head and leg tracheae removed.