An account of the Crustacea of Norway V6-1 Copepoda Cyclopoida

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AN ACCOUNT OF THE CRUSTACEA NORWAY WITH SHORT DESCRIPTIONS AND FIGURES OF ALL THE SPECIES BY G O SARS VOL VI COPEPODA CYCLOPOIDA PARTS I & II OITHONID^E, CYCLOPINID^E, CYCLOPIDjE WITH 16 (part) AUTOTYPIC PLATES BERGEN PUBLISHED BY THE BERGEN MUSEUM ( SOLD BY ALB CAMMERMEYEE'S FOELAQ, CHRISTIANIA 1913 INTRODUCTION Under the head Cydopoida whole the may be fleas (Cyclops), said a number of Copepoda, which on be built upon the type of our to though exhibiting pearance and I comprise many common fresh-water modifications, both as to their general ap- to their habits, the latter affecting chiefly the structure of the oral The present group, or sub-order, exhibits some relations both to the Calanoida and to the Harpacticoida, and also shows a certain approach to some parts of sub-orders other the and Notodelphyoida the generally families Caligoida, Whereas easily recognisable has distinguished by the present author, especially to the though the Cyclopoid type may always be the extensive group Harpacticoida by earlier authors been comprised within a single family, the Harpacticidce, several referable to were established very early, though present sub-order under a common type has not been recognised their real connexion According the to the system proposed by Dr Giesbrecht, the Cydopoida, 2nd the Harpacticoida, should be included in the of his like primary divisions, the This very extensive and heterogeneous group has been divided so-called Podoplea by that author into sections, Isokerandria and Ampliartlwandria, according to the non-prehensile each section prepared the primary families, which family Aster oclieridce, 57 comprising recent work on to or prehensile character of the anterior antennae in the male, the adopt this several p have I been enumerated classification, which appears to me quite artificial, like grouping of the Copepoda into Oymnoplea and Podoplea sense here adopted, in his am, however, by no means In the the sub-order Cydopoida comprises families referred by Dr Giesbrecht partly to the Isokerandria and partly to the Ampliartlwandria, whereas other families included by that author in the latter section are wholly as types of distinct sub-orders One removed of these, the Harpacticoida, has been treated of in the preceding volume, the remaining sub-orders, Notodelphyoida, Monstrilloida, Caligoida and Lernceoida, being reserved for the succeeding volumes of the present work Crustacea As mentioned above, than with case the is the habits of the much more Cyclopoida are Some Calanoida and Harpaeticoida the instance the species of the genus Oithona, are true pelagic animals, a chief part of the plankton in almost forms, like the Harpaeticoida^ bottom different at live all regions of the Oceans for constituting Several other near the shores among algse or on a muddy and a great number of forms lead a more or depths, In most may be however, the parasitism cases, less animals, in some invertebrate different pronounced parasitic existence, attacking instances also fishes varied of them, said to be merely temporary, though there are also a few examples of a more permanent parasitism, for instance in the case of Eryasilus The and Nicothoe and degree of parasitism has a great influence on the structure and indeed we have group of parts, this feature a in The Copepoda well-marked tions, for which I both types, to the again differing conspicuously from the non- accordingly divide the Cyclopoida into natural sec- well-known names: gnathostoma, siphono- These names were taken in a much wider sense, them for an exact subdivision of this good guide to retain the propose stoma and poecilostoma restrict of the oral parts, parasitic forms exhibit, as regards the structure of the oral We may forms parasitic mode different viz., first proposed by Thorell, but were to divide the entire order group of Copepoda which will I Copepoda here be treated of in the present volume As to the characters general appearance of the body, as a typical the Harpaeticoida by far the this rule, looks rather different group, the external from that found in the very sharp demarcation of the chief divisions of the body, the anterior one being So distinguishing more or less tumefied, the posterior very narrow Cyclopoida more resemble the Calanoida than the Harpaeticoida, though they are easily distinguished from them by the very moveable articulation between the last trunk-segments, connected with the firmly the posterior genital of which, segment, appearance of belonging more properly to so the as a rule, that, at posterior first is very small and sight, than to it has the the anterior division of the body more elongated than in the HarThere are, paeticoida and are composed of a greater number of articulations a or also instances of more less some however, great reduction of these limbs, The both in size anterior and antennae in the number are, as a rule, of joints The posterior antenna are generally exopodite such a Only ramus in a few In several of the parasitic simple, without any outer forms is ramus