Choose another family AcartiidaeAegisthidaeArctokonstantinidaeArietellidaeAugaptilidaeBathypontiidaeBoholinidaeCalanidaeCandaciidaeCentropagidaeClausidiidaeClausocalanidaeClytemnestridaeCorycaeidaeDiaixidaeDiscoidaeEctinosomatidaeEpacteriscidaeEucalanidaeEuchaetidaeEuterpinidaeFosshageniidaeGiselinidaeHeterorhabdidaeHyperbionychidaeKyphocalanidaeLubbockiidaeLucicutiidaeMecynoceridaeMegacalanidaeMegapontiidaeMesaiokeratidaeMetridinidaeMiraciidaeMisophriidaeMonstrillidaeMormonillidaeNullosetigeridaeOithonidaeOncaeidaePalpophriidaeParacalanidaeParalubbockiidaeParapontellidaeParkiidaePhaennidaePlatycopiidaePontellidaePontoeciellidaePseudocyclopidaePseudocyclopiidaePseudodiaptomidaeRataniidaeRhincalanidaeRidgewayiidaeRostrocalanidaeRyocalanidaeSapphirinidaeScolecitrichidaeSpeleoithonidaeSpeleophriidaeSpinocalanidaeStephidaeSulcanidaeTemoridaeThalestridaeTharybidaeThaumatopsyllidaeTisbidaeTortanidaeUrocopiidaeincertae sedis (Calanoida)incertae sedis (Cyclopoida)

Calanoida ( Order )

details

    Clausocalanoidea ( Superfamily )

details

 Abbreviations or symbols

issued from : E.L. Markhaseva & K. Schulz in Mitt. hamb. zool. Mus. Inst., 2008, 105. [p.49, Fig.12].
Geographical distribution of benthopelagic Aetideidae in the Atlantic Ocean including Polar regions (Markhaseva, 1996, 1997; Markhaseva & Schnack-Schiel, 2003; Markhaseva & Schilz, 2006; Schulz, 2002; Schulz & Markhaseva, 2000, and unpublished original data).

issued from : E.L. Markhaseva & V.YU. Razzhivin in Okeanol., 1984, 29 (3). [p.612, Gig.1].
Vertical distribution of the Aetideidae in the Kuril-Kamchatka trench region.
Thickness of bars indicates frequency of occurrence (percentage of total number of collections in the depth interval in question);
Numbering of the species in circle: 1- Aetideus pacificus; 2- Aetideopsis multiserrata; 3- A. rostrata; 4- A. retusa**; 5- Batheuchaeta animala**; 6- B. gurjanovae; 7- B. hepneri**; 8- B. lamellata; 9- Pseudeuchaeta spinata**; 10- Batheuchaeta peculiaris**; 11- Chiridius pacificus; 12- C. polaris; 13- Chiridiella abyssalis; 14- Ch. bichela**; 15- Ch. gibba**; 16- Ch. pacifica; 17, Ch. smoki**; 18- Ch. subaequalis**; 19- Euchirella curticauda; 20- E. formosa; 21- Gaetanus intermedius; 22- G. paracurvicornis; 23- G. brevispinus; 24- G. brevirostris; 25- G. inermis*; 26- G. robustus; 27- G. tenuispinus; 28- G. minutus; 29- Pseudochirella accepta; 30- P. batillipa*; 31- P. dubia; 32- P. pacifica; 33- P. palliata**; 34- P. obtusa; 35- P. tanakai**.
The species not previously identified in the region are marked by a siigle asterisk and those not previously reported in the Pacific by a double asterisk.

issued from : E.L. Markhaseva & F.D. Ferrari in Invert. Zool., 2005, 2 (2). [p.162, Table 4]
Setation of oral parts in females Aetideidae (Clausocalanoidea) and ancestral condition of setation.

issued from : E.L. Markhaseva in Pelagic Biogeography ICoPB II. Proceedings of the 2nd International Conference. Final report of SCOR/IOC working group 93. Noordwijkerhout, The Netherlands 9-14 July 1995. Workshop Report No.142. UNESCO, 1998. [p.252, Fig.3]
Distribution of benthopelagic aetideids in the World Ocean.

issued from : E.L. Markhaseva in Pelagic Biogeography ICoPB II. Proceedings of the 2nd International Conference. Final report of SCOR/IOC working group 93. Noordwijkerhout, The Netherlands 9-14 July 1995. Workshop Report No.142. UNESCO, 1998. [p.253, Fig.4]
Distribution of benthopelagic aetideids in the World Ocean.

issued from : B.H.R. Othman & J.G. Greenwood in J. Plankton Res., 1987, 9 (6). [p.1137, Table I].
Comparison of some characterristics of 13 species of Bradyidius.

