HOUDE: BREGMACEROTIDAE 



307 



atlanticus but larvae of the two species are easily separated by 

 pigmentation differences. There is slight overlap in meristics of 

 B. nectabanus and B. canton, although B. canton generally has 

 lower counts. The very wide range in dorsal and anal fin ray 

 counts attributed to B. nectabanus possibly has resulted from 

 identification errors. 



Adult complements of median and of caudal fin rays are 

 present at 7.5-9.5 mm SL. Three or four pelvic fin rays develop 

 early in larvae, most precociously in B. macclellandi and B. 

 Type A, just after appearance of the occipital ray. In other 

 species pelvic rays appear at 3.5-4.5 mm length prior to ap- 

 pearance of the occipital ray. As larval development proceeds 

 an additional 2-3 pelvic rays ossify, giving the adult comple- 

 ment of 5-7 rays. 



Relationships 



Family relationships. — The bregmacerotids are gadiform fishes 

 (Fahay and Markle, this volume) of uncertain affinities and with 

 no obvious close relatives (Cohen, this volume), but generally 

 thought to be most closely related to the Muraenolepidae, Mor- 

 idae and Melanonidae (Nelson, 1976; Fahay and Markle, this 

 volume). Although affinities are unclear, bregmacerotids are 

 clearly gadiforms. They have high vertebral numbers (Table 83), 

 a long tail and long median fins with numerous rays (Cohen, 

 this volume; Fahay and Markle, this volume). A well-developed 

 caudal fin, separate from the dorsal and anal fins, is present. 

 Accessory (x and \) bones, believed to be a primitive character 

 in Gadiformes, are present in the caudal complex. But the num- 

 ber of hypurals has been reduced to two inferior elements and 

 a platelike superior element, believed to represent fusion of 

 hypural elements 3-5 (Markle, 1982; Cohen, this volume). The 

 caudal fin of bregmacerotids is the most symmetrical in the 

 Gadiformes. Both Ahlstrom" and Markle ( 1 982) have illustrated 

 the caudal skeleton of a Bregmaceros sp.; Markle's specimen is 

 undoubtedly B. macclellandi. based on meristics that he gives. 

 The number of principal (branched) caudal rays is 12, among 

 the lowest in gadiform fishes. Procurrent (unbranched) rays are 

 numerous, 20-24 in number, equally divided between the dorsal 

 and ventral sides of the caudal complex. One principal ray is 

 associated with each inferior hypural, 8 are associated with the 

 superior hypural plate and one is associated with each epural 

 bone. No uroneural is illustrated by Ahlstrom' but Markle ( 1 982) 

 illustrated one and noted that its presence is unique among 

 gadoid fishes. Six vertebral centra appear to be involved in 

 caudal fin ray support. The first dorsal fin, which consists of a 

 single, elongate ray, is located on the occiput, a unique condition 

 in gadiform fishes. The pelagic, tropical-subtropical distribution 

 of bregmacerotids is unusual among gadiforms. 



Species relationships. — The species of Bregmaceros are remark- 

 ably similar. They have wide geographic distributions with little 

 apparent tendency to differentiate over their ranges of occur- 

 rence. Belyanina (1974) discussed the evolution and dispersal 

 of Bregmaceros. She believed that the family originated in the 

 Indo-Malayan Archipelago from which it dispersed with little 

 morphological modification. The present-day richness of species 

 in the Archipelago and the adjacent northern Indian Ocean lends 

 credence to that hypothesis. Five species (B. macclellandi, B. 

 atlanticus, B. nectabanus, B. rarisquamosus and B. arabicus) 

 presently occur in the proposed area of origin. Three species, 

 {B. bathymaster, B. contort and B. Type A) do not occur there. 

 The first two of these resemble B. nectabanus and may be de- 

 rived from it. The western Atlantic B. Type A is enigmatic 



Bregmaceros 

 Proposed Species Relationships 



B. rtectabanus 



.B can fori 

 .B. bathymaster 



B arabicus 

 B. rarisquamosus 



B. macclellandi 

 B. atlanticus 



B. japonlcus 



'<>^\ /Bregmacerotidae 



Fig. 157. Proposed species relationships of the Bregmacerotidae. 

 The possible relationships, indicated by the branching points, are based 

 on interpretations of species distributions and on meristic characters 

 and larval pigmentation. 



because it differs substantially from all described species. Be- 

 lyanina (1974, 1980) believed that B. nectabanus was the com- 

 mon neritic Bregmaceros in the western Atlantic but subsequent 

 research (Milliken, 1975; Houde, 1981; Milliken and Houde, 

 1984) has demonstrated that the western Atlantic species, B. 

 cantori, differs substantially in modal vertebral numbers and 

 median fin ray counts, and also that the larvae differ significantly 

 in pigmentation characteristics. 



Based on the species characteristics and known distributions, 

 possible relationships among species are proposed in Fig. 157. 

 Belyanina ( 1974) believed that the two oceanic species, B. mac- 

 clellandi and B. atlanticus, evolved from neritic species. It seems 

 equally probable that the neritic species evolved from the two 

 circumtropical, oceanic species. B. macclellandi and B. atlan- 

 ticus are very similar. They have relatively high meristic counts 

 and are darkly pigmented. Their larvae are heavily pigmented 

 and tend to be deeper-bodied than larvae of neritic species. The 

 neritic species, except B. arabicus. have vertebral numbers and 

 median fin ray counts much lower than those of B. macclellandi 

 and B. atlanticus. As larvae the neritic species are relatively 

 thin-bodied and lightly pigmented (Table 84, Figs. 1 5 3 and 1 54). 



Bregmaceros nectabanus. B. arabicus and B. rarisquamosus 

 overlap broadly in their ranges of occurrence, as do B. mac- 

 clellandi and B. atlanticus and, to a lesser extent, B. cantori and 

 B. Type A. Species frequently are collected together as larvae 



