256 



ONTOGENY AND SYSTEMATICS OF FISHES-AHLSTROM SYMPOSIUM 



Table 68. Distribution of Larval Character States Among 

 Myctophiform Families. 



* Number of denved character slates. 



repeatedly emphasized (i.e., Okiyama, 1974b, 1979b, 1981. 

 Johnson, 1974b, 1982). Contrary to earlier understanding (Oki- 

 yama, 1974b), much diversity of this character has been re- 

 vealed. Based on the number and shape of the sections, a pro- 

 visional classification is as follows: (A) Dorsomedial pigment 

 sections; (A-1) Single patch— Aulopidae, Chlorophthalnms. 

 Bathytyphlops. Rosenblattichthys. Scopelarchoides (in part); (A- 

 2) Many (three or more)— Bathysauridae, Bathypterois (in part), 

 Sudis. Omosudidae, Evermannellidae; (A-3) Single to many 

 patches with growth— Paralepididae (except Sudis). (B) Paired 

 pigment sections— Harpadontidae, Synodontidae. (C) Dorso- 

 medial and paired pigment sections— Scopelarchoides (in part), 

 Scopelarchus. (D) No pigment sections— Neoscopelidae (except 

 Solivomer), Myctophidae, Ipiiops. Bathymicrops. Bathypterois 

 (in part), Benthalhella. Notosudidae, Alepisauridae, Anotop- 

 teridae. 



Rare exceptions are also known for several of these types. 

 The only known exception to the presence of the A-3 type in 

 paralepidids is in Notolepis coatsi with a single pigment section 

 throughout all stages (Efremenko, 1978, 1983a). However, the 

 ontogenetic development of this section into the extensive per- 

 itoneal pigment tube around the gut as in other paralepidids 

 reveals little phylogenetic difference for this exception. Among 

 those having B-type, some Synodus reportedly lack the peri- 

 toneal pigment sections and may represent an extremely spe- 

 cialized character state (Cressey, 1981). On the contrary, a my- 

 tophid, Protomyctophuin anderssoni. is known to develop the 

 serially arranged paired pigment patches similar to those of B- 

 type(MoserandAhlstrom, 1974; Efremenko, 1976). Their over- 

 all resemblance including this pigmentation may be a result of 

 a simple convergence. 



As is clear from the above classification, character states are 

 remarkably diverse in the Scopelarchidae and Ipnopidae. C- 

 type, peculiar to the former, is of particular significance in sug- 

 gesting the possible direction differentiating the paired and un- 

 paired character states (Johnson, 1974b). Unclear limits of the 

 family are partly responsible for the confusion in Ipnopidae. 



It is generally agreed that the presence of a single, dorsomedial 

 peritoneal pigment section (A-1 type) represents the primitive 

 state. Since A-3 and C types are referable to the ranges of either 

 A-1 or 2, four states are recognized as in Johnson ( 1 982); (0) = 



A single, dorsomedial peritoneal pigment section. (1) = Multi- 

 ple (3 or more), serially arranged, unpaired peritoneal pigment 

 sections. (2) = Multiple (3 or more), serially arranged, paired 

 peritoneal pigment sections. (3) = Peritoneal pigment section 

 absent. 



Position of anus f2A— Contrary to the usual pattern of the anus 

 location immediately anterior to the anal fin origin in much 

 teleosts, a more or less wide preanal interspace is commonly 

 shared by many taxa of this order. This character can be of much 

 use in distinguishing the groups of Myctophiformes (Rosen, 

 1 97 1 ; Okiyama, 1 979b). The character states of the diverse anus 

 location relative to the pelvic fins are not recognized herewith 

 due to the unclear patterns of occurrence. 



The ontogenetic rearward shift of the anus is restricted to 

 some speciose families such as Scopelarchidae, Paralepididae 

 (except Sudis), Notosudidae, and Myctophidae (in part). There 

 is, however, a sharp contrast in the final condition among them: 

 no preanal interspace in Myctophidae and Scopelarchidae vs a 

 distinct space in the remaining two. As in Kendall ( 1982), who 

 employed this character in the first step of branching, two char- 

 acter states are recognized. (0) = Anus with interspace from the 

 origin of the anal fin. (1) = Anus just in front of the ongin of 

 the anal fin. 



Fin features (3). — Except Bathysauridae with magnificently en- 

 larged fins, the elongated pectoral fins are the pronounced larval 

 character found in many representatives of this order. The Ip- 

 nopidae displays the most diverse pattern of specialized pectoral 

 form in being bifid, large and fan-like, or extremely elongated. 

 Parallel features are known to occur sporadically in some spe- 

 cialized myctophidae (Moser and Ahlstrom, 1970, 1974). Sco- 

 pelarchidae is another member of less cohesiveness in this char- 

 acter; prominent pectoral fins are peculiar to Rosenblattichthys, 

 the most specialized genus in this family (Johnson, 1974b). 

 Likewise, only the aberrant genus Sudis has elongated pectoral 

 fins in Paralepididae. The character states recognized are: (0) = 

 All fins short. (1) = Only pectoral fins elongated. (2) = All fins 

 elongated. 



Sequence of fin formation i^-^A- Although current knowledge is 

 far from complete, dichotomous patterns can be recognized in 

 the sequence of fin formation, especially in the pectoral fins. 

 Johnson (1982) defined the derived character state of Rosen- 

 blattichthys by the development of pectorals prior to all fins 

 except caudal. The precocious nature of this fin apparently rep- 

 resents the derived state. (0) = Pectoral fins not precocious. (1) = 

 Pectoral fins precocious. 



Eye shape (5). — Moser and Ahlstrom (1974) showed that two 

 types of eyes, i.e., round and narrow, reflect the major two 

 lineages of Myctophidae with several exceptions. These patterns 

 are commonly duplicated at familial levels in this order. In view 

 of the specialized morphology of the narrow eyes including the 

 peculiar choroid tissue and following the suggested phylogeny 

 of Myctophidae (Moser and Ahlstrom, 1974), round or nearly 

 round eyes are regarded primitive. The states recognized are: 

 (0) = Eyes rounded or nearly rounded. (1) = Eyes narrowed. 



Head armature (6).— The development of head spines is rare 

 or rather exceptional particularly in the adult myctophiform 

 fishes. However, larvae of at least five families have head ar- 

 mature. These include preopercular spines and supraorbital and/ 



