Asterocheres genodon Stock, 1966

Bandera, Eugenia & Conradi, Mercedes, 2013, Redescription of five Asterocheres species (Copepoda: Siphonostomatoida) and a description of a new species discovered in the collections of the Zoological Museum of Amsterdam, Journal of Natural History 47 (5 - 12), pp. 597-618 : 598-601

Asterocheres genodon Stock, 1966

( Figure 1 )

Material examined

Holotype female (ZMA-Co.100.956) and seven paratype females (ZMA-Co.100.956b) associated with the sponge Haliclona sp. at Chenal du Trou d´Eau Douce ( Mauritius) at 6–10 m depth collected 7 February 1964, by J.H. Stock.

Description

Female. Body cyclopiform, with oval cephalothorax and cylindrical urosome (fig. 6A; Stock 1966 and fig. 39A; Kim 2010). Mean body length 880 µm (810–940 µm) and maximum width 520 µm (490–550 µm), based on five specimens. All appendages as redescribed by Kim (2010), except for antennule and maxillule.

Antennule 21-segmented ( Figure 1A ), about 450 µm long. Segmental fusion pattern as follows (roman numerals indicating ancestral segments): 1(I)-2, 2(II)-2, 3(III)-2, 4(IV)-2, 5(V)-2, 6(VI)-2, 7(VII)-2, 8(VIII)-2, 9(IX-XII)-7, 10(XIII)-1+1 spiniform element, 11(XIV)-1+1 spine, 12(XV)-2, 13(XVI)-2, 14(XVII)-2, 15(XVIII)-2, 16(XIX)-2, 17(XX)-2, 18(XXI)-2+1 aesthetasc, 19(XXII)-2, 20(XXIII-XXIV)-4 and 21(XXV- XXVIII)-7. Segment 10(XIII) reduced and partly overlapped by distal expansion of compound segment 9(IX-XII).

Maxillule bilobed ( Figure 1B ). Inner lobe three times longer and wider than outer. Inner lobe with tuft of long spinules medially and row of spinules laterally, bearing five terminal setae, one of them short and naked. Outer lobe with two subterminal setae (one of them barbed) and two plumose terminal setae.

Male described by Kim (2010).

Remarks

This species, which lives associated with the sponge Haliclona sp. in Chenal du Trou d´Eau Douce ( Mauritius), was collected by Jan Stock in 1964 and described and illustrated in 1966. Recently, this species has been thoroughly redescribed by Kim (2010) with material from Madagascar collected by A.G. Humes. Despite this exhaustive redescription, the study of the holotype has revealed two small discrepancies in the oral appendages: (1) the segmental fusion pattern of antennule in female is 1(I)-2, 2(II)-2, 3(III)-2, 4(IV)-2, 5(V)-2, 6(VI)-2, 7(VII)-2, 8(VIII)-2, 9(IX-XII)-7, 10(XIII)-1+1 spiniform element, 11(XIV)-1+1 spine, 12(XV)-2, 13(XVI)-2, 14(XVII)-2, 15(XVIII)-2, 16(XIX)-2, 17(XX)-2, 18(XXI)-2+1 aesthetasc, 19(XXII)-2, 20(XXIII-XXIV)-4 and 21(XXV-XXVIII)-7 and the setation described by Kim (2010) is different: 1(I)-2, 2(II)-2, 3(III)-2, 4(IV)-2, 5(V)-2, 6(VI)-2, 7(VII)-2, 8(VIII)-2, 9(IX-XII)-7, 10(XIII)- 2, 11(XIV)-2, 12(XV)-2, 13(XVI)-2, 14(XVII)-2, 15(XVIII)-2, 16(XIX)-2, 17(XX)-2, 18(XXI)-2+1 aesthetasc, 19(XXII-XXIII)-4, 20(XXIV)-2 and 21(XXV-XXVIII)-7; (2) the outer lobe of maxillule shows four plumose distal setae instead of the naked setae illustrated by Kim (2010).

After the redefinition of the genus Asterocheres by Kim (2010), only 60 valid species are considered as belonging to this genus. Asterocheres genodon belongs to the group of Asterocheres species with 21-segmented antennules in females, which comprises 22 species. These species are: A. astroidicola Conradi, Bandera and López-González, 2006 , A. echinicola (Norman, 1868) , A. ellisi Hamond, 1968 , A. flustrae Ivanenko and Smurov, 1997 , A. hirsutus Bandera, Conradi and López-González, 2005 , A. jeanyeatmanae Yeatman, 1970 , A. kervillei Canu, 1898 , A. latus (Brady, 1872) , A. lilljeborgi Boeck, 1859 , A. madeirensis Bandera, Conradi and López-González, 2007 , A. minutus (Claus, 1889) , A. nudicoxus Kim, 2010 , A. peniculatus Kim, 2010 , A. reginae Boxshall and Huys, 1994 , A. simulans (Scott, 1898) , A. siphonatus Giesbrecht, 1897 , A. suberitis Giesbrecht, 1897 , A. tarifensis Conradi and Bandera, 2011 , A. tenerus (Hansen, 1923) , A. tenuicornis Brady, 1910 , A. tubiporae Kim, 2004 and A. urabensis Kim, 2004 .

Asterocheres genodon can be easily separated from five of these species, A. echinicola , A. madeirensis , A. minutus , A. nudicoxus and A. siphonatus , by the number of segments in the mandibular palp. Whereas these species have a one-segmented mandibular palp, A. genodon has two segments in the mandibular palp ( Bandera et al. 2007; Bandera and Conradi 2009c; Kim 2010; Conradi and Bandera 2011).

The oral cone of A. genodon forms an elongate siphon, reaching slightly beyond the intercoxal plate of leg 2. However, the siphon of A. peniculatus , A. hirsutus , A. ellisi , A. urabensis and A. latus only reaches to the intercoxal plate of leg 1 ( Kim 2004a, 2010; Bandera et al. 2005; Bandera and Conradi 2009b, 2009c); in A. flustrae , A. reginae , A. simulans , A. suberitis , A. jeanyeatmanae , A. tarifensis , A. kervillei and A. tubiporae , the siphon extends only to the insertion of maxillipeds ( Yeatman 1970; Boxshall and Huys 1994; Ivanenko 1997; Ivanenko and Smurov 1997; Kim 2004b; Bandera and Conradi 2009a, 2009c; Conradi and Bandera 2011); and in A. lilljeborgi the siphon extends only to the maxilla (according to Ivanenko and Ferrari 2003).

Eiselt’s illustration of the habitus of A. tenuicornis shows a caudal ramus six times longer than wide ( Eiselt 1965). In contrast, A. genodon has a caudal ramus slightly longer than wide.

Finally, A. genodon can be differentiated from the remaining two species, A. astroidicola and A. tenerus , by having a ventral seta on the caudal ramus (illustrated and described by Kim 2010). As Kim mentioned, this ventral seta on the caudal ramus is also reported in A. dysideae Humes, 1996 . This feature is very rare in the genus because it is absent in most species. However, this “seta I” on the caudal ramus was observed by Boxshall and Huys (1994) in A. reginae , although in this case this seta was much shorter and lateral.

Figures

Figure 1. Asterocheres genodon Stock, 1966, holotype (female). (A) Antennule; (B) maxillule.