EARLY DEVELOPMENT OF THE LONGHORN SCULPIN, 

 MYOXOCEPHALUS OCTODECEMSPINOSUS 1 



William A. Walsh and William A. Lund . Jr 



ABSTRACT 



Illustrations and descriptions of the early development of longhorn sculpin, Myoxocephalus octodecem- 

 npinosus, reared in the laboratory included six symmetrical cleavages, cell multiplication, blastula formation, 

 gastrulation, eight embryonic and six larval stages, and a juvenile stage. Development at 5 C began with ini- 

 tial cleavage at 8 hours, proceeded to gastrulation at 132 hours, early embryogenesis at 168 hours, and hatch- 

 ing between 36 and 65 days, with maximum activity between 41 and 48 days. Absorption of the yolk sac was 

 completed about 10 days after hatching, metamorphosis to the juvenile stage occurred at about 55 days, and 

 adult pigmentation developed between 65 and 104 days. 



Characters useful for the identification of longhorn sculpin eggs included egg color, egg capsule diameter, 

 width of the peri vitelline space, and appearance of the chorion. Identification of longhorn sculpin larvae and 

 juveniles was possible utilizing size, pigmentation, meristics, and cephalic spination. 



Comparison of reared longhorn sculpin larvae with descriptions of larvae collected in the Gulf of Maine and 

 Canadian waters revealed some differences in pigmentation, development of anal and dorsal fins, and dura- 

 tion of retention of the embrvonic finfold. 



Longhorn sculpin, Myoxocephalus octodecemspino- 

 sus, is a common inhabitant of the coastal waters of 

 the northwest Atlantic; it occurs north to the Gulf of 

 St. Lawrence and is common around Prince Edward 

 Island, the Scotian shelf (Leim and Scott 1966), and 

 south regularly to New Jersey (Bigelow and 

 Schroeder 1953). It is found from very shallow water 

 out to at least 50 fathoms (Huntsman 1922; Vladykov 

 and McKenzie 1935). 



In Block Island Sound, R.I., longhorn sculpins move 

 inshore to spawn from November through February, 

 and maximum spawning occurs from mid-December 

 to mid- January (Morrow 1951). They deposit demer- 

 sal egg masses of various colors (Morrow 1951; 

 Bigelow and Schroeder 1953; Leim and Scott 1966). 



Little is known about the early life history of this 

 species. Chenoweth (1973) believed that three 

 species of Myoxocephalus utilize the estuaries near 

 Boothbay Harbor, Maine, as primary spawning and 

 nursery areas because larval longhorn sculpins, 

 shorthorn sculpins, M. scorpius, and grubbies, M. 

 aenaeus, are abundant in the upper reaches of 

 estuaries in late winter and early spring. Herman 

 (1963) reported that Myoxocephalus spp., which are 

 the predominant larvae in January and March 

 ichthyoplankton collections in Narragansett Bay, 

 R.I., are mostly longhorns. Khan (1971) stated that 

 longhorn sculpin larvae are common in the Gulf of St. 



'Contribution No. 150 from the University of Connecticut, Marine 

 Research Laboratory, Noank, Conn. 



'The University of Connecticut, Department of Marine Sciences, 

 Marine Research Laboratory, Noank, CT 06:140. 



Lawrence and the Gulf of Maine in late winter and 

 early spring. Pearcy and Richards (1962) and 

 Wheatland (1956) believed that M. aenaeus larvae 

 are predominant in the Mystic River, Conn., estuary 

 and Long Island Sound and that longhorn sculpin lar- 

 vae are rare or absent. 



Little detailed information on the early develop- 

 ment of M. octodecemspinosus is published. Morrow 

 (1951) described gametogenesis and ripe ovarian 

 eggs and stated that longhorn sculpins mature in 

 their third year, at about 24 cm TL ( total length) , and 

 an average female produces about 8,000 eggs annual- 

 ly. Khan (1971) provided illustrations and descrip- 

 tions of longhorn sculpin larvae from ichthyo- 

 plankton collections. This paper presents a complete 

 description of the early development of M. 

 octodecemspinosus. 



MATERIALS AND METHODS 



Ripe longhorn sculpins were obtained during 

 December 1980 and maintained at ambient tempera- 

 ture in continuous- flow aquaria. Eggs were artificially 

 fertilized on seven occasions in 20 cm glass finger- 

 bowls containing about 1 ,000 ml of filtered seawater. 

 Eggs were kept in 20 cm fingerbowls and 4,000 ml 

 glass beakers in either a temperature-controlled 

 water bath at 5.0° ± 0.5°C or at ambient temperature 

 in a bath of running seawater. Water in the closed sys- 

 tem was initially changed two or three times weekly, 

 but was changed daily after the presence of bacterial 

 contamination was detected in some containers. 



Manuscript accepted February 1 983. 

 FISHKKY BULLETIN: VOL si. NO. 4. L983. 



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