Caligus dactylus, Ho & Lin & Chang, 2007

Ho, Ju-Shey, Lin, Ching-Long & Chang, Wen-Been, 2007, Four species of Caligus Müller, 1785 (Copepoda, Siphonostomatoida, Caligidae) parasitic on marine fishes of Taiwan, Journal of Natural History 41 (5 - 8), pp. 401-417: 408-412

publication ID 10.1080/00222930701203853

persistent identifier

treatment provided by


scientific name

Caligus dactylus

n. sp.

Caligus dactylus   n. sp.

( Figures 5–7 View Figure 5 View Figure 6 View Figure 7 )

Material examined

Fifty-one ♀♀, 18 „„ and two larvae on gill filaments of 23 starry flying gurnard, Dactyloptena peterseni (Nyström)   , collected on 28 May 2004 at Da-hsi Fishing Port of I-Lan County. Holotype female ( USNM 1086716 View Materials ), allotype male ( USNM 1086717 View Materials ), and 30 paratypes ( USNM 1086718 View Materials , 1086719 View Materials ; 20♀♀, 10 „„) have been deposited in the US National Museum of Natural History, Smithsonian Institution , Washington, DC and the remaining paratypes and other specimens kept in the author’s ( CLL) collection.  


Body ( Figure 5A View Figure 5 ) 2.55 (2.38–2.76) long, excluding setae on caudal ramus. Cephalothoracic shield subtriangular, 1.19 (1.08–1.30)X1.15 (1.08–1.20), excluding lateral hyaline membrane. Fourth pediger distinctly wider than long, 0.18 (0.15–0.22)X0.34 (0.30–0.36). Genital complex subsquare, 0.84 (0.78–0.90)X0.85 (0.76–0.90), with small knob in egg sac attachment area ( Figure 7A View Figure 7 ). Abdomen ( Figure 7A View Figure 7 ) one-segmented, with lateral bulge, 0.30 (0.25–0.34)X0.26 (0.24–0.28). Caudal ramus ( Figure 7A View Figure 7 ) longer than wide, 70 (61–81)X55 (49–65) mm, armed with usual three short and three long setae. Egg sac 2.45 long and containing 23 eggs.

Antennule ( Figure 5B View Figure 5 ) two-segmented; both proximal and distal segments armed as in C. arii   ; distal segment long, about 3.75 times as long as wide. Antenna ( Figure 5C View Figure 5 ) threesegmented; proximal segment smallest, unarmed; middle segment subrectangular and unarmed; distal segment a claw strongly bent at tip and carrying two setae in basal region. Postantennal process ( Figure 5C View Figure 5 ) small spine with two papillae in basal region bearing two setules, another similar setule-bearing papilla nearby on cephalon. Mandible ( Figure 5D View Figure 5 ) as in C. arii   . Maxillule ( Figure 5C View Figure 5 ) comprising short, bluntly pointed digitiform process and papilla bearing three unequal setae. Maxilla ( Figure 5E View Figure 5 ) generally constructed as in C. arii   , except brachium (distal segment) being shorter than lacertus (proximal segment).

Maxilliped ( Figure 5F View Figure 5 ) three-segmented; proximal segment (corpus) robust, produced on basal, medial surface (myxal area) into large pointed tooth-like process with distal trough; middle segment (shaft) as long as terminal claw, bearing medial seta at its tip; in closing, claw tip inserted into trough on tip of myxal process. Box of sternal furca ( Figure 5G View Figure 5 ) subsquare, carrying two parallel tines with truncate tip.