or there a slight rudiment of of the poecilostomous Cyclopoida these antennae are transformed into powerful prehensile organs The oral mentioned above, are of very different structure as parts, in the sections of Cyclopoida The natatory pacticoida, developed legs are, and subequal considerable the Har- in the basal part broad and flattened and the rami generally well with The in size ones and never prehensile a and stouter than as a rule, shorter reduction 1st pair are smaller than the succeeding In a few of the parasitic forms, for instance Canceritta, of the found to have taken place, at is natatory legs least in the female The last pair of legs are always very small and simple in structure, being in most cases exactly alike in the two sexes The ova are carried as never, in the ovisacs, which are lateral or even subdorsal, in ventral Harpacticoida, digenous species of Corycceus, have is I Only in one instance, viz., in our in- found only a single ovisac, which, however, attached quite dorsally The Cyclopoida are species of the genus Cyclops for instance Ergasilus, are well and allied also in fresh water also true fresh-water animals Section General Characters by numerous and some of the forms, parasitic forms, represented Gnathostoma Anterior antennse in male distinctly hinged antennae without any outer ramus, and carrying on the tip a setse Oral parts adapted maxillae strongly dentate for mastication number Posterior of curved Masticatory parts of mandibles and Maxillipeds not subchelate; the posterior ones smaller than the anterior, and of the same appearance in the two sexes Natatory legs well developed, with both rami generally 3-articulate Remarks The several forms belonging to been combined within a single family, the Cydopidce to distinguish at least well-defined families of these families are characterised below represented in the this It section is, have generally however, very easy gnathostomous Cyclopoida fauna of Norway, and will All be shortly Fam Characters and slender Body Oithonidae of a very delicate structure, with thin and pellucid integuments Anterior antennae in female very slender and provided with long those diverging setae; male much more robust and distinctly geni- in Posterior antennae comparatively small, with the culate Oral parts well developed, and paratively 3-articulate of joints reduced rather different in structure from those in other Cyclopoida, being partly armed with slender number claw-like spines Natatory legs with com- edged with unusually long setae rarni Last pair and partly confluent with the corresponding segment shape and armature in the two sexes of legs rudimentary rami differing in Remarks in several in the This family We the Oithona in the anterior very doubtful, though Cyclopoida In case this this some resemblance true, exhibits in the structure of but the posterior antennae are very different and built wholly on the type of the Calanoida still it is appearance of the body as also general antennae; entitled to constitute the type not know as yet any other genus referable to The genus Mormonilla of Giesbrecht, family to and may accordingly be present section, of a distinct group founded upon the genus Oiihona Baird, which is rather conspicuously from the other genera included differs respects Caudal The systematic may position of this genus is be found to be nearest related to the it perhaps it must be regarded as the type of a very anomalous family of the gnathostomous Cyclopoida Gen OlthOna, Syn Generic division Characters only slightly defined from the produced in dilated, Body the 1st pedigerous front to a : Baird, 1843 Scribella, Dana slender and attenuated, with the posterior very narrow, linear in form anterior Head segment by a well-marked suture, and generally sharply-pointed rostrum, wanting, however, in male Anterior antennae long and slender, scarcely tapered distally, and composed of a limited tennae the 1st number abruptly of joints, some of which are imperfectly defined Posterior an- bent in the middle, and apparently only consisting of joints, carrying about in the middle behind a short seta arising from a knob- Mandibular palp with the basal part greatly produced, pediform, terminating in claw-like spines, inner ramus represented by a very small seti- like prominence some distance from ferous appendage attached outside the basal part at its outer ramus well developed and abruptly reflexed, being composed of Maxillae with the masticatory lobe well defined setse carrying long plumose carrying a number of sharp claw-like spines accompanied inside by a thick form appendage, end, joints with palp lamellar, outer the distal lobe very small, and seti- proximal lobe well developed, recurved, and provided at the tip with long plumose setse ) Both pairs of slender maxillipecls and elongated, the anterior ones 5-articuiate, the posterior ones 4-articulate, both carrying long anteriorly-curving spines tatory no with legs developed distinctly Na- inside the 1st joint of the outer seta ramus very slender and serrate outside, spines of ramus, apical spine outer edge more perfectly developed in male than in female Last pair of legs