Diaixidae Family - Marine Planktonic Copepods

Calanoida ( Order )	details
Clausocalanoidea ( Superfamily )	details

Abbreviations or symbols

Diaixidae Sars, 1902 ( Clausocalanoidea )

Ref.:

Sars, 1902 (1903) (p.57); van Breemen, 1908 a (p.81); Gurney, 1931 a (p.85); Rose, 1933 a (p.159); Andronov, 1974 a (p.1005); 1979 (p.100, clé spp.); Connell, 1981 (p.493); Bowman & Abele, 1982 (p.9); Razouls, 1982 (p.377); 1993 (p.310); Bradford & al., 1983 (p.122); Brodsky & al., 1983 (p.144, 147); Mauchline, 1988 (p.734, 740, Rem.: pores cuticulaires); Huys & Boxshall, 1991 (p.54, 419); Othman & Greenwood, 1994 (p.989, Redef.); Bradford-Grieve & al., 1999 (p.881, 903, 933); Ohtsuka & Huys, 2001 (p.461); Ohtsuka & al., 2003 (p.53, 62, Rem.); Boxshall & Halsey, 2004 (p.15; 49; 95: Déf., Key G.); Ferrari & Markhaseva, 2005 (p.45, Rem.);Vives & Shmeleva, 2007 (p.638); Blanco-Bercial & al., 2011 (p.103, Table 1, Fig.2, 3, 4, Biol. mol, phylogeny)
Bradford-Grieve J.M., (2002 onwards). Key to calanoid copepod families. Version 1 : 2 oct 2002. http://www.crustacea.net/crustace/calanoida/index.htm

Rem.:

Boxshall & Halsey (2004, p.96) exclude the Pseudophaenna genus from the family of Tharybidae to be included in this family.
7 G.: Anawekia, Byrathis, Diaixis, Procenognatha, Pseudophaennna, Ranthaxus, + 1 G (provisionally): Sensiava, Xancithrix.
The types of setae on the appendage Mx2 include this family in the 'Bradfordian' grioup of families.

(1) Anawekia Othman & Greenwood, 1994

Species, varieties and details

Ref.:

Othman & Greenwood, 1994 (p.989); Mauchline, 1998 (p.78: F; p.81: M); Bradford-Grieve, 2004 (p.287); Boxshall & Halsey, 2004 (p.96)

Rem.:

3 spp.:

(2) Byrathis Markhaseva & Ferrari, 2005

Species, varieties and details

Ref.:

Markhaseva & Ferrari, 2005 a (p.128: Def.); Schulz, 2006 (p.67: Rem.); Markhaseva & Renz, 2011 (p.49, 66: Rem.)

Rem.:

type:Xanthocalanus macrocephalon. 7 spp.

After Markhaseva & Renz (2011, p.66) the genus Byrathis can be divided into 2 groups : 1- B. divae, B. penicillatus, B. laptevorum. Medium sized copepods ; the genital double-somite has no surface ornamentation ; the Mx1 proximal basal endite and exopod are with 3 and 6 (or more) setae, respectively ; the Mx2 endopod bears 5 brush-like sensory setae. 2- B. macrocephalon, B. volcali, B. sp. Smaller size than the first group ; presence of surface ornamentation on the genital double-somite ; the M1 proximal basal endite and exopod with 2 and 5 (or less) setae, respectively ; the Mx2 endopod with only 3 brush-like sensory setae.
For the authors, the adult male B. arnei which is described for the first time, is distinguished from all other clausocalanoideans that possess sensory setae on the Mx1 and Mxp (bradfordian families) in the morphology of A1 and P5. Right P5 and left A1 are symmetrical, 22-segmented. In this genus the ancestral segments XXII-XXIII are fused on both sides (apomorphy). This is a unique case for bradfordian genera which known males in which segments XXII-XXIII are fused only in the right A1 as in Scolecitrichidae (stricto sensu) and Diaixidae s.l. (sensu Markhaseva & Ferrari, 2005), and as in Brodskius, Tharybis, Plesioscolecithrix and Xanthocalanus. In Kirnesius they are fused only in the left A1.
The authors put in the genus Byrathis in the family Diaixidae.
According to Markhaseva & Renz (2011, p.68) the morphology of Byrathis combines primitive and derived characters : 1- primitive character : Setation of A2 exopod proximal segments as 1, 1-1-1 in both sexes ; Mx2 praecoxal endite (in B. arnei) female with 5 setae ; females Mxp praecoxal endites setation with 1, 2, 3 setae from proximal to distal, and male coxa and basis nearly symmetrical.
2 – derived character : Md gnathobase of female with crest ; Mx1 distal basal endite with only 2-3 setae.
Apomorphies for the genus are male A1 with both ancestral segments XXII-XXIII fused and female M1 praecoxal arthrite with 2 proximal marginal setae curved proximally.
The mosaic combination of primitive and derived features is an example of heterobathmy typical of these benthopelagic clausocalanoideans.

issued from : E.L. Markhaseva & Renz in Zootaxa, 2011, 2889. [p.61, Fig.9]. Distribution of species of Byrathis in the World Ocean.
B. macrocephalon (black rhomboid).
B. penicillatus (circle outlined).
B. laurenae (black square).
B. arnei (big triangle outlined).
B. divae (black small triangle).
B. lapterovum (rhomboid outlined).
B. volcani (rhomboid outlined with crest).

