14 



Fishery Bulletin 88(1), 1990 



The environmental distribution of S. lessoniana in 

 North Queensland waters includes offshore reef en- 

 vii-onments as well as nearshore/estuarine habitats. Its 

 distribution thus overlaps that of /. pygniaeus. 



Materials and methods 



The two primaiy components of this study involved 

 (1) the collection of juvenile Sepioteuthis lessoniana 

 specimens, which were maintained alive and stained 

 with tetracycline or calcein to determine statolith ring 

 periodicity, and (2) the collection of field specimens, 

 which were fixed shortly after capture and subsequent- 

 ly used for age and gonad analysis. Thus all age esti- 

 mates were taken from field specimens that were not 

 exposed to artificial maintenance. 



Juvenile S. lessoniana were often seen along break- 

 waters in the Townsville region and occasionally in a 

 local estuary. Specimens commonly sheltered under 

 flotsam or floating pieces of ropes, singly or in schools 

 of up to 20. Juveniles were dipnetted and transported 

 back to the lab for subsequent tetracycline staining and 

 maintenance. Collections were made between May 

 1988 and February 1989. 



Larger individuals for ageing were captured using 

 squid jigs at night off the Picnic Bay jetty (lat. 1 9° 1 1 'S. 

 long. 146°50'E) on Magnetic Island (a continental 

 island ~7 km off Townsville) and the Australian In- 

 stitute of Marine Science jetty south of Townsville (lat. 

 19°17'S, long. 147°03'E). Night jigging took place 

 between November 1988 and February 1989. 



Squids were aged (i.e., statolith rings counted) and 

 examination of reproductive sti-uctures was carried out 

 to ascertain the level of maturity. Maturity was deter- 

 mined by the presence of spermatophores in the sper- 

 matophore sac in males and the presence of mature 

 oocytes in females. 



Maintenance and tetracycline staining 



Captured 5. lessoniana were transported back to the 

 lab and were maintained in 1500-L and 2500-L round 

 tanks located outside so that squids would maintain 

 normal diel periodicity. Specimens were kept alive as 

 long as possible to provide maximum statolith growth 

 before being sacrificed for examination, although in 

 many instances the maintenance was terminated by 

 death of the squid or sometimes by individuals jump- 

 ing out of the tank. Squids which survived the first few 

 days of captivity were maintained for between 9 and 

 39 days. Seawater from a closed recirculating system 

 continually flowed through the tanks. Feeding was (/(/ 

 libitum. Common food organisms maintained in the 

 tanks were the crustacean Acetes sibogae ansfralis and 

 Ambassid, Mugilid, and Clupeid fish species. On several 



occasions squids were induced to eat previously frozen 

 prawns. Up to seven squids were maintained concur- 

 rently in one tank. Their typical behavior was to hover 

 motionless in a school, aligned in the same direction. 

 The methods for tetracycline staining were the same 

 as used for Idiosepius pygmaeus (Jackson 1989). Speci- 

 mens were normally stained on the day of capture, and 

 if they survived long enough they were exposed to a 

 second staining at least 9 days later, with an interval 

 of 9-20 days between stainings. In one experimental 

 treatment, five squid were initially exposed for 1.5 

 hours to 100 mg of dissolved calcein per liter of sea- 

 water, and then stained a second time 11 days later 

 with tetracycline (250 mg/L, 2 hours). The calcein stain- 

 ing produced a very faint green fluorescence compared 

 with the very strong more yellow-green tetracycline 

 hydrochloride fluorescence. Exposure to calcein at a 

 higher concentration or for a longer time period is likely 

 to produce more prominent fluorescence under UV 

 irradiation. 



Preparation and observation of 

 statolith microstructure 



Sepioteufliis lesso)iiana specimens were preserved in 

 10% borax-buffered seawater formalin to fix tissues 

 and gonads. All length measurements refer to dorsal 

 mantle length (DML). Statoliths were removed the next 

 day within 12 hours to avoid damage from prolonged 

 exposure to formalin. Statoliths were exposed to a 1% 

 bleach solution for several minutes to remove excess 

 tissue, rinsed in distilled water, dehydrated with 100% 

 ethanol and mounted in the thermoplastic cement 

 Crystal Bond. Crystal Bond was found to be an ex- 

 cellent mountant, as it is completely translucent, does 

 not fluoresce under UV irradiation, and statoliths can 

 be easily manipulated or turned-over because it ijuick- 

 ly melts at a low temperature and hardens relatively 

 rapidly after removal from heat. 



Statoliths were then ground by hand on wet 1200- 

 grade carborundum paper. The scratches from the 

 grinding were removed by polishing the specimens 

 either by hand on wet suede with 0.05 jl* alumina 

 powder, or by using a modified gem polishing machine 

 equipped with a microscope slide-holding arm, in which 

 the statolith was lowered onto a fi-inch rotating disc 

 to which was attached a wet Leco Lecloth impregnated 

 with alumina powder. 



Statoliths rings were usually best visualized by grind- 

 ing and polishing the statolith on the anterior (concave) 

 surface only; however, in some statoliths that were 

 particularly opaque or thick, the ring structure was 



Referenoo to tradi' n;imes (iocs not imply tTKiorst'iiiciit liy the 

 National IMarine Fisheries Service, NOAA 



