Fig 1.
External anatomy of the postcleithral and caudal tube organs (A) Platytroctes apus (SIO 55-244, 136.4 mm SL) showing location of postcleithral tube organ (left white box) and caudal tube organs (right white box).
(B) Postcleithral tube organ in P. apus (SIO 77-54) showing terminal opening and modified scale (ms). (C) Caudal tube organs on dorsal margin of caudal peduncle in P. apus (SIO 55-244). Arrows indicate the terminal opening of the postcleithral and caudal tube organs.
Table 1.
Platytroctid species examined for histological analysis of postcleithral and caudal tube organ structure in this study.
Fig 2.
Generalized illustration showing internal postcleithral tube organ anatomy.
Abbreviations: scale (s, red), epithelium (ep, dark pink), dermis (d, blue), tube organ (t), pigment layer (pl, brown), modified scale (ms, red), luminescent fluid (lf, pink), muscle (m, red). Arrow indicates terminal tube opening, which is directed posteriorly.
Fig 3.
Longitudinal sections through the postcleithral tube organ.
(A) Mirorictus taningi (SIO 14-136) and (B) Searsia koefoedi (MCZ 168583). Potential developing luminescent-fluid cells (*) in (C) Mirorictus taningi (SIO 14-136) and (D) Platytroctes apus (SIO 77-54). Anterior is to the left in all figure panels, such that the posteriorly-directed terminal opening of the tube organ is to the right. Abbreviations: scale (s), dermis (d), tube organ (t), pigment layer (pl), modified scale (ms), luminescent fluid (lf), muscle (m), nucleus (n), blue cells (bc), red blood cells (rb), blood vessel (v), epithelium (ep).
Fig 4.
Longitudinal sections of the postcleithral tube organ.
(A and B) Normichthys yahganorum (SIO 61-45), (C) Normichthys operosus (MCZ 163242), (D) Holtbyrnia melanocephala (LACM 31065-9), (E) Mentodus facilis (LACM 9706-42), (F) Platytroctes apus (SIO 77-54), and (G) Sagamichthys abei (SIO 18-4). Anterior is to the left in all figure panels, such that the posteriorly-directed terminal opening of the tube organ is to the right. Abbreviations: scale (s), dermis (d), tube organ (t), pigment layer (pl), modified scale (ms), luminescent fluid (lf), muscle (m), blood vessel (v), potential developing luminescent-fluid cells (*). Arrow in panel B points towards terminal tube opening.
Table 2.
Ranges in diameter of luminescent fluid cells, blue cells, potential developing luminescent fluid cells, and blood cells.
Fig 5.
Longitudinal histological sections and external anatomy of the caudal tube organ in P. apus (SIO 77-54).
(A) Two dorsal caudal tube organs in lateral view and (B) potential developing luminescent-fluid cells (*) in the lumen of a caudal tube organ in P. apus. Variation in the number of dorsal caudal tube organs in Platytroctes apus, showing (C) two (USNM 206894), (D) three (USNM 206894), (E) four (USNM 206893), and (F) five (USNM 201649) caudal tube organs. Arrows point towards terminal caudal tube opening. Note: Ventral tube organs on the caudal peduncle in P. apus also vary in number. Anterior is to the left in all figure panels, such that the posteriorly-directed terminal openings of the caudal tube organs are located to the right. Abbreviations: dermis (d), tube organ (t), pigment layer (pl), modified scale (ms), luminescent fluid (lf), muscle (m).