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Comprehensive Description

provided by Smithsonian Contributions to Zoology
Acanthomolgus bilobipes

TYPE MATERIAL.—11 ♀ ♀, 26 ♂ ♂ from a gorgonian, Antillogorgia acerosa (Pallas), in 3 m, Lime Cay, near Kingston, Jamaica, 30 August 1959, collected by AGH and RUG. Holotype ♀, allotype, and 31 paratypes (8 ♀ ♀, 23 ♂ ♂) deposited in USNM, the remaining paratypes (dissected) in the collection of AGH.

OTHER MATERIAL EXAMINED.—From Antillogorgia acerosa: 9 ♀ ♀, 4 ♂ ♂, in 7 m, Oistin’s Bay, Christchurch, Barbados, 15 July 1959. From Antillogorgia elastica Bieschowsky: 7 ♀ ♀, 2 ♂ ♂, in 4 m, lee side of Terremoto Reef (Cayo Terremoto), southeast of La Parguera, southwestern Puerto Rico, 6 August 1959; and 10 ♀ ♀, 3 ♂ ♂, in 3 m, Terremoto Reef, 9 August 1959. All collected by AGH and RUG.

All of the gorgonians had basket stars, Astrophyton muricatum Lamarck, entwined about them. Acanthomolgus bilobipes is believed to be associated with the gorgonian rather than with the basket star, since it always occurred in washings of gorgonians and basket stars together, never in washings of basket stars alone. Unfortunately, gorgonians without basket stars were not examined in the field. Doridicola astrophyticus, described elsewhere in this work, is apparently an associate of basket stars, since it was found in washings of these echinoderms living apart from gorgonians.

FEMALE.—The body (Figure 53a) has a moderately slender prosome. The length (without the setae on the caudal rami) is 0.94 mm (0.86–0.98 mm) and the greatest width 0.45 mm (0.41–0.47 mm) based on ten specimens in lactic acid. The ratio of the length to the width of the prosome is 1.54:1. The ratio of the length of the prosome to that of the urosome is 2.41:1. The segment of leg 1 is set off dorsally from the cephalosome by a transverse furrow. The epimeral areas of the pedigerous segments are as indicated in the figure.

The segment of leg 5 (Figure 53b) is 64 × 122 μ. There is no ventral intersegmental sclerite between this segment and the genital segment. The genital segment is 114 × 140 μ in greatest dimensions, in dorsal view of characteristic form (with slight wings at the maximum width terminating in a small knob). The areas of attachment of the egg sac are located dorsolaterally near the middle of the segment. Each area (Figure 53c) bears two long naked setae, 28 μ. The three postgenital segments are 39 × 75 μ, 32 × 69 μ, and 30 × 68 μ from anterior to posterior.

The caudal ramus (Figure 53d) is 23 × 28 μ, wider than long. The outer lateral seta is 68 μ and naked. The dorsal seta is 30 μ and naked. The outermost terminal seta is 91 μ with proximal inner spinules. The innermost terminal seta is 133 μ with bilateral spinules. The two long median terminal setae are 345 μ (outer) and 480 μ (inner), both with spinules and inserted between dorsal (unornamented) and ventral (with a row of spinules) flaps.

The body surface has a few hairs (sensilla) as shown in Figure 53a,b.

The egg sac is unknown.

The rostrum (Figure 53e) has a broadly rounded posteroventral margin.

The first antenna (Figure 53f) is slender and 356 μ long. The lengths of its seven segments (measured along their posterior nonsetiferous margins) are 24 (60 μ along the anterior margin), 99, 22, 50, 50, 41, and 34 μ respectively. The armature is 4, 13, 6, 3, 4 + 1 aesthete, 2 + 1 aesthete, and 7 + 1 aesthete. All the setae are naked.

The second antenna (Figure 53g) has a small seta and a few minute spinules on both first and second segments. The third segment has three setae. The fourth segment, 67 μ along its outer edge, 40 μ along its inner edge, and 22 μ wide, has terminally two somewhat unequal claws, the stouter one 35 μ along its axis, the more slender one 33 μ, and five slender setae. All the setae are naked.

The labrum (Figure 53h) has two posteroventral lobes.

The mandible (Figure 53i) resembles that in other species of the genus. The paragnath, indicated by broken lines in Figure 53c, is a small hairy lobe. The first maxilla (Figure 53j) has three elements. The second maxilla (Figure 53k) has the usual form for the genus. The maxilliped (Figure 54a) has a few spinules on the first segment. The second segment has two unequal setae. The third segment has a barbed spine and a small setule and terminates in a barbed spiniform process.