issued from : E.L. Markhaseva in Pelagic Biogeography ICoPB II. Proceedings of the 2nd International Conference. Final report of SCOR/IOC working group 93. Noordwijkerhout, The Netherlands 9-14 July 1995. Workshop Report No.142. UNESCO, 1998. [p. 252, Fig.2]
Distribution of Bradyidius in the World Ocean.

issued from : J.C. von Vaupel Klein in Crustaceana, Supplt 9, Studies on Copepoda, III, 1984. [p.168].
Females.
Adoption of the hypothesis of species-group relationships as documented in the cladogram yields the following classification, which takes into account phyletic sequencing.
Nota: Given the preliminary status of the present results, a formal recognition of any of these groupings at the subgeneric level would be premature; even a future status as separate subgenera does not seem desirable, with the possible exception of both the rostrata-group and its alleged sister-group, because of the many derived differences

issued from : J.C. von Vaupel Klein in Zool. Verh. Leiden, 1998, 323. [p.384, Fig.1].
General body shape of the females and putative phylogenetic relationships among the eight species-groups recognized in Euchirella. (modified from Von Vaupel Klein, 1984).

Author's remarks: << The species-groups recognized comprise one to six described species each.
Within such groups, differences among members mainly pertain to the structures involved in reproduction, i.-e, the genital somite in the female along with the spines on the 1st basipodal segment of her P4, as well as the P5 in the male. On the contrary, the overall body shape of the vaious species in a group appears to be remarkably uniform.
However, in two of the species-group, both the E. curticauda- and the E. rostrata-group, we find cases of species which exhibit overall external appearances that are so similar as to become close to indistinguishable,
These cases comprise the pair E. curticauda Giesbrecht, 1888 versus E. maxima Wolfenden, 1905, as well as E. rostrata (Claus, 1866) versus the couple E. latirostris Farran, 1929 plus E. rostromagna Wolfenden, 1911. In another instance, which involves the relationship between E. latirostris and E. rostromagna, also the body size is virtualy equal, but in this case a distinction in the species’ respective distributions over the vertical water column may be assumed.
Almost all Euchirella species exhibit cosmopolitan distribution or nearly so. (Von Vaupel Klein, 1984, p.31), or at least are distributed circumglobally on the southern Hemisphere. The species pairs or triplets here under consideration are no exception, implying that in each case a substantial overlap in distributional ranges exists.
In view of the largely coinciding areas of E. curticauda and E. maximaon the one hand, and those of E. rostrata vis-à-vis E. latirostris/E. rostromagna, on the other, two cases of niche-partitioning were surmised already (Von Vaupel Klein, 1982a ; 1982b ; 1984 ; 1992).
These data have next been examined in the light of the work of Hutchinson (1959), who was the first to make an attempt at quantifying the phenomenon (presumably) non-overlapping niches of the species that together make up a biocoenosis. His approach involved determining the actual size of primary structures of the feeding apparatus in the various forms at issue, a feature that consequently has been examined in the present study as well. Likewise, the striking similarity in both body shape and size of E. rostromagna and E. latirostris, geographically co-occurring in the southern ocean, has been probed under a hypothesis of habitat-segregation.
The concept of niche-partitioning, i.e., the splitting of a single ancestral, ecologiocal niche into two new (hence narrower) niches, was introduced into evolutionary biology and systamatics by Maynard Smith (1962 ; 1966) as an essential component of his classical model of sympatric speciation. The principle would adequately explain the absence of competition, hence the conditions for non-interfering coexistence, in two structurally similar forms
Habitat-segregation is a concept derived from Mayr’s (1963) scenario alludind to the micro-geographic variant of dichopatric [pertaining to populations or species having geographical ranges separated to the extent that individuals from the two populations never meet and gene flow is not possible (after Lincoln, Boxshall & Clark, 1982)] speciation and explains the geographical co-occurrence of closely relaed species through the effective separation of their factually relevant, respective habitats.
Copepods of the genus Euchirella have been shown to live on a mixed diet with a prevailing raptorial component.
The general observation that interspecific size-differences are instrumental in consolidating niches in a biocoenosis has since long been made for aquatic communities (cf. Hutchinson, 1951). The fact that also intraspecific variation in body dimensions is found in, i.e. neritic marine copepods occurring in (temporal or spatial sequences of) more finely structured habitats, underlines the importance of an adequate body size for properly performing a given role in a biotic community (cf. Steuer, 1923 ; Myers & Runge, 1987 ; Runge & Myers, 1987 ; Pessitti & al., 19877).
To consider the size of food gathering or –processing attibutes in determining possible disticness of niches has been based on the work of Hutshinson (1959). According to his survey, differences at the specific level between the trophic structures of adult organisms can be described by a factor 1.1 to 1.4, with an average of 1.28. This applies if 1/ the species at issue are closely related, i.e. congeneric ; 2/ have a similar morphology and 3/ are occurring sympatrically [differenciation and attainment of reproductive isolation of populations that are not geographycally separated and which overlap in their distibution ( inLincoln, Boxshall & Clark, 1982)]. In other words : if they would be potential competitors for food resources within the same biocoenosis. According to general ecological principles (cf. Odum, 1959), there can be no doubt that every species has its own niche (art least one, cf. Von Vaupel Klein, 1984, p.156-157). Also, the observation that the acquisition, handling, and ingestion of food makes up an important aspect of a species’ niche can hardly be surprising : next to shelter and breeding sites (or, more generally, the opportunity to successfully reproduce), fodd prominently figures among the chief requirements to maitain a viable population within an ecological community.