(3) Diaixis Sars, 1902

Species, varieties and details

Ref.:

Sars, 1902 (1903) (p.58); van Breemen, 1908 a (p.81); Rose, 1933 a (p.160); Andronov,1979 (p.100, clé spp.); Connell, 1981 (p.493); Razouls, 1982 (p.377); Bradford & al., 1983 (p.122); Mauchline, 1988 (p.734); Razouls, 1993 (p.310); Othman & Greenwood, 1994 (p.988, Redef., 2 groupes: 'pygmaea' et 'centrura'); Mauchline, 1998 (p.78, 88: F; p.81, 89: M); Bradford-Grieve & al., 1999 (p.881, 934: clé spp.); Andronov, 2002 (p.2, 11, clé spp.); Bradford-Grieve, 2004 (p.287); Boxshall & Halsey, 2004 (p.96); Vives & Shmeleva, 2007 (p.639, spp. Key)

Rem.:

Type: Scplecithrix hibernica A. Scott, 1896.
more or less hyperbenthic forms. 8 spp. + 1 unspecified:

Remarks on dimensions and sex ratio:

The mean size of the females is 0,913 mm (n= 8; S= 0,144; Cv= 0,158) and of the males 0,791 mm (n= 7; S= 0,091; Cv= 0,115). The size ratio (M/F) is 0,910 or 91% (n= 7; S= 0,045; Cv= 0,05). The sex ratio (F/M) is 1,29.

(4) Procenognatha Markhaseva & Schulz, 2010

Species, varieties and details

Ref.:

Markhaseva & Schulz, 2010 (p.4)

Rem.:

type species: Procenognatha semisensata. 1 sp.
After Markhaseva & Schulz (2010, p.5) the genus is defined by :
1- praecoxal arthrite of Mx1 with proximalmost posterior seta swollen in its basal part (vs. not swollen in other ‘bradfordians’) ; the latter character is an apomorphy of the genus.
2- Mx2 endopod with 3 sclerotized terminal setae (vs. worm-like sensory setae in remaning ‘bradfordian’ genera).
3- Mx2 endopod with 9 setae (3 sclerotized setae + 1 sclerotized and brush-like seta + 5 brush-like setae).
Right A1 male with traces of geniculation.

A high number and unique combination of plesiomorphic characters exhibited by this genus suggest that the type species is the most primitive among ‘bradfordian taxa’. The following combination of characters distinguishes Procenognatha from all other ‘bradfordian’ genera :
1- ancestral setation of A2 exopod (1, 1-1-1, 1, 1, 1, 1, 1 and 3).
2- Mx2 endopod with a total number of 9 setae.
3- presence of 3 sclerotized setae on Mx2 endopod terminally (a unique plesiomorphy for ‘bradfordians).
4- syncoxa of Mxp with ancestral setation formula (1, 2, 3).
5- Male A1 with traces of geniculation ; oral parts not reduced ; biramous P5.

Procenognatha is closely related to Cenognatha. They share the following combination of characters:
1- short rostrum with 2 filaments.
2- biramous right P5 in the male.
3- a similar setation and segmentation pattern of the oral parts.
Procenognatha is distinguished from Cenognatha by rounded posterior corners of the prosome (vs. extended into 2 spines in Cenognatha) and the details of setation of oral parts: a- endopod segment 1 of Md with 2 setae (vs. 3 setae in Cenognatha); b- Mx1 endopod with 12 setae and Mx1 exopod with 7 setae (vs. 7, 9 or 11; 9-10 setae in Cenognatha, respectively); c- setal number (9) and composition of Mx2 endopod plus distal basal endite setae (vs. 7-8 setae in Cenognatha).