The ventral area between the maxillipeds and the first pair of legs (Figure 54b) is not protuberant. A line connects the bases of the maxillipeds.

Legs 1–4 (Figures 54c-f) are segmented and armed as in other species of the genus. Leg 1 (Figure 54c) has a small posterior protrusion on the outer side of the coxa. The inner coxal seta in legs 1–3 is long and plumose, but in leg 4 it is short (14 μ) and naked. The inner margin of the basis of legs 1–3 is haired, but in leg 4 it is smooth. The exopod of leg 4 (Figure 54f) is 156 μ long. The first segment of the endopod is 36 × 24 μ (not including the spiniform processes), with the inner distal spine 27 μ and naked. The second segment is 91 μ long (with the processes) and 15 μ in least width near the middle; the two terminal fringed spines are 33 μ (outer) and 63 μ (inner). Both segments have the outer margins haired.

Leg 5 (Figure 54g) has a free segment, 83 × 43 μ, its outer surface finely spinulose, its inner margin bilobed. The two naked terminal setae are 57 μ and 95 μ.

Leg 6 is represented by the two setae near the attachment of each egg sac (Figure 53c).

The color in life in transmitted light is translucid to very light tan, the eye red.

MALE.—The body (Figure 54h) has a prosome more slender than in the female. The length (excluding the ramal setae) is 0.76 mm (0.72–0.79 mm) and the greatest width 0.28 mm (0.26–0.30 mm), based on ten specimens in lactic acid. The ratio of the length to the width of the prosome is 1.81:1. The ratio of the length of the prosome to that of the urosome is 1.93:1.

The segment of leg 5 (Figure 55a) is 33 × 76 μ. There is no ventral intersegmental sclerite. The genital segment is 135 × 135 μ. The four postgenital segments are 23 × 52 μ, 20 × 50 μ, 14 × 48 μ, and 20 × 50 μ from anterior to posterior.

The caudal ramus is similar to that of the female.

The body surface is ornamented with hairs as in the female.

The rostrum is like that of the female.

The first antenna resembles that of the female but has three additional aesthetes (Figure 54h), two on the second segment and one on the fourth segment, so that the formula is 4, 13 + 2 aesthetes, 6, 3 + 1 aesthete, 4 + 1 aesthete, 2 + 1 aesthete, and 7 + 1 aesthete. The second antenna (Figure 55b) is much like that of the female, but the setae on the first and second segments and one on the third segment are finely pectinate, and segments 1, 2, and 4 have minute spinules on their inner surfaces.

The labrum, mandible, paragnath, first maxilla, and second maxilla are like those of the female. The maxilliped (Figure 55c) has an unarmed first segment. The second segment has two setae and two rows of spines. The third segment is unarmed. The claw is 185 μ along its axis, with an unusually large terminal lamella, weakly divided midway, and with two very unequal proximal setae.

The ventral area between the maxillipeds and the first pair of legs is like that in the female.

Legs 1–4 are segmented as in the female. Leg 1 is armed as in the female except for the last segment of the endopod (Figure 55d) which has the formula I,I,4. Leg 2 is similar to that of the female but the last segment of the endopod (Figure 55e) has the middle spine weaker than the other two and the inner spinous process much longer. Legs 3 and 4 are like those of the female.

Leg 5 (Figure 55a) has a slender free segment, 33 × 8 μ, not bilobed as in the female. The two terminal elements are 14 μ and 44 μ. The outer surface of the free segment has only a few spinules.

Leg 6 (Figure 55a) is a posteroventral flap on the genital segment bearing two slender naked setae 25 μ and 36 μ.

The spermatophore is unknown.

The color in life is like that of the female.

ETYMOLOGY.—The specific name bilobipes (from the Latin bis, twice; lobus, a lobe; and pes, a foot) alludes to the bilobed inner margin of the free segment of leg 5 in the female.

MATERIAL.—404 ♀ ♀, 581 ♂ ♂, and 646 copepodids from single colony of the gorgonian Solenocaulon tortuosum Gray, on sand in 15 m, in pass between Nosy Komba and Nosy Bé, northwestern Madagascar, 13 April 1966, collected by R. Plante. Holotype ♀, allotype, and 730 paratypes (280 ♀ ♀, 450 ♂ ♂) deposited in USNM; 200 paratypes (100 ♀ ♀, 100 ♂ ♂) in ZMA; and the remaining paratypes and copepodids in the collection of AGH.