Then, if two species share the qsame area and habitat, in other words, are components of the same biocoenosis, and show different shapes but differ decidedly in size, the conclusion that their apparently unhampered coexistence must be based on differences in the size of their nourishment, of which the dimensions of their feeding structures would bear witness, seems fully justified. As regards the size factor (cf. Hutchinson, 1959), the actual value of it not be completely universal, but the fact that such a factor 1/ does constitute a real feature of ecological relationships among congeners, and 2/ has a fairly constant value among comparable organisms in comparable communities, may firmly be rooted in the competitive exclusion principle of Harding (1960).
This aspect of congeneric coexistence in the pelagic environment may well be expected. Thus, the present observations are meant to provide the first data in the quest for (the value of) a niche-discriminating size factor in the pelagic environment. The size-factors found, ranging between 1.60 and 2.10 (with average values of 1.65-1.96, see tables 1-2) are well above the 1.28 zestablished by Hutchinson (1959), which may be surmised to constitute an intrinsic characteristic of the biocoenosis here under considration.
To represent the actual size of the feeding structures of the organisms at issue, that of the maxillipeds may be considerd a relevant dimension since aetideid (and also euchaetid) copepods use their maxillipeds, which are remarkably modified for seizing and/or holding prey. This implies that these appendages can provide appropriate parameters for detecting differences in performance of catching food items of different size ranges, hence for defining the nutritional aspect of a species’ niche.
Thus, the mere fact that such differences are found between two phylogenetically closely related species sharing the same biocoenosis, may well be interpreted as strong evidence in favour of a case of niche-partitioning. This becomes the more convincing if one realizes that the plankton communities under consideration are known to comprise close to a hundred species of calanoids alone, which, each with 12 distinct feeding stages [ecophases after Dussart], will thus account for an odd 1200 niches already (cf. Von Vaupel Klein, 1984, p.155-157). Among them are invariably at least 20-30 species of Euchirella and Pseudochirella, and /or Euchaeta/Paraeuchaeta present, which organisms represent a trophic level of larger, predatory forms. This inevitablty evokes the asumption that apparently the subdivision of prey organisms, hence also the specialization among predators, must be extremely finely graded in an ecological sense (cf Mullin, 1967)
Then, taking into account the differences measured between E. curticauda and E. maxima on the one hand, and those between E. rostrata and E. rostromagna/E. latirostris on the other (see Tables 1-2), it seems justified to interpret both relationships as comprising the results of processes of niche-partitioning. With the emergence of two new species from a single ancestral form, the original niche of that ancestor has apparently been split up among the two daughter species, through their difference in size, warranting a minimum of competition between the two new forms which thus presumably hunt for similar organisms that fall, however, into distinctive size categories.
The assumption that food items for the large rand the smaller species in a pairwise comparison would be similar but differ in size, is further supported by comparing the lengths of the various structures of the maxillipeds in a relatve sense.
In E. curticauda, basipodal segment 1 : basipodal segment2 : largest seta as 26 + 37 + 37 = 100 (See Figure 2, p.387), while in E. maxima as 27 + 33 + 40 = 100. Like wise, in E. rostrata these valus were determined at 29 + 33 + 38 = 100, as comparated to 29 + 35 + 36 = 100 in E. rostromagna and 26 + 33 + 41 = 100 in E. latirostris. In each case, there appears to be no basis to suppose, within one group, any large discrepancies in the qualitative features of the prey involved. Comparison between species-groups seems unwarranted, given the distinctness in shape of the body as outlined above. However, behavioural aspects of the ecology of Euchirella spp. Are as yet largely unknown and even, virtually inaccessible in view of the species’ bathypelagic way of life.
As regards the situation observed in E. rostromagna and E. latirostris, which despite their closely somilar morphology and size occur largely sympatrically, the partitioning of niches does not seem probable (althrough subtle anatomical differences exist, the most conspicuous one involving the density of the setules on the large setae of the antenna (cf. Von Vaupel Klein, 1984, p.45-46), the small differences in feeding structures are not indicative of the two species occupying distinct niches, with practically coinciding horizontal distributions, may well separated in a vertical sense (E. rostromagna found at depths ranging from 0 to 500 m, E. latirostris between 500 and 1000 m). In this case, then, it would appear that the phenomenon of habitat-segregation is at issue : two closely related species inhabiting the same geographical range but avoiding contact
The actual effectiveness of a spatial separation of species by the simple distinctness of their (daytime) depth ranges as here postulated would not seem improbable. De Meester (1994) demonstrated that inhabiting vertically distinct ranges may constitute an effective means to separate distinct clones of cladocerans (Daphnia spp).

