Ontogeny and distribution of Hygophum benoiti (Pisces ...

M.P.OIivar and I.Palomera
Table I. Presence of H.benoiti larvae in the different cruises carried out in the North Western
Mediterranean
Month/year Latitude Presence
August 1984 40°30'-42°30'N +
September 1983 40°30'-42°30'N +
September/October 1984 40"30'-42°30'N +
October 1976 38°30'-42°30'N +
October 1982 41°30'-42°30'N +
October 1983 40°00'-41°30'N +
October 1983 40°30'-42°30'N +
December 1981 41°30'-42°30'N
January 1982 41°30'-42°30'N
March 1982 41°30'-42°30'N
April 1983 40°30'-42°30'N
May 1983 40 o 00'-41 o 30'N +
May 1983 40°30'-42°30'N +
May 1990 39°0O'-41°30'N +
May 1992 42°05'-42°00'N +
June 1983 40°30'-42°30'N +
June 1992 42°05'-42 1> 20'N . +
July 1983 40°30'-42 o 30'N +
June/July 1992 39°30'-43°30'N +
and our material in the ICM). Comparative material of H.proximum was also
obtained from Indo-Pacific collections from the waters around Australia
(Australian Museum) and Pacific collections from the waters around Japan
(Faculty of Fisheries, Kagoshima University).
Results
Based on pigmentation pattern, which was mainly useful in recently collected
material, we identified the larvae collected in June-July 1992 as H.benoiti
(Figure 2). Morphometric data on H.hygomii larvae from the Southwest Indian
Ocean used for comparative purposes (Figure 3) also showed differences
between H.benoiti and H.hygomii, which permitted us to re-identify all larvae of
Hygophum collected in previous cruises carried out in the North Western
Mediterranean and determine the spawning period of H.benoiti.
Morphology and morphometry
Larvae of H.benoiti were moderately slender, especially in pre-flexion stages.
As a proportion of body length, body depth at the pectoral base and head depth
showed significant allometric increases, with development (Figure 4). Relative
body depth and head depth were slightly smaller in H.benoiti than in H.hygomii
larvae (Figure 5).
In H.benoiti, the gut was slightly curved with a prominent fold-terminated
section. Pre-anal length versus body length was relatively constant with
development (Figure 4). The anterior section of the gut did not have transverse
rugae and was conspicuously thinner than the posterior section. The anterior
section was relatively longer in pre-flexion and flexion larvae (representing ~l/3
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