OTHER MATERIAL EXAMINED (all from Solenocaulon tortuosum).—214 ♀ ♀, 55 ♂ ♂, and 61 copepodids from single colony, in 15 m, in pass at Pte. Lokobe, Nosy Bé, 13 June 1967; and 42 ♀ ♀, 29 ♂ ♂, and 46 copepodids from four colonies, in 18 m, in pass at Pte. Lokobe, Nosy Bé, 3 July 1967. All collected by AGH.

FEMALE.—The body (Figure 56a) has a moderately expanded prosome. The length is 0.81 mm (0.75–0.84 mm) and the greatest width 0.38 mm (0.34–0.39 mm), based on ten specimens in lactic acid. The ratio of the length to the width of the prosome is 1.39:1. The ratio of the length of the prosome to that of the urosome is 1.79:1.

The segment of leg 5 (Figure 56b) is 60 × 112 μ. Between that segment and the genital segment there is a well-developed ventral intersegmental sclerite. The genital segment is 138 × 120 μ, a little longer than wide and not greatly expanded, with two pairs of hyaline lateral membranes. The areas of attachment of the egg sacs are situated dorsolaterally near the middle of the segment. Each area (Figure 56c) bears two small naked spiniform elements, 7 μ and 9 μ in length, with a pointed process between them. Medial to the larger element the cuticular fold is produced as a small thornlike prominence. The three postgenital segments are 35 × 58 μ, 31 × 56 μ, and 36 × 55 μ from anterior to posterior.

The caudal ramus (Figure 56d) is a little longer than wide, 33 × 25 μ. The outer lateral seta is 59 μ and the outermost terminal seta is 67 μ, both naked. The dorsal seta is 32 μ and very lightly feathered. The innermost terminal seta is 135 μ with its inner margin haired proximally and with a few minute spinules distally. The two long median terminal setae are 273 μ (outer) and 330 μ (inner), both with a few widely spaced minute inner spinules and both inserted between dorsal (unornamented) and ventral (with a marginal row of spinules) flaps.

The body surface is ornamented with a few hairs (sensilla) as shown in Figure 56a,b. The posteroventral margin of the anal segment bears a row of spinules on both sides.

The egg sac (Figure 56a) is elongated, oval, 300 × 140 μ, reaches beyond the caudal rami, and contains many eggs about 40 μ in diameter.

The rostrum (Figure 56a) is broadly rounded posteroventrally.

The first antenna (Figure 56f) is 284 μ long. The lengths of the séven segments (measured along their posterior nonsetiferous margins) are 25 (51 μ along the anterior margin), 85, 18, 37, 39, 28, and 26 μ respectively. The formula for the armature is 4, 13, 6, 3, 4 + 1 aesthete, 2 + 1 aesthete, and 7 + 1 aesthete. All the setae are naked.

The second antenna (Figure 56g) is 4–segmented. Each of the first two segments bears a naked seta. The third segment bears a naked spine and two naked setae. The last segment, 75 μ along its outer edge, 47 μ along its inner edge, and 20 μ wide, bears two terminal unequal claws. The stouter claw is 43 μ along its axis and the more slender claw 32 μ. Near the insertions of the claws are five small hyaline elements.

The labrum (Figure 56h) has two broad posteroventral lobes.

The mandible (Figure 56i), paragnath (Figure 56h), first maxilla (Figure 56j), and second maxilla (Figure 56k) resemble those of A. exilipes (Humes and Ho). The maxilliped (Figure 56l) has two very unequal setae on the second segment, the longer seta barbed along one edge, the shorter seta naked. The last segment bears a naked spine, a small naked setule, and an incompletely articulated spiniform process with minute barbules along one edge. The first segment is ornamented with slender spinules.

The ventral area between the maxillipeds and the first pair of legs (Figure 57a) is not protuberant. A sclerotized line connects the bases of the maxillipeds.

