Chlamydotheca arcuata (Sars, 1901)
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publication ID |
https://doi.org/ 10.3906/zoo-1512-13 |
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persistent identifier |
https://treatment.plazi.org/id/03D587C0-712C-E41A-FF64-5D4B407FE005 |
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treatment provided by |
Felipe |
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scientific name |
Chlamydotheca arcuata (Sars, 1901) |
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Chlamydotheca arcuata (Sars, 1901) View in CoL ( Figures 2A–2L View Figure 2 , 3A–3G View Figure 3 , 4A–4F View Figure 4 , 5A–5G View Figure 5 , 6A–6D View Figure 6 , 7A–7G View Figure 7 , 8A and 8B View Figure 8 , 9A– 9I View Figure 9 , 10A–10F View Figure 10 , 11A–11H View Figure 11 )
Along with the adults that were cultured for 2 to 5 days after being isolated, 3 to 5 eggs were found and gathered from the floor of the aquarium; these hatched asynchronously after incubation in culture media. All single eggs were covered with a jelly-like substance; in the absence of this substance, the surface appeared covered with small, regularly spaced tubercles ( Figures 2A–2C View Figure 2 ). Some of the eggs were attached to the internal surface of the valves ( Figure 2D View Figure 2 ).
3.1. Description of first instar (A-8; n = 10)
Cp: L 133–180; H 100–130. Anterior margin of carapace acuminated, posterior margin rounded. Surface of Cp with small puncta ( Figure 2E View Figure 2 ).
An1 ( Figure 4A View Figure 4 ). With 5 segments. Second segment with 1 ventral seta. Third segment with 2 long subequal dorsal setae and 1 short ventroapical seta. Terminal segment with 2 long setae, 1 ventroapical short seta, and 1 aesthetasc (y
a
).
An2 ( Figure 4B View Figure 4 ). Biramous with a protopod, endopod, and small exopod. Protopod with 1 subapical seta. The exopod is on the apical outer face of the protopod consisting of 1 seta. The endopod has 3 segments. First segment with 1 long subapical natatory and 1 short seta (anlage of aesthetasc Y) and with 1 long ventral seta. Second segment with 1 long G 3 seta and 1 short G 1 claw-like seta. Terminal segment with 2 large G M, Gm claw-like setae, 1 smooth g-seta, and 1 aesthetasc (y 3).
Md ( Figure 4C View Figure 4 ). Points backwards and attached to the body just above and to the side of the mouth region. Consists of 3 segments. Terminal segment with a long curved seta and 2 small setae.
3.2. Description of second instar (A-7; n = 6)
RV: L 216–290; H 161–280; LV: L 227–300; H 230–250. The maximum H in the anterior part of valve. Anterior margin rounded and acuminated at the posterior margin. Valves subequal, the RV overlaps the LV dorsally. Surface rough with numerous long setae in the posterior margin ( Figures 2F and 2G View Figure 2 ).
An1. Similar to A-8 instar, with setae proportionally longer than in the previous instar.
An2 ( Figure 4D View Figure 4 ). First segment of protopod with 1 long subapical ventral seta. Second segment same as the previous instar. The exopod consists of 1 long seta and 1 short seta. The aesthetasc (Y) is clearly visible in subapical position. Claws of the second segment of endopod proportionally longer than in the A-8 instar, this segment with the addition of 1 short G 2 ventral seta. Last segment same as the A-8 instar.
Md ( Figure 4E View Figure 4 ). Developed into a feeding appendage consisting of a coxa, a palp, and a respiratory plate (exopod). Coxa pointed dorsally and slightly raked backward. Coxa with 5 teeth, 1 subapical dorsal seta, and intervening setae protruding on either side towards the mouth. First segment of the palp with 2 apical ventral S 1 and S 2 setae. Second segment without setae. Last segment with 3 apical setae. Exopod consists of 2 rays.
Rlo. Appears for first time in the anterior region of the hypostome with 5 or 6 rounded teeth.
Mx ( Figure 4F View Figure 4 ). Appears for first time, consists of a stout palp and 3 endites. First and second endites with 2 and 3 apical setae, respectively. Third endite with 4 apical setae. Palp with 4 subequal apical setae.
