BROTHERS: OTOLITH STUDIES 



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Fig. 24. Pnmordia and cores of goby otoliths. (A) Sagilta of adult sirajo goby {Sicydiuni plumieri). (B) Sagitta from an unidentified goby larva. 



100 families of fishes, this soil of sagittal growth pattern appears 

 to be characteristic in a number of higher level taxa (e.g., many, 

 but not all, perciform families; some myctophids; certain but 

 not all anguilloid families, pleuronectiform, gadiform and scor- 

 paeniform fishes; Percopsis, and others). It is not certain whether 

 the presence of this character is consistent enough to be used 

 as a diagnostic feature, and it also occurs too late in development 

 to be of use in larval identification. Lapilli and asterisci tend to 

 show more gradual changes in shape and growth (Brothers and 

 McFarland, 1981) and I have not observed the discontinuous 

 pattern described above. Lapilli undergo transitions in incre- 

 mental patterns at about the same time that the sagitta changes 

 in growth form (Brothers and McFarland, 1981; Brothers, un- 

 published), however these are not obviously evidenced in ex- 

 ternal morphology of the former. 



An unusual and surprising character has been found in a 

 preliminary survey of several of the "lower" teleosts. This fea- 

 ture, the presence of otoconia in the sacculus and/or utriculus 

 in addition to the otoliths, has only been noted for non-teleos- 

 tean bony fishes, i.e., holosteans, chondrosteans, brachiopte- 

 rygians, dipnoans (Carlstrom, 1963) and probably Latimena 

 (Brothers, unpublished). Osteichthyan otoconia or statoconia 

 are numerous (hundreds to thousands), small (from a few to 

 1 00 ^m) calcareous bodies (vateritic, sometimes aragonitic) which 

 are found in close association with the otolith (Fig. 22). They 

 generally have a very characteristic lens shape, although some 

 may tend towards an hexagonal outline. Internal features are 

 variously developed; a primordium-like body is usually present 

 and incremental growth is seen in some. Unexpectedly, otoconia 

 were found in representatives of the following teleost families: 

 Albulidae, Congridae, Anguillidae, Muraenidae. Moringuidae, 

 Notopteridae, Osteoglossidae and Pantodontidae. The character 

 appears to be an example of a synplesiomorphy shared between 

 non-teleostean osteichthyans and two teleostean superorders, 

 and Osteoglossomorpha and the Elopomorpha. Not all species 

 and possibly families in the latter two groups show the character, 

 so apparently it has been lost independently more than once. 

 The presence of otoconia is usually not apparent until the early 

 juvenile stage, they are not seen in the few larvae I've had 

 available, however, their taxonomic interest warrants mention 

 here. 



Internal Morphology 



There are a number of taxonomically related trends in the 

 size and shape of the primordium and core of sagittae and lapilli. 

 Table 6 lists all the families (of 1 13 sampled) found to have 

 representatives with multiple or clustered primordia (inclusion 

 in the table does not necessarily indicate that all family members 

 have the character). In some, particularly the salmonids and 

 related families, the primordia are clearly separated and may 

 each be surrounded by discrete multiple cores, whereas in others, 

 such as the Atheriniformes and Gasterosteiformes, the multiple 

 primordia are more lightly grouped and are usually surrounded 

 by a single core (Fig. 23). 



Two other primordium and core characters have been found 

 to be unique to certain taxa. In the gobies and related families 

 ( 1 5 genera; Gobiidae, Microdesmidae, Eleotridae, and Gobioid- 

 idae) all species invariably have an elongate primordium in the 

 sagittae and lapilli (usually with a slight central constnction. Fig. 

 24) which has not been seen in any other group. Since this feature 

 is present at hatching, it allows for rapid and certain identifi- 

 cation of these speciose families. The parrotfishes (Scaridae, 4 

 genera examined) appear to have a family-specific early growth 

 pattern in the sagitta which also allows for the identification of 

 very young larvae. The nearly spherical primordium and core 

 grow asymmetrically for about the first 5 days, adding new 

 increments in a restricted area on the distal face before the 

 growth pattern changes to one producing a hemispherical larval 

 otolith. The result of this pattern (Fig. 25) is that the core is 

 clearly on a different focal plane from a section normal to the 

 majority of larval growth increments. The core is therefore 

 asymmetrically placed nearer to the proximal or internal face 

 of the sagitta. This feature is easily observed in whole larval 

 otoliths and has not been found in related families such as the 

 labrids, although these families share other larval otolith char- 

 acters. 



A second class of internal features has obvious external man- 

 ifestations described above, although they may be distinguished 

 externally for only a discrete period in development. "Secondary 

 growth centers" appear in optical sections or SEM views as foci 

 for increment formation removed from the core (Fig. 2 1 ). Sp)ecies 

 in which otoconia occur are also found to have these bodies 



