|
|
Taxonomy
Family
Metridinidae Sars, 1902 ( Arietelloidea )
Syn.:
Metridiidae Sars, 1902 (1903) (p.110); Sewell, 1932 (p.247); Gurney, 1931 a (p.84); Rose,1933 a (p.175); Sewell, 1947 (p.165), Rem.; Brodsky, 1950 (1967) (p.81, 289); Mazza, 1967 (p.185); Andronov, 1974 a (p.1005); Brodsky & al., 1983 (p.141, 145); Zheng Zhong & al., 1984 (1989) (p.242)
Ref.:
Dunn & Hulsemann, 1979 (p.53: emend.); Razouls, 1982 (p.405); 1993 (p.307); Bowman & Abele, 1982 (p.9); Bull. Zool. Nomencl, 1984 ( N°41,1, p.19); Sazhina, 1985 (p.114, Nauplius); Mauchline, 1988 (p.711: cuticular pores); Huys & Boxshall, 1991 (p.464); Madhupratap & al., 1996 (p.863, Table 5: %/copepods); Chihara & Murano, 1997 (p.837); Cuoc & al., 1997 (p.651, Fig.6: female genital area); Bradford-Grieve & al., 1999 (p.883, 901, 903, 947, Genera Key); Bradford-Grieve, 1999 b (p.110, Déf., Rem.); Soh & al., 1999 (p.122, phylogeny); Ohtsuka & Huys, 2001 (p.461); Boxshall & Halsey, 2004 (p.13; 49; 145: Def.; p.146: Genera Key); Vives & Shmeleva, 2007 (p.356, clé des Genera Key); Blanco-Bercial & al., 2011 (p.103, Table 1, Fig.2, 3, 4, Biol. mol, phylogeny); Laakmann & al., 2019 (p.330, fig. 2, 3, phylogenetic relationships); Hirai & al., 2020 (p.1, Fig.4: metabarcoding, Fig.8: OTUs distribution patterns, Fig.9: phylogenetic analysis )
Rem.:
3 G.: Gaussia, Metridia, Pleuromamma.
For numerous authors, after mouthpart morphology and gut contents, and dietary preferences of laboratory reared specimens, this family appears to be omnivorous.
Key to genera after Boxshall & Halsey (2004, p.146) :
1 - Prosome with conspicuous black or dark brown spot on one side of 1st pedigerous somite ........ Pleuromamma.
1' - Prosome lacking such spot ......... 2.
2 - Posterolateral angles of prosome produced into wing-like expansions, tapering to point; anal somite with long posterior processes located dorsolateral to caudal rami ...... Gaussia.
2' - Posterolateral angles of prosome usually rounded, if pointed then not with wing-like expansions; anal somite typically with short posterior processes .......... Metridia.
Definition after Bradford-Grieve (1999b, p.110) Female :
- Body elongate.
- Cephalosome and pediger 1 separate, pedigers 4 and 5 fused.
- Posterolateral corners of the last thoracic segment usually rounded, expanded in Gaussia.
- Pediger segment 1Pleuromamma.
- Urosome 3-segmented.
- Caudal rami often asymmetrical with up to 6 setae.
- Genital segment with copulatory pores and seminal receptacles paired in Gaussia and Metridia, unpaired in Pleuromamma ; gonopores and egg laying ducts paired.
- Rostrum with paired filaments.
- A1 23- or 34-segmented (segments 1 and 2 fused, 5 and 7 separate, 8 and 9 fused, 10-22 separate, apical segment double).
- A2 with basipods 1 and 2 separate with 1 and 2 setae respectively ; endopod 2-segmented, bilobed distal segment with 1-2, 8-9 + 6-7 setae ; exopod 7-segmented with 1, 2 , 1, 1, 1, 1, 4 setae respectively.
- Md with well-developed blade, palp basipod 2 with 4 setae ; endopod 2-segmented with 4 and 10 setae respectively ; exopod 5-segmented with 1, 1, 1, 1, 2 setae respectively.