Armature on rami of legs 1–4 as follows (Roman numerals indicating spines and Arabic numerals, setae):

Exopod Endopod

Leg 1 1-0; I,II,I,3 (Vestigial)

Leg 2 I-1; I-1; II,I,5 0–1; 0–2; 6

Leg 3 I-0; I-1; III,4 0–1; 6

Leg 4 I-0; I,III (Absent)

Leg 1 ( Figure 6A View Figure 6 ) protopod with plumose, outer seta and another small, plumose, inner seta in addition to a papilla bearing two setules; vestigial endopod small, tipped with two setules; first segment of exopod with row of setules on posterior edge and pecten near base of outer spiniform seta; middle two of terminal four elements with twisting rows of setules but no accessory process; pecten near base of two outer, terminal elements. Leg 2 ( Figure 6B View Figure 6 ) coxa small, with large plumose inner seta on posterior edge and small setulebearing papilla on ventral surface; basis with simple, outer seta and medial papilla bearing long setule; both outer and medial edges of protopod fringed with large marginal membrane; similar membrane on outer margin of elongated, proximal segment of exopod; outer spines on basal two segments of exopod long. Leg 3 ( Figure 6C View Figure 6 ) protopod (apron) with short, outer and long, inner seta; large marginal membrane on outer edge following serrated margin and another marginal membrane on posterior edge of basis inner to velum; setule-bearing papilla on basis near both ends of this posterior membrane; and rows of denticles on lateral edge, another patch of spinules and setule-bearing papilla on ventral surface of protopod. Leg 4 ( Figure 6D View Figure 6 ) protopod with small, plumose, outer seta; pectens on two exopodal segments at insertion of each of five outer spines. Leg 5 ( Figure 7A View Figure 7 ) represented by two papillae on posterolateral margin of genital complex, with one bearing one small, plumose setae and another bearing three similar setae.


Body ( Figure 7B View Figure 7 ) 1.92 (1.78–2.00) long, excluding setae on caudal rami. Cephalothoracic shield suborbicular, 1.04 (1.00–1.08)X0.95 (0.90–0.98), excluding lateral marginal membranes. Fourth pediger distinctly wider than long, 0.16 (0.14–0.18)X0.30 (0.30– 0.32). Genital complex much smaller than cephalothoracic shield, 0.40 (0.38–0.42)X0.34 (0.32–0.35). Abdomen slender and one-segmented, 0.25 (0.22–0.27)X0.13 (0.13–0.14). Caudal ramus longer than wide, 89 (81–97)X66 (65–69) mm.

Antenna ( Figure 7C View Figure 7 ) three-segmented; proximal segment smallest and unarmed; middle segment largest, without armature except light corrugation on medial surface; terminal segment a sharp claw armed with two basal inner setae and a large, basal tooth. Leg 5 ( Figure 7D View Figure 7 ) constructed as in female but located differently from female, close to midway along lateral margin of genital complex. Leg 6 ( Figure 7D View Figure 7 ) represented by a lobe tipped with two plumose setae located on posterolateral corner of genital complex.


The specific name dactylus   is Greek (5 a finger or toe), and refers to the thumb-like myxal process on the corpus of the maxilliped.


This new species is characteristic in having the following features in the female: (1) the length of abdomen is less than one-half that of genital complex; (2) the genital complex is wider than long; (3) the corpus of the maxilliped is equipped with a large myxal process; (4) tines on the sternal furca are parallel and truncate at tip; (5) the middle two of the terminal four elements on the exopod of leg 1 have no accessory process; and (6) the armature formula of leg 4 is I-0; I,III. Checking the known species of Caligus   revealed that the above combination of six characters is shared with only one species, namely Caligus priacanthi Pillai, 1961   .

Caligus priacanthi   is so far known only from India. Pillai (1961) reported the female only in his original description of the species, but description of the male was later provided by Prabha and Pillai (1986). Comparison with those two works showed that C. dactylus   can not be identified with C. priacanthi   . The differences seen in the female are the structures of the proximal segment on the antenna, calamus on the maxilla, tines on the sternal furca, outer spines on the proximal and middle segments of the exopod of leg 2; and in the male, the abdomen and the myxal process on the maxilliped. Besides, the hosts are different. The Indian C. priacanthi   is a parasite of the moontail bullseye, Priacanthus hamrur (Forsskål)   .


University of Stellenbosch














Caligus dactylus

Ho, Ju-Shey, Lin, Ching-Long & Chang, Wen-Been 2007

C. dactylus

Ho & Lin & Chang 2007

Caligus priacanthi

Pillai 1961

C. priacanthi

Pillai 1961

C. priacanthi

Pillai 1961