404 



ONTOGENY AND SYSTEMATICS OF FISHES-AHLSTROM SYMPOSIUM 



fin rays. Size at hatching has not been well documented for 

 gasterosteiforms. Gasterosteids and Solenostomus may hatch at 

 3.0 mm TL (Padmanabhan, 1961; Hardy, 1978a), while Aulo- 

 rhynchus hatch at 5.5-8.0 mm TL (Marliave, 1976). Presence 

 of bony plates rather than scales is the rule in this order. These 

 plates are typically present and easily seen by the time notochord 

 flexion is complete (Figs. 218 and 219). Several groups develop 

 small spinules in the skin on the body early in development. 

 Macrorhamphosus develops spinules at about 6 mm TL (Sparta, 

 1936). All species of Fisliilaha go through a so-called "villosa 

 stage" (Liitken, 1880) during which they are covered with small 

 spinules (Fig. 219C). Pigmentation of species for which larvae 

 have been described varies from very heavy pigmentation in 

 Gasterosteidae and Macrorhamphosidae to rather light pig- 

 mentation in Syngnathidae and Fistulariidae. The young of sev- 

 eral species of syngnathids have conspicuous dark bars (D'An- 

 cona, 1933c; Takai and Mizokami, 1959; and Fritzsche, 1980) 

 (Fig. 2 1 8C). Dawson et al. ( 1979) reported the presence of elon- 

 gate dermal appendages in young of the syngnathid genus Yozia 

 (Fig. 218D). They believed that these appendages have a buoy- 

 ant function for aid in distribution of the pelagic young. 



Relationships 



Besides the hypothesis of relationships proposed by Pietsch 

 (1978b), there are several other recent hypotheses. Greenwood, 

 et al. (1966) proposed the following classification scheme: 



Order Gasterosteiformes 

 Suborder Gasterosteoidei 



Family Gasterosteidae 



Family Aulorhynchidae 



Family Indostomidae 

 Suborder Aulostomoidei 



Family Aulostomidae 



Family Fistulariidae 



Family Macrorhamphosidae 



Family Centriscidae 

 Suborder Syngnathoidei 



Family Solenostomidae 



Family Syngnathidae 

 Order Pegasiformes 



Family Pegasidae 



The family Indostomidae has at various times been thought to 

 be related to the gasterosteiforms (Bolin, 1936b; Berg, 1940). 

 But, Pietsch (1978b) has pointed out that the specific relation- 

 ship of this family must await further investigation. I have, 

 therefore, not included this monotypic family (I ndostoiniis par- 

 adoxus) in this account. 



Banister (1967) proposed a classification based on his osteo- 

 logical studies as follows: 



Order Aulorhynchiformes 



Family Aulorhynchidae 



Family Gasterosteidae 

 Order Aulostomiformes 

 Suborder Aulostomoidei 



Family Aulostomidae 



Family Fistulariidae 



Family Solenostomidae 



Family Syngnathidae 

 Suborder Centriscoidei 



Family Macrorhamphosidae 



Family Centriscidae 



His scheme differs little from previous ideas except in use of 

 new ordinal names (to reduce confusion?) and inclusion of the 

 closely related macrorhamphosids and centriscids in their own 

 suborder. Characters of his Centriscoidei are ( I ) separate meta- 

 pterygoid present and anterior end of quadrate normal; (2) nasals 

 large and elongated; (3) five or more modified anterior vertebrae; 

 (4) supraethmoid contributes little to dorsum of snout; (5) post- 

 temporal pyramidal; (6) caudal fin skeleton uniform, with single 

 large hypural plate; (7) vertebral number low (about 20); (8) no 

 sign of reduction in pharyngeal skeleton; and (9) intemeurals 

 for vertebrae five and six absent. Banister's (1967) hypothesis 

 of relationships has not been published. 



Nelson (1976) proposed a classification that was similar to 

 that of Greenwood et al. (1966) except that the families Gas- 

 terosteidae and Aulorhynchidae were recognized as forming the 

 order Gasterosteiformes while the remainder of the families 

 were placed in Syngnathiformes. This separation was done 

 pending clarification of relationships and establishment of 

 monophyly. As noted earlier, Pietsch (1978b) was able to link 

 the two groups based on the intermediate nature of the pega- 

 soids. 



Ida (1976) demonstrated that the monotypic Hypopiychus 

 dybowskii Steindachner resembled gasterosteids and aulorhyn- 

 chids in osteology, mode of life, and reproduction. He, therefore, 

 removed this species from the Perciformes and placed it close 

 to the Gasterosteidae and Aulorhynchidae in the suborder Gas- 

 terosteoidei of his order Syngnathiformes. 



Early life history stages have contributed little to the devel- 

 opment of the above hypotheses of relationships. Pietsch ( 1 978b) 

 showed that snout structure of Pegasus and Macrorhamphosus 

 is very much alike at small sizes even though it is quite different 

 in adults. Ida (1976) used egg morphology as one of the char- 

 acters supporting his placement of the Hypoptychidae close to 

 the Gasterosteidae. 



Considering the paucity of developmental descriptions for 

 species of the Gasterosteiformes, it is difficult to test existing 

 hypotheses of relationships using developmental characters. 

 However, it is interesting to note the sequence of fin formation 

 seems to support the close relationship of the Gasterosteidae 

 and Aulorhynchidae. Aulorhynchus forms the pectoral fins first, 

 followed by the caudal, second dorsal and anal fins (Marliave, 

 1976). The gasterosteid Apeltes follows the same sequence 

 (Hardy, 1978a). Gasterosteus forms the pectoral fins after the 

 anal fin (Hardy, 1978a). Few developmental sequences are known 

 for the other gasterosteiforms. Those that are available show 

 that for the pegasids, macrorhamphosids and syngnathids the 

 sequence begins with the development of the dorsal fin followed 

 by the anal, caudal and pectoral. It may well be that the sequence 

 of fin formation will provide evidence for the retention of the 

 Gasterosteidae and Aulorhynchidae in their own order or sub- 

 order. Additionally Macrorhamphosus. Acoliscus and Fislularia 

 develop a dorsal finfold that extends on to the head which might 

 be given as evidence in support of Pietsch's (1978b) infraorder 

 Macrorhamphosa. However, pegasids also have this anteriorly 

 placed finfold (Leis and Rennis, 1983). This coupled with the 

 low myomere numbers for pegasids and macrorhamphosids may 

 indicate that these two groups should be placed closer together 

 than is presently indicated in Pietsch's treatment. This question 

 must remain unresolved pending further descriptive and com- 

 parative work on gasterosteiform larvae. 



Studies of the relationships of Gasterosteiformes to other taxa 

 have been dominated by unsupported hypotheses. Gosline(197I) 

 proposed that the "origin for both gasterosteoids and synga- 