- Mx1 inner lobe 1 with about 15 spines and setae, inner lobes 2 and 3 with 4-5 and 4 setae ; basipod 2 with 5-7 setae ; endopod 2-segmented with 6, 9-12 setae ; exopod with 11 setae ; outer lobes 1 and 2 with 9 and 1 setae.
- Mx2 with lobes 1-5 with 5 (9 in P. xiphias), 3, 3, 3, 4 setae respectively ; endopod 4-segmented with 3-4, 3, 2, 2 setae or reduced.
- Mxp 7-segmented, basipod 1 with 1, 2, 4, 4 setae ; basipod 2 with 3 setae plus 2 setae on the incorporated 1st endopodal segment ; endopod 5-segmented with 4, 4, 3, 3, 4 setae respectively.
- Swimming legs with both rami 3-segmented.
- Exopods of P2-P4 large, and flat, outer edge spines small.
- P1 basipod 2 inner seta situated on its anterior surface and passing across the face of endopodal segment 1
- Endopod segment 1 of P2 typically incised and ornamented with 1 or more hook-like spinous processes ; endopods typically small, cylindrical.
Male :
- Urosome 5-segmented, sometimes strongly asymmetrical.
- A1 usually prehensile on the left.
- Mouthparts similar to those of female.
For numerous authors, after mouthpart morphology and gut contents, and dietary preferences of laboratory reared specimens, this family appears to be omnivorous.
Key to genera after Boxshall & Halsey (2004, p.146) :
1 - Prosome with conspicuous black or dark brown spot on one side of 1st pedigerous somite ........ Pleuromamma.
1' - Prosome lacking such spot ......... 2.
2 - Posterolateral angles of prosome produced into wing-like expansions, tapering to point; anal somite with long posterior processes located dorsolateral to caudal rami ...... Gaussia.
2' - Posterolateral angles of prosome usually rounded, if pointed then not with wing-like expansions; anal somite typically with short posterior processes .......... Metridia.
Definition after Bradford-Grieve (1999b, p.110) Female :
- Body elongate.
- Cephalosome and pediger 1 separate, pedigers 4 and 5 fused.
- Posterolateral corners of the last thoracic segment usually rounded, expanded in Gaussia.
- Pediger segment 1
- Urosome 3-segmented.
- Caudal rami often asymmetrical with up to 6 setae.
- Genital segment with copulatory pores and seminal receptacles paired in Gaussia and Metridia, unpaired in Pleuromamma ; gonopores and egg laying ducts paired.
- Rostrum with paired filaments.
- A1 23- or 34-segmented (segments 1 and 2 fused, 5 and 7 separate, 8 and 9 fused, 10-22 separate, apical segment double).
- A2 with basipods 1 and 2 separate with 1 and 2 setae respectively ; endopod 2-segmented, bilobed distal segment with 1-2, 8-9 + 6-7 setae ; exopod 7-segmented with 1, 2 , 1, 1, 1, 1, 4 setae respectively.
- Md with well-developed blade, palp basipod 2 with 4 setae ; endopod 2-segmented with 4 and 10 setae respectively ; exopod 5-segmented with 1, 1, 1, 1, 2 setae respectively.
- Mx1 inner lobe 1 with about 15 spines and setae, inner lobes 2 and 3 with 4-5 and 4 setae ; basipod 2 with 5-7 setae ; endopod 2-segmented with 6, 9-12 setae ; exopod with 11 setae ; outer lobes 1 and 2 with 9 and 1 setae.
- Mx2 with lobes 1-5 with 5 (9 in P. xiphias), 3, 3, 3, 4 setae respectively ; endopod 4-segmented with 3-4, 3, 2, 2 setae or reduced.
- Mxp 7-segmented, basipod 1 with 1, 2, 4, 4 setae ; basipod 2 with 3 setae plus 2 setae on the incorporated 1st endopodal segment ; endopod 5-segmented with 4, 4, 3, 3, 4 setae respectively.
- Swimming legs with both rami 3-segmented.
- Exopods of P2-P4 large, and flat, outer edge spines small.