In most groups of Euchirella, speciation seems to be intimately connected with Reproductive Isolating MechanismsSpecific Mate Recognition Systems or SMRS’s, cf. Paterson, 1985) involving the (secondary) reproductive organs, i.e. the genital somite of the female in conjunction with the male’s P5 and/or with the coupler of the spermatophorecf. Von Vaupel Klein, 1982b, p.72-84). However, this aspect seems less relevant in the E. rostrata-group, in which the females all have smooth, symmetrical genital somites. The situation in the E. curticauda-group is almost similar. Here, the asymmetry found in E. maxima is only slight compared to that in most other species-groups (cf. Von Vaupel Klein, 1982b ; 1984). However, size differences (of almost a factor 2) alone may well account for the existence of an effective RIM already, whence reproductive isolation might at least be assumed to have evolved concurrently with the separation of the niches.
Viewed the other way around, a simultaneous progress in both niche-partitioning and (the reproductive aspects of) speciation would even seem imperative given the observation by Paterson (1985, p.28) that species, once established, constitute rather stable units, their ecological niches included. This obviously implies that the actual divergence process would provide the best (if not only) opportunity to effectuate such changes, whence a shift in niche(s) and the development of RIM’s would have to be closely intertwined by necessity.

habitat-segregation, as inferred for E. latirostris and E. rostromagna, obviously has a comparable effect : in the absence of actual encounters, mechanical isolation by differences in secondary reproductive structures will have no selective value, meaning the genital somite’s can ‘afford’ to be similar. The aforegoing reasoning, of course, entirely departs from a mechanical point of view, thus disregarding possible chemical and /or (subtle) tactile cues which may well be of influence in the actual mating process (no data available as yet).

In view of the above, though having ruled out various specific modes of speciation to match the three separate cases investigated, multiple possibilities still remain :something which obviously prevents an unequivocal conclusion to be drawn. More data will have to be incorporated in order to allow anything of a conclusion about the mechanism(s) involved, especially if speciation mechanisms throughout the entire genus are to be considered. Among these are, detailed data on both recent and past distribution patterns of the species within a framework of paleogeographic conditions, unambiguaous figures on vertical ranges.br>In view of the alleged uniformity of the pelagic realm, a relatively high incidence of sympatric and stasipatric [formation of new species as a result of chromosomal rearrangements giving homozygotes which are adaptively superior in a particular part of the geographical range of the ancestral species (Lincoln & al., 1982] memechanisms has often been assumed in the past, such in contrast to the conditions in neritic habitats (cf. Battaglia, 1982). However, the observation that, with the exception of the macrogeographic mode (cf. Von Vaupel Klein, 1984, p.155-157), all models would seem suited to accound for speciation events in the marine pelagial, decidedly precludes making suppositions involving a quantitative preponderance of any (sub-)mode of speciation at the moment . >>

issued from : H.B. Owre & M. Foyo in Fauna Caribaea, 1967, 1, Crustacea, 1: Copepoda. [p.44, Figs.243-247].
Habitus comparison between species in the Florida Current.
Female (in lateral view): 243, Gaetanus kruppii; 244, G. latifrons; 245, G. miles; 246, G. minor; 247, G. pileatus.

issued from : E.L. Markhaseva & K. Schulz in Mitt. hamb. zool. Mus. Inst., 2008, 105. [p.33, Table 1].
Selected character states of Lutamator and Prolutamator females.

issued from : E.L. Markhaseva & K. Schulz in Mitt. hamb. zool. Mus. Inst., 2008, 105. [p.33, Table 1].
Selected character states of Lutamator and Prolutamator females.