头足类耳石轮纹研究进展

头足类耳石与鱿类一样，是一种很好的信息载体，它具备2个基本条件，即：1）信息的输入稳定；2）所输入的信息能得到良好的储存。因此耳石研究可拓宽人类对头足类生物学的了解范畴，尤其是加深对繁殖生物学的认识，丰富渔业资源管理的方法和手段。本文从研究方法和应用方面，综述30年来头足类耳石及其轮纹的研究成果及进展，期望为头足类生物学研究提供有效的方法。     

Distribution, larval stage duration and growth of the sea lamprey ammocoetes, Petromyzon marinus L., in a highly modified river basin

Abstract  – Larval stage duration of the sea lamprey, Petromyzon marinus , in the River Mondego is estimated to last for 4 years. The number of annuli provides reliable age estimates when compared with length–frequency distributions analysis. The growth rate of the sea lamprey ammocoetes displays strong seasonal patterns, and reaches its highest value during the first 2 years of larval stage. About 69% of the length increment between hatching and metamorphosis is attained at the end of the second year. There is a longitudinal gradient associated with ammocoete distribution along the river. Relative abundance of ammocoetes decreases downstream from the Açude-Ponte dam, the first obstruction encountered by the adult sea lampreys in their upstream spawning migration along the River Mondego.     

Spatial difference in elemental signatures within early ontogenetic statolith for identifying Jumbo flying squid natal origins

Signatures of trace elements and isotopes in the parts of hard structures formed in the early ontogenetic stages can be used as potential natural tags of adult cephalopods to trace their origins. The Jumbo flying squid, Dosidicus gigas, is widely distributed in the eastern Pacific Ocean. Fourteen detected elemental signatures (⁷Li, ²³Na, ²⁴Mg, ³⁹K, ⁴³Ca ⁵⁵Mn, ⁵⁹Co, ⁶⁰Ni, ⁶³Cu, ⁶⁶Zn, ⁸⁸Sr, ¹³⁷Ba, ²⁰⁸Pb and ²³⁸U) were determined in the nuclear zone (N), representing the embryonic stage, and the postnuclear zone (PN), representing the paralarval stage of statoliths for adult D. gigas collected off the Costa Rican, Peruvian and Chilean Exclusive Economic Zones (EEZs) using laser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS). All measured signatures were significantly different between embryonic and paralarval statoliths, except for Sr, Ba and Pb. Over the three regions, a significant difference was found for Na and Ba within embryonic statoliths and Zn and Ba within paralarval statoliths. A high Ba/Ca ratio in statoliths obtained from Costa Rica was because of the prevalence of strong upwelling in the area. Elemental signatures, especially Ba/Ca, in early ontogenetic statoliths could be used as a proxy for distinguishing different geographical groups and identifying natal origins. However, elemental signatures in embryonic statoliths tended to be a better natural tag than those in paralarval statoliths indicating that paralarvae with the same origin had distinct dispersal pathways. Additionally, stepwise discriminant analysis (SDA) showed there were at least two migration‐based groups: ‘northern’ and ‘southern’ in the eastern Pacific Ocean. Overall, the derived results can improve our knowledge of the population structure, connectivity and life history of D. gigas.