- P1 basipod 2 inner seta situated on its anterior surface and passing across the face of endopodal segment 1
- Endopod segment 1 of P2 typically incised and ornamented with 1 or more hook-like spinous processes ; endopods typically small, cylindrical.
Male :
- Urosome 5-segmented, sometimes strongly asymmetrical.
- A1 usually prehensile on the left.
- Mouthparts similar to those of female.
Figures
;)
Plate 1
issued from :C. Cuoc, D. Defaye, M. Brunet, R. Notonier & J. Mazza in Mar. Biol., 1997, 129. [p.13, Fig.6].
Diagrammatic representation of main evolutionary trends in organization of female genital area in calanoïds for Metridinidae (modified after Huys & Boxshall, 1991 and Ohtsuka & al., 1994).
*: seminal duct of Pleuromamma may be situated on left or right, according to individual.
issued from :C. Cuoc, D. Defaye, M. Brunet, R. Notonier & J. Mazza in Mar. Biol., 1997, 129. [p.13, Fig.6].
Diagrammatic representation of main evolutionary trends in organization of female genital area in calanoïds for Metridinidae (modified after Huys & Boxshall, 1991 and Ohtsuka & al., 1994).
*: seminal duct of Pleuromamma may be situated on left or right, according to individual.
;)
Plate 2
issued from :C. Cuoc, D. Defaye, M. Brunet, R. Notonier & J. Mazza in Mar. Biol., 1997, 129. [p.661, Fig.5].
Metridinidae. Schematic three-dimensional interpretation of structure and function of egg-laying ducts.
A1, A2 Dorsal representations of egg-laying duct when closed (A1) and open (A2).
B1, B2 details of part duct when closed (B1) and open (B2), showing how contraction and relaxation of muscles of egg-laying duct resulut in coordinated opening and closing of the gonopores and seminal ducts (black arrows), allowing release of gametes (open arrows) (the shell ducts, which open into the egg-laying ducts, are not shown on diagram).
issued from :C. Cuoc, D. Defaye, M. Brunet, R. Notonier & J. Mazza in Mar. Biol., 1997, 129. [p.661, Fig.5].
Metridinidae. Schematic three-dimensional interpretation of structure and function of egg-laying ducts.
A1, A2 Dorsal representations of egg-laying duct when closed (A1) and open (A2).
B1, B2 details of part duct when closed (B1) and open (B2), showing how contraction and relaxation of muscles of egg-laying duct resulut in coordinated opening and closing of the gonopores and seminal ducts (black arrows), allowing release of gametes (open arrows) (the shell ducts, which open into the egg-laying ducts, are not shown on diagram).
;){kind=small}
Plate 3
Issued from : G.A. Boxshall & S.H. Halsey in An Introduction to Copepod Diversity. The Ray Society, 2004, No 166, Part. I. [p.145].
Armature formula of swimming legs P1 to P4.
Nota: Female P5 with transverse plate formed by fusion of coxae and intercoxal sclerite; each leg uniramous, comprising basis plus 1, 2 or 3-segmenhted exopod; basis and 1st exopodal segment typically with outer seta and spine respectively, 2nd exopodal segment with outer spine and inner seta, 3rd segment with 2 to 4 distal elements (I-0; II,I,3 in Metridia); 2nd and 3rd exopodal segments often fused, which setation reduced.
- Male P5 asymmetrical, carried on plate formed by fused coxae and intercoxal sclerite. Right leg comprising basis with outer seta and 3-segmented exopod; 2nd exopodal segment with inner spinous process in some genera; 3rd segment with 1 or 2 minute distal setae. left leg comprising basis with outer seta and 2 or 3-segmented exopod; 1st exopodal segment bearing curved inner process, distal segment swollen, often curved or claw-like.
- Eggs released into water.
Issued from : G.A. Boxshall & S.H. Halsey in An Introduction to Copepod Diversity. The Ray Society, 2004, No 166, Part. I. [p.145].
Armature formula of swimming legs P1 to P4.
