The freshwater calanoida (crustacea : copepoda) of Singapore and Peninsular Malaysia

The systematics and geographical distribution of Malaysian and Singapore freshwater calanoid copepods are discussed in details. Neodiaptomus handeli Brehm, N. laii Kiefer, N. blachei (Brehm), N. botulifer Kiefer, N. mephistopheles Brehm, Pseudodiaptomus (Schmackeria) dauglishi Sewell, P. (S.) tollingerae Sewell and Tropodiaptomus spp. Kiefer are all present in the northwestern part of the Peninsula. There are only 4 species, namely, N. handeli, N. botulifer, N. meggitti Kiefer and Tropodiaptomus sp. in the southern half of the Peninsula. The whole of the east coast also has 4 species, i.e. N. handeli, N. malaindosinensis (n.n.), P. (S.) tollingerae and one species of Tropodiaptomus. The only species that cut across a wide range of geographical barriers are N. handeli and Tropodiaptomus.     

Lipid storage in Diaptomus kenai (Copepoda; Calanoida): effects of inter- and intraspecific variation in food quality

In nature, changes in nutrient levels and phytoplankton community structure can represent variation in food quality and quantity. Because zooplankton can be highly susceptible to starvation, individuals could enhance their survival, growth, and reproduction during periods of unfavorable food conditions by maintaining and utilizing energy stores. Patterns of lipid accumulation and depletion in Diaptomus kenai, a calanoid copepod from an oligotrophic montane lake, were monitored over a variety of food conditions. The results suggest that, while lipid storage in D. kenai is affected by phytoplankton community structure and abundance, total lipid stores respond more to gradual changes in food regime than to sudden changes in food supply.     

The lipid biochemistry of calanoid copepods

Calanus species, particularly those in high latitudes, can accumulate large oil reserves consisting predominantly of wax esters. These wax esters consist predominantly of 16:0, 20:1 (n–9) and 22:1 (n–11) fatty alcohols, mainly formed de novo by the animals from non-lipid dietary precursors, esterified with various fatty acids that are often polyunsaturated fatty acids and largely of dietary, phytoplanktonic origin. Wax ester formation is maximal in copepodite stages IV and V. The lipids are elaborated not primarily for buoyancy regulation but as a source of metabolic energy during overwintering, particularly for reproduction. Large quantities of wax esters are utilised for gonadal development when stage V copepodites mature to females. Development of stage V copepodites to males is not accompanied by wax ester utilisation but males consume large amounts of these lipids in physical activity during reproduction. The role of wax esters in the life history of calanoids is illustrated with particular reference to a comparison of Calanus finmarchicus and Metridia longa in Balsfjord, northern Norway.     

Geographic distribution of the bathypelagic genus paraeuchaeta (Copepoda,Calanoida)

The geographic distribution of the bathypelagic calanoid genus Paraeuchaeta was investigated by examining midwater trawl and plankton net samples collected mostly from depths exceeding 1000 m throughout the world's oceans. Of the 81 species referred to Paraeuchaeta, the geographic ranges of about 50 species could be defined with reasonable certainty. Contrary to early authors, the number of species having a worldwide distribution was surprisingly small (12 species or 15% of the 81 species of the genus) as compared to common species endemic to various geographic regions (34 species or 42% of the total of 81). Almost twice as many species were found in the Indo-Pacific Ocean as in either the Atlantic or the Southern Ocean. Faunistically, the northern Atlantic, mid-Atlantic, northern Pacific, East Pacific, Indo-West Pacific, and Southern Ocean were distinct in terms of endemic species. A number of species were found to be endemic to highly productive areas, where they were usually very abundant. Rare species, on the other hand, were generally found to be widely distributed, although some were too rare for their range to be determined with certainty. To explain these findings, the following hypothesis is proposed: Bathypelagic calanoids endemic to and abundant in eutrophic areas are those adapted to eutrophic conditions of their habitats and therefore cannot expand their ranges into contiguous oligotrophic waters even if the other environmental conditions are favorable. Other species, on the other hand, generally have extensive geographic ranges because of their survival ability in widely expanding oligotrophic conditions and the absence of physicochemical barriers at bathypelagic depths of the world's oceans.