of this represented by a small conical joint terminating in a long seta; seta from issuing seems to answer a in female much elongated and each another similar of the segment side from the basal joint of these legs to that arising Caudal rami poida prominence on knob-like itself, in other Cyclo- strongly divergent, with the middle apical setse each crossing other the at base; those in male of quite normal appearance to Remarks The present genus was a plumifera, include species, established in the year 1843 by Baird, taken in the tropical part of the Atlantic Another genus with the same name has been established by Alder and Hancock for a nudibranchiate of Baird, its with that have in Mollusc; but as this name must be changed of Baird, genus The genus and likewise of later date recent times been described is of younger date than that Dana Scribella of is identical Several species of this genus from different parts of the Oceans Thus Dr Giesbrecht records no less than species, and some additional species have been named by about the right close relation tomical other examination described by Dr conspicuously though proposed To of the nearly the is, some such delicate others, allied however, of these to the difficulty Giesbrecht, from separate, of identification and partly There authors which and nana, still species, is considerable confusion partly connected with an exact ana- fragile animals seems in owing to their One some respects of the species to differ more and may perhaps be regarded as the type of a genus, fauna of Norway for which the name belong well-defined Oithonina may be to be de- lobes, but find species, scribed below ) that these I have formerly described these lobes as the exopodal and epipodal names cannot properly be retained, since they unquestionably, as is clearly seen in the present genus, answer to the inner and outer rami of the mandibular palp As, however, both these lobes are always attached outside the palp, I find it more appropriate to give them the indifferent names of proximal and distal outer lobes Oithona spinirostris, i (PI & Glaus ii) Oithona spinirostris, Glaus, Die freilebenden Copepoden, p 105, PI XI, figs Oithona challengeri, Thompson Syn: plumifera, Scott, (not Baird) atlantica, Fai-ran Female Specific Characters narrow division fusiform in Body exceedingly slender, with the anterior the greatest width scarcely exceeding Vs of shape, No conspicuous plumes the length and occurring somewhat in front of the middle Rostrum strong, spiniform, and only very slightly curved, so present laterally as to be visible in the dorsal aspect of the animal Tail not much shorter than and very narrow genital segment about the length of the succeeding segments combined, and conspicuously dilated in its anterior part Caudal rami nearly as long as the anal segment and rather divergent, seta of the anterior division ; outer edge attached close to the base, the middle apical setse almost twice the length of the antennae Eye narrow tail linear in form and of a deep red colour slender and elongated, reaching, very when reflexed, to the Anterior end of the and composed of about 12 more or less distinctly defined joints of rather unequal length and carrying scattered exceedingly long setse 1st pair of natatory legs with the inner ramus pointing in different directions 2nd caudal segment, ramus spiniferous distinctly 3-articulate, all joints of outer outside 2nd and 3rd pair with no spine outside the middle joint of the outer ramus, terminal joint of ramus, as in the 1st pair, with spines outside this outside the ramus and with only a single setiform spine Ovisacs narrow oblong in form and greatly divergent, joints of the outer first outside the terminal joint in some sac in a extending nearly at right angles to the axis of the body, each cases containing only a limited number of very pellucid ova, generally arranged double row Male much the smaller genital any trace a of segment greatly female than less body being comparatively wanting rostrum swollen, to in female and of quite and of a rather different appearance, slender, with the front obtusely truncate Tail distinctly receive the shorter than the anal segment and not at than 4th pair with no spines all spermatophores divergent, apical setse normal appearance and 5-articulate, with the 1st or Caudal rami much shorter Anterior antennse scarcely longer than the anterior division of the body and exhibiting the usual geniculation middle with all section the only slightly joints tumefied, of the outer terminal one biarticulate ramus spiniferous ; Natatory legs outside, such spines being on present legs much 2nd and 3rd the terminal joint in the both sexes highly pellucid and nearly colourless, though in adult in Body females generally a light orange pigment A also the sides of the head part of Setse of last pair of pairs sherter than in female the large oil-bubble and smaller ones trunk, seen clothing the oral area and partly is is often found within the posterior at the limit between the head and the 1st pedigerous segment Length of adult female 1.35 mm., of male 0.82 mm Remarks I regard it as beyond all doubt that the