Nota: Female P5 with transverse plate formed by fusion of coxae and intercoxal sclerite; each leg uniramous, comprising basis plus 1, 2 or 3-segmenhted exopod; basis and 1st exopodal segment typically with outer seta and spine respectively, 2nd exopodal segment with outer spine and inner seta, 3rd segment with 2 to 4 distal elements (I-0; II,I,3 in Metridia); 2nd and 3rd exopodal segments often fused, which setation reduced.
- Male P5 asymmetrical, carried on plate formed by fused coxae and intercoxal sclerite. Right leg comprising basis with outer seta and 3-segmented exopod; 2nd exopodal segment with inner spinous process in some genera; 3rd segment with 1 or 2 minute distal setae. left leg comprising basis with outer seta and 2 or 3-segmented exopod; 1st exopodal segment bearing curved inner process, distal segment swollen, often curved or claw-like.
- Eggs released into water.
;)
Plate 4
Issued from : G.A. Boxshall & S.H. Halsey in An Introduction to Copepod Diversity. The Ray Society, 2004, No 166, Part. I. [p.147, Fig.31].
Metridinidae: A, Metridia princeps habitus female; B, P2; C, female P5; D, habitus male; E, male P5; F, Pleuromamma xiphias habitus female. [Dars, 1924].
Issued from : G.A. Boxshall & S.H. Halsey in An Introduction to Copepod Diversity. The Ray Society, 2004, No 166, Part. I. [p.147, Fig.31].
Metridinidae: A, Metridia princeps habitus female; B, P2; C, female P5; D, habitus male; E, male P5; F, Pleuromamma xiphias habitus female. [Dars, 1924].
;){kind=small}
Plate 5
Issued from : J.M. Bradford-Grieve in NIWA Biodiversity memoir 111, 1999. [p.110].
Spine and seta formula typically (but sometimes reduced) of the swimming legs P1 to P4.
- Female P5 uniramous , small, symmetrical 2-4-segmented, basipod 1 and coupler (= intercoxal sclerite) fused; basipod 2 and exopod segment 1 usually with an outer setae and spine respectively; exopod segment 2 with 2-4 setae, terminal exopod segments may be fused.
- Male P5 assymmetrical, attached to a plate formed from fusion of basipod 1 and coupler; right leg (or left) comprising basipod 2 with an outer seta and a 2?-3-segmented exopod; exopod segment 2 with an inner spinous process in some genera; exopod segment 3 with 1 or 2 minute distal setae; left leg (or right) comprising basipod 2 with an outer seta and a 2-or 3-segment exopod; exopod segment 1 bearing a curved inner process, distal segment swollen, often curved or claw-like.
Issued from : J.M. Bradford-Grieve in NIWA Biodiversity memoir 111, 1999. [p.110].
Spine and seta formula typically (but sometimes reduced) of the swimming legs P1 to P4.
- Female P5 uniramous , small, symmetrical 2-4-segmented, basipod 1 and coupler (= intercoxal sclerite) fused; basipod 2 and exopod segment 1 usually with an outer setae and spine respectively; exopod segment 2 with 2-4 setae, terminal exopod segments may be fused.
- Male P5 assymmetrical, attached to a plate formed from fusion of basipod 1 and coupler; right leg (or left) comprising basipod 2 with an outer seta and a 2?-3-segmented exopod; exopod segment 2 with an inner spinous process in some genera; exopod segment 3 with 1 or 2 minute distal setae; left leg (or right) comprising basipod 2 with an outer seta and a 2-or 3-segment exopod; exopod segment 1 bearing a curved inner process, distal segment swollen, often curved or claw-like.
Genus
Ref.:
Wolfenden, 1905 a (p.5); 1911 (p.289); Sewell, 1932 (p.176); Davis, 1949 (p.50); Brodsky, 1950 (1967) (p.312); Tanaka, 1963 (p.26); Barnes & Case, 1972 (p.66: Rem.); Saraswathy, 1973 (p.190, Redef.); Razouls, 1982 (p.418); Gardner & Szabo, 1982 (p.347); Mauchline, 1988 (p.709); Björnberg & Campaner, 1988 (p.351); Hulsemann, 1988 (p.188); Razouls, 1993 (p.307); Mauchline, 1998 (p.67); Bradford-Grieve & al., 1999 (p.948: clé spp.); Bradford-Grieve, 1999 b (p.110, Déf., Rem.); Soh & al., 1999 (p.122, phylogeny); Boxshall & Halsey, 2004 (p.146); Vives & Shmeleva, 2007 (p.357)
Ref.:
Type: Pleuromma princeps T. Scott, 1894. Total: 4 spp.
