Recomendaciones

Mostly large copepods with elongated and often transparent bodies. Stage V females can have a swollen genital segment and resemble a stage V, but the segmentation is not clearly defined and if there is any uncertainty whether the specimen is mature, it probably is not. The female urosome is very short, 3 or 4-segmented, 5-segmented in the male, the furca usually fused to the anal segment in both sexes. Females often have a broad genital segment. Most have in dorsal view, a typical triangular anterior cephalosome. Cephalosome and first pedigerous segment fused, pedigerous segments 4 and 5 partially fused, rostrum with 2 long filaments. In some species the first antenna reaches well beyond the urosome. Female P5 missing or only on one side, or uniramous on the left and biramous on the right.

The number and arrangement of small integumental organs over the body is a useful character in identification (see Bradford-Grieve, 1994) but requires special preparation of the specimens.

Genus Eucalanus

Female urosome 4-segmented. The posterior margins of pedigerous segments 2-4 and urosome segment 1 without any spines. P5 missing in female, uniramous on both sides in the male.

Eucalanus elongatus (Dana, 1849)

Length: females: 5.75-8.50 mm; males: 3.75-5.00 mm.

Female: Characterised by the pointed postero-lateral corners of the metasome. Transparent body. Anterior cephalosome triangular, urosome 4-segmented, genital segment longer than wide. Left furca wider and longer than the right. A1 extending beyond the furca by around the last 4 segments. Second inner seta of right furca elongated, if not broken off.

Male: Also has lateral points on the posterior metasome. Transparent body, anterior cephalosome bluntly rounded. A1 extending beyond the furca by around the last 4 segments. Urosome 5- segmented, genital segment slightly wider than long. Both P5 legs 4-segmented, terminating in spines; right leg shorter than the left, terminal segment reaching around the third segment of the left leg.

Recorded: Madagascar

Eucalanus elongatus: Female. A, dorsal; B, rostrum ventral. Male. C, dorsal; D, P5. Figures from Giesbrecht (1892).

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Genus Pareucalanus

Includes the largest of the Eucalanidae. Female urosome 3-segmented and the posterior margins of pedigerous segments 2-4 and urosome segment 1 without any spines. P5 missing in the female, uniramous, simple in the male, the right leg shorter than the left, not extending beyond the distal part of left leg segment 2.

Pareucalanus attenuatus (Dana, 1849)

Length: females: 3.55-7.00 mm; males: 2.95-6.04 mm. There appears to be small and large forms and great variability in appearance of specimens. It is possible that some of the specimens are P. sewelli (Fleminger, 1973) but they are very difficult to tell apart without detailed examination of the integumental organs.

Female: In dorsal view, generally with a triangular, bluntly pointed cephalosome, very elongated anterior to the A2 and sometimes narrows in this region. In lateral view the anterior cephalosome is quite pointed. Posterior prosome corners rounded. A1 extends beyond the furca by the last 6-7 joints. No P5 present; genital segment is longer than wide; furca fused to the anal segment, one of the left furcal setae longer than the others.

Male: Anterior cephalosome triangular. A1 extends beyond the furca by the last 6-7 joints. Genital segment wider than long; P5 very simple, the left leg longer than the right, both legs of 4 segments and in both the terminal segment bears a spine. Furca fused to anal segment. One of the left furcal setae longer than the others.

Recorded: Rodrigues, Seychelles, Zuza, Madagascar, Aldabra, CPR.

Pareucalanus attenuatus: Female. A, lateral; B, dorsal; C, head lateral; D, genital segment lateral. Male. E, dorsal; F, P5. Figures A, B, E, F from Mori (1937); figures C, D from Vervoort (1946).

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Genus Subeucalanus

Female urosome 3-segmented, the posterior margins of pedigerous segments 2-4 and urosome segment 1 without any spines. No P5 in female, uniramous in male, with only left leg present.

Subeucalanus crassus (Giesbrecht, 1888)

Length: females: 2.46-3.70 mm; males: 2.40-3.10 mm.

Female: Body robust, anterior cephalosome rounded and short. A1 reaches just beyond the furca. Urosome 3-segmented, genital segment wider than long and markedly onion shaped. Furca slightly asymmetrical, anal segment fused with the furca. The left second terminal seta of the furca is slightly longer than that of the right.

Male: Does not have distinct secondary sexual characters. A1 reaches around the end of the furca. Genital segment longer than wide. P5 right foot absent, left foot uniramous, 4-segmented, with terminal spine.

Recorded: Rodrigues, Madagascar.

Subeucalanus crassus: Female. A, dorsal; B, lateral; C, dorsal; D, genital segment dorsal; E genital segment lateral. Male. F, dorsal; G, P5. Figures A, D, E from Bradford-Grieve (1994); figures B, C, F, G from Fleminger (1973).

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Subeucalanus mucronatus (Giesbrecht, 1888) Length: females: 2.8-3.3 mm; males: 2.7-2.9 mm.

Female: Anterior cephalosome triangular and sharply pointed, both dorsally and laterally. Genital segment longer than wide; furca asymmetrical. Second inner seta on the right furca thicker than other setae and elongated, if not broken off.

Male: Anterior cephalosome rounded, quite square laterally. Right P5 absent. The terminal spine on the left P5 is shorter than the terminal segment, which separates it from S. subtenuis. Second inner seta on the right furca thicker and longer than other setae, if not broken off.

Recorded: Zuza, Madagascar, Aldabra.

Subeucalanus mucronatus: Female. A, dorsal; B, dorsal; C, lateral. Male. D, dorsal; E, P5. Figures B, C from Fleminger (1973); figures A, D, E from Mori (1937).