Pediform anlage of CR ( Figure 4G View Figure 4 ) consisting of 1 segment with a long terminal curved seta.
3.3. Description of third instar (A-6; n = 3)
Cp: L 314–370; H 214. The maximum H displaced behind the middle. Outline subtriangular. Anterior margin rounded, posterior margin more pointed than in previous instars. Dorsal margin straight. Ventral margin concave. Duplicature well developed in the anterior part. Numerous normal pores with small setae ( Figure 2H View Figure 2 ).
An1 ( Figure 5A View Figure 5 ). Similar to A-7 instar. First segment lost. Second segment with an additional long seta. Third segment with long setae and proportionally longer. Fourth segment with an additional long ventral seta.
An2 ( Figure 5B View Figure 5 ). Exopod with 1 short additional seta. Aesthetasc (Y) slightly shifted in position towards the protopod. The first segment of the endopod with 2 additional long natatory setae. Terminal segment remains unchanged, but aesthetasc y 3 is now bifurcated.
Md ( Figure 5C View Figure 5 ). Slightly larger compared to previous instars. Coxa with cuspate teeth. Palp with 3 recognizable segments. First segment with 1 additional plumose β-seta, 2 long smooth subapical ventral setae, and 1 dorsoapical seta. Second segment with 2 ventral setae and 1 γ-seta with a swollen base. Terminal segment with 1 additional claw-like seta.
Rlo ( Figure 5D View Figure 5 ). With 9 teeth.
Mx ( Figure 5E View Figure 5 ). The palp has 2 segments. First segment with 2 dorsoapical setae. Respiratory plate with 13 rays.
T1 ( Figure 5F View Figure 5 ). Anlage of T1 protrudes from behind the base of Mx, consists of 1 segment.
CR ( Figure 5G View Figure 5 ). Same as in previous A-7 instar.
3.4. Description of fourth instar (A-5; n = 2)
RV: L 450–650; H 485–510. LV: L 500–714; H 550. Anterior margin of RV with 1 spine. Posterior margin with a row of small spines on the ventral side. Ornamentation most strongly developed, consisting of a gentle reticulate pattern and numerous setae. Muscle scars long and strongly marked, situated in the middle part of the valve above the maximum L ( Figures 2I–2K View Figure 2 ). Internal margins of both valves with a row of small spines ( Figure 2L View Figure 2 ).
An1 ( Figure 6A View Figure 6 ). Second segment with an additional short dorsoapical seta.
An2 ( Figure 6B View Figure 6 ). Claws of the second segment of endopod are proportionally longer than in the previous instar. Second segment of endopod with the addition of 1 short ventroapical seta. Terminal segment remainder unchanged.
Md and Rlo. Same as in the A-6 instar.
Mx ( Figure 6C View Figure 6 ). Third endite with the addition of 1 plumose apical seta. One of the apical seta of the first segment of palp appears plumose.
T1 not obtained.
T2 ( Figure 6D View Figure 6 ). Consist of 3 segments. Terminal segment with 1 long curved serrated claw and 2 short setae .
CR. Same as in the previous instar.
3.5. Description of fifth instar (A-4; n = 3)
Cp: L 785–800; H 514–600. The maximum H in the middle L. Ventral side more convex than in the A-5 instar but not too high. Surface of carapace with a delicate reticulation in the posterior margin. Normal pores more numerous than in the A-5 instar ( Figures 3A and 3B View Figure 3 ).
An1 ( Figure 7A View Figure 7 ). First segment of endopod with a long dorsal seta.
An2 ( Figure 7B View Figure 7 ). Same as in the A-5 instar.
Md ( Figure 7C View Figure 7 ). Coxa with 2 additional plumose ventroapical setae. Palp with 4 recognizable segments. First segment with 2 plumose S 1 and S 2 setae. Second segment with 3 subequal dorsoapical setae and with 1 plumose seta and 1 smooth seta ventrally. Third segment of palp with 2 unequal smooth setae and 2 subequal setae dorsally inserted. γ-Seta smooth. Last segment with 4 unequal apical setae.
Rlo. Same as in the A-5 instar.
Mx ( Figure 7D View Figure 7 ). Third endite with 4 dorsoapical setae and 2 apical setae now transformed into claw-like Zahnborsten setae.