Diagnosis after Bradford-Grieve (1999b, p.110) :
-As for family definition.
- Head with a small conical knob anteriorly.
- Metasome without a differentiated luminous organ.
- Posterolateral corners of metasome produced into spines which are more prominent in female than male.
- Genital segment of female symmetrically or asymmetrically inflated, sometimes with a black mass ventrally
- Urosome female segment 2 with distolateral borders produced into small flaps.
- Anal segment in both sexes produced into large pterygoid processes terminated with a pore and with fine hairs on both sides of segment which arise from ventral surface.
- Caudal rami with a blunt process on distal border.
- Right A1 of male geniculate, segment 12 with a small rounded glandular structure in addition to an aesthetasc and a seta.
- Mx1 with a small but distinct outer lobe 2 bearing a single plumose seta.
- Endopod segment 1 of P2 with 2 inner hooks.
- Female P5 3-4-segmented, segment 3 with a long plumose seta, segment 4 with 2 shorter plumose setae.
- Male P5 3-segmented; left segment 3 with 2 strong processes, 1 directed distally and the other proximally; right segment 3 with 4 setae, distal half of segment with an undulating inner margin.
Diagnosis after Bradford-Grieve (1999b, p.110) :
-As for family definition.
- Head with a small conical knob anteriorly.
- Metasome without a differentiated luminous organ.
- Posterolateral corners of metasome produced into spines which are more prominent in female than male.
- Genital segment of female symmetrically or asymmetrically inflated, sometimes with a black mass ventrally
- Urosome female segment 2 with distolateral borders produced into small flaps.
- Anal segment in both sexes produced into large pterygoid processes terminated with a pore and with fine hairs on both sides of segment which arise from ventral surface.
- Caudal rami with a blunt process on distal border.
- Right A1 of male geniculate, segment 12 with a small rounded glandular structure in addition to an aesthetasc and a seta.
- Mx1 with a small but distinct outer lobe 2 bearing a single plumose seta.
- Endopod segment 1 of P2 with 2 inner hooks.
- Female P5 3-4-segmented, segment 3 with a long plumose seta, segment 4 with 2 shorter plumose setae.
- Male P5 3-segmented; left segment 3 with 2 strong processes, 1 directed distally and the other proximally; right segment 3 with 4 setae, distal half of segment with an undulating inner margin.
Remarks on dimensions and sex ratio
The mean female size is 10,09 mm (n= 4; S= 0,477; Cv= 0,047) and the mean male size is 9,60 mm (n= 3; S= 0,854; Cv= 0,089). The size ratio (M/F) is 0,948 or 94,8 % (n= 3; S= 0,046; Cv= 0,049)
Figures
;)
Plate 1
Issued from : J.M. Bradford-Grieve in NIWA Biodiversity Memoir 111, 1999. [p.111, Fig.74]. Gaussia princeps.
Female: A, dorsal view; B, P5. Male: C, lateral view; D, P5 (R = right leg, L = left leg).
Issued from : J.M. Bradford-Grieve in NIWA Biodiversity Memoir 111, 1999. [p.111, Fig.74]. Gaussia princeps.
Female: A, dorsal view; B, P5. Male: C, lateral view; D, P5 (R = right leg, L = left leg).