(5) Pseudophaenna Sars, 1902

Species, varieties and details

Ref.:

Sars,1902 (1903) (p.43); van Breemen, 1908 a (p.57); Rose, 1933 a (p.126); Bradford, 1973 (p.138, Rem.); Razouls, 1982 (p.287, 368); Bradford & al., 1983 (p.123, Déf., p.126); Razouls, 1993 (p.311); Mauchline, 1998 (p.87: F; p.89: M); Vyshkvartzeva, 2001 (p.77: Rem.); Bradford-Grieve, 2004 (p.287); Boxshall & Halsey, 2004 (p.96)

Rem.:

This genus, placed among Tharybidae, is transferred in this family by Boxshall & Halsey (2004, p.96, 210). 1 sp.:

(6) Ranthaxus Markhaseva & Schulz, 2010

Species, varieties and details

Ref.:

Markhaseva & Schulz, 2010 (p.13, Table 1))

Rem.:

issued from : E.L. Markhaseva & K. Schulz in Proc. Zool. Inst. RAS, 2010, 314 (1). [p.13, 17]
Remarks :
Mx1 : 1 worm-like sensory seta present additionally to sclerotized setae on distal basal endite and endopod (vs. Sensory setae absent on distal basal endite in other ‘’bradfordians’)
Mx2 : Endopod plus distal basal endite with 4 long plus 2 short worm-like sensory setae (vs. 6 worm-like sensory setae of equal length in Rostrocalanus)
Mxp : Very long worm-like sensory seta on distal praecoxal endite, reaching the distal part of basis (vs. Worm-like seta short or absent on distal endite in other ‘bradfordians’). Endopod segment 1 (endopodal segment incorporated into basis) and terminal segment with 1 of setae on each segment transformed into sensory and worm-like setae (vs. Sensory setae absent from endopod in other ‘bradfordians’).

This genus is closely related to Xantharus and Paraxantharus Schulz, 2006 and shares with both genera the same number of setae on most of endites and segments of oral parts (See Table1 for these genus). However, the new genus is well distinguished from these genera by the presence of worm-like sensory setae on Mx1, Mxp basis and endopod, a smaller number (6) of sensory setae on Mx2 endopod, and by very long worm-like sensory setae on Mxp syncoxa.
This genus shares an apomorphy (character derived from and differing from an ancestral condition) with Xantharus in that segments 19 and 20 (XXII and XXIII) of A1 are markedly reduced in size compared to segment 18 (XXI) and in a very long aesthatasc on segment 18, but it differs in the primitive type of exopod setation of A2 (1, 1-1-1, 1, 1, 1, 1, 1, and 3), which Ranthaxus shares with Paraxantharus (see Table 1).
The presence of sensory setae on the distal praecoxal endite and coxal endites of Mx2 is shared with Puchinia Vyshvartzeva (1989), however, Puchinia is not allied to the new genus by number of characters.

issued from : E.L. Markhaseva & Schulz in Proc. Zool. Inst. RAS, 2010, 314 (1). [p.16, Table.1].
Selected character states of Ranthaxus Females.
Abbreviations: br = brush-like; sel = sclerotized; w = worm-like sensory setae.

(7) Sensiava Markhaseva & Schulz, 2006

Species, varieties and details

Ref.:

Markhaseva & Schulz, 2006 (p.1); Markhaseva & Renz, 2011 (p.67, Rem.)

Rem.:

Type species: Sensiava longiseta. 1 sp.
Temporarily included by the authors in Diaixidae family.
For Markhaseva & Schulz (2006, p.13) excepting the A1, the new genus fits the diagnosis of the superfamily Clausocalanoida. However, in respect of the male grasping A1 Sensiava longiseta contradicts its diagnosis. The geniculated A1 of the new genus is the most striking example of a modified risht A1 in males of Clausocalanoidea, but not the only recorded case among the representatives in the superfamily. The male of the rare aetideid benthopelagic genus Azygokeras has morphologically modified ancestral segments XIX-XXVI in right A1 (Koeller & Littlepage, 1976) ; Markhaseva & Ferrari, 2005), a tharybid genus described from close to the sea floor, also has the right A1 modified . Fusion of ancestral segments XXII-XXIII of the right A1 might be considered remnants of an ancestral geniculation (Schulz, 2005) and are observed in a number of Clausocalanoidean taxa (Kirnesius, Scolecitrichopsis, Tharybis, Xantharus, Xanthocalanus and some species of Aetideopsis. As a consequence the diagnosis of the superfamily Clausocalanoidea should be emended by exclusion of the non-geniculate A1 as a diagnostic character.
Discovery of a new benthopelagic copepod genus in vicinity of the floor of the deep-sea demonstrates that the diagnoses of some families (e ;g., Bradfordian families), which have been based on the morphological characters of their pelagic representatives, are inadequate.

(8) Xancithrix Markhaseva, 2012

Species, varieties and details

Ref.:

Markhaseva, 2012 (p.296)

Rem.:

Type species: Xancjthrix ohmani. 1 sp.