T1 ( Figure 7E View Figure 7 ). Masticatory process with 4 smooth subapical and 5 smooth apical setae.
T2 ( Figure 7F View Figure 7 ). First segment of endopod with 1 ventral seta and second segment with 1 ventral apical seta. Last segment is unchanged from the A-5 instar.
T3 ( Figure 7F View Figure 7 ). Anlage consists of 1 segment.
CR ( Figure 7G View Figure 7 ). With 1 posterior seta (sp) and 2 subequal claws (Ga, Gp). The CR looks relatively lightly sclerotized and hence may not be functional in this instar; this is corroborated by the absence of any supporting attachment of the endoskeleton.
3.6. Description of sixth instar (A-3; n = 4)
Cp: L 900–1003; H 670–770. Surface of carapace less reticulate than in the previous instars with additional pustules in the anterior margin ( Figures 3C and 3E View Figure 3 ). Muscle scars consist of a group of 6, the ventral scars longer than the others ( Figures 3D and 3E View Figure 3 ).
An1 ( Figure 8A View Figure 8 ). With 6 segments that result from the fourth segment splitting into 2 smaller quadrate segments. First segment of endopod large, broad, and subrectangular in shape and supporting 2 plumose subapical setae on its dorsal edge; the ventral seta appears plumose. Second segment of endopod short with ventral seta plumose. Third segment of endopod as an elongated rectangle and with a length approximately twice the width, supporting a long ventral seta and a short dorsal seta apically. Fourth segment of endopod subquadrate bears a long ventral seta and 1 short dorsal seta. Fifth segment of endopod with 2 long ventral setae and 1 short dorsal seta. Last segment as A-4 instar.
An2 ( Figure 8B View Figure 8 ). First segment of protopod with 3 additional short ventral setae. The setae of the second segment of protopod appear plumose. First segment of endopod with 2 additional long setae and 1 short natatory seta (a total of 4+1). Second segment of endopod with 2 additional mediodorsal setae. Ventrally are 4 long t-setae and apically the aesthetasc (y 2); claws (G 1, G 3) become bigger than in the previous instars. Last segment with claw GM, Gm well developed and serrated, seta g, and aesthetasc y 3.
Md ( Figure 9A View Figure 9 ). Coxa with 6 teeth. Two pectinate setae appear between the first and second teeth. Third segment of palp with 2 smooth ventral setae and 4 smooth subapical dorsal setae. Last segment with 3 claw-like setae and 4 smooth setae. Exopod with 7 rays.
Rlo. Same as in the A-4 instar.
Mx ( Figure 9B View Figure 9 ). Third endite with the addition of 1 plumose subapical seta and 2 bipectinate apical setae. The short apical seta present in previous instars now is subapical and plumose. First segment of palp with 1 additional apical seta and 4 subapical setae. Second segment of palp with 1 additional smooth apical seta. Respiratory plate ( Figure 9C View Figure 9 ) with 28 rays.
T1 ( Figure 9D View Figure 9 ). Protopod with 2 additional plumose setae (d, b). Masticatory process with 5 additional setae. All setae appear plumose. Endopod with 3 setae (h 1, h 2, h 3). Exopod with 5 rays.
T2 ( Figure 9E View Figure 9 ). Second segment of protopod with 1 additional plumose subapical ventral seta. First segment of endopod stout with 2 additional subapical setae. Second segment with 1 ventroapical seta. Third segment with 1 additional subapical ventral seta. The claw of the last segment present in the A-4 instar with a row of small teeth.
T3 ( Figures 9F and 9G View Figure 9 ). Developed into a cleaning limb, consisting of 3 elongated segments. First segment with 1 plumose subapical ventral seta and 2 subapical plumose setae. Second segment with 1 subapical plumose ventral seta. Third segment capped in a fully developed cleaning pincer organ as seen in adult specimens.
CR ( Figure 9H View Figure 9 ). Proportionally larger than in the A-4 instar and finely denticulate. Posterior (sp) seta and both claws (Ga, Gp) appear plumose. An additional anterior seta (sa).
CRa ( Figure 9I View Figure 9 ). Appears in this instar as a slender and bifurcating attachment.