Genus
Ref.:
Giesbrecht, 1892 (p.61, 339); Giesbrecht & Schmeil, 1898 (p.105, spp. Key); Sars, 1900 (p.99); Wheeler, 1901 (p.175); Sars, 1902 (1903) (p.110); Esterly, 1905 (p.177); van Breemen, 1908 a (p.107, spp. Key); A. Scott, 1909 (p.120); Esterly, 1924 (p.96); Wilson, 1932 a (p.117, spp. Key); Sewell, 1932 (p.247); Rose, 1933 a (p.175, spp. Key); Mori, 1937 (1964) (p.67); Sewell, 1947 (p.165, 166); Farran, 1948 c (n°14, p.3); Davis, 1949 (p.47); Brodsky, 1950 (1967) (p.289, spp. Key); Tanaka, 1963 (p.15); Björnberg, 1972 (p.30, 31); Björnberg & al., 1981 (p.640); Razouls, 1982 (p.405); Gardner & Szabo, 1982 (p.321); Mauchline, 1988 (p.708); Razouls, 1993 (p.307); Bucklin & al., 1995 (p.655); Chihara & Murano, 1997 (p.837); Mauchline, 1998 (p.67); Bradford-Grieve & al., 1999 (p.948, spp. Key); Bradford-Grieve, 1999 b (p.112, Def.); Soh & al., 1999 (p.122, phylogeny); Boxshall & Halsey, 2004 (p.146); Vives & Shmeleva, 2007 (p.359, spp. Key)
Ref.:
Type: Metridia armata Boeck, 1865 (= Calanus longus (Lubbock, 1854). Total: 25 spp. (of which 3 doubtful) + 3 unidentified.
Diagnosis after Bradford-Grieve (1999 b, p.112) :
- As in family definition.
- Urosome narrow.
- Body without a differentiated luminous organ.
- A2 with exopod a little longer than endopod, 6-segmented.
- P2 endopod segment 1 with a strong pair of internal hooks one larger than the other.
- Female P5 3- or 4-segmented with 2 or 3 long plumose terminal setae.
- Male P5 5-segmented, more or less curved ; on right (or left) the last segment is slightly widened, the antepenultimate segment with a long curved inner appendage.
Diagnosis after Bradford-Grieve (1999 b, p.112) :
- As in family definition.
- Urosome narrow.
- Body without a differentiated luminous organ.
- A2 with exopod a little longer than endopod, 6-segmented.
- P2 endopod segment 1 with a strong pair of internal hooks one larger than the other.
- Female P5 3- or 4-segmented with 2 or 3 long plumose terminal setae.
- Male P5 5-segmented, more or less curved ; on right (or left) the last segment is slightly widened, the antepenultimate segment with a long curved inner appendage.
Remarks on dimensions and sex ratio
The mean female size is 4,858 mm (n= 23; S= 2,580; Cv= 0,53) and the mean male size is 4,050 mm (n= 22; S= 2,61; Cv= 0,64). The coefficients of variance indicate a strong heterogeneity of the sizes (7 species have sizes > 7 mm and 6 species 3 mm or less) The size ratio (M/F) is 0,848 ou 84,8 % (n= 20; S= 0,101; Cv= 0,119). The sex-ratio (F/M) is 1,05.
In the first group (body size < 6 mm) from all measurements: the mean female size is 3.167 mm (n = 31; SD = 1.0338), and for male 2.426 mm (n = 31; SD = 0.7570). The size ratio male: female is 0.798 (n = 15; 0.0996).
In the second group (body size > 6.5 mm): the mean female size is 8.584 (n = 13; SD = 1.1045), and for male 8.106 (n = 12; SD = 1.0588). The size ratio male: female is 0.938 (n = 6; SD = 0.0522). The ex ratio is nearest of 1.
In the first group (body size < 6 mm) from all measurements: the mean female size is 3.167 mm (n = 31; SD = 1.0338), and for male 2.426 mm (n = 31; SD = 0.7570). The size ratio male: female is 0.798 (n = 15; 0.0996).
In the second group (body size > 6.5 mm): the mean female size is 8.584 (n = 13; SD = 1.1045), and for male 8.106 (n = 12; SD = 1.0588). The size ratio male: female is 0.938 (n = 6; SD = 0.0522). The ex ratio is nearest of 1.
