Abstract. - Cephalopods were 

 examined from more than 3000 zoo- 

 plankton samples collected over a 

 two-year period from coastal and 

 estuarine waters of southwest Loui- 

 siana. In total, 270 cephalopods were 

 taken in 164 of these samples; 267 

 specimens from 161 samples were 

 Lolliguncula brevis. They were found 

 in coastal waters from April through 

 January, but in estuarine waters only 

 in May, July, and August. Maximum 

 standardized abundance was found 

 in the nearbottom waters of the es- 

 tuary in May. Overall, paralarval 

 L. brevis were most often collected 

 nearbottom in inshore coastal waters 

 during May-June. This species was 

 not collected in the estuary at salin- 

 ities below 27 x 10 " 3 . Although they 

 were found in coastal waters with 

 lower salinities (22 x 10 " 3 ), abun- 

 dance was generally greatest in 

 waters with salinities of about 26 x 

 10" 3 . Somewhat surprisingly, para- 

 larval L. brevis were collected 

 throughout the range of dissolved 

 oxygen concentrations sampled, in- 

 cluding waters considered to be 

 hypoxic, with <2mL/L dissolved 

 oxygen. Contents of the digestive 

 tract were examined in 50 paralar- 

 vae; 18% of these contained solid 

 food while others were inflated with 

 a semiliquid mush or clear liquid. 



Observations on the 

 Paralarval Ecology of a 

 Euryhaline Squid Lolliguncula brevis 

 (Cephalopoda: Loliginidae) 



Michael Vecchione 



Systematics Laboratory, National Marine Fisheries Service. NOAA 

 National Museum of Natural History, Washington, DC. 20560 



Manuscript accepted 30 January 1991. 

 Fishery Bulletin, U.S. 89:515-521 (1991). 



The squid genus Lolliguncula is in- 

 teresting from an evolutionary view- 

 point because this coastal genus in- 

 cludes the only species of cephalopod 

 known typically to inhabit low-salin- 

 ity estuaries, L. brevis. Thus, it is a 

 clear-cut example of adaptive radia- 

 tion of the stenohaline Class Cepha- 

 lopoda toward euryhalinity. Adapta- 

 tion to an unusual environment may 

 involve physiological or behavioral 

 changes in an organism at any point 

 in its life history. The physiology of 

 euryhalinity in this species has been 

 studied using trawl-caught squids 

 from Galveston Bay, Texas (Hendrix 

 et al. 1981, Segawa and Hanlon 1988, 

 Wells et al. 1988). The distribution of 

 adults and advanced juveniles has 

 been reported from trawling studies 

 of estuarine and coastal waters of 

 Texas (Hixon 1980) and Florida (Dra- 

 govich and Kelly 1963 and 1967, 

 Laughlin and Livingston 1982). Al- 

 though morphological aspects of the 

 development of this species have 

 been described (Hall 1970, Hunter 

 and Simon 1975, McConnathy et al. 

 1980, Vecchione 1982b), the only 

 published report on the distribution 

 of paralarvae (see Young and Har- 

 man 1988 for a discussion of the 

 term) was a brief note on distribution 

 near the northern limit of the species' 

 range (Vecchione 1982a). 



Studies of the early life history of 

 cephalopods have been relatively 

 infrequent because of logistical and 

 taxonomic difficulties (Vecchione 

 1987). However, such studies should 



eventually be useful for comparisons 

 with other taxa in the development 

 of early-life-history theory (Vecchi- 

 one 1986). I report here on the distri- 

 bution of paralarval L. brevis col- 

 lected during two concurrent studies 

 of zooplankton and associated hydro- 

 graphic parameters in the coastal 

 and estuarine waters of southwest 

 Louisiana. 



Vecchione (1987) concluded that 

 starvation resulting from failure of 

 first feeding may contribute substan- 

 tially to cephalopod mortality and 

 subsequent recruitment failure. 

 Therefore, the contents of the diges- 

 tive tracts in a subset of the speci- 

 mens also were examined to deter- 

 mine whether paralarval feeding by 

 L. brevis is amenable to study. 



Materials and methods 



Details of the collection methods 

 have been presented by Vecchione et 

 al. (1983). The collecting methods dif- 

 fered as described below, reflecting 

 the two separate studies that were 

 conducted concurrently over a two- 

 year period. 



The coastal study used a 60 cm 

 opening/closing bongo sampler for 

 triplicate one-minute tows at two 

 discrete depths (three depths during 

 February-April 1981) at nine sta- 

 tions monthly for 22 months, Febru- 

 ary 1981-November 1982 (Fig. 1, M 

 and D stations). Towing speed was 

 1.5-2.5 knots. Most stations were 

 located at the 10 m isobath and the 



515 