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Subeucalanus pileatus (Giesbrecht, 1888)

Length: females: 1.80-2.50 mm; males: 1.80-2.25 mm.

Female: Prosome slender, widest at the posterior of the cephalosome; anterior cephalosome triangular, rounded anteriorly, more pointed than in E. subcrassus, but exact shape can be variable; urosome short, one sixth the length of the prosome. Posterior metasome more or less rounded. A1 passes the furca by around 5 segments. Urosome 3-segmented, genital segment slightly broader than long, moderately swollen in dorsal view, widest in the centre, moderately swollen in lateral view. The line of fusion between the furca and anal segment obvious. Furca are almost symmetrical, the second seta on the left greatly lengthened, but only slightly thicker than the other setae. P5 absent.

Male: Similar to the males of S. crassus but smaller. The P5 is 4-segmented and only present on the left. The terminal spine is shorter than the terminal segment.

Recorded: Rodrigues, Zuza.

Subeucalanus pileatus: Female. A, lateral; B, dorsal; C-E dorsal and lateral views of head shape variants; F, urosome ventral. Male. G, dorsal; H, head dorsal; I, P5. Figures A,B from Fleminger (1973): C-I from Giesbrecht (1892).

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Subeucalanus subcrassus (Giesbrecht, 1888) Length: females: 1.93-2.88; males: 2.40 mm.

Female: Similar to S. crassus but slimmer, head more pointed and extends further forward in lateral view, the second terminal seta on the left furca is much longer than the right seta and the genital segment is narrower. Anterior of cephalosome rounded; A1 extends beyond the furca by around 4 segments. Urosome 3-segmented, genital segment broader than long, with widest part in dorsal view on the posterior half of the segment, compare to E. pileatus where it is wider in the centre; furca fused with anal segment.

Male: P5 right absent, terminal seta on left P5 longer than the terminal segment. Second terminal setae of the furca are asymmetrical, as in the female.

Recorded: Rodrigues, Seychelles, Zuza, Madagascar, Aldabra.

Subeucalanus subcrassus: Female. A, dorsal; B, dorsal head profile; C, urosome ventral; D. anterior urosome and genital segment ventral; E, P3 endopod segment 2. Male. F, dorsal; G, P5. Figures A-E, G from Greenwood (1976); F from Mori (1937).

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Subeucalanus subtenuis (Giesbrecht, 1888)

Length: females: 2.61-3.15 mm; males: 2.70-2.75 mm.

Female: Similar to S. mucronatus, as the anterior of cephalosome triangular, but its apical portion is less sharply pointed. Furca asymmetrical.

Male: Anterior cephalosome rounded. Resembles S. mucronatus but the terminal spine on the left P5 is longer than the terminal segment. Also similar to S. crassus but has more developed asymmetry of the setae of the furca, the left second seta is much longer and thicker than the right seta.

Recorded: Rodrigues, Seychelles, CPR.

Subeucalanus subtenuis: Female. A, Lateral; B, dorsal; C, head dorsal; D head lateral; E, urosome ventral. Male. F, dorsal; G, head dorsal; H, P5. Figures A from Fleminger (1973); B-H from Giesbrecht (1892).

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Genus Rhincalanus

Long, very slim species with anterior cephalosome extended into a conical process, carrying on the ventral surface the rostral filaments. Cephalosome and first pedigerous segment fused. A1 is longer than the whole body. Metasome segments with lateral and dorsal spines. Urosome short, 3-segmented, the distal segment fused with the furca. The female P5 is uniramous, 3-segmented and very simple. The male P5 is also a very simple limb, biramous on one side.

Rhincalanus nasutus Giesbrecht, 1888

Length: females: 3.90-5.50 mm; males: 2.70-4.0 mm.

Female: Strongly pointed anterior cephalosome, but less so than in R. rostifrons. Prosome long and slender with lateral spines and dorsal pairs of spines on the posterior margin of the first 3 metasome segments. A1 around 1.5 times the length of the whole body. Urosome 3-segmented, with pair of small spines on dorsal surface of genital segment. Rostral filaments situated under the frontal projection and are hardly visible from above. P5 are uniramous and 3-segmented, with one seta on the second segment internally and three terminal setae.

Male: Prosome similar to female, but A1 considerably shorter. Spines on the metasome segments and on the first urosome segment similar to the female. Right P5 is uniramous, 3-segmented with a slender curved terminal spine. Left P5 biramous, endopodite 3-segmented with segments of almost equal length, exopodite 1-segmented with a long terminal plumose seta and outside of it a naked, very short seta.

Recorded: Madagascar

Rhincalanus nasutus: Female. A, lateral; B, dorsal; C, head ventral; D, head lateral; E, urosome ventral; F, P5. Male. G, dorsal; H, P5. Figures A, C-F, H from Sars (1903); B, G from Mori (1937).

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Rhincalanus rostifrons (Dana, 1849)

Length: females: 2.79-3.80 mm; males: 2.41-2.95 mm.

Female: Extremely extended point on the anterior cephalosome, with prominent rostral filaments which protrude laterally, visible in dorsal view. A1 around 1.5 times as long as whole body. P5 3-segmented, without seta on the second segment, the terminal segment extended into a stout curved point, with an internal toothed spine.

Male: Right P5 uniramous, 3-segmented with the terminal segment extended into a curved spine. Left P5 biramous with a 1-segmented exopodite bearing a curved terminal spine; a 2-segmented endopodite, the first segment longer than the second, the endopodite around the same length as the exopodite.

Recorded: Seychelles, Zuza, Madagascar, Aldabra, CPR.

Rhincalanus rostifrons: Female. A, dorsal; B, P5. Male. C, dorsal; D, P5. Figures from Mori (1937).

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