above-described form is name Oithona that originally recorded by Glaus under the generally been confounded with the very nearly as plumifera, from which, however, at once distinguished is it spinirostris allied species described It has by Baird by the absence of the very conspicuous brightly-coloured plumes projecting in the latter at each side of the reality species are richly belong name plumifera has been natatory legs, and are formed plumose, whereas in the form here under consideration they and not even project simple specific to the attached outside the 2nd basal joint of the legs, which in the said setse In addition to this distinguishing laterally Farran has recently pointed out some minute differences in the the oral parts between these two forms, which accordingly must be Mr character, structure in plumes by the ars and from which indeed the trunk, These derived of regarded as distinct, new name specific Mr Farran has proposed a though closely-allied species the for present species, viz., but atlantica, I think that his doubt about the identity of Glaus' species with the one here under question cannot properly be approved Occurrence have observed I coast, at least Norwegian so common the open to the up from which it form in many Trondhjem Fjord It different places is, and seems more properly as the next species, sea, this is however, not nearly to be only occasionally brought in on the an inhabitant of by the currents to the shores and fjords When in a always found freely suspended in kept living vessel the water, with the anterior antennae and the apparently animal serving as often rests with fresh sea-water, the specimens are caudal more generally setse long the action of the natatory time legs, nearly making an erect attitude, spread to each side, these parts a very effective balancing apparatus for in immobile, only In this attitude the now and a short bound to change its then, place by To judge from the structure of the oral parts, the animal must be of a very rapacious nature, first be probably seized feeding upon other small pelagic animals by the slender maxillipeds and by them thrown These may at in against the the of which indeed seems to be structure other oral killing than for masticating the prey parts, As Distribution fera, has it full a In all probability With wide range in the Oceans to that of the next species similar may be it certainty as yet rather difficult to determine is for form has generally been confounded with plumi- this true distribution its more adapted said be to distributed over the North Atlantic, as all also in the Mediterranean Oithona helgolandica, (PL Glaus III) Oithona helgolandica, Claus, Die freilebenden Copepoden, Syn : p 105, PI XI, 10 figs 12 Oithona spinifrons, Boeck pygmcea, Boeck Claus similis, spinirostris, Giesbrecht (not Claus) somewhat the but pointed, acutely so body, than in so less as the Body preceding species less dilated seta of outer edge shorter in anterior its and ever, armed is less however, exhibiting in are structure in some only with faintly small species, Genital part less divergent than in spinirostris, and composed of about 10 defined characteristic 1st some antennse and oral parts Posterior differences: joints, pair Natatory with legs, the outer how- ramus a manner similar to that in spinirostris, except that the apical spine strong and almost setiform; inner ramus apparently only biarticulate, the of the outer ramus, dentiform projection of the 1st or in that Caudal rami not nearly those in the preceding species outer joints being confluent joint Rostrum, as Anterior antennae, when reflexed, extending scarcely beyond the anterior division of the body, agreeing slender form, though bent downwards at a right angle to the axis of abruptly attaining the length of the anal segment, of which, usual of the not to be visible in the dorsal aspect of the animal somewhat segment Female Characters Specific 2nd joints spine 2nd and 3rd pairs with no spine outside the middle though margin Terminal joint of outside, attached close exhibiting at 4th pair this ramus to the end of the joint a small without any spines either on the in all pairs with only a single the end, and exhibiting moreover in the 2nd and 3rd pairs a very small dentiform prominence of the margin at about the Ovisacs narrow oblong and closely appressed to the sides of middle of the joint the tail, each sac containing only a single series of very large and pellucid ova Male and moreover closely resembling that of the preceding species, but of smaller size, differing somewhat in the armature of the natatory minal joint of the outer ramus having only spines outside legs, the ter- Copepoda Ergasiliciae Cyclopoida PI V\ > i G O Sars, del Ergasilus Sieboldi, Nordm CXI opepoda Cyclopoida Clausiidaf3 PI c a- o Or ji G O Sars, del Conchocheres malleolatus, Sars CXi! Copepoda Eunicicolidae Cyclopoida PI ' ^r-'- ^ m ft - &) -^-' S V,- O Sars, del Eunicicola Clausi, Kurz cxin Copepoda Cyclopoida Oithonidae PI / TfJ ~ A \ t G O Sars, del Paroithona parvula, Farran cxiv Copepoda Cyclopoida Cyclopinidae PI ' ! - *.*t - rA i
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