Pallisentis longus Rana & Kaur 2023

Species: Pallisentis longus

Host: Channa marulius (Hamilton, 1822)

Locality: Govind Sagar Lake, Bhakra, Himachal Pradesh (31.4047°N, 76.4968°E), India

Site of infection: Small intestine

Specimens submitted: Registration number– HARC /ZSI/ AC –5 and HARC /ZSI/Ac– 6 in slides P5 and P6 containing whole worms Holotype male and Allotype female, respectively stained in Gower’s carmine mounted with DPX were submitted to High Altitude Regional Centre– Zoological Survey of India, Solan, India.

Sequences generated: The sequences submitted to the NCBI database on the basis of 18S, 28S, and ITS1 – 5.8S – ITS have been allotted accession number OM480740, OM480745, and OM501882, respectively.

Etymology: The specific name has been derived from the longest trunk of the present specimens ever reported in the genus.

Specimens examined: 5 males and 5 females

Morphological description (Figure 2)

General: Proboscis oblong, proboscis hooks in 4 circles, 9 or 10 hooks per circle, gradually declining in size, hook roots directed posteriorly. Nuclei of apical organ not observed. Neck long, unarmed. 2 sets of spines in trunk: anterior (collar) spines and posterior (trunk) spines. Collar spines Y–shaped. Lemniscus sub-equal, present in anterior half of the trunk. Trunk spines Y shaped, last circle ending above testes in male, present till the posterior extremity in female but irregular in posterior circles. Cement gland very long, syncytial with 20–25 nuclei. Female gonopore near–terminal towards ventral side. Egg with three membranes, polar elongations of fertilization membrane absent.

Male: Trunk length 15–20 (17.5) mm, maximum width 0.5–0.7 (0.6) mm at anterior region of trunk. Proboscis 193.1–208.4 (200.7) long × 152.5–191.0 (171.7) wide. H1 73.5–94.3 (83.9) long × 16.7–20.5 wide, H2 61.9–81.3 (71.6) long × 10.0–14.4 (12.2) wide, H3 52.8–54.7 (53.8) long × 7.7–8.9 (8.3) wide, H4 38.6–48.7 (43.6) long × 5.2–6.8 (6.0) wide. Hook roots short, HR1 49.1–51.8 (50.4), HR2 32.8–34.5 (33.6), HR3 24.6–26.8 (25.7), HR4 21.6–23.5 (22.5). Neck unarmed, 307.9–376.2 (342.0) long × 187.3–232.7 (210.0) wide. Proboscis receptacle 837.9–972.3 (905.1) long × 180.4–209.8 (195.1) wide, Lemnisci (L) L1– 2493.7–2878.9 (2686.3) long × 87.7–88.0 (87.9) wide, L2– 2406.0–2722.8 (2564.4) long × 70.5–82.4 (76.4) wide. Collar spines 13–16 circles, 16–20 spines per circle, 25.6–34.5 (30.1) long, spine field covering 583.5–619.0 (601.3) region of trunk. Trunk spines Y shaped, 27–31 (29) circles, equally spaced, 14–20 spines per circle, 33.8–40.0 (36.9) long. Testes two, elongated, tandem, post equatorial. Anterior testis 1253.7–1444.2 (1348.9) long × 259.5–369.1 (314.3) wide, posterior testis 1116.2– 1341.2 (1228.7) long × 220.8–249.6 (235.2) wide. Cement gland 2333.5–3162.1 (2747.8) long × 220.8–249.6 (235.2) wide. Cement reservoir elongated 774.6–863.7 (819.1) long × 189.8–211.9 (200.8) wide, branch posteriorly into two ducts. Seminal vesicle behind the cement reservoir, 640.5–711.3 (675.9) long × 113.4–158.4 (135.9) wide, tapers to form vas efferens anteriorly and vas deferens posteriorly. Saefftigen’s pouch 836.8–987.0 (911.9) long × 85.0–95.4 (90.2) wide, posterior to seminal vesicle. Vas deferens, ducts of saefftigen’s pouch and cement reservoir enter bursa. Bursa 387.4–478.8 (433.1) long × 382.1–467.8 (425.0).

Female: Trunk length 20–44 (32) mm, much longer than male, maximum width 0.53–0.68 (0.60) mm at anterior region of trunk. Proboscis 180.9–240.8 (210.9) long × 174.0–225.6 (199.8) wide, H1 82.7–96.9 (89.8) long × 15.4–18.1 (16.8) wide, H2 67.8–79.2 (73.5) long × 10.5–14.1 (12.3) wide, H3 47.3–59.0 (53.1) long × 6.9–9.3 (8.1) wide, H4 31.8–49.8 (40.8) long × 6.9–7.3 (7.1) wide. HR1 50.7–52.8 (51.7), HR2 35.9–38.5 (37.2), HR3 25.4–27.1 (26.2), HR4 20.6–24.5 (22.6). Proboscis receptacle 813.3–844.4 (828.8) long × 238.3–285.3 (261.8) wide. Neck long, unarmed 263.0–324.5 (293.8) long × 225.5–269.9 (247.7) wide. L1 2014.7–2481.9 (2248.3) long × 77.8–82.1 (79.7) wide, L2– 2006.8–2382.0 (2194.4) long × 74.6–82.8 (78.7) wide. Collar spines 15–16 circles, 15–20 spines per circle, 36.4–41.7 (39.1) long, spine field covering 722.4–727.8 (725.1) region of trunk. Trunk spines 64–69 (66) circles, 16–20 in each circle, 3–5 in posterior most circles, 38.1–45.1 (41.6) long. Female reproductive system 780.3–845.1 (812.7) long, uterine bell 163.1–175.1 (169.1) long, leading into muscular uterus 464.1–495.7 (479.9) long, vagina 153.9–166.3 (160.1) long, bent towards the ventral side of the body. Egg 76.5–83.7 (80.1) long × 43.85–49.87 (46.86) wide.

Remarks

The present species is placed in the genus Pallisentis due to the presence of two well separated spined regions on the trunk and syncytial cement gland in males. It is the longest species ever reported in the genus. According to the updated key of Rana & Kaur (2021b) the present species shows some morphological resemblance with P. nagpurensis, P. roparensis, and P. clupei Gupta and Gupta, 1977 in the number of proboscis hooks and overlapping number of the collar and trunk spines. The trunk spines in case of the above–mentioned species are Y shaped, extending to posterior end in females only and the testes in the males are post equatorial in position. Further, the size of the proboscis hooks in P. longus is considerably overlapping with the P. roparensis and P. nagpurensis (Table 1). However, the species described in the present study differs from P. nagpurensis and P. roparensis in the many aspects like the size of neck, proboscis receptacle, lemniscus, number and arrangement of the trunk spines. Additionally, the organs of the reproductive system in both the sexes in the present species differs much from the reproductive organs of the P. roparensis (Table 2).

P. longus also differs from the other less similar species including P. clupei in the size of proboscis hooks, distribution of trunk spines, number of cement gland nuclei in males and having longer reproductive organs in both the sexes. The size of the hooks in P. clupei is longer than the P. longus. Trunk spines in the males of P. clupei are 28–30 in circles extending up to the posterior end of the anterior testis while in case of P. longus 27–31 circles of trunk spines end above the anterior testis. The number of cement gland nuclei is much less in P. clupei (9–16) in comparison to the P. longus (20–25). The organs of male and female reproductive organs are significantly longer in P. longus and female gonopore is near–terminal in P. longus while terminal female gonopore is present in P. clupei.