Ecological Significance of the Neglecta Form of Thysanoessa Inermis (KrØYer) (Euphausiacea)

Author: Berkes, Fikret

Source: Crustaceana, Volume 33, Number 1, 1977 , pp. 39-46(8)

Publisher: BRILL

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Abstract:

Studies were carried out on the numerical proportion, variation in the degree of leg elongation, distribution, and food and feeding of the two morphological forms of Thysanoessa inermis in the Gulf of St. Lawrence. Almost all of the older larvae are of neglecta form with long second thoracic legs and divided eyes, but the proportion of the short-legged inermis form in the population increases progressively with age. The vertical and geographical distributions of the two forms are similar, and the two forms tend to occur together (Fager-McGowan Affinity Index of 1.55). According to stomach content studies, both forms were omnivorous, but neglecta stomachs contained significantly more animal matter than did inermis stomachs in August and January samples. In May, the season of food abundance, stomach contents of the two forms were similar. Studies with live animals support the inferences from stomach content data that animal food is more readily taken by neglecta than by inermis. The ecological significance of the neglecta form may lie in its food specialization and the consequent benefit of this to the population.

Document Type: Research article

DOI: http://dx.doi.org/10.1163/156854077X00214

Affiliations: 1: Marine Sciences Centre, McGill University, Montreal, Canada

Publication date: 1977-01-01