CHAPTER '
THE LARVAE
The literature describing the development of species of Euphausiacea
is large but is reviewed by Sheard (1953) and Mauchline (1959). Further
descriptions of the larval development have been published since 1959
including a paper by Soulier (1965b) who suggests a method of comparing the development of different species. Some details are known
about the production, by the gonads, of eggs and spermatozoa and also
about the embryology of euphausiids. The egg is fertilized externally
and a nauplius emerges from it. This larva develops to a second
nauplius or a pseudometanauplius which in turn develops into a
metanauplius. The later stages of development of euphausiid larvae
have been given peculiar names, first ascribed to them by G. 0. Sars
(1885). Claus (1863) was the first to examine the larvae of euphausiids
but he did not recognize them as such ; instead, he gave them generic
and specific names because he thought he had found new species. Sars
simply applied these names-calyptopis, furcilia, and cyrtopia-to the
various phases in the development of euphausiids. He defined the
phases of development as follows :
1. NaupZius stage. Body oval, unsegmented. No compound
eyes. Three pairs of limbs only present, the anterior (antennulae)
simple, the two other (antennae and mandibular legs) biramous,
natatory.
Form of the body as in the nauplius
stage. Two pairs of limbs (antennulae and antennae) only developed ;
mandibular legs lost. Mandibles, maxillae, and maxillipeds present
merely as bud-like prominences.
3. Calyptopis stage. Body divided into two principal divisions.
Carapace distinct, forming anteriorly a hood-like expansion. Tail
becoming segmented. Compound eyes still imperfectly developed,
immobile, and covered by the carapace. Mandibles, maxillae, and
maxillipeds distinct, but no trace of legs and pleopoda. Uropoda
becoming developed.
4. Furcilia stage. Compound eyes more fully developed, mobile
and projecting beyond the sides of the carapace. Antennae still
2. Metanauplius stage.
103
THE LARVAE
The literature describing the development of species of Euphausiacea
is large but is reviewed by Sheard (1953) and Mauchline (1959). Further
descriptions of the larval development have been published since 1959
including a paper by Soulier (1965b) who suggests a method of comparing the development of different species. Some details are known
about the production, by the gonads, of eggs and spermatozoa and also
about the embryology of euphausiids. The egg is fertilized externally
and a nauplius emerges from it. This larva develops to a second
nauplius or a pseudometanauplius which in turn develops into a
metanauplius. The later stages of development of euphausiid larvae
have been given peculiar names, first ascribed to them by G. 0. Sars
(1885). Claus (1863) was the first to examine the larvae of euphausiids
but he did not recognize them as such ; instead, he gave them generic
and specific names because he thought he had found new species. Sars
simply applied these names-calyptopis, furcilia, and cyrtopia-to the
various phases in the development of euphausiids. He defined the
phases of development as follows :
1. NaupZius stage. Body oval, unsegmented. No compound
eyes. Three pairs of limbs only present, the anterior (antennulae)
simple, the two other (antennae and mandibular legs) biramous,
natatory.
Form of the body as in the nauplius
stage. Two pairs of limbs (antennulae and antennae) only developed ;
mandibular legs lost. Mandibles, maxillae, and maxillipeds present
merely as bud-like prominences.
3. Calyptopis stage. Body divided into two principal divisions.
Carapace distinct, forming anteriorly a hood-like expansion. Tail
becoming segmented. Compound eyes still imperfectly developed,
immobile, and covered by the carapace. Mandibles, maxillae, and
maxillipeds distinct, but no trace of legs and pleopoda. Uropoda
becoming developed.
4. Furcilia stage. Compound eyes more fully developed, mobile
and projecting beyond the sides of the carapace. Antennae still
2. Metanauplius stage.
103