Genus
Syn.:
Diaptomus (part.) Lubbock,1856; Pleuromma Claus,1863 (p.195); Giesbrecht, 1892 (p.61, 347); Dahl, 1893 (p.105, clé spp.); Wheeler, 1901 (p.76)
Ref.:
in Giesbrecht & Schmeil, 1898 (p.108, spp. Key); Sars,1902 (1903) (p.114); Esterly, 1905 (p.174); van Breemen, 1908 a (p.103, clé spp.); A. Scott, 1909 (p.122); Sewell, 1932 (p.263); Wilson, 1932 a (p.123, spp. Key); Steuer, 1932 a (p.42, 62, 83, spp. Key); Rose, 1933 a (p.179, spp. Key); Mori, 1937 (1964) (p.68, spp. Key); Dakin & Colefax, 1940 (p.84, spp. Key); Farran, 1948 f (n°17, p.3); Davis, 1949 (p.51); Brodsky, 1950 (1967) (p.305, key spp.); Tanaka, 1963 (p.22); Owre & Foyo, 1967 (p.70, clé spp.); Björnberg, 1972 (p.30,31); Björnberg & al., 1981 (p.640); Razouls, 1982 (p.412); Gardner & Szabo, 1982 (p.333); Ferrari, 1984 a (p.166: asymmetry); Mauchline, 1988 (p.709); Huys & Boxshall,1991 (p.63, 68); Razouls, 1993 (p.307); Park (J.S) & Mauchline, 1994 (p.107, Rem.: cuticular pores); Beckmann, 1995 (in Monoculus, n°29, p.6: asymmetry); Chihara & Murano, 1997 (p.838); Mauchline, 1998 (p.67); Bradford-Grieve & al., 1999 (p.947, 948: spp. Key); Bradford-Grieve, 1999 b (p.118, Def.); Soh & al., 1999 (p.122, phylogeny); Boxshall & Halsey, 2004 (p.146); Mulyadi, 2004 (p.10, spp. Key for Indonesian Seas); Vives & Shmeleva, 2007 (p.372, spp. Key)
Ref.:
Type: Diaptomus abdominalis Lubbock, 1856. Total: 11 spp. + 1 (juv.?).
Diagnosis after Bradford-Grieve (1999 b, p.118) :
- As in family definition.
- Urosome shorter than in Metridia, often asymmetrical, with curved segments and setal bundles.
- Head with a short acute apical process.
- Rostrum massive with 2 hairy filaments.
- Proximal part of A1 with large outer denticles.
- Asymmetrically situated circular, convex black spot on right or left side of cephalothorax (probably a luminous organ).
- Endopod segment 1 of P2 with an uncinateinner border as in Metridia, but right and left legs ofthen differ in size ; only one leg uncinate in some cases.
- Outer spine on exopod segment 1 of P3 with an elongate base, marked off by a deep notch.
- P5 of two types in female – with 3 free segments and 3 long setae on distal segment ; or with 1 free segment and 3 short spines on distal segment
- Right P5 of male distal segment strongly curved, round ; preceding segment of same leg with a long curved inner spine.
Diagnosis after Bradford-Grieve (1999 b, p.118) :
- As in family definition.
- Urosome shorter than in Metridia, often asymmetrical, with curved segments and setal bundles.
- Head with a short acute apical process.
- Rostrum massive with 2 hairy filaments.
- Proximal part of A1 with large outer denticles.
- Asymmetrically situated circular, convex black spot on right or left side of cephalothorax (probably a luminous organ).
- Endopod segment 1 of P2 with an uncinateinner border as in Metridia, but right and left legs ofthen differ in size ; only one leg uncinate in some cases.
- Outer spine on exopod segment 1 of P3 with an elongate base, marked off by a deep notch.
- P5 of two types in female – with 3 free segments and 3 long setae on distal segment ; or with 1 free segment and 3 short spines on distal segment
- Right P5 of male distal segment strongly curved, round ; preceding segment of same leg with a long curved inner spine.
Remarks on dimensions and sex ratio
The mean female size is 3.219 mm (n = 22; SD = 1.2217), and the mean male size is 2.973 mm (n = 22; SD = 1.2018). The size ratio (Male: Female) is 0.918 (n = 11; SD = 0.0893). The sex-ratio (Female: Male) is 1.