Mirapinnatoidei: Development and Relationships 



E. Bertelsen and N. B. Marshall 



FISHES of the Mirapinnatoidei are soft-rayed, scaleless, 

 oceanic teleosts with elongated body, jugular pelvic fins of 

 4-10 rays, a single dorsal fin opposed to the anal fin with origin 

 behind mid-standard length, pectorals lateral, caudal fin with 

 10 -(- 9 principal rays, cleft of mouth oblique to subvertical, 

 premaxillae excluding maxillae from gape, jaws no more than 

 slightly protrusible, branchiostegal rays 3-5 on epihyal, 4 on 

 ceratohyal, swimbladder, functional only in larvae, with two 

 posterior retia mirabilia that supply an anterior gas gland. An 

 isolated phylogenetic lineage of uncertain systematic position 

 but apparently most closely related to the Megalomycteroidei 

 and the Cetomimoidei. 



Development 



These fishes were originally placed in two families by Ber- 

 telsen and Marshall ( 1 956): ( 1 ) Mirapinnidae, with a single genus 

 and species Mirapinna esau(Fig. 202) based on a single subadult 

 female 39.5 mm SL caught at the surface off the Azores and (2) 

 Eutaeniophoridae, with two genera Eutaeniophorus and Para- 

 taeniophorus (Figs. 202 and 203) both known only in larval and 

 metamorphosis stages less than 55 mm SL that are epipelagic 

 in tropical and subtropical parts of all oceans. 



Examination of more recent material indicates that these fish- 

 es are better regarded as members of a single family. Mirapin- 

 nidae, containing the above mentioned 3 genera. Adults prob- 

 ably are mesopelagic. The genera and species are distinguished 

 by meristic and morphometric characters as well as differently 

 developed dermal structures (Table 101). Hair-like outgrowths 

 of the epidermis are found all over the head, body and fins of 

 Mirapinna esaii. The longest hairs measure from about 1 .0 to 

 1.5 mm in length and bear stalked glandular cells. The skin of 

 Eutaeniophorus and Parataeniophorus is densely covered with 

 minute papillae less than about 0.05 mm in length (Bertelsen 

 and Marshall, in preparation). Skin of the caudal fin of Eutae- 

 niophorus and Parataeniophorus is prolonged into a ribbon-like 

 streamer reaching lengths of 200-300% SL. Upper and lower 

 lobes of the caudal fin overlap in Mirapinna. 



Specimens. — \nc\ud\ng a number of unpublished records the 

 material of Mirapinnatoidei known to us consists of: One Mir- 

 apinna esau: the holotype, a 39.5 mm juvenile female; about 

 100 Eutaeniophorus festivus 8.0-53 mm; two Eutaeniophorus 

 n. sp. (in preparation) 12 and 16 mm; 32 Parataeniophorus 

 gulosus 8-35 mm; 3 Parataeniophorus hrevis 13.5, 29 and 46 

 mm; 2 Parataeniophorus n. sp. (in preparation) 9 and 1 1 mm; 

 about 40 unidentified small larvae (most probably E. festivus) 

 5-12 mm. Eggs of Mirapinnatoidei are unknown and no larval 

 Mirapinna has been recorded; [according to our reexamination 

 a specimen of about 16 mm referred to this species by Four- 

 manoir, (1971b) is a Parataeniophorus sp.]. All the specimens 

 have small immature gonads. A light brown pigmentation of 

 the skin appears at a larval length of about 20 mm and some 

 of the 35-53 mm largest specimens are dark brown and are 

 considered post-metamorphic juveniles. However the transfor- 



mation from larval to juvenile appearance is quite gradual with- 

 out any distinct specialized metamorphic stage. 



The youngest Eutaeniophorus larva described (6.5 mm SL) 

 has remains of a yolk sac, nearly unpigmented eyes, no rudiment 

 of pelvic fins, continuous embryonic fins without trace of fin 

 rays and, except for a ventral series of melanophores, the body 

 is completely unpigmented (Bertelsen and Marshall, 1958). Full 

 numbers of rays of the unpaired fins may be delected at 8-9 

 mm SL. Rudiments of pelvic fins are present at 6-7 mm SL, 

 the number of rays discemable at about 10 mm SL. Pectoral 

 fin rays are not well differentiated until lengths of about 20 mm 

 SL. The caudal streamer, characteristic of Eutaeniophorus and 

 Parataeniophorus, is present as a short rudiment in the 5-6 mm 

 youngest larvae; it increases with increasing SL. It is broken in 

 most specimens of more than about 10 mm. The greatest lengths 

 observed are 86% SL in a Parataeniophorus hrevis of 22.6 mm, 

 about 200% SL in two specimens of Eutaeniophorus of 12-15.5 

 mm SL (unpublished data), and no less than 300% in an E. 

 festivus of 35 mm (Fig. 203). 



All Eutaeniophorus larvae are very slender with body depth 

 less than 10% SL except for the largest specimens. Body depth 

 in Parataeniophorus species is less than 1 5% SL. Predorsal lengths 

 (snout to first dorsal finray) in these genera is 69 to 77% SL (cf 

 Table 101), 



All larvae have a fine peppering of melanophores on head 

 and body, slightly increasing in density with increasing SL, with 

 no distinct grouping except for a slight increase in density to- 

 wards the tail, on the dorsal part of the peritoneum, and along 



Table 101. Characteristics of Mirapinnatoidei. 



' Shorter in specimens less than 15 mm. 

 - Shorter in specimens less than 25 mm. 



380 