3.7. Description of seventh instar (A-2; n = 2)
Cp: L 1300–1500; H 900–960. Anterior margin of carapace with a fine flange. Posterior margin with a rhomboid pattern of ornamentation, also with many pores and delicate setae ( Figure 3F View Figure 3 ). Posterior margin of both valves with delicate denticles ( Figure 3G View Figure 3 ). Muscle scars in a central position.
An1 ( Figure 10A View Figure 10 ). With 7 segments. Second segment of endopod with 1 additional short ventral seta; third segment with 1 ventroapical seta and 1 short dorsoapical seta; fourth segment with 2 long subequal ventral setae and 2 unequal dorsal setae, the shorter plumose; fifth segment with 2 long ventral and 2 long dorsal setae. Fourth segment of endopod also with 4 long setae and 1 short natatory seta. Last segment is the same as in the A-3 instar.
An2 ( Figure 10B View Figure 10 ). Proportionally longer than in previous instars with 1 additional long natatory seta (5+1), with the chaetotaxy in the rest of the segments remaining unchanged.
Md ( Figure 10C View Figure 10 ). Dorsal setae of coxa appear plumose. Third segment of palp with γ-seta larger than in A-3 instar. One of the claw-like setae of the last segment appears serrated.
Rlo not obtained.
Mx ( Figure 10D View Figure 10 ). First endite with 2 plumose setae at the base. Third endite with 1 additional smooth seta. First segment of palp with 1 medial seta, second segment with an additional smooth seta.
T1 ( Figure 10E View Figure 10 ). Similar to A-3 instar, but 4 of the apical setae of the masticatory process appear serrated. Seta (b) present.
T2 ( Figure 10F View Figure 10 ). Same as in A-3 instar.
T3 ( Figures 11A and 11B View Figure 11 ), CR ( Figure 11C View Figure 11 ), and CRa ( Figure 11D View Figure 11 ). Same as in A-3 instar.
3.8. Description of eighth instar (A-1; n = 2)
LV: L 1650; H 980. No photographs were obtained for valves in this instar because they broke up during the mounting procedure.
An1 and An2. Same as in A-2 instar.
Md ( Figure 11E View Figure 11 ). Coxa with 7 teeth. Two short setae appear between the second and third tooth. Fifth and 6th teeth bicuspid. Seventh tooth bicuspid with a long seta behind.
Prmx ( Figure 11F View Figure 11 ). Same as in previous instar. Respiratory plate with 16 rays.
Rlo. Same as in A-2 instar.
T1 ( Figure 11G View Figure 11 ). With the addition of 2 (a) setae.
T2, T3, CR, and CRa. Unchanged from the previous instar.
Glo ( Figure 11H View Figure 11 ). Genital lobe present with genital operculum rounded, internally connected by tubes.
The order of appearance of appendages of Chlamydotheca arcuata from A-8 through A-1 is summarized in Table 1.
3.9. Description of adult (A)
Carapace tumid in dorsal view, maximum width just behind the middle, pointed and acuminated anteriorly and rounded posteriorly. Surface of valves smooth with delicate setae. RV (n = 200): L = 1990 ± 150 (1800–1990), H = 1003 ± 0.02 (100–109); LV (n = 200): L = 2150 ± 300 (2000–2200), H = 1190 ± 700 (1020–1190).
The chaetotaxy of limbs is the same as in previous instars, but in the adults the genital organ is completely developed. The vaginal opening is rimmed with chitinized rings and connected to the seminal receptacle by long, coiled canals.
3.10. Complete development
The complete development of C. arcuata lasted between 80 and 90 days. The nauplius A-8 hatched between 10 and 15 days after laying. The time elapsed between each molt varied with the extent of development ( Table 2). A great number of juveniles died upon reaching the sixth instar (i.e. A-3). The eighth and final molt occurred 20 to 30 days after the females had laid the eggs.
In the A-5 instar, we observed that the second thoracic limb had a definite shape, which indicates that the appendage had become a true walking limb. In the A-3 instar, we noted that the respiratory function was completed with the branchial plate at the eighth instar. When the fifth thoracic limb changed, another thoracic limb appeared along with the well-developed caudal ramus. This transformation is achieved when a newly formed appendage takes over the locomotor function of the preexisting appendage, which loses that function to adopt a different function (e.g., feeding).
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