Number Of Dorsal Fin Rays Research Articles

The Taxonomy and Distribution of the Species of Gambusia (Pisces: Poeciliidae) in Belize, Central America

nicaraguensis and the G. puncticulata yucatana complex; a key for their identification is presented. G. nicaraguensis is restricted in Belize to either offshore localities in full-strength sea water or river mouths in water of high salinity, and does not occur in fresh water as it does farther south where it is the only species of Gambusia present. G. luma exhibits geographic variation in Belize, the populations in the far southern portion of the country having fewer pectoral-fin rays. Northern and southern Belize populations of G. sexradiata differ in modal number of dorsal-fin rays, depth of the caudal peduncle, and coloration. These differences are discussed in relation to the past geological history of Belize. The G. p. yucatana complex is represented by marine populations at offshore localities and by two forms of G. p. yucatana (slender- and deep-bodied) on the mainland. The taxonomic status of G. p. yucatana is discussed, and information is presented supporting the hypothesis that the differences between these forms have a genetic basis and are not the result of environmental factors.

Incidence of Subcaudal Melanaphores in Pre-extrusion Larvae of Redfish Species in the Newfoundland-Labrador Area

Pre-extrusion larvae of female redfish from the Newfoundland-Labrador area in 1958-66 were examined for the presence or absence of subcaudal melanophores. The larval samples from the sharp-beaked mentel/a-type redfish were readily separated into two groups. one with all or nearly all of the larvae possessing subcaudal melanophores and recognized as Sebastes tescietus, and the other tending to have a small fraction or none of the larvae with these melanophores and recognized as Sebastes mentel/a. Moreover, the larvae of S. fasciatus had on the average a greater number of subcaudal melanophores which were also usually larger than those of S. mentel/a. However. the presence of these melanophores in many of the North American S. mentel/a contrasts with the reported absence of subcaudal melanophores in larvae of Icelandic and Northeast Atlantic and of the North Atlantic oceanic populations of S. mentel/a. The female parents of larvae assigned to S. fasciatus had significantly lower vertebral. anal fin-ray and dorsal fin-ray numbers than those of larvae assigned to S. mentel/a. The occurrence of subcaudal melanophores in Sebastes marinus larvae generally resembled that in the North American S. mentel/a (as distinct from S. fasciatus) except that the former tended to have more larvae with melanophores than the latter. The meristic characteristics of the S. marinus parents more closely resembled those of S. mentel/a than those of S. tescietus. butthe fin-ray numbers in S. marinus tended to be lower than in S. mentel/a. In the Northwest Atlantic area from Flemish Cap to southern Labrador, the spawning females of S. mentel/a appear to live deeper and extrude larvae earlier in the year than those of S. fasciatus and S. marinus. These differences in distribution and biology and the occurrence of large immature S. mentel/a in the northern part of Newfoundland-Labrador area have management implications which are discussed.

The influence of temperature change on number of dorsal fin rays developing in Fundulus majalis (Walbaum)

The influence of temperature change on number of dorsal fin rays developing in Fundulus majalis (Walbaum)

Vertebral and Other Meristic Characteristics of Greenland Halibut, Reinhardtius hippoglossoides, from the Northwest Atlantic

Vertebral averages were not useful in separating Greenland halibut stocks of the northwest Atlantic, apart from the possible separation of the Gulf of St. Lawrence population.Mean numbers of vertebrae did not differ significantly at the 5% level within the main areas in samples collected between 1950 and 1968 from Baffin Bay to the southern Grand Bank. Mean numbers of vertebrae for each of these main areas also were, with one exception, not significantly different. Mean vertebral numbers of Greenland halibut from the northern Gulf of St. Lawrence (61.850 ± 0.057 SE) differed (P < 0.001) from the overall mean for the remainder of the northwest Atlantic (61.575 ± 0.014).The similar means were associated with similar temperatures at depths of 800 m and over, where eggs and early larvae are presumed to develop. Means of vertebral numbers of males and females were not significantly different.Precaudal and caudal vertebral numbers were negatively correlated. Fused vertebrae were not numerous and did not show much localization except toward the posterior end of the vertebral column, especially in the two most posterior whole vertebrae. The numerical value of each fused partial vertebra was very close to one.Anal and dorsal fin-ray numbers were highly correlated but were not correlated significantly with vertebral numbers. The means of dorsal and anal fin-ray numbers in a few samples from west Greenland to the southern Grand Bank were not significantly different.

南洋産キビナゴの一種<i>Spratelloides delicatulus</i> (Bennet)及本邦近海より得たる其稚仔

Several young and a post-larva of Spratelloides delicatalus (Fig. 1, C, B) were found near Amami-Oosima, although the adult form of it (Fig. 1, A) has been known endemic to the South Seas. the post-larva represents the so-called “white-fish” stage, a form characteristic to the clupeoid post-larva with reansparent elongated body. the young obtained measures 36-41mm. in lengthe, covered with scales on trunk, shape and coloration of which are nearly similar to those of the adult, although the proportions of head, eye and fins are larger but that of body-height is amsller than in the adult fish. During the period of growth and metamorphosis from the post-larva to the young stage, dorsal fin shifts forward, and ventral fin backward, whereas the relative position of anus does not change at all. The number of dorsal fin-rays tends to decrease in larger specimens, since one or two hindermost ones become buried in the groove and are thus hardly made out.