Legs 1–4 (Figure 57b-e) have the same spine and setal formula as in other species of the genus. The inner coxal element of leg 4 is reduced to a small naked setule 5 μ long. The inner margin of the basis of leg 4 is smooth instead of having a row of hairs as in legs 1–3. The outer exopod spines of leg 1 have relatively small numbers of barbs on their proximal edges. The inner margins of the second and third segments of legs 1–3 lack hairs. The exopod of leg 4 is 146 μ. The endopod of leg 4 has outer hairs on both segments. The first segment is 30 × 27 μ (not including the spinous processes) and its inner distal naked spine is 32 μ. The second segment is 70 μ long (including the terminal spiniform processes), 25 μ in greatest width proximally, and 20 μ in least width distally; the outer terminal fringed spine is 21 μ, the inner spine is 53 μ, inwardly fringed but outwardly barbed.

Leg 5 (Figure 57f) has an elongated free segment 120 × 23 μ (the width taken at the middle); the width at the proximal inner expansion is 32 μ. The outer surface of the segment bears short, broad spines. The two terminal setae are 57 μ and naked and 78 μ with a narrow unilateral fringe. The seta on the body near the free segment is 33 μ and lightly feathered.

Leg 6 is probably represented by the two spiniform elements near the area of attachment of the egg sacs (Figure 56c).

The color in life in transmitted light is opaque, the eye red, the egg sacs grayish black.

MALE.—The body (Figure 57g) is more slender than in the female. The length is 0.64 mm (0.58–0.67 mm) and the greatest width is 0.25 mm (0.24–0.25 mm), based on ten specimens in lactic acid. The ratio of the length to the width of the prosome is 1.65:1. The ratio of the length of the prosome to that of the urosome is 1.59:1.

The segment of leg 5 (Figure 57h) is 32 × 57 μ. There is no ventral intersegmental sclerite. The genital segment is 138 × 122 μ. The four postgenital segments are 19 × 40 μ, 19 × 39 μ, 13 × 37 μ, and 21 × 39 μ from anterior to posterior.

The caudal ramus is like that of the female, but smaller, 23 × 19 μ.

The surface of the body is ornamented with hairs as in the female.

The rostrum is similar to that of the female.

The first antenna is segmented and armed as in the female but has three additional aesthetes as in A. astrictus. The second antenna is the same as in the female, without sexual dimorphism.

The labrum, mandible, paragnath, first maxilla, and second maxilla are like those of the female. The maxilliped (Figure 57i) resembles in general form that of A. varirostratus (Humes and Ho) but the claw is shorter, 108 μ along its axis (including the terminal lamella), and more strongly recurved.

The ventral area between the maxillipeds and the first pair of legs is like that of the female.

Legs 1–4 are segmented and armed as in the female except for the last segment of the endopod of leg 1 (Figure 58a) which has I,I,4 instead of I,5 as in the opposite sex. On the last segment of the endopod of leg 2 (Figure 58b) the three spines from outer to inner are 17.5, 15.5, and 22 μ (in the female 17, 14, and 22 μ) and more strongly barbed than in the opposite sex; and on the last segment of the endopod of leg 3 (Figure 58c) the spines are 20, 20, and 24 μ (in the female 21, 18, and 26 μ) and also are more strongly barbed. The endopod of leg 4 (Figure 58d) has a slightly more slender second segment than in the female. The dimensions of this endopod are as follows: first segment 22 × 17.5 μ (without the spiniform processes) and its spine 24 μ; second segment 46 μ long (including the terminal spiniform processes), 14 μ in greatest width proximally, and 11 μ in least width distally; the outer terminal spine is 18 μ, the inner spine 42 μ.

Leg 5 (Figure 57h) has an elongated, slender free segment, 30 × 7.5 μ, without a proximal expansion. The outer surface bears a few small spinules and the two terminal elements are 14 μ and 39 μ.

Leg 6 (Figure 57h) consists of a posteroventral flap on the genital segment bearing two naked setae, 21 μ and 30 μ.

The spermatophore (Figure 58e), attached to the female in pairs, is oval, 104 × 55 μ (without the neck).

The color in life in transmitted light resembles that of the female.

ETYMOLOGY.—The specific name hales (Greek in abundance) alludes to the great numbers of this copepod (more than 1,600 specimens) found on a single host colony (type collection).
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bibliographic citation
Humes, Arthur Grover and Stock, Jan H. 1973. "A revision of the family Lichomolgidae Kossmann, 1877, cyclopoid copepods mainly associated with marine invertebrates." Smithsonian Contributions to Zoology. 1-368. https://doi.org/10.5479/si.00810282.127

Distribution

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Curacao, West Indies; Lime Cay, near Kingston, Jamaica
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Ju-shey Ho [email]
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Ju-shey Ho [email]