Habitat use pattern of the giant parasitic nematode Crassicauda magna within the pygmy sperm whale Kogia breviceps

Abstract

The giant (>3 m) parasitic nematode Crassicauda magna infects kogiid whales, although only 3 studies to date have provided detailed descriptions of these worms, all based upon fragmented specimens. These fragments were found within the neck region of kogiids, an unusual anatomic site for this genus of parasites. C. magna is a species-specific parasite among kogiids, infecting only pygmy sperm whales Kogia breviceps, and with a primarily cervico-thoracic distribution. To date, however, the pattern of habitat use within the host and transmission path of this parasite remain unknown. We used detailed dissections (n = 12), histological examination of host tissues (n = 2), and scanning electron microscopy of excised nematodes (n = 7) to enhance our understanding of this host-parasite relationship. Results revealed that a critical habitat for the parasite is an exocrine gland in the whale's ventral cervical region. C. magna male and female tails were found intertwined within the glandular lumen, and eggs were observed within its presumed secretion, illuminating the transmission path out of the host. The cephalic ends of these worms were often meters away (curvilinearly), embedded deeply within epaxial muscle. A single worm's complete, tortuous 312 cm course, from the gland to its termination in the contralateral epaxial muscle, is described for the first time. This study also provides the first scanning electron micrographs of C. magna, which illustrate taxonomically important features of the heads and tails of both male and female worms.

Morphological and molecular characterization of adults and larvae of Crassicauda spp. (Nematoda: Spirurida) from Mediterranean fin whales Balaenoptera physalus (Linnaeus, 1758)

“…C. duguyi ), C. tortilis Skrjabin (1959), C. delamureana Skrjabin, 1966, C. fuelleborni Baylis, 1932, C. costata Skrjabin (1969), C. carbonelli Raga and Balbuena, 1990. These species occur in the kidneys ( C. giliakiana , C. anthonyi , C. bennetti , C. boopis , C. tortilis , C. delamureana , C. costata ), reproductive system ( C. crassicauda , C. carbonelli , C. fuelleborni ), pterygoid sinuses ( C. grampicola ) and subcutaneous tissues and “gill slit” gland ( C. magna ) of the host (Keenan-Bateman et al, 2018). Among them, four species have been described in the kidneys of mysticetes, i.e.…”

Gross and histological morphology of the cervical gill slit gland of the pygmy sperm whale (Kogia breviceps)

“…Thus, the only mammalian group for which chemical communication has not been definitively demonstrated are odontocete cetaceans (Gabe, 1967; Müller‐Schwarze, 1983; Wyatt, 2014a, 2014b). Herein we describe the gross and histological morphology of the cervical “gill slit” exocrine gland of the pygmy sperm whale ( Kogia breviceps ; Hubbs, 1951; Keenan‐Bateman et al, 2016, 2018), which suggest that this odontocete species may be capable of producing semiochemicals.…”

“…Several species of odontocete cetaceans, though, have been documented to possess exocrine skin glands with ducts that empty directly onto the skin surface. These include the (a) perianal glands of male delphinids and the beluga whale ( Delphinapterus leucas ; Caldwell et al, 1966; Ceruti et al, 1985; Kleinenberg, Yablokov, Bel'kovich, & Tarasevich, 1964; Morejohn, 1979; Nishiwaki & Kureha, 1975; Norris, 1966; Sokolov, 1982; Yablokov, 1961 as cited in Caldwell et al 1966), (b) preputial gland of the sperm whale ( Physeter macrocephalus ) (Yablokov, 1957 cited in Berzin, 1972), and (c) cervical “gill slit” gland of the pygmy sperm whale ( K. breviceps ) (Hubbs, 1951; Keenan‐Bateman et al, 2016, 2018). Despite the known chemical signaling roles that exocrine glands serve in terrestrial and other marine mammals, to date there has been little attention paid to these glands in cetaceans.…”

“…Hereafter, we will refer to it simply as the gill slit gland. The gill slit gland has been documented as a common site of infection for the giant (>3 m) parasitic nematode, Crassicauda magna , and aspects of its morphology have been briefly described in relation to the habitat it provides for the parasite (Keenan‐Bateman et al, 2018). The gland was found to provide a critical site for parasite reproduction and transmission of eggs into the environment.…”

Morphology of Eggs Crassicauda Sp. From Feces of Pacific Bottlenose Dolphin (Tursiops Truncatus Gillii)

“…Введение. Нематоды подотряда Spirurida рода Crassicauda паразитируют у китообразных и локализуются преимущественно в урогенитальной системе или в мускулатуре [1][2][3]. При значительной вариабельности размеров взрослых крассикауд (4 см -3,7 м) размеры яиц остаются практически неизменными (0,045 × 0,030 мм, толщина оболочки: 0,003-0,006 мм).…”